rice diseses

 

Row Spacing, Plant Population, and Yield Re

Row Spacing, Plant Population, and Yield Re Extension Agronomist - Cotton The manipulation of row spacing dimensions, plant populations, and the overall spacial arrangement of crop plants in a field has been the subject of considerable discussion among farmers and agronomists for many years. The crop canopy has often been manipulated by row spacing and population adjustments in an attempt to improve yields, production efficiencies, and profits. Similarly, plant breeders have altered plant architecture in an effort to improve light interception by crop plants. The development of conventional, narrow, and ultra narrow (UNR) crop systems and breeding for plants with columnar or bush-type architecture are examples of these types of manipulations to improve yield. The process of crop production requires the conversion of energy in sunlight into dry matter by fixation of CO2 from the atmosphere through the process of photosynthesis. Leaves are the primary site of photosynthesis in crop plants. Therefore, one might assume that the greater the number of leaves in a field, the better interception of sunlight and higher the yield. A common way of describing the surface area of leaves in a field is by the leaf area index (LAI). The LAI is the ratio of the leaf surface area (upper side only) of the crop to the ground area. The LAI for a crop will normally increase as the crop canopy develops. LAI values of greater than or equal to 4 (i.e. 4 times more area of leaves than ground) have been measured for irrigated cotton in Arizona. Cotton plants will also be effected to some extent by the fact that the leaves track the movement of the sun (heliotropic movement), which increases interception of light by the canopy. However, with an increasing LAI there will also be an increasing amount of shading of lower leaves in the canopy. As a result, agronomists recognize that an optimization of LAI is important in realizing the most efficient interception of sunlight and optimum photosynthesis. Another primary objective in a crop production system is to direct a high proportion of the dry matter into harvestable parts of the crop plant. The relationship between the harvestable portions of the plant (e.g. lint or seedcotton yield in cotton) and the total amount of dry matter produced by the crop is often referred to as the harvest index (HI). An important goal in a crop production system is to generate a high HI. For cotton production systems this translates to producing as many bolls per unit area (e.g. per acre) as possible to realize high yields. Therefore, maximum cotton production is a direct function of efficiently utilizing resources such as sunlight, water, and nutrients. The balance between vegetative and reproductive growth (i.e. harvest index for cotton) is critical in relation to any effort to improve yields. As noted above, an essential aspect of any crop production system is the development of a crop canopy that optimizes the interception of light, photosynthesis, and the allocation of dry matter to harvestable plant parts (yield). A crop canopy is commonly managed by manipulating row spacing, plant population, and plant type. Yield per unit area generally increases with plant density. Although, as plant density is increased yield per unit area will approach an upper limit, plateau, and then decline. Yield per plant tends to decrease with increasing plant density because competition for resources (light, water, and nutrients) between adjacent plants intensifies. Optimal plant populations (densities) for both conventional and narrow row cotton production systems often range between 30,000 to 60,000 plants per acre (ppa). Acceptable cotton plant populations have been reported between 20,000 to 75,000 ppa for irrigated cotton production systems in the desert Southwest. The optimal plant population for a given field will depend to some extent on soil type, variety, weather, pest populations, etc. In modern cotton production systems conventional row spacings commonly range from 36 to 40 inches. Narrow row systems are those less than 36 inches, often having 30 inch row spacings. In recent years, UNR cotton systems have been developed and evaluated in many parts of the US cottonbelt. The UNR systems that have been developed commonly have 6 to 10 inch row spacings and plant populations of 100,000 to 120,000 ppa. In general, these UNR systems have shown the most promise for drastically reducing the length of the growing season and increasing production on marginal lands. Therefore, UNR systems have been touted as having the potential of improving profitability by reducing inputs, risk, and increasing the ratio of yield to inputs. Success with UNR systems require control of plant population and uniformity, plant height with high population, and the use stripper harvesters (a complete change in harvesting equipment for picker harvesting areas). Additional concerns include difficulties in ginning and maintaining good grades. To date, very little information is available relative to the feasibility of developing or utilizing UNR cotton production in Arizona. Despite this fact, a number of Arizona growers are interested in developing and testing UNR systems in several areas around the state in 1999. The development of UNR systems represents an interesting way to manipulate crop canopy architecture, but it is difficult to predict how well this will work under irrigated conditions in Arizona. A conventional cotton production system in Arizona (e.g. an Upland cotton variety, 40 inch row spacing, and approximately 40,000 ppa) will commonly produce plants with an average of 21 fruiting branches by the time the crop experiences cut-out (end of primary fruiting cycle). Assuming the plants have at least 2 fruiting sites on each fruiting branch, the plants would have an average of at least 42 potential fruiting sites. With 50% retention of those sites at harvest and 3 plants/foot, this would provide approximately 63 bolls/foot of row. Using a general yield estimate of 20 bolls/foot equating to 1 bale lint/acre, this field would have a 3 bale yield potential. For a UNR system to be more profitable a greater number of bolls would have to be produced per unit area, or an equal number produced with lower inputs. Seemingly, the goal of a UNR system would be to optimize the earliest (lower) fruiting sites on the plants. Thus, the emphasis in crop management will likely be oriented toward the early stages of the growing season and fruiting cycle. Variations in crop canopy architecture as effected by row spacing, plant population, and plant type have been topics of interest for many generations and will continue to be subjects of further study and development. Results with the UNR systems that are being developed and tested should be followed with great interest. We need to evaluate them thoroughly and objectively and document the potentials they appear to offer.

Pest Management in Rice-Current Status and Future Prospects

Pest Management in Rice-Current Status and Future Prospects

IV.CULTURAL METHODS: 
Crop husbandry practices that have a dual purpose of crop production and protection form
the cultural methods. These practices were developed by the farmers through observation and
trial and error. The insect control component of these practices, learnt through generations is not
practiced and carried forward by the present day farmers. Cultural, mechanical and physical
methods of control are often complementary. The practices that have been followed such as
hand picking, roguing, trap cropping, mixed cropping and barrier crops are found to be beneficial
(Litsinger, 1994) except a few practices which are discussed below.
 i. Age of seedlings: Yields of modern cultivars decline dramatically when older seedlings are
planted but traditional cultivars by and large are not affected by seedling age. In both cases,
effects of seedling age on pest suppression are inconsistent. Now with the popularization of
System of Rice Intensification technique, the effect of planting 14-day old seedling on rice insects
needs to be studied.
ii. Synchronous planting vs. Asynchronous planting: The promotion of synchronous planting as a
means of controlling pests is often cited in the literature (eg. Loevinsohn et al., 1993) and is one of
the IPM tactics in vogue in many areas. The assumption is that non-synchronous planting patterns Page | 9
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Directorate of Rice Research,
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Ph: 91-40-24591218, 295 Fax: 91-40-24591217
promote pest problems because they give the rice pests a constant source of food. That analysis,
however, is based solely on a plant-herbivore model, and does not take into consideration natural
enemies and alternative prey. Examination of patterns of the BPH outbreaks in Northwest Java
from 1986 to 1991 (Sawada et al., 1991) revealed that the rice BPH outbreaks are more prevalent
and more serious in the synchronously planted areas than in the non synchronous planted
(‘staggered’) areas nearby. These differences were attributed to high levels of pest mortality
caused by the natural enemies in the staggered areas.
 Similar results were found in Malaysia (Wada and Salleh, 1992)

Banana Diseases

Diseases

Panama Wilt (Fusarium oxysporum f. sp. cubense): This is a soil-borne fungal disease and gets entry in the plant body through roots. It is most serious in poorly drained soil. Initial symptoms are yellowing of lower leaves, including leaf blades and petioles. The leaves hang around the pseudostem and wither. In the pseudostem of the diseased plant, yellowish to reddish streaks are noted with intensification of colour towards the rhizome. Wilt is severe in poor soil with continuous cropping of banana. Warm soil temperature, poor drainage, light soils and high soil moisture are congenial for the spread of the disease. 

