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Squash bugs are invading gardens, plus a bonus tip for your squash

Bob Dluzen
Special to The Detroit News

The bulk of the regular season planting is over, and now we’re in the growing phase and early harvest phase. With the plants growing, more plant pests show up. One highly susceptible plant is squash.

Squash plants are attacked by several pests; the first pests that usually show up are squash bugs.

Squash bugs are showing up about a week earlier than last year. Since insect growth is highly dependent on temperatures, the heat wave we just experienced has caused them to go through their life cycle faster.

These insects can cause serious damage to all members of the squash family (cucurbits) which includes: winter squash such as acorn and butternut; summer squash like zucchini and yellow crookneck; all types of pumpkins; most gourds; cucumbers are included as well.

Their favorite plant this time of the year are the summer squashes. Later as the population increases they will continue to spread to other types mentioned in our list of cucurbits.

I’ve noticed that cucumbers seem to be their last choice.

They do their damage by piercing plant leaves with their mouth parts and sucking out the sap. If enough squash bugs are present, they will stunt growth and can eventually kill the plant, especially if it is young or in the flowering stage.

The damaged area first appears yellow then eventually it turns brown and dries up.

If you only have a few squash plants, a good way to reduce the bug population is to destroy their eggs before they hatch. The small, coppery-colored, 1/16 inch eggs are laid in clusters on the underside of the leaves but often can be found on the upper surface as well.

Some gardeners remove the entire leaf containing the eggs. However, squash bug eggs can be easily scraped off using your thumb nail.

It’s important to check your squash plants every day for new egg clusters.

Killing the female bugs before they have a chance to lay those eggs in the first place is effective however they can be very hard to find.

One trick to finding adult squash bugs is to lay a board or piece of heavy cardboard on the ground near your plants. They will congregate under the board overnight. Then in the morning you’ll find them as you lift the board. This trick works best on bare soil without mulch. It will not work with squash plants growing through plastic mulch since the plastic already provides a hiding place for them.

A female squash bug caught in the act of laying eggs.

Organic insecticidal soap applied to squash leaves will reduce the percentage of viable eggs to a certain degree. The soaps are also effective at killing the newly hatched bugs and slightly grown nymphs.

Organic insecticides such as spinosad are very effective at killing the young nymphs, too. The adults however are very hard to kill using most organic materials which is why it’s critical to take care of the problem early.

The newly hatched squash bugs resemble tiny black spiders crawling around on the leaves. But if you take a closer look, you’ll see they only have six legs, not eight. Later, as they grow, they’ll fill out and look more like insects. It is at these first stages of growth that the bugs are easily killed. So check your plants now.

Here’s a bonus tip: Squash vine borers will be arriving soon. They can cause even more damage than squash bugs. If you are growing a variety that grows as a vine, prepare those plants right now by encouraging rooting along the vine. Covering the vine nodes with garden soil will cause roots to form at that spot. Then, later when the vine borers destroy part of the vine, the parts that have rooted will have a better chance to survive the attack.