What causes yellowing leaves on winter melon
Winter melon is a relatively easy vegetable to manage, because its vines are thick and sturdy, its root system is very strong with a high absorption capacity, and its leaves are large with obvious photosynthesis. But sometimes it also suffers from pests and diseases. If yellow leaves appear, the first step is to identify the specific cause before treating it. Now let us look at the specific causes of yellow leaves.
1. Gray leaf spot
After infection with gray leaf spot, winter melon leaves first develop chlorotic yellow spots, and the lesions are irregular. Afterwards the lesions gradually join together, and in the later stage they turn grayish brown, so yellow leaves appear in the early stage. Control mainly uses chlorothalonil for seed soaking and disinfection; when the disease occurs, spray a 50% thiophanate-methyl plus sulfur mixed suspension concentrate at 500 times dilution, generally once a week, and depending on the effect, spraying can be continued several more times.
2. Other causes
Waterlogging or malnutrition, soil compaction, and drought also have an effect; drought affects the roots' absorption of water and affects leaf and plant growth. Sometimes strong light scorching also causes yellow leaves. So it is essential to plant on higher ground, in a breathable, fertility-retaining sandy loam soil. Replenish nutrients regularly; do not wait until yellow leaves appear before starting to fertilize. After rain, loosen the soil more; in drought, water every day in the evening.
3. Too much fertilizer
Winter melon has a strong absorption capacity. If too much fertilizer is applied at once, the soil solution concentration becomes too high, affecting root absorption; applying chemical fertilizer too close to the roots easily burns them, and once the roots are damaged, their absorption capacity weakens, leading to insufficient nutrients and also causing yellow leaves. So it is best to apply more base and bottom fertilizer, and use farmyard manure for topdressing. Or use compound fertilizer that is not likely to burn roots, and water after fertilizing.
4. Nematode damage
Underground root-knot nematodes harm many vegetable crops. After winter melon is damaged by nematodes, it produces small fruit and yellow leaves; when the yellow leaves have no powdery or moldy substance on the surface, it may be nematode damage rather than a pathogen infection. After the leaves yellow, they gradually wither and die but do not fall off. So it is best to dig open the root zone soil and check; if there are nodular growths, it is damage. Use 1.8% abamectin at 500 times dilution to drench the roots, together with a fertilizer such as Giant Kelp No. 1 at 500 times dilution, drenching the roots together for faster recovery.
If winter melon shows yellowing leaves, there are actually quite a few causes, but the symptoms also differ somewhat; only by identifying them carefully and then improving, treating and preventing them can it be effective.