Who doesn’t love squash? Winter squash, zucchini, summer squash? Squash is a quintessential part of nearly any home garden. They are easy to grow, are prolific producers and love the heat of summer. However, as much as we humans love to eat the fruits of the squash plant, the Squash Beetle may love it even more than us.
Squash beetles can be a serious problem in the Wenatchee Valley. Although, the upper valley has historically been too cold to harbor large populations, Wenatchee and East Wenatchee suffer dearly from annual infestations….especially in home gardens. The incredibly warm summers and mild winters allow the squash beetle populations to persist from year to year. As our climate shifts, some of the problems that have been reserved for the warmest portions of the county will begin to show themselves in areas that have traditionally been problem free. The squash beetle is a likely candidate for movement up valley. Therefore, even if you have never experienced squash beetle problems before, it is a good thing to know how to recognize and control.
Infestations usually begin to show themselves in the late spring through mid-June as over-wintering adults emerge from garden debris and mulch and begin to reproduce and lay eggs. This is one instance where mulching your plants can exacerbate the problem. The beetles lay a series of copper colored, oval eggs along the undersides of the newly emerged squash leaves. Over the course of a week, the eggs begin to hatch and squash bug nymphs begin to feed on the squash leaves and stems. Both the adults and the nymphs are active feeders on squash plants and squash fruits. Their feeding will begin to cause water transport within the leaves of the squash to halt and leaves will begin to wilt. If the infestation is great enough, the plant will eventually die. During warm summers, squash beetles can complete two life cycles; the adults of the second cycle will over-winter to begin reproduction again in the spring.
So what can a gardener do to lessen their losses? The first recommendation is to remove mulch from around squash plants if you live in a neighborhood prone to squash beetle. Removing excess garden debris will help as well since this is where adults go to hide from the cold and to over-winter. Also, perform weekly leaf checks on the undersides of your squash leaves. If you see a cluster of small, copper colored eggs, squish them. It is much easier to squish the eggs than to squish adults and nymphs. The next tactic is to go out and pick your plants free of adult and nymph squash beetles. Either squish the adults and nymphs or put them into a sealable plastic bag and then allow them to cook in the sun within the bag before putting the container into the trash can…..this is one pest that you do not want to accidentally spread to someone else, so make sure the adults and nymphs are dead before throwing them out. Diatomaceous earth has also been proven effective in lessening the population of squash beetles. This is a method that has been approved for organic production. Several insecticides also work for control. Before applying an insecticide, seek advice on proper usage first. The Chelan/Douglas Master Gardener Diagnosis Clinic can be contacted for more information on chemical controls. Also, work with your neighbors. If you remain vigilant attendants to your gardens, it is possible to keep an area free from pest problems. When you work together to control squash beetles, everyone wins. Good Luck this Season and Happy Gardening!