Squash vine borers burrow into the stem of a healthy squash plant and destroy it from the inside. The adult is an orange and black moth that looks a lot like a wasp. If you notice the presence of adult moths, you can take immediate action to find the eggs before they develop into very destructive larvae.
Adult caterpillars overwinter in the soil and emerge in early summer (late June to early July) to lay eggs at the base of squash plants. As insects, they are mostly active at dusk and you can sometimes see them resting on the upper leaves of your plants.
After the tiny eggs hatch, the new larvae burrow into the stem of your plant and begin feeding. As the insects suck the sap and chew the stem, they cut off the flow of water to the rest of the plant and it will soon die.
How to Identify Squash Vine Borer Damage?
Damage caused by squash borers is very specific. Once you see it, you’ll always know what you’re looking at. At first, your squash will look very wilted even though the soil is still moist and the plant looked perfectly healthy the previous day.
This wilting occurs because water no longer moves through the stem and reaches the leaves. But the most specific indication of infection is the orange-yellow “frass” found at the base of the stem. It looks a bit like sticky sawdust and is the remains of stems chewed up by bull borer larvae.
Unfortunately, once visual signs of infestation appear, there is little you can do to save the plant. It can be heartbreaking, but take comfort in the fact that there are things you can do to protect future crops and also learn how to avoid squash vine borers altogether.
Squash Vine Borer Prevention Tips
In this article, We are going to discuss about 8 prevention tips.
Plant your squash not later than mid-July
The best and foolproof way to prevent this pesky pest is to wait and plant your summer and winter squash plants after mid-July. Zucchini and summer squash are fast growers, often bearing fruit 50 days after sowing.
So if you have a short growing season, I promise there’s plenty of time for a bumper crop. Timing can be a little tough for winter squash in some seasons, but if the delay saves the plant and the harvest, it’s definitely worth it. If you’re in a warm climate like Texas, plant your first crop in mid-March. This will ensure that you have time to harvest before the adult caterpillars emerge in May.
By waiting to plant (or planting early in warmer climates), emerging adult moths have nowhere convenient to lay their eggs, and they will naturally migrate to other areas. Not only does this save your current crop, but it can help save next year. Since no eggs were laid in your garden bed, no larvae overwintered in the soil.
Succession planting
If you don’t want to wait until late in the season to harvest your zucchini or summer squash, planting in succession can help. Often vine borers focus on one plant. My recommendation is to plant a new zucchini or summer squash every 4 weeks. If one plant dies, the next group of plants is ready to move on and produce. This works especially well with fast-growing summer squash varieties, but you can also do this with the cucurbit family (all gourds – squash, melons, pumpkins, etc.).
Practice crop rotation in your garden
Whether you’re ready for an early harvest of summer or winter squash, there are certainly things you can do to proactively protect your plants. The first and easiest way is to practice good crop rotation. This means, you won’t be planting your squash plants in an area where other cucurbits were previously planted. Just as with fungal disease prevention, this will ensure that your plants are different from winter squash borers in a different area of the garden.
Ideally, you’ll plant your new crop far enough away from previous years to ensure emerging pests can’t easily find their way to your young plants. If you’re planting in containers, it may help to completely change the dirt if you’ve had previous problems with squash borers.
Companion planting
The most common companion plants that will keep them away are nasturtiums and mint, as the scent of each plant keeps these pesky pests away from your garden. Not only this, but these two plants can keep other unwanted pests away from other vegetables in the garden.
Another popular vegetable companion is radish. They are a root vegetable, and will not compete for the nutrients your squash needs. Radishes also have a pungent smell that, like mint and nasturtium, is known to repel insects.
Use row cover
Using a row cover can be a surefire way to keep squash borers away from your zucchini plants (unless they overwinter in the soil under the cover).
Row covers are lightweight fabrics that provide light, air and moisture while keeping insects out. The downside of using row covers with squash plants is that it keeps out all insects, including pollinators. So, be forewarned, that if you choose to add row cover to your squash plants, you’re committing to hand-pollinating all the female flowers that bloom. This is 100% doable, but it’s always a good idea to know what you’re getting into.
Resistant varieties of plants
If you’re really struggling with squash vine borers in your area, you can focus on planting varieties that are naturally resistant to them. Not only will you avoid damaging your plants, but you’ll also have the opportunity to do something new. There are many interesting varieties of heirloom squash to grow and enjoy in your garden this year.
Introduce the parasitic wasp
In my experience, natural predators are the best defense against pests. Parasitic wasps are natural predators of many pests, including squash vine borers. If you are able to introduce them to your garden, they can help keep vine borer populations down.
Parasitic wasps are insects that are one of the best friends in your garden. They are probably best known for their love of aphids, but they also like to eat SVB eggs. Remember that one mature grape vine can lay up to 150 eggs.
So if you have a large infestation, only a few parasites can do the trick. But, if you have a healthy ecosystem that naturally attracts a host of predatory insects, you’ll be one step ahead of the game!
Perform surgery on your plant
If all else fails and you see a clear entry hole on the stem of your plant with some weeds around it, you can try a little surgery on the plant. This will only work if you catch the problem before your plant wilts. If this has happened, simply pull up the affected plant and plant new seeds. But, if you catch it in time, all you need is a sharp knife, a pair of tweezers, and a strong stomach. I actually find the process interesting, but it might not be everyone’s cup of tea.
Make a small incision at the top of the stem (not across it or you’ll cut the stem) near where the entry hole is located. Squash stems are hollow so you only need to cut enough to break the outer part of the stem.
