Transcript Chillies
Post harvest diseases Bacterial soft rot - Erwinia carotovora subsp. carotovora Anthracnose - Colletotrichum capsici Fruit rot - Alternaria solani Gray Mould - Botrytis cinerea Late blight -Phytophthora capsici Bacterial Soft Rot- Erwinia carotovora subsp. carotovora Symptoms Dark veinal tissue followed by leaf chlorosis and necrosis Internal dark brown discoloration Stem cankers develop - breakage of branches Wilting and drying Post-harvest softening of stem end of fruit Symptoms on fruits Fruit peduncle - highly susceptible & is frequently the initial point of infection Both ripe and green fruit may be affected Initially, the lesions on the fruit are light to dark-colored, watersoaked, and somewhat sunken In later stages, bacterial ooze may develop from affected areas, and secondary organisms follow, often invading the rotted tissue Affected fruit hang from the plant like a water-filled bag Rotting fruit Collapsed fruit Conditions for Disease Development Transmitted by irrigation water, but a wound is necessary for infection to occur High rate of nitrogen fertilization is associated with increased susceptibility to soft rot Post-harvest soft rot of pepper fruit arises when, infected fruit is harvested with healthy fruit harvest containers are contaminated with the bacteria fruit is subjected to contaminated wash water, contaminated surfaces or soil debris Bacterium Gram –ve, rod shaped bacterium 1 to 6 peritrichous flagella Epidemiology Warm, moist weather - highly favorable for infection Temperature - 25° to 30°C, RH - 95% Disease management Disease incidence could be reduced by ◦ Early detection of symptoms ◦ Disinfection of pruning tools ◦ Avoidance of wounding plants ◦ Remove plant debris - fallen, diseased leaves Seed treatment – 1% sodium hypochlorite for 30 sec, then rinse with clean water Avoid planting pepper crops following crops of potato or cabbage Rotate instead with crops of bean, corn and soybean Post-harvest disease management Use chlorinated water to reduce populations of soft rot bacteria and to reduce the risk of infection during washing Allow fruit to dry thoroughly During packing and storage, the fruit should be kept clean and maintained in a cool, dry place Anthracnose- Colletotrichum capsici Ripe fruits turning red are affected Small, black, circular spot appears on the fruit skin Badly diseased fruits turn straw colour or pale white colour, lose their pungency Diseased cut open fruits - lower surface of the skin is covered with minute, elevated sclerotia Advanced stage - seeds covered by a mat of fungal hyphae, turn rusty in colour Causal Organism - Colletotrichum capsici Mycelium - septate and inter and intra cellular Acervuli and stroma on the stem are hemispherical Conidia - in mass appear pinkish Epidemiology Temp - 28oC, RH - 95% High humid conditions when rain occurs after the fruits have started to ripen Mode of spread & survival Seed borne Secondary spread is by air borne conidia & rain Flies and other insects – responsible for dissemination of the spores from one fruit to another Control measures Use disease free seeds seed treatment - thiram 2 kg/ha or zineb 2.5 kg/ha Three sprayings with captan 0.2 % 1st spraying - just before flowering 2nd at the time of fruit formation 3rd - fortnight interval after second spraying Biocontrol P. fluorescens, Bacillus subtilis -effective (Rajavel, 2000) P. fluorescens and T. viride (Muthuraj, 1998) Saccharomyces cerevisiae & P. fluorescens (Jayalakshmi et al., 1998) Essential oil - Nigella sativa - antimicrobial activity Gray Mould - Botrytis cinerea Brownish spots develop near the soil line or cotyledons Water-soaked lesions on leaves & stems darken and collapse Water-soaked spots that rapidly expand into large yellowishgreen or grayish-brown, irregular lesions that are soft and spongy in texture Velvet-like fungus mycelium and spores are produced on the lesion surface under cool, humid conditions Water-soaked spots collapse Fungus Botrytis cinerea - abundant hyaline conidia (asexual spores) borne on grey, branching tree-like conidiophores It overwinters as sclerotia or intact mycelia, both of which germinate in spring to produce conidiophores The conidia are dispersed by wind and rain-water and cause new infections Conidia and hyphae Favourable conditions and spread Fungus sporulation and infection, is favored by cool and wet weather Temperatures of 17–23°C, RH - 90% Excessive application of nitrogen makes plants such as young transplants more susceptible to gray mold High canopy density creates conditions for extended leaf wetness at night and subsequent increased gray mold severity Control Field sanitation - remove and burn decaying infected plant parts Space seedlings and transplants to allow for free flow of air through the crop Treatment with hot air at 38oC for 48-72 h or hot water at 50oC to 53oC for 2 to 3 min Alternaria rot- Alternaria solani Brown lesions surrounded by a yellow halo develop on the fruit Lesions enlarge and result in the formation of irregular sunken patches with a dark brown margin and light grey centre Fungus Hyphae - septate, branched, light brown becoming darker with age Conidia - single, muriform, beaked and dark in color Source of infection - infected seeds and plant debris Spores of A. solani Alternaria solani conidia. Note the transverse and vertical septa and the long "beak" (arrow) Control • Fortnightly spraying of • Bordeaux mixture 1.0 % • Copperoxychloride 0.3 % • Difolatan 0.3 % • Mancozeb 0.2% • Reduction in the pathogenicity and development of these pathogens in inoculate peppers, • Treatment with hot air at 38oC for 48-72 h • Hot water at 50oC to 53oC for 2 to 3 min Late blight -Phytophthora capsici Infected leaf tissue - wilted, light green or gray-green, later becoming tan to white and scalded in appearance With moisture, leaf spots have a water soaked border Fruit rots - irregular in shape and olive green or light green with water soaked borders Rots expand rapidly and fruits can be completely diseased and desiccated, causing the formation of "mummified" fruits Infected seeds are brown and shriveled Fungus Produces microscopic, asexual spores called sporangia Sporangia - spherical to pyriform, hyaline, papillate and have a long pedicel attached to the base of the spore Pathogen grows well between 25 and 30oC Mode of spread Survives in the soil in host debris Roots, stems, and mummified fruits left in the field after harvest, harbor the pathogen for months Phytophthora capsici is also seed borne Control Rotation with non-susceptible crops will reduce the amount of Phytophthora capsici surviving in soil Fresh, clean seeds should be planted in new potting mix to establish healthy transplants Monitor seedlings as well as the field and remove diseased plants as soon as they occur