Powdery mildew appears as white, flour-like patches on leaves and stems. It is common on squash and zucchini, especially when foliage stays crowded and nights are humid. Early action can slow it, but the plant may still produce if the growing point remains healthy.
Confirm the pattern
Look for powdery spots on the upper leaf surface and sometimes the underside. Do not confuse them with dust, spray residue, or chewing damage. Check nearby plants because spores can spread through the bed.
Improve conditions
Remove badly affected leaves with clean pruners and discard them rather than composting them. Thin crowded growth where practical, keep weeds down, and water the soil at the base in the morning. Avoid wetting foliage late in the day and do not handle plants while they are wet.
Use treatment carefully
If the label permits use on edible squash, apply a garden fungicide or other treatment exactly as directed. Test a small area first, observe the harvest interval, and never mix products casually. Home remedies can burn leaves or harm beneficial insects when concentrations are wrong.
At the end of the season, remove infected vines and clean tools. Choose resistant varieties when available and rotate crops to reduce repeated pressure.