I'm growing both yellow squash and (still immature) zucchini this year - all started from seed. The yellow squash is doing extremely well - they all look healthy and my most mature plants are loaded with fruit. However, my zucchini has developed a problem. The lowest leaves curl up like a clenched fist and become so dry that that crumble when touched. I know I have whiteflies in the garden and have been using a weak oil/soap spray but whiteflies seem to be localized on a couple to tomato plants.

Even though I have both varieties of squash growing side by side this problem seems to be confined only to the (younger) zucchini plants. My eyesight isn't all that good but I've not been able to see any insects or eggs on the leaves. I'm afraid I'll lose the plants and that whatever is causing the problem will spread to the yellow squash.

My hope is that someone more experienced with Zucchini than I am can identify the problem and provide information of correcting it and/or protecting my yellow squash.

Please note that I have photos of the damage but I don't know how to attach them. If someone would tell me I'll post them.

Thanks

Richard