Control: Severely affected plants should be uprooted and burnt. Highly infected soil should not be replanted with banana at least for 3-4 years. Use of disease-free planting material and resistant cultivar are recommended. Growing of paddy followed by banana for 3-5 years once or twice, use of quick lime near the base of the plant and soaking with water and avoiding sunflower or sugarcane in crop rotation helps to reduce the disease incidence. Dipping of suckers in Carbendazim (10g/10 litres of water) followed by bimonthly drenching starting from 6 months after planting is also recommended. Application of bioagents, such as, Trichoderma viride or Pseudomonas fluorescence in the soil is effective. 

Leaf Spot, Leaf Streak or Sigatoka Disease (Mycosphaerella musicola) : Yellow sigatoka is one of the serious diseases affecting the banana crop. Initial symptoms appear in the form of light yellowish spots on the leaves. A small number of these enlarge, become oval; the colour also changes to dark brown. Still later, the centre of the spot dies, turning light grey surrounded by a brown ring. In severe cases, numerous spots coalesce, killing large parts of the leaf. Rainfall, dew and temperature determine the spread of the disease. Conditions favouring mass infection are most common during the rainy season with temperature above 21øC.


 

Control: Cultural practices such as improved drainage, control of weeds, removal of diseases suckers and adopting correct spacing is recommended. Dithane M-45 WP (in oil-water emulsion) and Dithane M-45 (in water only) controlled Mycosphaerella fjijiensis var. difformis in banana. Foliar spray of Copper Oxychloride (3 g/litre of water) or Thiophanate Methyl 1 g/ litres of water) control the disease effectively.

Anthracnose ( Gloeosporium musae) : The disease attacks banana plants at all stages of growth. Disease attacks the flowers, skin and distal ends of banana heads. The symptoms appear as large brown patches covered with a crimson growth of the fungus. The disease fruit turns black and the fruit is shrivelled.

Control: Spraying of Chlorothanlonil (0.2%) and Bavistin (1 %) four times at 15 days interval is recommended. Minimising bruising; proper sanitation of handling and prompt cooling to 14øC are essential in minimising the disease in cold storage. 

Cigar End Tip Rot (Verticillium theobromae, Trachsphaera fructigena and Gloeosporium musarum): A black necrosis spread from the perianth into the tip of immature fingers. The rotted portion of the banana finger is dry and tends to adhere to fruits (appears similar to the ash of a cigar). 

Control: Removal of pistil and perianth by hand 8-10 days after bunch formation and spraying the bunch with Dithane M -45 (0.1%) or Topsin M (0.1%) controls the disease effectively. Minimising bruising; prompt cooling to 14øC; proper sanitation of handling facilities reduce the incidence in the cold storage. 

Crown Rot (Colletotrichum musae, Fusarium sp., Verticillium theobromae, Botryodiploidia theobromae and Nigrospora sphaericu) : The characteristic symptoms are blackening of the crown tissues, which spreads to the pulp through the pedicel resulting rotting of the infected portion and separation of fingers from the hand. 

Control : Dipping the bunches or hands in Thiobendazole or Benomyl and/or using fungicide impregnated cellulose pad for packing is recommended. 

Stem-end Rot (Thielaviopsis paradoxa):The fungus enters through the cut stem or hand. The invaded flesh becomes soft and water-soaked. 

Control : Minimising bruising; prompt cooling to 14øC; proper sanitation of handling facilities and hot water treatment of hands (such as 5 minutes in 50øC water) helps in controlling the disease in cold storage. 

Pseudostem Heart Rot (Botrydiplodia sp.,Gloeosporium sp. and Fusarium sp.) :The first indication of heart rot is the presence of heart leaves with part of the lamina missing or decayed. In severe cases, the inner leaves of the crown first turn yellow, then brown and finally die. In more severe cases all the leaves and the plant die. 

Control : Adopting field sanitation, good drainage and proper spacing reduce the incidence of the disease. To prevent spread of the disease, spraying of Captan or Dithane M-45 or Dithane Z- 78 is effective. 

Head Rot (Erwinia carotovora):Newly planted suckers get affected, leading to rotting and emitting of foul odour. In older plants rotting at the collar region and leaf bases are seen. In advanced cases, trunk base becomes swollen and split. 

Control : Good drainage and soil conditioning can control the disease to some extent. Use of rhizomes with dead central buds and active lateral buds prevents the appearance of the disease. 

Bacterial Wilt or Moko Disease (Pseudomonas solanacearum) : The young plants are affected severely. In the initial stages the bacterial wilt is characterised by the yellowish discolouration of the inner leaf lamina close to the petiole. The leaf collapses near the junction of the lamina with the petiole. Within a week most of the leaves exhibit wilting symptoms. The presence of yellow fingers in an otherwise green stem often indicates the presence of moko disease. The most characteristic symptoms appear on the young suckers that have been cut once and begin regrowth. These are blackened and stunted. The tender leaves from the suckers turn yellow and necrotic.

Control : Early detection and destruction of the suspected plants may help in preventing the spread of the disease. All the tools used for pruning and cutting should be disinfected with formaldehyde. As the insects can carry the disease causing bacterium on the male flowers, removal of the male flowers as soon as the last female hand emerge help in minimising the spread of the disease.

Banana Bunchy Top Virus (BBTV): The disease is transmitted to the plant by the aphid vector Pentalonia nigronervosa and dwarf bananas are very susceptible to this disease. Primary symptoms of the disease are seen when infected suckers are planted. Such infected suckers putforth narrow leaves, which are chlorotic and exhibit mosaic symptoms. The affected leaves are britttle with their margins rolled upwards. Characteristic symptom of bunchy top virus is the presence of interrupted dark green streaks along the secondary veins of the lamina or the midrib of the petiole. The diseased plants remain stunted and do not produce bunch of any commercial value. 


 

Control : Systematic eradication of the diseased plants, suckers and the clumps is very essential. Planting materials should not be collected from places affected by this disease. The aphid should be controlled to check spread of the disease by spraying with Metasystox (0.1-0.5%). Plants adjacent to the healthy plants should also be sprayed. The affected plant should be killed with kerosene or herbicides such as 2, 4-D or 2, 4, 5-T. The rhizome should be dug out, cut into small sections and sprayed again so that no suckers can be produced which may harbour the virus. 

Banana Streak Virus (BSV) : A prominent symptom exhibited by BSV is yellow streaking of the leaves, which becomes progressively necrotic producing a black streaked appearance in older leaves. . The virus is transmitted mostly through infected planting materials, though mealy bugs (Planococcus citri) and more probably Saccharicoccus sacchari are also believed to transmit it. Shoot tip culture does not eliminate it from vegetatively propagated materials. 

Control: Control strategies include use of clean planting material and quarantine. Eradication of infected plants and control of vectors are effective in controlling the severity of the disease. 

Mosaic Virus: The disease is characterised by typical mosaic symptoms on the leaves. Mosaic plants are easily recognised by their dwarf growth and mottled, distorted leaves. The earliest symptoms appear on young leaves ass light green or yellowish streaks and bands giving a mottled appearance. The aphid vector Aphis gossypii transmits the disease. 

