Q. How do you deal with squash bugs? I can't believe the amount of infestation! Do row covers really work? Thanks,
- ---Rachel in central Ohio
- --- Haley in Norman, Oklahoma
- ---Jackie in Dinero, TX
Squash bugs are pretty much limited to decimating plants like winter squash, zucchini and pumpkins; sometimes cucumbers and melons. These bugs are nasty bad actors. Once they start feeding aggressively, the leaves droop, blacken, and fall off. The plant itself often dies; and even if it does survive, rarely produces any more fruit. And in some areas—including Oklahoma, where they seem to be especially nefarious—they are prime suspects in the transmission of Yellow Vine disease, a devastating plant virus.
Understanding their life cycle can be a big help in gaining the upper hand. The pests overwinter in the adult stage under mulch and other debris. So one tactic is to remove all the mulch in your garden about a month after you shut things down, burn or hot-compost it and replace it with a cover crop or a nice fresh mulch of shredded leaves, which should be in abundance at that time of year. Or hold off on the new mulch, place boards on the ground near where infested plants were growing, check them every morning for adults looking for a place to spend the winter and destroy them. (The adults; not the boards.)
And carefully mark where attacked plants were growing. We'll explain why in a minute.
The following season, start squash bug-prone plants a week or two earlier than usual or buy the next biggest size than you usually get at the garden center. If you DO start your own plants, make sure they stay close to their artificial lights and are well fed. (If you're not going to keep your starts under lights, don't bother starting them; weak, spindly, light-starved plants don't stand a chance against these pests.) The goal here is to set big, healthy, actively-growing plants out into the garden.
And be sure not to plant in the same spots as squash grew the previous year! This is why you marked the location of last year's problems; you don't want to place your plants where overwintering adults may already be lurking.
Remove any protective winter mulch and don't replace it, as mulch harbors the pests. Instead spread an inch of rich, finished compost on top of the soil to keep weeds down. It will also feed the plants perfectly. Reapply monthly or as needed.
And yes Rachel, protect those young plants with spun polyester row covers! Numerous studies have shown this to be the single most effective squash bug tactic. Make sure those covers are tight to the ground and check them frequently. You'll have to remove the covers when the first female flowers open, but that's fine; by now, you're off to a great start. (If you just plain despise these pests, you can always leave the covers on and hand-pollinate the plants.)
As soon as you remove your row covers, place boards loosely on the soil alongside your plants. The adults will hide under these boards at night, much like slugs. Unfortunately, as Oklahoma State University entomology Professor Dr. Scott Fargo explained in an ORGANIC GARDENING magazine back when I was Editor in '95, this doesn't work as well in really warm climes or at the peak of summer, as the adults hide under the boards to stay warm. But it works great wherever and whenever nights are a little cool.
Go out early in the morning and scrape any squash bugs (and/or slugs) off the bottoms of the boards into a bucket with some soapy water in the bottom. Do NOT be an environmental criminal and use kerosene or gasoline to drown insect pests; it is NOT necessary and there is no way to dispose of that toxic waste safely and legally.
When nights are warm, dust diatomaceous earth (a mined natural product) around the base of your plants. Incredibly sharp on a microscopic level, it will dehydrate and desiccate any squash bugs (and slugs) that try and cross over the white powder.
Hand pick and destroy any adults you see, especially early in the season. You'll greatly minimize problems if you prevent egg-laying by those codgers from last year. Tape a mirror to the bottom of an old hoe and use it to examine the undersides of the plants' leaves every morning. Destroy any shiny eggs you see; egg colors range from yellowish-brown and bronze to brick red. Any eggs you miss will hatch into nymphs, the wingless, immature stage of the squash bug. They start out a pale green, darken as they get older and look a little like smaller, doughy versions of the adults. Hand-pick or vacuum up these evil children. Or spray them with insecticidal soap, a light summer spray horticultural oil or a spinosad product. Call them vile names and insult their ancestors.
And finally, plant things like alyssum, calendula, daises, dill, fennel and mustard greens near your squash and cucumbers. Their small, pollen-and nectar-rich flowers will attract the Tachnid fly, an especially beneficial beneficial insect that preys on squash bugs.
And finally, finally, my good community gardening friend Don in Charlotte, NC sent me this article from ATTRA that he found very helpful.