All you need to know about cucumber beetles
These tiny beetles (just 1/4 inch long) are yellowish green, with black spots or stripes. The larvae eat roots of crops such as corn; adults feed on foliage of cucumber, muskmelon, pumpkin, and squash, as well as on flowers such as aster, dahlia, and rose. While adults do cause some damage by eating leaves and blossoms, they do more harm by spreading bacterial wilt among certain vegetables as they feed.
To control cucumber beetles, clean up and discard all plant debris in fall; it can serve as an overwintering site. Use floating row covers to prevent adults from reaching plants. Pyrethrin may control adults; parasitic nematodes will reduce the larval population. To save vegetable plants in the face of an infestation, look for varieties resistant to bacterial wilt.
Carbaryl is an effective chemical control against adults.