Combating Squash Bug – Strategies and Frustrations

When I first started gardening here in SE Washington, I was super excited to grow all kinds of winter squash. We moved from 7,000 ft gardening in Colorado, where winter squash had been VERY hard to grow. I couldn’t wait to grow delicata and spaghetti squash and Cinderella pumpkins and butternut. That first year, my squash did pretty well. And I saw this insect on one of my pie pumpkins and didn’t think much of it. I’m a live and let live girl, and so if I don’t see obvious damage, I don’t tend to destroy all insects.

The following year, my Cucurbita maxima species of squash, which included the Cinderella and the Lumina pumpkins, were dead within the first month of planting. And I started to notice a LOT of adult true bugs (order Hemiptera, characterized by piercing sucking mouth parts and an “X” shaped shield on their backs where the wings fold together – hemiptera means “half wing”) on my squash. And then I noticed eggs on the back of the leaves. And then I noticed the young gray nymphs of the insect in clusters on the plant. A bit of internet sleuthing and Oh My God! I have an infestation of squash bugs!

Being the good organic gardener that I am, I got online and looked at Peaceful Valley Organic’s Pest Control Solution Chart for things to control squash bugs. And the pest wasn’t listed. So I put it into their search. Nothing. So I started to look for more information from University Extension Offices, including “organic control” in my search. Nothing. Seriously? NOTHING? Yup. I eventually found this line: “There is little evidence that organic-approved insecticides are very effective against squash bugs”. They are even difficult to control with conventional insecticides like Seven!

Experts suggest cultural controls (i.e. fall clean up so they don’t have a place to overwinter, and hand picking adults off of the plants.) HAND PICKING. So I did that for one season. Squash bugs hide (and lay eggs) on the backside of leaves. If the plants are wet, they will come to the top of the leaves to dry off and you can pick them off, throwing them into a bucket of soapy water to drown. They are in the “stink bug” order, and can give off noxious odors, so best to wear gloves while performing this task.

I had a 100 ft row of squash, sprawling 5-6 ft across. I sprayed down the row with water and hand picked adult squash bugs off of the wet leaves every other day for MONTHS. (My first squash bugs show up on the 4th of July every year like clockwork). I missed a few of course, and eventually started seeing lots of the creepy spider legged nymphs, but I did get a harvest (but no C. maxima species. They seem to be wildly susceptible to the insect).

During my battle, I also kept an eye out for eggs. Using a reverse role of duct tape, I removed eggs whenever I found them. (They have a tough outer shell and are very difficult to just squish.) Just as an experiment, I put one of these roles of tape, covered in eggs, in a mason jar on my kitchen windowsill, just to see what would happen (it takes a couple of weeks for freshly laid eggs to hatch). They hatched. Not kidding. By the end of the season, I realized this method was an unsustainable solution (seriously, MONTHS of hand picking) and just stopped growing winter squash in 2014.

When the question of squash bugs comes up, gardening groups often suggest the following: neem oil (every small organic gardener’s answer to everything, sigh), homemade insecticidal soap (ie dish soap) mixed with various other things like peppermint oil, diatomaceous earth (DE) and companion planting with things like marigolds and basil. Some more expert online sources indicate that pyrethrin (an organic spray) has some effectiveness on the nymph stages (but this spray will also kill bees if it hits them). Sprays, in general, are more effective on the nymphs than the adults, but my the time you have lots of nymphs, the battle is already lost. Literally NONE of this is effective on any kind of large scale. Squash grow quickly. The number and length of vines and leaves is substantial. Managing to spray individual adults that are sheltering under a half decomposed leaf touching the ground…that’s a big ask. It’s VERY hard to spray effectively, due the sheer volume of foliage.

In experimental studies, row covers have proven to be the most effective deterrent, but because squash vines sprawl and cover so much ground, it can be hard to implement effectively unless you’re growing bush varieties. This publication from ATTRA (which stands for Appropriate Technology Transfer for Rural Areas, also known as the National Sustainable Agriculture Information Service, managed by the National Center for Appropriate Technology – NCAT) gives a good overview of current research.

Last year, after taking 6 years off from growing winter squash (I did keep growing a few summer squash every year – and hand pick off the squash bugs long enough to get a crop) I decided that maybe a long enough time had passed that the population was reduced and maybe I could pull off a crop. Here’s the strategies I employed.

I planted marigolds and Thai basil between the plants (unfortunately, they got buried in squash by mid season and mostly died from lack of sunlight). I put down a LARGE handful of DE at the base of each plant, where the squash bugs seem to congregate and do the most damage early in the season. I mixed up a SPRAY of DE (4 tbsp DE to 1 gallon of water) to coat the leaves of the plant front and back, and sprayed once a week, paying special attention to any new foliage. You need to keep the solution shaken as you’re spraying or the DE will settle out to the bottom. But the spray leaves a fine coating on the entire plant, offering some protection. (I always imagine a tiny version of the broken glass embedded on top of cement walls in Mexico to deter birds and would be robbers. Insert evil laugh here). Studies have shown that Surround, a commercially available kaolin clay foliar spray, has a similar effect. Note that DE is ineffective when wet, so it needs to be reapplied after a rain or overhead irrigation. My garden is on drip and we rarely get rain in the summertime, so for me, it mostly stayed put.

