Issue: May 3, 2008
You won't avoid squash bugs by planting late
Every time I have tried to grow squash in my garden, squash bugs have destroyed the plants and the crops. I have tried everything, but nothing seems to work. My neighbor told me I just need to wait until after July 4 to plant my squash and then I will not have a problem. Is that true? Can I wait that long and still have time for the squash to produce?
I have also heard that planting squash late will help you avoid squash bug problems. This will shorten your harvest season, but with squash, that may not be a problem since it is so prolific. However, when I tried late planting, the squash bugs overwhelmed my squash anyway. Yet, some people swear by this technique. It may just be a coincidence when this technique succeeds. However, to check into this, I called Dr. Carol Sutherland, NMSU Extension Service Entomology Specialist.
Dr. Sutherland explained that squash bugs are very strong flyers with a very good sense of smell. If they are in the area and they detect your squash, they will appear in your garden. This can happen any time during the summer. Then, you will have problems.
She explained that squash is not their only food supply. They feed on any cucurbit (squash, cucumber, ornamental gourds, and even native gourds). They do have favorite plants, and if they are feeding on native gourds and detect your squash, they will leave the gourds and infest your squash. If you choose to not plant squash for several years, this will not assure a year without squash bugs if these alternate hosts exist nearby, or if neighbors' gardens have been supporting squash bugs.
Some gardeners have told me that they have had little problem with squash bugs on climbing squash (such as butternut squash) supported on trellises. Dr. Sutherland suggested that if a preferred variety of squash (zucchini or yellow squash) was available, the squash bugs may ignore the butternut, but if only the butternut squash was available, the squash bugs would probably infest them. The growth habit of the butternut and other climbing squash may also be less favored by the squash bugs, but nevertheless, there is no guarantee that the squash bugs will leave them alone.
Dr. Sutherland explained further that the manner in which the squash bug feeds creates greater problems. It feeds with "sucking/piercing" mouth parts that suck the sap from the host plant. When feeding in this manner, the squash bug also injects some saliva into the plant to predigest some of the vasculature cells of the squash plant. If this enzyme damages enough of the vascular system, the whole plant may die.
According to Dr. Sutherland, squash bugs are very difficult to control. Most insecticides available to homeowners (organic or otherwise) have limited effectiveness when used to treat the insect in the adult stage. They are most effective within a few days after the eggs hatch. She suggests that you take a hint from their name and "squash" the squash bugs. She also suggests that you hand pick (or scrape) the bugs and their eggs from the plant into a can of soapy water. Manual removal is the most effective manner for homeowners to manage this common garden pest.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: firstname.lastname@example.org, office: 505-865-7340, ext. 113.
Please copy your County Extension Agent and indicate your county of residence when you submit your question!