Downy mildew Host range Musk melon, Sponge gourd and Bitter gourd etc. Symptoms: Yellow, angular spots restricted by veins resembling mosaic mottling appear on upper surface of leaves The corresponding lower surface of these spots shows a purplish downy growth in moist weather The spots turn necrotic with age The diseased leaves become yellow and fall down Diseased plants get stunted and die Fruits produced may not mature and have a poor taste Survival and spread: Primary: Oospores in soil and sporangia from perennial collateral weed hosts in the vicinity Secondary: Wind borne and rain splashed conidia (sporangia) or autonomous zoospores Favourable conditions: Relative humidity > 90% High soil moisture Frequent rains Powdery mildew Host range: Pumpkins, bottle gourd, coccinia, cucumber, ridge gourd, Bitter gourd is less affected. Symptoms: Whitish or dirty grey, powdery growth on foliage, stems and young growing parts The superficial growth ultimately covers the entire leaf area The diseased areas turn brown and dry leading to premature defoliation and death Fruits remain underdeveloped and are deformed Survival and spread: Primary: Dormant mycelium or cleistothecia in infected plant debris or conidia from collateral hosts Secondary: Wind borne conidia Favourable conditions: Morning relative humidity > 90% Cool and dry weather Cucumber mosaic Wide host range: Cucumber, Pumpkin, gourds, Cowpea, tomato, chilli, etc. Cucumovirus with spherical particles having ssRNA Symptoms: Symptoms appear on the youngest and still expanding leaves when infection occurs at 6 – 8 leaves stage Typical mosaic pattern develops on young leaves Leaves curl downwards and become mottled, distorted, wrinkled and reduced in size Veins appear bunchy because of shortening of internodes When infection occurs at midseason previous growth remains normal and produces normal fruit Fruit set is very less if infection occurs early in crop growth Fruits are often misshapen, mottled, warty and reduced in size Survival and spread: Primary: Virus particles on collateral and other weeds, ornamentals or crops Hosts: Banana, clover, corn, passion fruit, safflower, spinach, sugarbeet, wild cucumber, Commelina communis, C. diffusa, C. nudiflora, Solanum elaegnifolium, Phytolacca sp., periwinkle, Gladiolus sp., Impatiens sp. and Phlox Secondary: Virus particles transmitted by aphids (Aphis craccivora, Myzus persicae) and spotted and striped cucumber beetles Cercospora leaf spot Host range: Common on watermelon, muskmelon and cucumber Symptoms: Minute water soaked spots or yellow specks develop initially on leaves Spots enlarge rapidly and becomes circular to irregular with pale brown, tan or white centers and purple to almost black margins Spots coalesce to form large blotches The leaf may dry and die presenting the leaf a scorched appearance Fruits are also occasionally attacked Survival and spread: Primary: Dormant mycelium or conidia on infected plant debris or collateral hosts Secondary: Wind borne conidia Fusarium wilt Damage symptoms: The first symptom of the disease is clearing of the veinlets and chlorosis of the leaves. The younger leaves may die in succession and the entire may wilt and die in a course of few days. Soon the petiole and the leaves droop and wilt. In young trailing plant, symptom consists of clearing of veinlet and dropping of petioles. In field, yellowing of the lower leaves first and affected leaflets wilt and die. The symptoms continue in subsequent leaves. At later stage, browning of vascular system occurs. Plants become stunted and die. Survival and spread: Soil and implements Favourable conditions: Relatively high soil moisture and soil temperature Diseases cycles Downy mildew: Pseudoperonospora cubensis Powdery mildew: Erysiphe cichoracearum DC, Sphaerotheca fuligena (Schltdl.) Pollacci Cercospora leaf spot: Cercospora leaf spot C. citrullina, C. melonis, C. lagenarium Fusarium wilt: Fusarium oxysporum Schlecht IPM for Cucurbitaceous Vegetable To know the IPM practices for Cucurbitaceous Vegetable, click here Source: NIPHM, Directorate of Plant Protection, Quarantine & Storage