And I mostly won the battle, until about early September. At that point, I was running out of gas on the weekly spraying, and some of the plants were starting to struggle, but I had enough fruit set that I was able to get a good harvest. I did not plant winter squash this year in my main garden, as I’m sure by the end of the season the numbers had built up again enough that this years crop would have been hard hit.

A few thoughts and observations for getting a harvest:

• Squash bugs can carry plant viruses. Sometimes the plant will die from a viral infection even when the actual bug damage is still minimal. I’ve lost 4 out of my 9 summer squash this year and another is on its way out due to this issue. So its not just the bug damage, its the disease issues.
• Butternut squash, in my experience, seems to be less susceptible to squash bug damage. While the crop takes forever to mature, and so gets LOTS of bug exposure, the plants don’t seem to die from the bug pressure (and can root along the vine as well). Butternut is Cucurbita moschata, so this may hold true for this group in general.
• Most summer and a lot of winter squash (acorn, delicata, lots of pumpkin varieties, spaghetti) are Cucurbita pepo. Most C. pepo varieties seems to be pretty tasty to squash bugs. Planting shorter season varieties might be a good strategy for getting a harvest before the plants succumb.
• Trap crops are another strategy. Plant a type of squash you know the squash bugs will love (I hear yellow summer squash or crook neck works), and then focus your removal/spray efforts on THAT plant (that you may never plan to actually eat) to decrease numbers elsewhere in your garden.
• Moving the location of your squash bed every year can be helpful. It will take longer for the flying adult squash bugs to find your plot if they didn’t overwinter in the area. But a few feet is probably not going to be enough. I’d suggest a whole other section of your property (like in the front yard rather than the back yard).
• Growing bush varieties of squash and utilizing row covers is probably your best bet for getting a good crop, except that bees can’t pollinate the fruit if you have a row cover over your plants. Maybe leave it on until the female flowers start to bloom and then remove it, so the plants get a head start?
• Hand picking/removing adults and eggs can be somewhat effective if you only have a few plants. But you need to be diligent. A week off and the battle may be lost.
• It’s often suggested to just replant your squash every few weeks to ensure a harvest (the idea being that the bugs are only around for part of the season). But I understand squash bugs can have two complete life cycles in the southern United States. And I still see adult bugs in late September/early October, so I’m unclear how this would actually be effective unless they stop mating/laying eggs late in the season. In my area, the soil simply isn’t warm enough to plant squash earlier than mid May. The plants will survive, but won’t be actively growing, so nothing is gained.
• I really don’t think the marigolds or Thai basil did anything (though they were pretty). Squash bugs can fly. I imagine they aren’t deterred much by a bit of smelly herb, and it’s difficult to not have the companion plants get buried by the squash vines by mid July. You’ll see nasturtiums also suggested as a companion plant, but they are often done growing/blooming by the heat of July when you most need their affect. Even assuming all three of these work, I imagine their area of influence is likely within a few inches of the actual plant.
• I DO think that the handful of DE at the base of the plant and the DE spray coating the leaves helped quite a bit. Remember, DE isn’t effective and will wash away into the soil when wet. So overhead irrigation is incompatible with this strategy.
• One year I grew 8 ball zucchini. These squash are round in shape (the number of times I answered the question, “What do you do with them” at farmers market kept me from growing them again). The squash bugs did not like this variety (confirmed by a fellow farmer who grew the same variety) and virtually left it alone while everything else was being inundated. I find that the Costata Romanesca zucchini variety, which I’ve been growing for several years now, also seems to be less preferred by squash bugs (it’s a HUGE plant and needs a LOT of room).

• I imagine that, if you have the room and resources, growing vertically could be beneficial. Squash bugs thrive on hiding under leaves near the ground so as not to be eaten by predator birds or picked off by humans. Growing vertically would mean fewer places to hide and easier picking.
• Keeping old dying leaves trimmed off might also be beneficial to reduce hiding places.
• Letting chickens into your garden area at the end of the season should help decrease the overwintering adult population. Cleaning up all leaves, chunks of wood, pieces of cardboard or other ground cloth, rocks or pavers etc. can also help, to remove overwintering locations, but for me, is unrealistic.
• Even with cultural controls, remember, squash bugs can fly. No squash had been grown around me the first year I gardened here, yet they found me.
• Tachinid flies parasitize squash bugs. You can plant varieties of buckwheat around your garden to attract them. However, squash bugs may continue to feed and lay eggs for a while after they have been parasitized. Therefore, studies have shown that even when parasitism levels were as high as 80 percent, they did not prevent measurable economic damage.
• I have heard that squash bugs can sometimes also attack melons and cucumbers (which are cousins to the Cucurbita genus (Cuminus). I have not personally had any issues with them on my melons or cucumbers and often have them growing nearby.
• I am SO SO grateful that I’m not also dealing with Squash Vine Borer. They are not found in the western United States.

© Miles Away Farm 2022, where we are soooo frustrated that there aren’t better organic solutions to squash bugs, but hope springs eternal every spring! Want more content? Sign up for a monthly newsletter to your email inbox HERE.