Chilli:. ANTHRACNOSE

Chilli: Capsicum annuum L.
Family: Solanaceae

1. ANTHRACNOSE

Anthracnose disease is a major problem in India and one of the more significant economic constraints to chilli production worldwide, especially in tropical and subtropical regions. The disease causes both pre- and post-harvest fruit decay. Chilli anthracnose usually develops under high humid conditions when rain occurs after the fruits have started to ripen with reported losses of up to 84%. Economic losses caused by the disease are mainly attributed to lower fruit quality.

Chilli anthracnose was first reported in India on chillies from the Coimbatore. Anthracnose incited by Colletotrichum spp is one of the most damaging diseases of chilli in India. The severity of the disease varies depending on cultivars grown and the weather conditions prevailing in a particular region. In severe instances, the pre harvest and post harvest infections together account for more than 50% of the crop losses. Three species, namely C. capsici, C. gloeosporioides and C. acutatum were known earlier to cause anthracnose in chilli. However C. capsici was the most predominant species in the major chilli growing states namely Karnataka and Andhra Pradesh.

Symptoms: Anthracnose is the common name for plant diseases characterized by very dark, sunken lesions, containing spores. The disease appears as small circular spots that coalesce to form large elliptical spots on fruits and leaves. Under severe conditions, defoliation of affected plants occurs. The disease has been observed to occur in three phases, they are: (i) Seedling blight or damping off, ii) Leaf spot and die back, and (iii) Anthracnose or fruit rot. Capsicum fruit rot reduces fruit dry weight and quantities of capsaicin and oleoresin. In anthracnose or fruit rot caused by C. capsici, the ripe fruits turning red are mostly affected. The disease is characterized by the appearance of small black circular spots on the skin of the fruits that spread in the direction of the long axis, thus becoming more or less elliptical. As the infection progresses, the spots get either diffused and black, greenish or dirty grey in colour or they are markedly delimited by a thick and sharp black outline enclosing a lighter black or straw coloured area. In some cases, the lesions are brown and then turn black from the formation of setae and sclerotia. Severe infection results in change of fruit colour from red to straw or white. Numerous acervuli are scattered on the discoloured area of the infected fruit. When a diseased fruit is cut open, the lower surface of the skin is covered with minute, spherical, black stromatic masses or sclerotia of the fungus. A mat of fungal hyphae covers the seeds. Such seeds turn rusty in colour. Affected fruits are deformed, white in colour and lose their pungency. Ultimately, the diseased fruit shrivels and dry up.

The disease symptoms of die-back starts from growing point of flower bud and the tops of the affected branches wither and turn brown. The disease infection move downwards and shows die-back. The infected parts get enamel white colour which is punctuated by scattered, black, bristly and minute elevations (acervuli) of the pathogen. The symptoms often appeared after rainy season and prolonged dew on the plants.

Disease Cycle: The fungus is both internally and externally seed-borne. Sowing such contaminated seeds results in pre emergent and post emergent damping-off of seedlings in nursery and field. These infected seedlings form the primary sources of inoculum. The fungus survives in an active form on the stems and branches causing die-back symptoms. The wet conditions caused due to monsoon rains that occur during the June-October period help in the outbreak and spread of the disease.

The pathogen survives between seasons in plant debris or on weed hosts. Alternative hosts include other solanaceae (tomato, potato, eggplant) plants. Fruits are infected when spores of the fungus or infested debris are rain splashed onto chilli plants. New spores are produced within the infected tissue and are then dispersed to other fruits. Infection usually occurs during warm, wet weather. Temperatures around 26 °C are optimum for disease development, although infection occurs at both higher and lower temperatures. Severe losses occur during rainy weather because the spores are washed or splashed to other fruits, resulting in more infections. The disease is more likely to develop on mature fruits, although it can occur on immature fruits as well.

Disease Management: Rot and die back caused by Colletotrichum capsici is the major disease of chilli in India. The integrated management techniques are recommended, as no single specific management program including crop rotation can eliminate chilli anthracnose.

Cultural control-

• Planting of contaminated seed or transplants facilitates disease spread. Use of healthy pathogen-free chilli seed or transplants should be adopted.
• Early removal of affected plants will control the spread of the diseases.
• Transplants should be kept clean by controlling weeds and solanaceous volunteers in the vicinity of the transplant houses
• Stagnation of water should not be allowed in nursery beds and fields in order to avoid fungal infection. The field should have good drainage and be free from infected plant debris.

Use of resistant cultivars-

• The use of resistant varieties for anthracnose disease viz., IIHR 275-13-5, IIHR345-6, IIHR 332 -109, CC4, Ujwala, Perennial, H-1, H-4, H-6, CA 87-4. S- 20-1, Lorai and BG-1 will be useful in disease control.

Use of chemicals-

• The disease can be controlled by seed and foliar spray treatment with perenox, azoxystrobin, chlorothalonil, copper, difenoconazole, famoxadone, iprodione, procymidone, tolylfluanid and carbendizim.00
• The fungicide traditionally recommended for anthracnose management in chilli is Maneb (2.5g per liter) (Smith, 2000), although it does not consistently control the severe form of anthracnose on chilli fruits
• The strobilurin fungicides azoxystrobin, trifloxystrobin and pyraclostrobin (1ml/liter) and difenconazole (1ml per liter) have recently been labeled for the control of the anthracnose disease. The first foliar spray is given at the first pair of leaf stage and subsequent sprays done twice at 20-day intervals.

Biological control-

• Antagonistic Pseudomonas fluorescens as seed treatment and as well as spray treatment @108 CFU.g-1 were found to be effective against C. capsici (Srinivas et al., 2005; Jeger and Jeffries, 1988)
• Trichoderma species are able to effectively control C. capsici infection in chilli.
• Other biological control agents that have been tested for efficacy against Colletotrichum include Bacillus subtilis and Candida oleophila.

Use of plant extracts-

• Plant products have been tested in many laboratories. Seed and spray treatment showed that the crude extract from rhizome, leaves and creeping branches of sweetflag (Acorus calamus L.), palmorosa (Cymbopogon martinii) oil, Ocimum sanctum leaf extract, and neem (Azadirachta indica) oil could restrict growth of the anthracnose fungus.