Powdery mildew : Most Persistent Fungal Problem Of Grapes
Powdery mildew is the most persistent fungal problem of grapes in India and one of the most widespread fungal diseases of grapevines in the world. The disease generally is considered economically important . It is caused by the fungal pathogen Erysiphe necator and seen as ash-grey to white powdery growth on green tissue of the vine. It affects both table grapes and wine grapes. If uncontrolled, it can cause serious crop losses and impair wine quality Powdery mildew can result in reduced vine growth, yield, fruit quality, and winter hardiness. Varieties of Vitis vinifera and its hybrids generally are much more susceptible than other varieties.
The powdery mildew fungus can infect all green tissues of the vine. Small, white or grayish-white patches of fungal growth appear on the upper or lower leaf surface. These patches usually enlarge until the entire upper leaf surface has a powdery, white to gray coating. The patches may remain limited throughout most of the season. Severely affected leaves may curl upward during hot, dry weather. Expanding leaves that are infected may become distorted and stunted. On young shoots, infections are more likely to be limited, and they appear as dark-brown to black patches that remain as dark patches on the surface of dormant canes.
Leaves are most susceptible when they are expanding. Infections result in small yellow-green blotches 2-10mm in diameter with an irregular outline on the upper surface of leaves in spring. The blotches form an ash-grey to white powdery growth of hyphae which develops conidia on both sides of the leaf surface. Web-like hyphae and chains of conidia are clearly visible with a 10x hand lens. In the field this fungal growth is flat, as the conidia chains are constantly broken. The blotches enlarge and may merge to cover the whole leaf. Smaller veins on the underside of the infected leaves may turn brown . The earliest infected leaves become distorted and discoloured, sometimes giving the vines a wilted appearance. Severely diseased leaves blacken, dry out and fall prematurely in hot weather. Leaves become more resistant to infection with age, but are never completely resistant.
If blossom clusters are affected, the flowers may wither and drop without setting fruit. Infections on cluster stems often go unnoticed, but can be very damaging. Infected cluster stems may wither and dry up, resulting in berry drop (shelling). Affected berries may have patches of fungal growth on the surface similar to those on the leaves, or the entire berry may be covered with the white, powdery growth. Infected berries often are misshapen or have rusty spots on the surface. Severely infected berries may develop irregular shapes, crack or split and rot. Red varieties may colour unevenly. Post-veraison, berries develop a brown web-like pattern on the surface, very noticeable on white varieties. Over time berries become resistant to powdery mildew infection and thus once this occurs the fungus is killed inside the berry leaving scar tissue on the berry.
HPM helps grape farmers achieve optimal yield by providing outstanding disease-control solutions. HPM helps farmers more efficiently produce high quality crops by bringing new products. HPM’s Stuff prevent grape from powdery mildew. Stuff is safe and has not shown any phyto- toxicity, when used at recommended dosages. Effective against many diseases complexes on large number of crops. Multisite activity prevent in developing resistance. Broad spectrum, Systemic & Contact, with protective & curative action. Being systemic, it enters in system of plant and protects the plant from inside and being contact it protects the plant from outside. Mancozeb remains on the plant surface & acts by contact action (Preventive). Carbedazim absorbed through roots and green tissues, acts as protective and curative. Provides long duration control of 7-10 days. It contains plant nutrients Zn & Mn, which improves root growth in plant. It provides excellent phytotonic effect on plants making them appear green and healthy.