Answer: Based on your description, there are several possible causes. Flea beetles normally make many tiny holes like shot-holes in the leaves but don't normally kill the plants. Flea beetles are very tiny little black insects which jump when disturbed, so you should see them if they are the culprit. The infestations are usually worst on new transplants early in the season. Control measures would include cultivating the soil to disturb their egg masses and cleaning out weeds bordering the garden because they can serve as alternate hosts. If the infestation is really severe, you might wish to apply rotenone according to the label instructions.
A Colorado potato beetle attack will also damage the leaves. You can hand pick the egg masses, the larvae and the adults (these are all large enough to be seen easily) or apply a strain of Bt (Bacillus thuringiensis) listed as effective against them, again being careful to follow the label instructions. In addition, crop rotation and use of a thick mulch can help reduce colonization.
Healthy plants withstand insect attacks best, so keep in mind that eggplants need a deep rich soil well enriched with organic matter. The soil should be kept quite moist and yet be well drained (not soggy). Another consideration is that eggplants really prefer warm weather and so your plants may be suffering from cool nights. Nighttime temperatures should be reliably into the fifties for optimum results without protection.
A final possibility is that the plants are suffering from some type of foliar disease. If you don't think the problem is caused by beetles, you might wish to take a sample to your local County Extension office for a definitive diagnosis and recommended control, if any.
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