Photo of squash bugs provided by the Greene County Master Gardeners.
Question: What can be done to eliminate squash bugs? I’ve tried Sevin, but it doesn’t seem to help.
Answer: Adult squash bugs are difficult to eliminate with insecticides. From anecdotal reports and research, Sevin has limited effectiveness for this application. Since squash bugs can multiply rapidly, the best strategy is to tackle squash bugs at their earliest stage. The Master Gardener Demonstration Vegetable Garden was affected by squash bugs this year.
Squash bugs emerge as adults in the spring and lay masses of eggs on the underside of leaves. They prefer plants in the cucurbit family such as summer squash, winter squash and pumpkins. Their eggs hatch in about 10 days and the nymphs begin feeding on the plants. Nymphs have needle-like mouth parts and they suck plant juices from the stems and leaves, thereby interfering with nutrient transfer in the plant. The leaves will develop spots and turn black. The Plants will begin to wilt and vines will start turning black and drying out.
An effective strategy is to look for masses of eggs on the leaves. The eggs are about 1/8 inch long and light brown in color. Scrape the eggs off of the leaves and crush them. Once the nymphs hatch, they remain in tight knit clusters and look like a bunch of small spiders when they scatter. The nymphs go through several changes and take a little over a month to reach the adult stage. At that time, they are about 5/8 inch long. Both adults and nymphs can be knocked off the leaves into a bucket of soapy water. Or, just pick them off and squish the squash bugs. I tried using a spray composed of insecticidal soap and Neem oil on them, and it seemed to reduce the population, but did not eliminate them. The spray has to come into direct contact with the insects to work. There are foliar insecticides that are suggested, but they should target the young nymphs. The active ingredients in some of these products are permethrin or lambda-cyhalothrin.
Another method that can be used is to trap the adult squash bugs. You can lay boards, roofing shingles or cardboard on the ground near the base of the plant. The adults will hide under the flat material during the night. The next day, you can squash them or drop them in soapy water. I laid some thick cardboard pieces on the ground near the base of a summer squash and some pumpkins this summer. I checked a couple of days later, and there was a bunch of squash bugs in hiding. Once I turned the cardboard over, they scattered fast and I didn’t get them all. So, the next time I was ready!
Cloth row covers can also be used to protect young plants in the spring. There are covers that allow light and rain to reach the plant, but keep the squash bugs away. However, once the plant begins to bloom, the covers need to be removed so that pollinators can reach the pollen.
Once the crop is harvested, it’s best to remove the affected vines and plants from the garden and destroy them. Adult squash bugs will overwinter in protected shelters nearby such as piles of leaves, mulch, under stones and around buildings. Eliminate any debris that you can to prevent the squash bugs from staying nearby. Then, in the spring, rotate the crops so that you don’t plant cucurbits in the same area the following year.
For more information, visit https://extension.entm.purdue.edu/public... to read about E-30-W Cucurbit Insect Management.
This question was answered by Lila Massa, Greene County Master Gardener. Send your garden-related questions directly to the Master Gardeners for consideration to be answered. Email your question to GardenQuestions45@gmail.com or send by mail to Ask A Greene Gardener, c/o Greene County Extension, 4513 W SR 54, Bloomfield, IN 47424.