Controlling Cucumber Beetles and Squash Bugs With Fewer Insecticides? Yes, it’s Possible!

Cucumber beetles and squash bugs are two serious insect problems of the cucurbits – cucumber, summer squash, winter squash, pumpkin, watermelon and zucchini.  They are both difficult to control, but new research gives an option to reduce their numbers using low-chemical control.

The Culprits
Cucumber beetles and squash bug adults both cause damage through their feeding. Cucumber beetles introduce bacterial wilt, a disease causing plants to suddenly wilt and die. Squash bug feeding introduces another bacteria responsible for a disease called yellow vine decline, causing rapid browning, drying, wilting and death of plants.

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Adult striped cucumber beetles and southern corn rootworm/spotted cucumber beetle feeding on overmature pumpkin. Whitney Cranshaw, Colorado State University, Bugwood.org

There are two main species of cucumber beetles found in the vegetable garden – striped and spotted. Striped cucumber beetle adults are yellowish green and approximately ¼ inch long with three black stripes down their back. Adults overwinter in plant debris and other protected areas near the garden. There are one to two generations per summer.

Spotted cucumber beetle adults are yellowish green and approximately ¼ inch long with twelve black spots on their backs. They do not overwinter in Nebraska. They die out in fall and migrate north or are blown in by storm fronts in June and July. There are two to three generations each summer.

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Mating pair of squash bugs (Anasa tristis). Whitney Cranshaw, Colorado State University, Bugwood.org

Adult squash bugs are 5/8 inches long and approximately 1/3 inch wide.  They are brownish black insects, sometimes mottled with gray or light brown on the back and wings that lay across their flat back.  The insects have an unpleasant odor when crushed.  Adults overwinter in leaf litter and debris, emerging in spring as the cucurbit vines begin to grow.  One to two generations occurs each summer.

Trap Cropping
This control method uses the insects’ preference for certain cucurbit species over others, pulling them away from your desirable cucurbits, allowing you to kill them.  Research conducted by Jaime Pinero, vegetable specialist at Lincoln University in Jefferson City, MO, indicated Blue Hubbard squash is a very attractive plant to both cucumber beetles and squash bugs making it an excellent trap crop.

The key to this technique is starting Blue Hubbard transplants in the house two weeks before you plan to start your cucurbit crops in the garden. Cucurbits are usually direct seeded in the garden, not purchased as transplants from a garden center. When planting your cucurbit seeds outside, put the Blue Hubbard plants around the edge of the garden or in the corners. Pinero’s research for small commercial growers showed only 6-8 Blue Hubbard plants were needed for successful insect protection of 100 or so cucurbit plants. So a small home planting may only need 2-3 trap plants.

Pinero recommends Inspecting the hubbards weekly for signs of cucumber beetles or squash bugs and targeting your insect control just to these plants. Spray the hubbards with Eight (permethrin), bifenthrin, neem or spinosad products when insects appear. Or if you don’t want to use chemical control, then pull out the hubbards and destroy them when insects and/or eggs are on them. It’s important to always have hubbards present in your garden, drawing insects to them and away from your desired crops. Have new transplants ready to go as needed.

Continue to monitor the trap plants throughout the summer and repeat your control until harvest of your desirable cucurbits is done.

This method won’t completely eliminate insects on your desirable cucurbits, but it will significantly reduce them.

If you want to try this technique in your garden this summer, the time to start your Blue Hubbard transplants is now. Look for seeds at your local nursery/garden center or in mail-order catalogs and sow them inside, using individual seed pots.

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