Answer: I don't know if the pests you found were the cause of the problem or a secondary problem (insects move in when a plant is stressed). Some common zucchini pests include cut worms, cucumber beetles, squash bugs, and vine borers. But there are also diseases that can cause sudden wilting. These include zucchini powdery mildew, bacterial wilt, downy mildew, yellow mosaic virus, and Botrytis Blight.
Once the zucchini plant is infected with any of these disease problems, it is nearly always fatal to the zucchini plant. So, the best way to fix disease problems on growing zucchini is to just make sure that the zucchini plant does not get them in the first place.
This can be done mostly through appropriate care of the zucchini plant. Making sure that the plant gets plenty of sun, the right about of water every week, avoiding top watering and good air flow through proper spacing of plants will go a long way towards helping the plant fend off many of these diseases. Also, keeping common zucchini pests away from the plant will also help curb the diseases that these insects often carry with them.
It may be too late to save your plants this year but you can try to avoid the same problems next year by planting your zucchini in a different garden spot, amending the soil with organic matter prior to planting, and spreading a mulch of straw or other organic material around the bases of your plants to deter insect pests.
Best wishes with your harvest!
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