Two major types of cucumber beetles battle gardeners for their crops: the striped cucumber beetle (Acalymma vittatum) and the spotted cucumber beetle (Diabrotica undecimpuntata).
The striped cucumber beetle is about 1/4 inch long with a black head and 3 distinct parallel black stripes on its yellow wing covers.
The spotted cucumber beetle is about the same size but has a yellowish-green body and 12 black spots on its wing covers.
These pests have very similar life cycles. They differ most significantly in what they eat. The striped cucumber beetle feeds almost exclusively on cucurbits (such as cucumbers, cataloupes, melons, and squash) in the adult stage. The larvae, called rootworms, cannot live on any other plants than those of the cucurbit group. The spotted cucumber beetle, however, isn’t nearly as picky about what it eats and has been recorded on nearly 300 different crop plants and ornamentals. Besides the physical damage they cause to plants, both of these beetles transmit serious diseases--bacterial wilt disease and mosaic virus.
Cucumber beetles are commonly found throughout the United States but are especially serious in the South, particularly where soils are heavy. The spotted cucumber beetle is also called the southern corn rootworm because its larval stage is a major pest in commercial corn fields.
Their Growth Stages
Cucumber beetles overwinter as adults in plant debris or dense grass, so the more marauding birds you have on your property in the winter the better chance they will get a few beetles. In the spring, when temperatures reach 60°F or higher, the beetles emerge and move to new vine growth in the vegetable garden, appearing at least 2 weeks before we plant cucumbers and summer squash. They can feed on pollen and leaves of many plants until their favorite plants are up. The beetles lay orange-yellow eggs on the undersides of the leaves. The larvae hatching from these eggs bore into roots and stems. They are wormlike, yellowish-white, and grow to 3/4 inch long. In late summer, they pupate in the soil and emerge as adults in about a week. There is only 1 generation of beetles in the North, but there can be 2 to 4 in the South.