Many of us love to grow and eat squash, but that endeavor does not come without challenges. Two primary challenges to successfully growing squash are the squash bug and the squash vine borer.

I’ve had problems with the squash vine borer in my home garden, but at the Master Gardener Seed to Supper Farm, our issues are mostly with squash bugs. So, let’s talk about how we can try to control this pest in an environmentally friendly way.

Squash Bugs

One thing to know is that if you have grown squash and have had a problem with squash bugs, you probably will again. This is because squash bugs overwinter underground or in the plant debris left in your garden. As temperatures warm up in the spring, they will be exiting their underground homes to find a mate and have babies. This emergence begins in late April and early May, so right about now.

Defending against this insect will require diligence on your part, meaning that as soon as you get your squash plants in the ground, you’re going to need to keep an eye out for squash bugs.

In small numbers, squash bugs are pretty good at hiding so the first sign of a squash bug problem will probably occur when you notice squash bug eggs on your plants. Squash bugs tend to lay their eggs on the underside of the leaves, meaning you will need to turn over leaves to look for eggs. However, last year at our farm, they were laying eggs everywhere - under leaves, on top of leaves, and on stems. Their eggs are oval, kind of shiny, and copper in color. When you find squash bug eggs on a leaf, you can cut off that leaf and throw it away of just squeeze the eggs between your fingers. Gloves would be recommended for this squishing activity.

Their eggs hatch in about a week, revealing small, greenish nymphs. Squash bugs go through several instars (growth stages) on their way to becoming an adult. The younger ones are more vulnerable to pesticide applications than the older ones. In large infestations, you will probably see young and old squash bugs alongside one another. It takes a village, I guess. In Oklahoma, we tend to get two generations of squash bugs.

The adult and nymphal squash bugs feed with what we call piercing-sucking mouth parts meaning that they stick this pointy mouth part into the plant to suck out the life-giving juice. This activity damages the plant making it unable to move water and nutrients throughout the plant. Ultimately, this causes the plant to die.

Control of squash bugs is challenging to say the least for those of us who lean more toward organic methodologies. Spinosad can be effective on younger squash bugs but in our experience at the farm, to keep from losing all our squash plants we had to move to a synthetic pesticide called permethrin.

One of the reasons many of us use organic pesticides is that not only are they safer to use but they have a shorter pre-harvest interval. The pre-harvest interval is the number of days between when you can use a pesticide product and safely harvest your vegetables. Some synthetics have a pre-harvest interval of three weeks, but permethrin has a pre-harvest interval of one day which tells me that it’s a pretty safe product to use. Because of this we used permethrin on our squash plants last year and were pleased with the results.

A non-pesticide strategy would include laying a 2x4 on the ground overnight by your plants and then checking underneath in the morning. Squash bugs tend to congregate in places like this overnight so when you remove the board, you might just have all your problem insect right there for you to dispose of as you choose.

Squash Vine Borers

The adult squash vine borer is a moth with black and orange coloring. Female squash vine borers begin to lay their eggs about the time squash plants begin to flower and each female can lay up to 200 eggs. After hatching in about 7 to 10 days, they immediately tunnel inside the plant and begin to eat. They eat for about 30 days but this eating will likely destroy your squash plant before the 30 days are over.

Destroying squash vine borer eggs is your first line of defense, but this plan does come with challenges because the squash vine borer tends to lay its eggs on the stem, right about soil level. This is a challenging place to keep an eye on. After the larvae mature, they exit the plant and dig down into the soil to pupate and overwinter.

We typically discover the presence of squash vine borers when we see damage to the stems of our squash plants. And by damage, I mean gaping holes and piles of frass (poop). Their frass looks kind of like soggy sawdust. Once you see it, you’ll know.

There are several strategies you can try once you detect the presence of a squash vine borer in your plant. First of all you can slice open the stem and remove the larvae. After completing this procedure, you can bury that portion of the stem underground and hope it survives. This has never worked for me.

Bacillus thuringiensis is an organic pesticide that kills caterpillars and is a good choice to fight against squash vine borers if you catch them early enough. To use this pesticide, you’ll need to inject the pesticide into the stem of the plant, so the larvae are sure to dine on it. Again, in my experience, once you see the damage, your plant is toast, but it doesn’t hurt to try.

Since both of these insects overwinter in the soil, it’s a good idea to till the soil early in the season to expose these overwintering insects to the elements. Crop rotation can also help keep the squash insects from building up in one area.

Squash vine borers and squash bugs have contributed to me not trying to grow squash at home anymore and instead I lean more into cucumbers and butternut squash in the fall. In fall gardens, we tend to have a lesser pest load which is a good thing in my book. See you in the garden.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org