Control: The plantation should be kept free from weeds. Suckers from infected clumps should not be used for planting. Weeds in the nearby area should be removed as the virus survives in them during offseason. Use of suitable insecticide to reduce spread of the disease is also suggested. 

Banana Bract Mosaic Virus (BBMV): The symptoms appear as yellow green bands or mottling over an entire area of young leaves. The affected leaves show abnormal thickening of veins. Bunch development is affected. 

Control: Removal and destruction of affected plants along with rhizome. Growing cucurbits in and around banana field should be avoided. 

Insect pest

Pseudostem Borer (Odoiporus longicollis) : Adults are either reddish brown or black. The pest is active during summer and monsoon months. The grubs bore into the stem and feed within the stem. An initial symptom is in the form of exudation of plant sap and blackened mass that comes out from the hole bore by the grub. Finally the whole plant dies.




Control: In case of severe infection the affected plants should be uprooted and burnt. Celphos (3 tablets/plant) is recommended for control of egg, larva, pupa and adult population of the insect, application of. After placing the tablet inside the pseudostem, the slit should be plastered with mud. Clean cultivation is an important measure for its control. Application of Carbofuran (3 g of granules/stool) is very effective to control the pest. Alternately, application of Endosulphan (0.04%) or Carbaryl WP (0.1%) also controls the pest population. 

Rhizome Weevil (Cosmopolites sordidus) : The larvae or grub of the weevil borer feeds by tunnelling in the banana plant. In severe cases, the tunnels extend several feet up the stem. The corm decays and becomes a mass of rotten tissue. Injury to corm prevents nourishment going to the plant. Leaves turn yellow, wither and die maturely. In heavily infected plantations, production is low. Adults feed on dead or dying banana plants and live under newly cut or rotting pseudostems. The female weevil either lays its eggs in the rotting pseudostem or moves to a living plant where eggs are inserted singly into a hole. The borers spread from plantation to plantation through planting material.



Control : Plantations should be clear of debris in which borers can survive. It is most important to use clean planting material from fields, known to be free of weevils. Pieces of old rhizomes or pseudostems 1-2 feet long are cut down split and placed on the plantation floor between plants. Adult beetles migrate into these stems and can be collected by hand and poisoned. Before planting dipping of suckers in Monocrotophos (0.5%) for 30 minutes to protect rhizome from weevil attack. 

Banana Aphid (Pentalonia nigronervosa): The insect, is the vector of the virus causing bunchy top disease. Yellowish green nymphs and adults suck cell sap and devitalise plants. Affected parts become discoloured and malformed. High humidity favours rapid multiplication of this pest. The aphids are mostly observed on the lower surface of the leaves. 



Control: Spraying of Monocrotophos (0.05%) or Malathion (0.1%) at 10-15 days interval contains aphid population effectively. To prevent recurrence of the pest granular insecticides like Phorate @ 1.0 kg a.i./ha should be applied to soil. 

Fruit and Leaf Scarring Beetle (Colaspis hypochlora) : Occurrence of this pest is usually high during the rainy season. The adult beetle feeds on young leaves and skin of young fruits. Infested fruits get spotted and severe scarring of fruit skin leads to underdeveloped fruit of less commercial value.




Control: Removal of grass weeds from plantations where the population of this pest is high can often reduce the population levels enough to avoid the use of insecticides. Unless the beetles are causing serious economic losses the use of insecticides should be avoided. In case of severe infestation spraying with Endosulphan (0.04%) or Carbaryl WP (0.1 %) controls the pest population. 

Burrowing Nematode (Radopholus similis): The first symptom of the disease is a small dark spot on the root. The nematode deposit eggs in the root tissue. Larvae after hatching form the eggs feed on the root tissue. Fungi rapidly invade such damaged root tissue. The number of fruits in the bunch is reduced and individual fruits are small. Affected plants do not respond to fertilizers, irrigation or cultural practices. Nematode population is built up rapidly in ratoon crops. 

Control : Application of Carbofuran 3G or Phorate 10G @10 g/pit at the time of planting or application of neem cake (250-400 g/pit) at the time of planting reduces the pest population. Control measures such as application of nematicides to the growing infected plants and planting of nematode-free corms in fallow soil are recommended. Recently granular nematicides are becoming popular. They are easy to apply by hand to the soil around the mat at times combined with fertilizers. Some have systemic action. They are carried down into the soil by rain or irrigation water. Three applications of Nemacur (Phenamiphos) are effective in controlling the nematodes.

Disorders

Chilling Injury: Symptoms include surface discoloration, sub-epidermal tissues reveal dark-brown streaks, failure to ripen, and, in severe cases, flesh browning. Chilling injury results from exposing bananas to temperatures below 13øC for a few hours to a few days, depending on cultivar, maturity, and temperature. 

Skin Abrasions: Abrasions result from skin scuffing against other fruits or surfaces of handling equipment or shipping boxes. When exposed to low (<90%) relative humidity conditions, water loss from scuffed areas is accelerated and their colour turns brown to black. 

Impact Bruising: Dropping of bananas may induce browning of the flesh without damage to the skin.Bananas are harvested raw and ripened artificially. The dwarf bananas are ready for harvest within 1114 months after planting, while tall cultivars take about 14-16 months to harvest. A bunch usually takes 90-120 days to mature after shooting, depending on climate and cultural practices. The maturity of banana is indicated by drying of top leaves, change in colour of fruits from dark green to light green and tendency of the floral end of the fruit to fall by slightest touch by hand. The mature fruit becomes plumpy and all the angles are filled in completely. When tapped the fruit gives metallic sound. The method of harvesting depends on the height of the plant. Low growing varieties are harvested by cutting through the bunch stalk about 30-35 cm above the top hand. With taller varieties, the stem of the plant will be partly cut through to bring the bunch down within the harvester's reach. 

 List of rice diseases

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This article is a List of Diseases of rice (Oryza sativa).

Contents 1 Bacterial diseases 2 Fungal diseases 3 Miscellaneous diseases and disorders 4 See also 5 External links 6 References

Bacterial diseases

Bacterial diseases
Bacterial blight [1]	Xanthomonas oryzae pv. oryzae = X. campestris pv. oryzae
Bacterial leaf streak [2]	Xanthomonas oryzae pv. oryzicola
Foot rot	Erwinia chrysanthemi
Grain rot	Burkholderia glumae
Pecky rice (kernel spotting)	Damage by bacteria (see also underfungal and miscellaneous diseases)
Sheath brown rot	Pseudomonas fuscovaginae

Fungal diseases

Fungal diseases
Aggregate sheath spot	Ceratobasidium oryzae-sativae Rhizoctonia oryzae-sativae [anamorph]
Black kernel	Curvularia lunata Cochliobolus lunatus [teleomorph]
Blast (leaf, neck [rotten neck], nodal and collar)	Pyricularia grisea = Pyricularia oryzae Magnaporthe grisea [teleomorph]
Brown spot	Cochliobolus miyabeanus Bipolaris oryzae [anamorph]
Crown sheath rot	Gaeumannomyces graminis
Downy mildew	Sclerophthora macrospora
Eyespot	Drechslera gigantea
False smut	Ustilaginoidea virens
Kernel smut	Tilletia barclayana = Neovossia horrida
Leaf smut	Entyloma oryzae
Leaf scald	Microdochium oryzae = Rhynchosporium oryzae
Narrow brown leaf spot	Cercospora janseana = Cercospora oryzae Sphaerulina oryzina [teleomorph]
Pecky rice (kernel spotting)	Damage by many fungi including Cochliobolus miyabeanus Curvularia spp. Fusarium spp. Microdochium oryzae Sarocladium oryzae and other fungi.
Root rots	Fusarium spp. Pythium spp. Pythium dissotocum Pythium spinosum
Seedling blight	Cochliobolus miyabeanus Curvularia spp. Fusarium spp. Rhizoctonia solani Sclerotium rolfsii Athelia rolfsii [teleomorph] and other pathogenic fungi.
Sheath blight	Thanatephorus cucumeris Rhizoctonia solani [anamorph]
Sheath rot	Sarocladium oryzae = Acrocylindrium oryzae
Sheath spot	Rhizoctonia oryzae
Stackburn (Alternaria leaf spot)	Alternaria padwickii
Stem rot	Magnaporthe salvinii Sclerotium oryzae [synanamorph]
Water-mold (seed-rot and seedling disease)	Achlya conspicua Achlya klebsiana Fusarium spp. Pythium spp. Pythium dissotocum Pythium spinosum

