Common Squash Pests: Squash Bugs and Squash Vine Borers

In the Garden · Summer Garden · The Beginner's Garden Podcast

Updated August 2020.

It never fails. In early summer, just as we begin harvesting a few fresh squash and zucchini, some of the most common and menacing insects threaten our crops.

Squash bugs, the most common, can take over visibly and quickly. Squash vine borers, though unseen mostly, work behind the scenes, and most people don’t realize they’ve got a problem until it’s too late.

In today’s episode of the Beginner’s Garden Podcast, I talk about the two most common pests plaguing our squash, zucchini, and pumpkin plants.

Click below to listen:

How to Detect the Squash Bugs

Squash bugs are little bugs, about 3/4 of an inch long, that are related to the stink bug family. They are typically grayish-brown and their backs look like a shield. This is one of the best ways to identify them. Chances are if you’ve had a squash or zucchini plant, you’ve probably already seen these.

You will also be able to detect squash bugs by the clusters of eggs they lay on the underside of leaves:

squash bug eggs

As they hatch, these bugs become squash bug nymphs, which are extremely destructive to your plant:

squash bug nymphs

Squash bugs destroy the plant by sucking the juices (or life) out of the leaves. Later in the season, you can even find these sucking juice out of the actual fruit. Typically, squash bugs are usually found at the base of the plant.

How to Detect the Squash Vine Borer

The adult squash vine borer moth lays her eggs on the base of the squash or zucchini plant. Where you’ll find the squash bug eggs in clusters, the vine borer differs in that it’s usually only one egg. This makes it super hard to detect. I’ve even confused these with specks of dirt.

Squash Vine Borer Moth:

Squash Vine Borer Egg:

Check your squash and zucchini plants; this little thing will kill them. The copper-colored egg will hatch into a squash vine borer, which will eat your plant from the inside out. Unless you’re looking, you won’t know it until it’s too late. If you find an egg, scrape it off and dispose of it. Keep checking throughout the season.

After the squash vine borer hatches it will (as the name implies) bore into the stem and eat the plant from the inside out. They will continue to munch until the plant dies. What makes this super hard to detect is that the plant will look fine because the destruction is happening on the inside.

The first sign of the squash vine borer is typically that your plant has wilted overnight and looks to be in need of water. This means that the vine borer has eaten enough and has left your plant to die.

Another sign of the squash vine borer is sawdust-like frass at the base of the plant. Once you see this for the first time, it’s easy to identify and know what to look for from that point on. But what do you do once you discover the borer has already invaded your plant? Time to do some surgery! Keep reading for a demonstration of this process.

Identification is the Best Prevention

Both of these issues, the squash bug and the squash vine borer are something you will want to look for daily. The longer you can keep these handled and your plant healthy, the better harvest you will have.

The Best Ways to Combat Squash Bugs Before They Take Over

If you have a lot of mulch surrounding your squash, which I do recommend for the garden, you may find yourself with a lot of squash bugs. They burrow in mulch and overwinter. Some even recommend leaving mulch out of your squash bed to help cut back on the squash bugs.

My preferred method of helping combat squash bugs is to carry a bucket of soapy water (a gallon of water to a teaspoon of dish soap) with me to the garden. I usually wear garden gloves and pick them off, and throw them in the soapy water.

This may feel monotonous and not worth your time, but think of each bug in the water as a squash bug that didn’t get to lay eggs on your plant. Make sure you get as many adult bugs as you can, especially as early in the season as possible.

Even more important than catching the adult squash bugs is to remove their eggs. They love to lay their eggs in the “V’ part of the leaves where the veins are.

Next, you need to locate any eggs and scrape them off with your fingernail. Alternatively, you can take a piece of duct tape, press the duct tape to the eggs and pull them off that way. Some people crush them, but I don’t recommend this as they are hard to crush and can damage your leaves.

Squash bugs like to harbor underneath debris. Take a piece of wood or even a cardboard box piece and lay it near the stem of the squash plant. In the mornings, come back and turn it over and you’ll find there will be many that you can then easily remove.

