Adult cucumber beetles are 5 mm (¼”) in length, greenish yellow and are identified differently by their backs. The spotted cucumber beetle has six large black spots on its back, and the western cucumber beetle has stripes instead of spots.
The cucumber beetle feeds on the nectar of cucumber, squash and melon flowers. The larvae suck the sap of the plants. The greatest damage comes from bacterial wilt which the cucumber beetles carry. It can wipe out an entire plant very quickly.
It is important to control cucumber beetles early in the season. Once a population gets established in your garden, it is very difficult to get rid of them. Protect your garden with an insect net until they start flowering. Then you need to lift the net to allow bees and other pollinators in. If you find cucumber beetles at this point use a spray of hot peppers, water and garlic.
Repellent plants: Broccoli, calendula, catnip, goldenrod, nasturtiums, radish, rue and tansy. If you want to try marigolds to repel them use the more pungent varieties like African, French or Mexican marigolds.
Mulching can help since the larvae spend a part of their lifecycle buried in the soil at the base of the plant.