Miscellaneous diseases and disorders

Miscellaneous diseases and disorders
Alkalinity or salt damage	Excessive salt concentration in soil or water
Bronzing	Zinc deficiency
Cold injury	Low temperatures
Panicle blight	Cause undetermined
Pecky rice (kernel spotting)	Feeding injury by rice stink bug, Oebalus pugnax
Straighthead[3]	Arsenic induced, unknown physiological disorder
White tip (see nematodes)	Aphelenchoides besseyi

agriculture machines

agriculture machines

Glossary

A

abdomen. The posterior body division of an arthropod.
abiotic disease. A disease caused by factors other than pathogens.
abiotic disorder. A disease caused by factors other than a pathogen; physiological disorder.
achene. A simple, one-seeded fruit in which the seed is attached to the ovary wall at only one point, such as the "seed" on the surface of a strawberry.
adventitious. A structure arising from an unusual place, such as roots growing from leaves or stems.
aestivation. A state of inactivity during the summer months.
albedo. White, spongy inner part of citrus fruit rind.
alkaline. Basic, having a pH greater than 7.
allelopathy. The ability of a plant species to produce substances that are toxic to certain other plants.
allowable depletion. The proportion of available water that can be used before irrigation is needed.
angular leaf spot. Bacterial blight.
annual. A plant that normally completes its life cycle of seed germination, vegetative growth, reproduction, and death in a single year.
antagonists. Organisms that release toxins or otherwise change conditions so that activity or growth of other organisms (especially pests) is reduced.
antenna (plural: antennae). The paired segmented sensory organs, borne one on each side of the head, commonly termed horns or feelers.
anthers. The pollen-producing organs of flowers.
anticoagulant. A substance that prevents blood clotting, resulting in internal hemorrhaging; may be used as a rodenticide.
apical dominance. Growth of the bud at the apex of a stem or tuber while growth of all other buds on the stem or tuber is inhibited.
apothecia (plural). Cup-shaped, spore-bearing structures produced by certain types of fungi such as Sclerotinia.
ascospores. A spore produced within the saclike cell of the sexual state of a fungus.
auricle. A small earlike projection from the base of a leaf or petal.
available water. The amount of water held in the soil that can be extracted by plants.
awn. A slender bristlelike organ usually at the apex of a plant structure.
axil. The upper angle between a twig or leaf and the stem from which it is growing.
axillary bud. A bud formed in an axil.

B

B.t. Abbreviation for Bacillus thuringiensis.
Bacillus thuringiensis. A bacterium that causes disease in many insects, especially caterpillars; formulations of the bacteria are used as insecticides.
bacterium (plural: bacteria). A single-celled, microscopic, plantlike organism that lacks a nucleus. Most bacteria obtain their nitrogen and energy from organic matter; some bacteria cause plant or animal diseases.
band application. An application in which a material such as fertilizer or herbicide is applied in strips, usually to the bed or seed row.
basin. A portion of a rice field bounded by levees.
beneficials. Organisms that provide a benefit to crop production, applied especially to natural enemies of pests and to pollinators such as bees.
biennial. A plant that completes its life cycle in two years and usually does not flower until the second season.
binomial sampling. A sampling method that involves recording only the presence or absence of members of the population being sampled (such as an insect pest) on a sample unit (such as a leaf), rather than counting the numbers of individuals; presence/absence sampling.
biodegradation. The breaking down of a chemical by organisms in the environment.
biofix. An identifiable event that signals when to begin degree-day accumulation.
biological control. The action of parasites, predators, or pathogens in maintaining another organism's population density at a lower average level than would occur in their absence. Biological control may occur naturally in the field or result from manipulation or introduction of biological control agents by people.
biotic disease. Disease caused by a pathogen, such as a bacterium, fungus, mycoplasma, or virus.
biotype. A strain of a species that has certain biological characters separating it from other individuals of that species.
blackarm. Bacterial blight lesions on stems.
blank. Nut with no kernel-consists of only the collapsed pellicle (skin).
blanking. Producing no grain or seed (used to describe individual florets of the rice panicle).
blight. A disease characterized by general and rapid killing of leaves, flowers, and branches.
blind node. The first node formed on a strawberry runner that usually does not form a daughter plant.
bolt. To initiate the growth of flower structures.
boot. A bulge in the upper leaf sheath caused by the expansion of the developing panicle.
bordeaux mixture. A fungicide made of a mixture of hydrated lime and copper sulfate.
border harvesting. A harvesting method that leaves a strip of uncut hay along every other border; next harvest these borders are mowed and the alternate borders are left standing.
borrow pits. Depressions on either side of a levee created when soil is removed from the field to build the levee.
botanical. Derived from plants or plant parts.
bract. A modified leaf at the base of a flower.
broad-spectrum pesticide. A pesticide that kills a large number of unrelated species.
broadcast application. The application of a material such as fertilizer or herbicide to the entire surface of a field.
brood. All the individuals of a generation that hatch at about the same time.
bud. Bud that forms in the axil of a leaf.
bulb. An underground storage organ, composed chiefly of enlarged, fleshy leaf bases.

