Cucumbers, zucchini, pumpkins are all staples of a summer garden, and for good reason. They are typically very productive and easy to grow even for a beginner gardener. Unfortunately, depending on where you live, pests tend to get in the way. The pests and pest transmitted diseases that cucurbits (squash family plants) are susceptible to, can turn something nearly impossible to screw up into something you can’t grow to save your life. Cucurbits are susceptible to wilt from cucumber beetles, collapse from stem borer damage, and squash bugs. In this article we are going to take a look at one of our own personal nemeses squash bugs.
Let’s start by learning how to recognize squash bugs.
The adult bugs are large flat bugs that are dark grey or brownish in color. You might see yellowish stripes or spots around the perimeter of their abdomen. The portion of their abdomen sticking out behind their wings is typically darker, looking almost black. The younger nymphs are much smaller, and start out sort of grayish green with black legs. They get progressively darker as they get larger. Nymphs are often seen in large clusters on the plants. Beware, they like to hide on the bottoms of leaves.
Squash bug eggs will be seen as fairly large, randomly shaped, reddish brown dot clusters. The will mainly be located on the backs of the leaves, often between the veins near where the petiole attaches to the leaf. Occasionally you will see them located on the tops of leaves. The eggs are very distinct and easy to find.
Depending on where you live there will be between 1 and 3 generations produced per year. Northern climates only have 1 generation whereas climates further south can have up to 3. Thus, early control is important, otherwise the 2nd and 3rd generations will get larger and larger creating a massive population available to overwinter.
Squash bugs harm your plants by their feeding activities.
While they do not transmit wilt like cucumber beetles, they suck sap and cause severe damage where they have fed. This damage can look similar to wilt. You will often see leaves that are stippled yellow with dying brown spots in areas that squash bugs have fed. The amount of damage will be directly proportional to the quantity of bugs feeding. Thus, it is extremely important to keep their numbers down. A few squash bugs are unlikely to cause your plant any real harm, but many will kill it. And as you might imagine, left to their own devices they multiply rapidly.
Moving on to the squash bug lifecycle, we find that they overwinter as adults. They hide in sheltered places like under plant debris, and near foundations. In the spring these adults emerge and fly to squash plants where they mate and lay eggs. They lay eggs from emergence through mid-summer. You are likely to see everything from just hatched nymphs to adults all at the same time. In the fall any nymphs that haven’t matured die with the first frost, and the adults take shelter for the winter.
Now that we know how to identify squash bugs, and what their lifecycle looks like, how do we keep them from killing our plants?
We just mentioned that the adult bugs overwinter in sheltered places like under plant debris. Thus, one of the first things you should do is clean out your garden. Remove all squash plant debris and destroy it. Also remove weeds in the fall to reduce overwintering sites for the adults. Do your best to kill as many adults as you can so that they can’t overwinter to infest your garden in the spring.
It can also help to remove plant debris during the growing season to reduce the number of places the bugs can hide. You should keep your plants well-watered and fertilized. Strong, sturdy, rapidly growing plants will be better able to cope with some feeding damage than young or unhealthy plants.
Next, you should start scouting your plants in early summer.
Start watching for adult bugs and eggs on your plants. When exactly squash bugs typically appear will depend on where you live. Your local extension or university publications should be able to help you determine exactly when they emerge in your area. Keep in mind that squash bugs like to hide on the bottoms of leaves, and that they also lay their eggs there. It is important to check the bottoms of leaves or you’re likely to miss seeing them until they have built up large numbers.
Any bugs or eggs found should destroyed by squishing them or placing them in soapy water. Once you have found adult squash bugs on your plants, you will want to check them every few days and continue to destroy any adults, nymphs, or eggs that you see. If there is one, there are likely to be others arriving within the next few days and weeks.
Because squash bugs are good at hiding, something that might help you is to set traps for them. Simply lay out boards or a similar object near the plants for them to hide under. Many of the squash bugs will shelter under the boards overnight allowing you to easily collect and destroy them in the morning.
What about using row covers like we do for various other pests?
Unfortunately, while we love row covers for controlling pests in our garden this is one pest where they are minimally effective. Nonetheless, they can still be helpful under a couple different circumstances. Firstly, if you are planting a crop when squash bugs are active, you should cover them with a row cover until the plants are large and flowering. Small seedlings are the most susceptible to dying from squash bugs due to their small size. Keeping the plants protected until they are large can help skew things in your favor.
Secondly, if you have had major problems with squash bugs killing your cucurbit crops several years in a row, you may wish to invest in some parthenocarpic varieties. These are varieties developed for things like growing in greenhouses. They are able to set and mature fruit without pollination. Parthenocarpic varieties can be grown under a row cover for the entire season.
Unfortunately, the drawback to using parthenocarpic seed is that variety choices are very limited. As far as we know, there are only parthenocarpic cucumber and zucchini varieties available. This means that if you wish to grow winter squash, melons or pumpkins you’d still have to remove row covers on those plants.
Pesticides are not usually suggested for home gardeners.
Squash bugs can be difficult for home gardeners to control using pesticides, and pesticides are not recommended. Pesticides are most effective on nymphs, and it can be difficult to get good enough coverage to control them as they are very good at hiding on the undersides of leaves. Plus, you risk harming your pollinators as squash bugs are active while the cucurbit plants are flowering.
We hope this helps you to control this extremely frustrating pest. If you don’t manage to do so this year, don’t give up. Change tactics and try again. If all else fails, avoid growing squash plants for a year or two to allow your garden a pest reset period. Then try again focusing on early pest control.
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