Homegrown: Squash bugs

Each year I plant summer squash and the bugs get at least one or two plants in spite of my spraying and dusting. Please give me some ideas how to control them better.

— Dick

What I’ve found to be the most effective approach to controlling squash bugs is to use a variety of control measures and above all, start on them early — don’t wait until the plants are overrun with them. A full-grown squash bug is difficult to control so starting early is important in getting on top of this pest. The smaller the insect, the easier it is to control.

The first thing to do is to monitor your plants once or twice a week, looking for the eggs on the underside of the leaves. They’re pretty easy to spot; they’re football-shaped and reddish brown to orange in color. Squashing the eggs keeps the next generation from joining in the fight you already have on your hands.

This alone isn’t enough to control the problem; it just makes the job easier. You’ll have to apply some insecticides to kill the existing insects. If you’re looking for an organic material, try Diatomaceous Earth, Sabadilla or Neem. Diatomaceous Earth is a naturally occurring mineral that’s made up of fossilized plankton-like organisms called diatoms that form a sharp, hard shell. To an insect it’s like crawling through a barrel of glass shards and barbed wire. It abrades the waxy “skin” on the bug as well as causing lots of tiny cuts and punctures. The result is that the insect desiccates and dies. Just sprinkle it out at the base of the plant and on the underside of the leaves and be sure to wear a dust mask as the dust can irritate some people. When it gets wet, it loses its effectiveness and will need to be reapplied.

Sabadilla is a botanical insecticide that’s derived from the seeds of a South American lily. It works extremely well on squash bugs, but it has become difficult to find the past several years. Neem has been used for years and years. It acts either as a repellent, an “anti-feedant” (causes the insect to stop feeding), or as a growth regulator that prevents the normal growth of the insect, leading to its death. Honestly, I’ve been less than impressed with Neem’s effectiveness.

You might see some recommendations to use row covers which are a lightly spun-bonded fabric that’s placed over your plants to physically keep bugs away from them. It needs to be in contact with the ground on all sides of the plant or simply cover the entire garden with it. Though this works fine for a lot of different insect problems, I don’t think in this case that it’s a good solution. Squash need bees and flies to pollinize the flowers and the row cover prevents them from doing that.

Placing flat boards or shingles on the ground near your squash plants can also work. The bugs tend to congregate there at night and the boards can be thrown away early the next morning. Another organic method is to practice what’s called good sanitation. That is, this fall when the garden is done, be sure to remove all the old debris from the garden; this is where the insect overwinters as an adult.

There are several synthetic insecticides such as Permethrin and Bifenthrin that do a good job on squash bugs. Concentrate on the base of the stems of the plant and on the undersides of the leaves. You might see some recommendations to use Sevin, but I don’t think it works all that well on them.

Above all, avoid spraying when bees and flies are present. Only spray when they’re not active, primarily late in the day.

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Dennis Hill is the nursery manager at Bookcliff Gardens, http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 Road 26, Grand Junction 81506; or e-mail .(JavaScript must be enabled to view this email address).


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