Prevention and control methods for white spots on new leaves, dry leaves, curling and shrinking in Welsh onions
What to do when new leaves of Welsh onions have white spots, dry leaves, curling and shrinking? Many diseases and pests can cause dry yellow leaves in Welsh onions, including downy mildew, gray mold, Phytophthora blight, viral disease, seedcorn maggot, and others. Since spraying pesticides for downy mildew, gray mold, and Phytophthora blight had no effect, the Welsh onions are most likely affected by viral disease and damage from seedcorn maggot, which can be controlled according to...
What to do when new leaves of Welsh onions have white spots, dry leaves, curling and shrinking? Please explain
Many diseases and pests can cause dry yellow leaves in Welsh onions, including downy mildew, gray mold, Phytophthora blight, viral disease, seedcorn maggot, and others. Since spraying pesticides for downy mildew, gray mold, and Phytophthora blight had no effect, the Welsh onions are most likely affected by viral disease and damage from seedcorn maggot, which can be controlled according to the specific symptoms.
Viral disease symptoms: irregular yellow-green mottling or yellow stripes of varying lengths appear on the leaves, the leaves become twisted and thin, and the leaf tips gradually turn yellow. When the disease is severe, Welsh onion growth slows or stops, and eventually the whole plant dies. In the early stage of the disease, spray with 1.5% Zhibingling emulsion at 1000 times dilution, 20% moroxydine hydrochloride plus copper acetate wettable powder at 500 times dilution, and 10% mixed fatty acid emulsion at 100 times dilution for control, with an interval of 7-10 days, spraying 2-3 times consecutively.
Seedcorn maggot damage: the larvae bore into the rhizome of Welsh onions underground, causing the underground part to rot and become moldy, the aboveground part to wilt, the leaf tips to wither and turn yellow, or the whole plant's leaves to turn yellow. In severe cases, Welsh onion growth stops or the plants even die. To control seedcorn maggot larvae, drench the roots with 75% cyromazine wettable powder at 3000 times dilution, 40% phoxim emulsifiable concentrate at 3000 times dilution, 48% chlorpyrifos emulsifiable concentrate at 3000 times dilution, or 5% hexaflumuron emulsifiable concentrate at 3000 times dilution.
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