All of a sudden they were there, what you ask? Small, black spotted flying objects that sprang and darted continuously among the vegetable plants, nearby roses and annual lantana. Are these miniature UFOs (which have been in the news of late)? Maybe the UFOs released these yellow and black spotted beetles on a quick fly over the Front Range? Something isn’t right here. My mind isn’t ready for a spotted yellow beetle infestation this late in the growing season. I just want to pluck more ripe tomatoes for next week’s salads and sandwiches before the white flakes fall from above!
The flying yellow objects are spotted cucumber beetle, also known as southern corn rootworm, proper scientific name is Diabotica undecimpunctata howardi.
No doubt you’ve seen one or five on your cucurbits (cukes, pumpkins, squash, cantaloupe, watermelons) over the years, but nothing like the scores that have been flying these past couple of weeks. I couldn’t take them anymore (or eat anymore yellow cucumbers, a banner, delicious year for sure), so I cut, dug and tossed the vines this past weekend. The Italian striped zucchini is harboring these pesky pests too, but I can’t bring myself to pull the plant. Soon.
A third inch in size, adult beetles overwinter outside in protected sites. When temperatures warm up in spring they start moving around and laying eggs near their favorite cucurbits. Eggs become larvae, pupae and adults in only fifteen days. In Colorado we have at least two summer generations. Adult beetles chew on a wide range of ornamental leaves and flowers.
There are some ways to battle these small flying pests, but at this late date in the season, it’s probably best to just let them play out their existence (I am). Next year consider some of the cultural techniques if you wish. Sprays generally don’t work all that well and why not let any natural predators get them on their own. Use of chemical sprays upsets the balance of allowing beneficial predator insects free reign to seek and destroy their pest for a quick meal.
Here’s a list of controls to consider next year – taken from the Department of Entomology in Washington State. Click here to read the full article with more information.
- Natural predators to spotted cucumber beetles include wolf spiders and ground beetles. We have both here in Colorado.
- Rotate your crops each growing season so pests don’t get accustomed to the same place to dine. The beetles can still fly, so this isn’t a guarantee, but still wise to rotate yearly.
- Try using transplant cucurbits instead of direct seeding (I know, these crops are SO easy to start from seed directly in the garden spot where they will grow). Transplants lessen exposure to cucumber beetle feeding when they are just ramping up for the summer. Also delay transplanting until later or mid-summer when these pests are out hustling earlier planted cucurbits in other gardens.
- Use the lightest weight floating row covers to prevent beetle access to your plants. When plants start flowering, remove the covers so bees can get in and pollinate.
- Use weed and herbicide-free straw mulch to prevent beetles easy movement from one plant to another. Straw also helps conceal and protect predator wolf spiders. As straw breaks down over the summer it helps with the springtail population which also feeds wolf spiders.
- Metallic colored mulch has been shown to repel beetle feeding.
- Plant resistant vegetable varieties.
Cucumber Beetles University of Minnesota
The Spotted Cucumber Beetle Colorado State University
Utah State Striped and Spotted Cucumber Beetle includes resistant varieties
|Spotted Cucumber Beetle on Annual Lantana|