C

calcareous soil. Doil containing high levels of calcium carbonate.
calibrate. To standardize or correct the measuring devices on instruments; to adjust nozzles on a spray rig properly.
calyx. The sepals of a flower; they enclose the unopened flower bud.
cambium. Thin layer of undifferentiated, actively growing tissue between phloem and xylem.
canker. A dead, discolored, often sunken area (lesion) on a root, trunk, stem, or branch.
canopy. The leafy parts of vines or trees.
carcinogen. A substance or agent capable of causing cancer.
caterpillar. The larva of a butterfly, moth, sawfly, or scorpionfly.
catfacing. Disfigurement or malformation of fruit; in the case of strawberries, usually the result of injury to developing achenes by Lygus bugs or low temperature.
catkin. A spikelike cluster of unisexual flowers, e.g., the male flowers of walnut.
cauda. A process resembling a tail.
certified seed or planting stock. Seeds, tubers or young plants certified by a recognized authority to be free of or to contain less than a minimum number of specified pests or pathogens.
certified transplants. Strawberry plants that have received a certification tag from the California Department of Food and Agriculture, production practices must meet standards for freedom from pest problems and plant samples from production fields must test free of viruses.
check. The part of a rice field between two levees.
chilling. In strawberries, exposure to temperatures low enough to induce the production of food reserves needed to support vigorous vegetative growth.
chlamydospore. Thick-walled spore formed from the cell of a fungus hypha.
chlorophyll. The green pigment of plants that captures the energy from sunlight necessary for photosynthesis.
chlorosis. Yellowing or bleaching of normally green plant tissue usually caused by the loss of chlorophyll.
chorion. The outer membrane of an insect egg.
circulative virus. A virus that systemically infects its insect vector and usually is transmitted for the remainder of the vector's life; persistent virus.
cocoon. A sheath, usually of silk, formed by an insect larva as a chamber for pupation.
cohort. A group.
cole crops. Any of the group of crucifer family crops that are varieties of the species Brassica oleracea, including cabbage, broccoli, cauliflower, and brussel spouts.
coleoptile. A sheathlike structure enclosing the shoot of a grass seedling.
collar region. In grasses, the region where the leaf blade and sheath meet; it is used in identifying species; in trees, the trunk area at the soil line.
companion planting. The practice of planting certain plant species-often herbs-in close association with crop plants to repel pests.
competitive exclusion agent. Organism capable of outcompeting other organisms, thus excluding them from the environment.
conidium (plural: conidia). A type of asexual fungal spore.
control action guideline. A guideline used to determine if pest control action is needed.
control action threshold. Pest population level at which treatment is necessary to prevent economic loss, also called economic threshold.
cornicle. Two tubular structures located on the posterior part of an aphid's abdomen.
cortex. Tissue between the phloem and the epidermis in roots and stems.
cotyledon. A leaf formed within the seed and present on a seedling at germination; seed leaf.
cover crops. Cultivation of a second type of crop primarily to improve the production system for a primary crop; examples include grasses or legumes maintained in orchards or vineyards and legume or other crops grown during the winter season to improve soil condition.
crawler. The active first instar of a scale insect.
crochets. Tiny hooks on the prolegs of caterpillars.
cross resistance. In pest management, resistance of a pest population to a pesticide to which it has not been exposed that accompanies the development of resistance to a pesticide to which it has been exposed.
crown. The part of the alfalfa plant from which new shoots are produced, emerging at soil surface just above taproot; the point at or just below the soil surface where the main stem (trunk) and roots join. Also used to refer to the topmost limbs on a tree or shrub; the shortened stem of a strawberry plant, from which roots, leaves, and fruit trusses arise.
culm. The jointed stem of grasses.
cultivar. A specially developed agricultural plant variety.
curing. Holding potato tubers under warm, humid conditions that favor wound healing.
cutout. A period of reduced growth and square production following a fruiting cycle.

D

damping-off. Destruction of seedlings by one or a combination of pathogens that weaken the stem or root.
daughter plants. Vegetative progeny of strawberry plants; plants that develop along the runners produced by another strawberry plant called the mother plant.
day-neutral. The term applied to strawberry cultivars that produce flower buds more or less independently of day length; everbearing.
degree-day. A unit combining temperature and time used in monitoring growth and development of organisms.
dehiscence. Opening naturally and regularly along lines of weakness; in fruits, opening along sutures to release seeds.
delayed dormant. Refers to the treatment period in fruit tree crops, beginning when buds begin to swell until the beginning of green tip development.
determinate. Having stems and branches that stop growing at a certain point, usually after producing flowers. In cotton, this term is applied to varieties with a distinct interruption in growth following fruit set.
developmental threshold. The lowest temperature at which growth occurs in a given species.
diapause. A period of physiologically controlled dormancy in insects.
disease. Any disturbance of a plant that interferes with its normal structure, function, or economic value.
disk. A type of cultivator made up of many circular blades used for weed control and soil preparation.
dormant. To become inactive during winter or periods of cold weather.
dough stage. A stage in grain development when the grain turns from a liquid to a soft doughy consistency before hardening.
drag off. The practice of removing soil from the tops of potato hills before sprout emergence.
drift. The aerial dispersal of a substance such as a pesticide beyond the intended application area.
DTPA. A chemical solution used to determine available zinc in the soil: [[(carboxymethyl) imino] bis (ethyleneitrilo)l tetra-acetic acid.
dwarfing. A stunting of normal growth characterized in plants by smaller than normal leaves and stems.

E

economic threshold. A level of pest population or damage at which the cost of control action equals the crop value gained from control action.
ectoparasite. A parasite that lives on the outside of its host.
embryo. The small plantlet within the seeds in almond, the embryo develops into the kernel.
endoparasite. A parasite that lives inside its host.
endosperm. The tissue containing stored food in a seed that surrounds the embryo and is eventually digested by the embryo as it grows.
English walnut. The walnut species (Juglans regia) used for the selection of commercial scion cultivars; origin believed in Persia (= Persian walnut).
entomophagous nematodes. Nematodes that eat insects.
epicotyl. The part of an embryo or seedling above the attachment point of the cotyledon(s).
epidermis. The outermost layer of living cells on the surface of a plant or animal.
evapotranspiration. The loss of soil moisture due to evaporation from the soil surface and transpiration by plants.
everbearing. Term applied to strawberry cultivars that produce flowers and fruit all year as long as temperatures are favorable; often used synonymously with day-neutral.
exclusion. Keeping a pest and crop separate from one another.
extrafloral nectary. A nectary located outside the flower.
eye. A collection of several buds on the surface of a potato tuber, one of which will sprout and form a new stem when conditions are favorable.

F

fallow. Cultivated land that is allowed to lie dormant, with no crops growing on it, during a growing season.
feeder roots. The youngest roots with root hairs, important in absorption of water and minerals.
field capacity. The moisture level in soil after saturation and runoff.
flag leaf. The terminal leaf of a grass plant; the last emerging leaf below the grain head.
flavedo. Outer part of the rind of citrus fruit, bearing oil glands and pigments.
flight. Period of flying activity of moths from one generation.
floret. An individual flower in a grass spikelet.
flower bud. A bud in which flower parts are contained.
frass. Solid fecal material produced by insects.
fruiting bodies. In fungi, reproductive structures containing spores.
fumigation. Treatment with a pesticide active ingredient that is a gas under treatment conditions.
fungicide. A pesticide used for control of fungi.
fungus (plural: fungi). A multicellular lower plant lacking chlorophyll, such as mold, mildew, smut, or rust. The fungus body normally consists of filamentous strands called mycelium and reproduces through dispersal of spores.

G

gall. Localized swelling or outgrowth of plant tissue, often formed in response to the action of a pathogen or other pest.
girdle. Damage that completely encircles a stem or root, often resulting in death of plant parts above or below the girdle.
glume. The outer brack of a grass spikelet.
glycoalkaloid. A bitter-tasting compound present in potato foliage and in the epidermis of potato tubers.
gossypol. A substance poisonous to many animals, produced by numerous small glands in most cotton varieties.
graft union. Place where the rootstock joins the scion or top part of a grafted tree or vine.
ground cover. Any of various low, dense-growing plants, as ivy, pachysandra, etc., used for covering the ground, as in places where it is difficult to grow grass.

H

head. The inflorescence of many grass plants, including small grains.
heat unit. Synonym for degree-day.
herbicide. A pesticide used to control weeds.
hibernaculum  (plural: hibernacula). A shelter occupied during the winter by an insect, notably peach twig borer.
honeydew. An excretion from insects, such as aphids, mealybugs, whiteflies, and soft scales, consisting of modified plant sap.
horticultural oils. Highly refined petroleum (or seed derived) oils that are manufactured specifically to control pests on plants.
host. A plant or animal that provides sustenance for another organism.
hypha (plural: hyphae). One of the filaments forming the body, or mycelium, of a fungus.
hypocotyl. The portion of an embryo or seedling between the cotyledons and the developing root tip.

