Garden Series: Cucumber Beetles

Cucumber Beetles

Cucumber beetles are very common in this area, and will damage almost any plant that is grown in the garden. As their name suggests, they damage cucumbers, however, squash, melons, tomatoes, corn, beans, and other cucurbits also get attention from these beetles. There are three different types of cucumber beetles: spotted cucumber beetle, striped cucumber beetle, and banded cucumber beetle.

Cucumber beetles feed on foliage, flowers and the rinds or pods of many vegetables and fruits. The worm-like larvae live in the ground and can damage roots of vegetables or tubers such as sweet potatoes. They can also enter the rinds of melons that contact the ground. The damage often appears as holes chewed in leaves or chunks bitten out of fruit/vegetables rinds and pods. However, the most significant damage caused by cucumber beetles are the diseases they can transmit, specifically by the striped cucumber beetle.

The striped cucumber beetle is a yellow beetle about ¼ inch long with three straight black stripes on its back. These beetles, like the other types of cucumber, chew holes in leaves and fruits/vegetables. However, when they feed, they can transmit bacterial wilt. The bacterium that causes this disease overwinters in the gut of striped cucumber beetles, and infected bugs can transmit it to plants via saliva when it feeds. There is nothing that can be done to save a plant that has bacterial wilt. If wilt is suspected, a simple at home test can confirm it. Cut the stem of the infected plant and mash the ends with your fingers. Next, press the ends together then slowly pull them apart. If the juices have a “roping” effect, that is a positive result for wilt. The bacteria in the plant’s sap cause the roping effect.

The spotted cucumber beetle (also known as the southern corn rootworm) and the banded cucumber beetle closely resemble each other. Both are about the same size as the striped cucumber beetle. The spotted cucumber beetle is yellow and has twelve black spots on its back while the banded cucumber beetle is green with yellow horizontal bands across its back. Both of these beetles are found throughout the garden on most plants, and chew holes in leaves, pods, and fruits. The damage from these tends to be a more of a nuisance than a problem, however in large numbers they can be problematic.

There are a number of chemicals available to control cucumber beetles. Products containing carbaryl, bifenthrin, permethrin, malathion, or imidacloprid are recommended by LSU. As with all pesticides, pay close attention to the label, especially the pre-harvest interval (the amount of time you must wait after spraying before harvesting). Also, keep pollinators in mind when you spray. For summer crops, pay special attention to any instructions about temperature requirements.

For more information contact Randall Mallette, County Agent, at the local LSU AgCenter Extension Office 318-357-2224.