Rick Foster
Entomology
Purdue University

Striped cucumber beetles are out, sometimes in very large numbers, in many areas of Indiana. Unfortunately, organic growers have few or no viable options for managing striped cucumber beetles after they arrive. The better approach is to try to avoid having the problem. Growers should keep in mind that muskmelons and cucumbers are susceptible to bacterial wilt of cucurbits, a disease whose causal agent is carried by striped cucumber beetles. These crops need to be protected from cucumber beetles more aggressively than watermelons, most squashes and pumpkins, which are less susceptible to the disease.

There are several strategies that can be used to avoid problems with striped cucumber beetles. One approach is to plant less susceptible cucurbit crops, such as zucchini, in the vicinity of muskmelons and cucumbers to act as a trap crop. Zucchini is much more attractive to the beetles, so most beetles will go to those plants, and the feeding damage can usually be overcome by the zucchini plant. Another approach is, prior to the emergence of the striped cucumber beetles, cover muskmelon and cucumbers with row covers. Either floating row covers or row covers supported by wire hoops can be used to act as a physical barrier to the beetles. Be sure to remove the row covers when the plants start to flower so that bees can pollinate the crops. In many situations, by the time plants are flowering, beetle populations may have begun to diminish, and the plants are old enough that they will be able to produce fruit before the disease symptoms occur. There is at least one variety of cucumbers (Saladin) that is resistant to bacterial wilt. There are no varieties of muskmelons of that have this resistance.

There are several compounds which are mentioned in the popular literature as being effective in managing cucumber beetles, such as Surround (kaolin clay) and pyrethrin. I am not aware of any scientific studies that have shown that these products are effective. Melon growers use Surround to protect fruit from sunscald, but data are not available (as far as I know) that show that Surround repels striped cucumber beetles. Pyrethrins tend to not be very effective against insects with chewing mouthparts such as beetles. The better approach for organic growers is to try to avoid the problem.

I would interested in hearing from growers who try the resistant cucumber variety or use Surround or pyrethrin for cucumber beetle control (rfoster@purdue.edu).

Striped cucumber beetle adult.


Striped cucumber beetles feeding at leaf edge.


Heavy feeding by striped cucumber beetles can
reduce a leaf to tatters, as seen on this pumpkin
seedling.


Striped cucumber beetles often feed on the
underside of cotyledons. Be sure to check there
when scouting fields.


The stem of this buttercup squash seedling
shows evidence of heavy feeding by striped
cucumber beetles. Squash varieties differ in
their attractiveness to the beetles.