I

immune. Exempt from infection by a given pathogen.
incorporate. To mix a material such as an herbicide into the soil by mechanical action.
indeterminate. Having a growth pattern in which stems continue growing indefinitely; with flower clusters, the opening of the lower (lateral) flowers first, and the terminal one opening later.
indexing. Testing a plant for a virus infection, usually by grafting tissue from it onto an indicator plant.
infection. The entry of a pathogen into a host and establishment of the pathogen as a parasite of the host.
infestation. The presence of a large number of pest organisms in an area or field, on the surface of a host or anything that might contact a host, or in the soil.
inflorescence. Ilower cluster.
inner bark. In older trees, the living part of the bark, the phloem.
inoculum. Any part or stage of a pathogen, such as spores or virus particles, that can infect a host.
inorganic. Containing no carbon; generally used to indicate materials (for example, fertilizers) that are of mineral origin.
instar. The larval or nymph stage of an immature insect between successive molts.
integrated pest management (IPM). A pest management strategy that focuses on long-term prevention or suppression of pest problems through a combination of techniques such as encouraging biological control, use of resistant varieties, and adoption of alternate cultural practices such as modification of irrigation or pruning to make the habitat less conducive to pest development. Pesticides are used only when careful monitoring indicates they are needed according to preestablished guidelines, treatment thresholds, or to prevent pests from significantly interfering with the purposes for which plants are being grown.
internode. The portion of a stem between two nodes.
invertebrate. An animal having no internal skeleton.

J

jointing. Elongation of rice internodes before flowering.
June bearing. A term applied to short-day strawberry cultivars.
juvenile. Immature form of a nematode that hatches from an egg and molts several times before becoming an adult.

K

L

larva (plural: larvae). The immature form of insects that develop through the process of complete metamorphosis including egg, several larval stages, pupa, and adult. In mites, the first-stage immature is also called a larva.
latent. Producing no visible symptoms (generally refers to an infection or a pathogen).
latent period. The time between when a vector acquires a pathogen and when the vector becomes able to transmit the pathogen to a new host; also, the time between infection of a host plant and production of inoculum by the infection.
layby application. An application, usually of fertilizer or herbicide, after the crop is well established; especially, an application at the latest time in the season when it is still possible to pass through the field with a tractor.
leaching fraction. The proportion of applied irrigation water that is added to meet the crop's leaching requirement.
leaching requirement. The amount of water in excess of a crop's evapotranspiration requirement that is needed to maintain maximum yield by leaching harmful salts from the root zone.
leaf area index. The ratio between the total leaf surface area of a plant and the surface area of ground that is covered by the plant.
leaf margin. The outer edge of the leaf; leaf margins may be smooth, lobed, indented, etc.
lenticels. Natural openings in the surface of a tuber or stem, similar to leaf stomata, that can open and close and allow gas exchange.
lepidopterous. Of or pertaining to the Order Lepidoptera, the moths and butterflys.
lesion. Localized area of diseased or discolored tissue.
ligule. In many grasses, a short membranous projection on the inner side of the leaf blade at the junction where the leaf blade and leaf sheath meet.
locule. One of the seed chambers in the ovary or boll.
lodging. The toppling of plants of a grain crop before harvest, often from wind, rain, or waterfowl.

M

mandibles. Jaws; the forward-most pair of mouthparts of an insect.
meconium. Fecal pellet excreted by a larva before pupation.
meristem. The collection of cells at the growing point of a plant that are capable of cell division.
metamorphosis. The change in form that takes place as insects grow from immatures to adults.
microbial pesticides. Pesticides that consist of bacteria, fungi, viruses, or other microorganisms used for control of weeds, invertebrates, or plant pathogens.
microorganism. An organism of microscopic size, such as a bacterium, virus, fungus, viroid, or mycoplasma.
micropropagation. Generation of new, disease-free potato plants from tiny pieces of meristem tissue.
microsclerotia (singular: microsclerotium). Very small sclerotia, such as those produced by the Verticillium wilt fungus.
milk stage. The early stage of grain development when the grain is filled with a milky liquid.
mineral oils. Synonymous with horticultural oils.
minituber. A small tuber produced under greenhouse conditions on a small potato plant generated by micropropagation.
modify environmental factors. Factors such as moisture and heat, and, in the case of certain organic materials that decay, to gradually improve soil quality. Plant derived in (organic) or synthetic materials may be used.
molt. In insects and other arthropods, the shedding of skin before entering another stage of growth.
monitoring. Carefully watching and recording information on the activities, growth, development, and abundance of organisms or other factors on a regular basis over a period of time, often utilizing very specific procedures.
mulch. A layer of material placed on the soil surface to prevent weed growth.
mummy. Unharvested nut remaining on the tree (also called sticktight); the crusty skin of an aphid whose inside has been consumed by a parasite.
mutation. The abrupt appearance of a new, heritable characteristic as the result of a change in the genetic material of one individual cell.
mycelium (plural: mycelia). The vegetative body of a fungus, consisting of a mass of slender filaments called hyphae.
mycoplasma. A member of the genus Mycoplasma. Mycoplasmas, unlike viruses, can reproduce in the absence of a host and are the smallest free-living organisms; they have a unit membrane but no cell wall as do bacteria.
mycorrhizae. Beneficial associations between plant roots and fungi.

N

narrow-range oil. A highly refined petroleum or seed-derived oil that is manufactured specifically to control pests on plants, also called horticultural oil.
natural enemies. Predators, parasites, or pathogens that are considered beneficial because they attack and kill organisms that we normally consider to be pests.
necrosis. Death of tissue accompanied by dark brown discoloration, usually occurring in a well-defined part of a plant, such as the portion of a leaf between leaf veins or the xylem or phloem in a stem or tuber.
nectary. A gland that secretes nectar.
nodes. The leafbearing joints on plant stems.
nonpersistent virus. A virus that is carried on the mouthparts of its insect vector and is lost after the vector feeds once or a few times; styletborne virus.
nucellus. In plants, the watery tissue composing the chief part of the young ovule in the flower and inside the seed during early development. It furnishes nutrients to the young embryo and is digested by the developing endosperm and embryo.
nymph. The immature stage of insects such as grasshoppers and aphids, that hatch from eggs and gradually acquire adult form through a series of molts without passing through a pupal stage.

O

organic. A material (e.g. pesticide) whose molecules contain carbon and hydrogen atoms. Also may refer to plants or animals which are grown without the use of synthetic fertilizers or pesticides.
outer bark. In older trees, the dead part of the bark.
oviposit. To lay or deposit eggs.
oviposition. The laying or depositing of eggs.

