A: Several beetles (some spotted or striped) have been known to cause damage to the cucurbit plant family, which includes melons, squashes and cucumbers. The larvae of these beetles feed on roots of the plants as soon as they start to grow by boring into the roots and stems. The plant can die immediately or the feeding may cause it to be stunted which reduces the potential output of the plant. Often these beetles survive the winter, waiting for the next season of plants to arrive. During the growing season, the adult beetles feed on the nectar, leaves, fruit or flowers of the plant but they do far less damage than larvae. Another serious problem with cucumber beetles is their ability to transmit fungal, viral and bacterial diseases. Infected plants eventually wilt and die. If you find your squash or cucumbers have the wilt or root rot, they should be removed and destroyed.
Next year consider choosing a variety of cucurbit seed which has proven to have some resistance to these diseases. Handpicking to remove the beetles is time-consuming but works well. Eliminate weeds in and around the garden as they often supply an additional food sources for the adult beetle. Some over the counter insecticides may give you some control over the adult beetle but once the larvae are in the stem or root, little can be done. A granular insecticide works best when applied at planting or soon afterward.