Why Are Winter Melon Leaves Turning Yellow? Causes and Control Methods
Winter melon is a relatively easy vegetable to manage when growing, because the winter melon vines are fairly thick and sturdy, the root system is also very strong, its absorption capacity is very high, the leaves are large, and the photosynthesis effect is obvious. But sometimes it also suffers damage from pests and diseases. If there is a yellow leaf phenomenon, first you must distinguish the specific cause and then treat it accordingly. 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. Afterward the lesions gradually join together, and in the later stage the lesions turn grayish brown, so there is a yellow leaf phenomenon in the early stage. For control, mainly use chlorothalonil to soak the seeds for disinfection; when the disease occurs, spray a 500-times solution of 50% sulfur mixed suspension concentrate. Generally spray once a week, observe the effect, and continue spraying several more times if needed.
2. Other causes
Waterlogging or poor nutrition, soil compaction, and also the effect of drought; drought affects the roots' absorption of water and will affect leaf and plant growth. Sometimes strong light scorching also causes the yellow leaf phenomenon. Therefore, it must be planted on higher ground, in sandy loam soil that is air-permeable and retains fertilizer. Supplement nutrients regularly; do not wait until yellow leaves indicate the need before starting to fertilize. After rain, loosen the soil more; in drought, pay attention to watering every day in the evening.
3. Too much fertilizer
Winter melon has a strong absorption capacity. If too much fertilizer is applied at one time, the soil solution concentration becomes too high, affecting root absorption. Using chemical fertilizer too close to the roots easily burns them; after the root system is damaged, its absorption capacity weakens, which leads to insufficient nutrition and also produces the yellow leaf phenomenon. So it is best to apply more base fertilizer and bottom fertilizer, and use farmyard manure for topdressing. Or use compound fertilizer that is not likely to burn the roots, and water after fertilizing.
4. Nematode damage
Underground root-knot nematodes harm many vegetable crops. After winter melon is damaged by nematodes, the phenomenon of small melons and yellow leaves appears. When leaves are yellow and there is no powdery matter, mold-like matter, or the like on the surface, it may be nematode damage and not infection by a pathogen. 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 a 500-times root drench of 1.8% abamectin, together with some fertilizer such as a 500-times solution of Giant Kelp No. 1, for root drenching; recovery is fast.
If winter melon shows the phenomenon of leaves turning yellow, there are actually quite a few causes, but the symptoms are also somewhat different. Only by carefully identifying them and then making improvements and carrying out control can it be effective.