P

packing tissue. Firm, membranous tissue lining the walnut shell and separating the kernel halves.
panicle. A branching cluster of flowers held on a stem, such as the flowering parts of most grasses.
pappus. The modified calyx of flowers in the sunflower family; usually takes the form of bristles, scales, or awns.
parasite. An organism that derives its food from the body of another organism, the host, without killing the host directly; also an insect that spends its immature stages in the body of a host that dies just before the parasite emerges (this type is also called a parasitoid).
parthenocarpy. Development of fruit without fertilization and seed.
parthenogenesis. Development of an egg without fertilization.
pathogen. A disease-causing organism.
peduncle. The stem of an individual flower or fruit.
peg roots. Primary roots.
pellicle. The covering (skin) that encloses the kernel; it is white during development but becomes brown at maturity.
perennial. A plant that can live three or more years and flower at least twice.
periderm. Several layers of corky cells located on the outside of the epidermis of a potato tuber and containing high amounts of suberin.
perithecium (plural: perithecia). A globular to flask-shaped fruiting body that has an apical pore through which the spores (ascospores) are released.
persistent virus. A virus that systemically infects its insect vector and usually is transmitted for the remainder of the vector's life.
pest resurgence. The rapid rebound of a pest population after it has been controlled.
pesticide. Any substance or mixture intended for preventing, destroying, repelling, killing, or mitigating problems caused by any insects, rodents, weeds, nematodes, fungi, or other pests; and any other substance or mixture intended for use as a plant growth regulator, defoliant, or desiccant.
pesticide resistance. The genetically acquired ability of an organism to survive a pesticide application at doses that once killed most individuals of the same species.
petiole. The stalk connecting the leaf to a stem.
pH. A value used to express relative acidity or alkalinity.
phenoxy herbicides. A group of herbicides derived from phenoxy-acetic acid, including 2,4-D, 2,4,5-T, 2,4-DB, MCPA and silvex.
pheromone. A substance secreted by an organism to affect the behavior or development of other members of the same species; sex pheromones that attract the opposite sex for mating are used in monitoring certain insects.
phloem. The food-conducting tissue of a plant, made up of sieve tubes, companion cells, phloem parenchyma, and fibers.
phloem-feeding. An organism that withdraws nutrients from the food-conducting tissue of a plant's vascular system.
photosynthate. The products of photosynthesis, used to support growth, respiration, and fruit production.
photosynthesis. The process by which plants convert sunlight into energy.
physiological disorder. A disorder caused by factors other than a pathogen; abiotic disorder.
phytotoxicity. The ability of a material such as a pesticide or fertilizer to cause injury to plants.
pinhead square. A square approximately 1/8 inch (3mm) or less in length.
pistil. Female part of the flower, usually consisting of ovules, ovary, style, and stigma.
pollinator. The agent of pollen transfer, usually bees.
pollinizer. The producer of pollen; the variety used as a source of pollen for cross-pollination.
pome fruit. A simple fleshy fruit, the outer portion of which is formed by the floral parts that surround the ovary.
postemergence herbicide. Herbicide applied after the emergence of weeds.
predator. Any animal (including insects and mites) that kills other animals (prey) and feeds on them.
preemergence herbicide. Herbicide applied before emergence of weeds.
primary bloom. The first production of flowers on a potato plant, occurring after 8 to 12 leaves have been formed on the mainstem and generally coinciding with the beginning of the tuber growth phase.
primary inoculum. The initial source of a pathogen that starts disease development in a given location.
primary roots. Roots that develop from the crown of a strawberry plant.
proleg. A fleshy, unsegmented leg of caterpillars.
propagules. Any part of a plant from which a new plant can grow, including seeds, bulbs, rootstocks, etc.
protectant fungicide. Fungicide that protects a plant from infection by a pathogen.
protective coverings. Any cloth, screen, plastic or other material placed over growing plants to prevent damage by pests or harsh weather.
prothorax. The anterior of the three thoracic segments of an insect.
pupa. The nonfeeding, inactive stage between larva and adult in insects with complete metamorphosis.
pupate. To molt from the larval stage to the pupa.
pustule. Small blisterlike elevation of epidermis from which spores emerge.
pycnidium (plural: pycnidia). Small, spherical or flask-shaped structure, formed by certain types of fungi, inside which spores are produced.

Q

quadrant. One of four equal parts into which a field is divided for monitoring.
quarantine. A period of enforced isolation that is required to prevent movement of undesireable organisms.

R

random sample. A sampling plan in which locations for samples are not predetermined either by previous sampling in that field or the relationship of one sample site to another.
rat-tail bloom. A secondary bloom in Bartlett pears that results when terminal buds form and open on the current season's growth.
receptacle. The apex of the flower stem that bears the organs of the flower.
regrowth bud. The buds on alfalfa crowns that become new stems.
reproductive bud. The buds on alfalfa stems that become flowers.
reservoir. The site where a pest population or quantity of inoculum can survive in the absence of a host crop, and from which a new crop may be invaded.
residue management. Management of rice straw and stubble after harvest.
resistant. Able to tolerate conditions (such as pesticide sprays or pest damage) harmful to other strains of the same species.
respiration. The process by which nutrients are metabolized to provide energy needed for cellular activity.
rhizome. A horizontal, underground shoot, especially one that forms roots at the nodes to produce new plants.
rogue. To remove diseased plants from a field.
rolling. Mechanical crushing of potato vines to hasten vine death, sometimes used synonymously with vine-killing.
rootstock. An underground stem or rhizome; lower portion of a graft which develops into the root system.
rosette. A cluster of leaves arranged in a compact circular pattern, often at a shoot tip or on a shortened stem.
rosetted bloom. A flower whose petals have been tied together with silk by a pink bollworm larva.
rosetting. Abnormal growth caused by certain pathogens in which new potato foliage is stunted and tightly bunched.
rotation. The practice of purposefully alternating crop species grown on the same plot of land.
row covers. Any fabric or protective covering placed over rows of plants to protect them from pest damage or harsh climate.
rue leaf. Any leaf produced after the seed leaves (cotyledons).
rugose. A rough appearance of leaves in which veins are sunken and interveinal tissue raised, caused by certain virus infections.
ruminant. Any of the hoofed mammals (including cattle, deer, sheep) that chew the cud.
runner. Stolon of a strawberry plant, on which a daughter plant may develop.
russeting. Thickening of the periderm on tubers of russet cultivars that occurs after vine senescence.