Five Ways to Prevent Squash Vine Borer Infestations

The best way to combat the squash vine borer is to avoid an infestation in the first place. Here are five ways to prevent an infestation, though in my experience, none of these is fail-safe.

Cover your crops with floating row covers until they start flowering. Of course, when they flower, you need to remove these so the bees can pollinate them (unless you plan to hand-pollinate). In my experience, you’ll still have a moth laying eggs, but the plant will be well established and you can still have a hearty harvest before the plant succumbs.

Handpick off the eggs. This can feel like a futile effort, especially if one egg remains because it will, indeed, kill your plant.

Keep your plant healthy. A healthy plant that starts off strong, will provide a bountiful harvest even if it eventually succumbs to the squash vine borer.

Wrap the bottom stems with aluminum foil or gauze. This is said to prevent the vine borer from laying eggs. I have tried this and it didn’t work as well for me. My plant was growing so fast that it was hard to keep up with the wrapping, but I know others who have used this technique with success.

Plant icicle radish plants around your squash. Perhaps there is a natural repellent in this radish plant. I’ve tested this a few years with moderate success. It seems the borer eventually gets to the plant but the harvest has lasted longer.

Vary Your Planting Times. As demonstrated by the video below, the most consistent way I’ve found to prevent squash vine borers is to plant at times where the borer moth isn’t active. For me, this is late summer and even early spring if weather allows.

VIDEO: THE BEST WAY TO PREVENT SQUASH BUGS AND SQUASH VINE BORERS

Two Ways to Remove the Borer Without [hopefully] Killing the Plant

If you have identified the sawdust looking waste at the base of your plant, you must remove the borer to keep your plant alive for as long as possible.

Take a sharp knife, slit the stem at the point where you see the waste and cut upwards. In my experience, the borer is eating towards the leaves of the plant and not downwards. Pry open that stem until you can locate the white grub looking worm with a black head. Take tweezers or even your fingernail and pull it out.

Extracting squash vine borer grub

If you notice heavy sawdust waste, you may even have two or three of the borers. They must all be removed. If you slit a little further and you’ve gotten to stem that is hard and hollow, that means they’ve not eaten past that and it’s safe to say you can stop looking.

From this point, you need to cover and bury the stem with damp soil. Hopefully, the plant will produce new roots and be able to recover. In my experience, this doesn’t always work. If the plant is healthy and there were few borers, there’s a strong chance of recovery.

If your plant is small, stunted, or had multiple borers that decimated quite a bit of your plant, chances are it won’t likely recover. Here’s a video of the surgery process:

VIDEO: SQUASH VINE BORER – HOW TO DETECT IT & HOW TO GET RID OF IT

Now, if you’re like me and the thought of doing “surgery” on your plant, infested by a little disgusting looking worm, is just not something you’re up to, you can try injecting the plant with bacterial thuringiensis (BT).

BT is something I will use in my garden for worms and grubs and for the most part doesn’t have a detrimental effect on the rest of the garden. Take the concentrate, mix it to the correct dosage and inject it into the stem of the plant where the borer is getting ready to eat.

Using Succession Planting for a Longer Harvest

Succession planting my second and third planting has helped me tremendously. I have planted my second planting where my peas were and my third planting where I pulled up potatoes.

Planting where potatoes have been is so beneficial because the soil has already been aerated and loosened.

Shifting Mindset for a Better Harvest and Less Frustration

Overall, for me and my garden, it has helped tremendously to plan for the pests. I plan for the squash bugs and borers and I plan on how to deal with them. I also plan on my plants to die from these, but planning ahead of time has shifted my garden into a more proactive approach.

The best way I do this is to plant three plantings of squash and zucchini each season. I start in early spring, the second at the beginning of summer, and the last planting in late summer. This helps shift my mindset in knowing that if an early planting succumbs to the bugs or borers, the whole season isn’t a bust.

Hopefully, once you adopt this new mindset, your garden experience will be even better, even if those stubborn little pests arrive.

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