Homegrown column July 25, 2009

I have squash bugs! How do I get rid of them? I have two zucchini that quit growing and turned yellow. I saw two bugs walking down the stem of the yellow squash plant today. Please help.
— Darlene

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 their 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 made up of fossilized plankton-like organisms called diatoms that form a sharp, hard shell. To us,
Diatomaceous Earth feels smooth, but to an insect it’s like crawling through a barrel of glass shards and barbed wire.

It abrades the waxy “skin” on the bug and causes lots of tiny cuts and punctures. The result is that the insect desiccates and dies.

Just sprinkle Diatomaceous Earth 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.

The only problem is that 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 bug, but it has become difficult to find the past several years.

Neem is an extract from a bean from a tree native to India where it’s been used for years and years.

It’s not precisely a poison that kills the insect but rather acts either as a repellent, an “anti-feedant” (causes the insect to stop feeding) or a growth regulator preventing the normal growth of the insect, leading to its death.

Honestly, I’ve been less than impressed with Neem’s effectiveness.

Another nontoxic method of control you sometimes see mentioned is row covers.

This is a light spun-bonded fabric that’s placed over 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. It’s permeable, so air and water will penetrate it. Most will transmit about 90 percent of the light, so your plants will grow just fine.

Though this works fine for many different insect problems, I don’t think in this case that its a good solution.

Squash need bees and flies to pollinize the flowers and the row cover prevents that.

You can also cut down squash bugs’ numbers by placing flat boards or shingles on the ground near your squash plants.

The bugs tend to congregate there at night and the boards can be thrown away (with the bugs) early the next morning (or just squish em!).

One last 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.

The insect over winters as an adult, hiding in nooks and crannies and dead leaves and debris is a favorite spot for it.

There are several synthetic insecticides that do a good job on squash bugs. Again, start early since a small, immature bug is easier to kill than a full grown adult.

Also, since squash bugs tend to spend most of their time around the base of the stems of the plant and on the undersides of the leaves, applying any insecticide should concentrate on those areas. Permethrin and bifenthrin both do a really good job.

You might see some recommendations to use Sevin, but I don’t think it works all that well on them.

Since squash plants depend on bees and flies for pollinization, avoid spraying when these little helpers are present. Only spray when they’re not active, primarily late in the day.

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


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