S

sanitation. Any activity that reduces the spread of pathogen inoculum, such as removal and destruction of infected plant parts, cleaning of tools and field equipment.
scion. The portion above a graft that becomes the trunk, branch, and tree top; the cultivar or variety.
sclerotium (plural: sclerotia). A compact mass of hardened mycelium that serves as a dormant stage in some fungi.
secondary bloom. A second production of flowers on a potato plant, occurring at the end of the mainstem of an indeterminate cultivar; secondary bloom may occur on a determinate cultivar at leaf axils along the mainstem.
secondary infection. Infection by microorganisms that enter the host through an injury caused previously by another pathogen.
secondary outbreak. The increase of a nontarget pest to harmful levels following a pesticide application, caused by destruction of natural enemies that normally control the nontarget pest.
secondary roots. The network of fine roots that develops from the primary roots of a strawberry plant and picks up water and nutrients from the soil; white roots.
secondary spread. The spread of a pathogen within a field after the initial or primary infection.
secondary stems. Stems formed by stolons that emerge from the soil.
sedges. A group of grasslike, herbaceous plants that, unlike grasses, have unjointed stems. Stems are usually solid and often triangular in cross section.
seed leaf. The leaf formed in a seed and present on a seedling at germination; cotyledon.
seed piece. Portion of a potato tuber containing at least one eye that is planted to produce a new potato plant.
seedcotton. Harvested lint that is still attached to seeds; i.e., the lint before ginning.
selective pesticide. Pesticides that are toxic primarily to the target pest (and perhaps a few related species), leaving most other organisms, including natural enemies, unharmed.
self fruitful. The ability to set fruit with pollen from the same flower or tree.
senescence. The stage of growth in a plant or plant part from maturity to death, characterized by an accumulation of metabolic products, an increased respiratory rate, and a loss in dry weight.
sepal. One of the outermost flower structures which usually enclose the other flower parts in the bud.
sequential sampling. A sampling method in which the number of samples is not fixed in advance.
sessile. Attached or fastened, incapable of moving from place to place; attached directly without a stem.
seta (plural: setae). A bristle.
sheath. The part of a grass leaf that encloses the stem below the collar region.
short day. Term applied to strawberry cultivars that require a period of time with day length shorter than a minimum (about 14 hours) for the induction of flower buds; June-bearing.
side dressing. Fertilizer or other material added to the soil around a growing crop.
sieve tubes. See phloem.
skeletonize. To remove leaf tissue between the veins, leaving the network of veins intact.
soil profile. A vertical section of the soil through all its horizontal layers, extending into the parent material.
solarization. The practice of heating soil to levels lethal to pests through application of clear plastic to the soil surface for 4 to 6 weeks during sunny, warm weather.
sooty mold. A sooty coating on foliage or fruit, formed by the dark mycelia of fungi that live in the honeydew secreted by certain insects.
specific gravity. The ratio of the density of a substance to the density of pure water; specific gravity of potato tubers is used as a measure of their dry matter content.
spikelets. The collection of individual grass florets that are borne at the end of the smallest branch of the inflorescence.
spike. An elongated inflorescence in which the individual flowers are borne tightly against the main stem or rachis.
spiracle. An external opening of the system of ducts, or tracheae, that serves as a respiratory system in insects.
sporangium (plural: sporangia). A structure in which asexual spores are produced.
spore. A reproductive body produced by certain fungi and other organisms, capable of growing into a new individual under proper conditions.
sporulation. The production of spores.
spraing (sprain). Reddish brown spots, rings, or arcs in tuber tissue caused by tobacco rattle virus; corky ringspot.
sprout. The new stem formed from the eye of a potato tuber.
sprout inhibitor. A chemical applied to potato vines or to stored tubers to prevent sprouting.
spur. Short woody shoot that is the primary fruiting structure for most fruit trees.
square. A cotton flower bud.
staminate flower. A male flower.
stand decline. The gradual (over a period of 3-5 years) debilitation of the plants in an alfalfa field caused by the combined effects of pests and unfavorable environmental conditions.
stand establishment in an alfalfa field. The period of plant establishment between planting and first cutting.
stele. The central cylinder inside the cortex of the roots and stems of vascular plants; contains the vascular or conducting tissue.
sticktight. Nut that remains on the tree after harvest (also called mummy); nut with husk firmly adhering to shell.
stipe. A stalk.
stolon. A trailing aboveground stem or shoot, often rooting at the nodes and forming new plants.
stoma (plural: stomata). Natural opening in a leaf surface that serves for gas exchange and water evaporation and has the ability to open and close in response to environmental conditions.
stroma. A compact, usually spore-producing structure formed from fungal mycelium on the surface of a host.
stub cotton. A cotton crop in which the stalks are cut down after harvest but the crown and rootstock are left in the ground to regrow the following season.
styletborne virus. A virus that is carried on the mouthparts of its insect vector and is lost after the vector feeds once or a few times; nonpersistent virus.
suberin. A waxy substance, resistant to microbial attack, formed in the corky cells of periderm layers.
suberization. The formation of periderm layers on the cut surfaces or wounds of potato tubers.
substituted dinitroanilines. A class of herbicides widely used for preplant application in cotton.
sucker. Shoot arising from the trunk or rootstock.
summer planting. A system of strawberry culture in which planting occurs in summer and fruit production begins the following spring.
sun checking. Cracking or breaking of whole kernels of grain caused by exposure to alternating conditions of dew, sun, and water stress.
suture. Visible seam on hull.
synthetic organic pesticides. Manufactured pesticides produced from petroleum and containing largely carbon and hydrogen atoms in their basic structure.
systemic. Capable of moving throughout a plant or other organism, usually in the vascular system.

T

tail water. Irrigation water that has drained from a field.
taproot. The large primary root that grows vertically downward, giving off small lateral roots.
target pest. A pest species that a control action is intended to destroy.
teliospore. Thick-walled dark spore of rust and smut fungi that is able to survive adverse conditions.
tensiometer. A device for measuring soil moisture, consisting of a buried tube of water that develops a partial vacuum as surrounding soil dries out.
terminal. The growing tip of a stem, especially the main stem.
terminal spikelet stage. Stage in the development of the wheat spike when the primordia of the terminal spikelet are formed.
terrestrial biotype. A strain of an organism adapted to growing on land rather than in water.
tertiary bloom. The third production of flowers that occurs at the end of the growing stem of an indeterminate potato cultivar.
tertiary tiller. Branch of a grass plant that develops from the axil of a secondary tiller.
thorax. The second of three major divisions in the body of an insect, and the one bearing the legs and wings.
thurberia weevil. A race of the boll weevil that feeds on wild cotton.
tiller. Branch stem of a grass plant.
tolerance. Inherent lack of susceptibility to a pesticide. Also, the ability of a plant to grow in spite of infection by a pathogen.
tolerance level. Maximum percentage of a disease or pest symptom allowed during field inspections for certification of a seed lot; levels are different with each field generation and may vary from state to state.
top crop. Fruit produced in the second fruiting cycle of cotton, mainly on upper branches.
toxin. A poisonous substance produced by a living organism.
translocated herbicide. Herbicide that is able to move throughout a plant after being applied to leaf surfaces.
transpiration. The evaporation of water vapor from plants, mostly through stomata.
trap crop. A crop or portion of a crop intended to attract pests so they can be destroyed by treating a relatively small area or by destroying the trap crop and the pests together.
treatment threshold. The level of pest population at which a pesticide or other control measure is needed to prevent eventual economic injury to the crop.
true leaf. Any leaf produced after the cotyledons.
tuber. An enlarged, fleshy, underground stem with buds capable of producing new plants.
tuberization. The formation of tubers at the ends of stolons; tuber initiation.

U

unfurled. Unopened.
urediospore. Spore produced by a rust fungus that spreads the infection to other hosts.

V

variety. An identifiable strain within a species, usually referring to a strain which arises in nature as opposed to a cultivar which is specifically bred for particular properties; sometimes used synonymously with cultivar.
vascular ring. A thin area of potato tuber tissue between the cortex and the medulla in which vascular tissue is concentrated.
vascular system. The system of plant tissues that conducts water, mineral nutrients, and products of photosynthesis through the plant, consisting of the xylem and phloem.
vascular tissue. Plant tissue that conducts water and nutrients throughout the plant.
vector. An organism able to transport and transmit a pathogen to a host.
vegetative. Plant parts or plant growth not involved in the production of seed, such as roots, stems, and leaves.
vein banding. Dark brown discoloration of the veins on the undersides of potato leaflets caused by potato virus Y.
véraison. Beginning of fruit ripening, recognized by berry softening and beginning of pigmentation in colored varieties.
vigor. The capacity of a strawberry plant for active vegetative growth.
viroid. A portion of infectious nucleic acid, without the protein coat of a virus.
virulence. The relative infectiousness of a bacteria or virus, or its ability to overcome the resistance of the host metabolism.
virus. A very small organism that can multiply only within living cells of other organisms and is capable of producing disease symptoms in some plants and animals.
volunteer crop. The undesired emergence of a significant stand of a self-seeded, previously planted crop in a field purposely planted with another crop.

W

white roots. Secondary roots.
windowpane. The removal of the epidermal layer of leaf tissue leaving small segments of clear tissue.
wing. Extension of the nut shell at the suture line; varies in size according to cultivar.
winter planting. A system of planting strawberries in mid to late fall that depends on growth during winter months for production of an early spring crop.

X

xanthosis. A collection of symptoms consisting of distorted leaf growth and yellow leaf margins that develops in strawberry plants infected by mottle virus and either crinkle virus or mild yellow edge virus; yellows.
xylem. Plant tissue that conducts water and nutrients from the roots up through the plant.

Y

Y-leaf. The most recently matured leaf.

Z

zonate. Marked with zones or bands; belted; striped.