Squash Vine Borer
Insect Identification
Images
The squash vine borer (SVB) is a pest that causes substantial damage to plants such as zucchini and squash. A plant infested with the SVB will die without action from the gardener. However, hope is not lost as methods of control and prevention are available to those who know what to look for.
Adult Squash Vine Borer
Squash Vine Borer Larva
Squash Vine Borer Damage
Damage
The SVB is a unique pest in that it lives most of its life as a larva embedded in the vine of plants. Initially, the only indication of the SVB is a small hole at the base of your plant. As the insect matures and consumes more of the plant, you will begin noticing a a sawdust-like frass being pushed out of the stem of the plant near the soil line. Eventually the plant will begin wilting as if it is being starved of water. By this time it is too late and the plant must be removed and destroyed.
Affected Plants
The squash vine borer (SVB) is known to be a significant pest of squash (including zucchini) and pumpkin plants but can also attack the following plants
- Cucurbits
- Cucumbers
- Summer squash
- Pumpkins
- Watermelon
Management
The list below includes methods to prevent, control, and remove the SVB from susceptible plants.
Delayed Planting
- One of the most effective ways to protect your plants against the squash vine borer is to keep squash out of your garden until later into the season. In this area, most people recommend planting squash in mid May to early June. However, that is when the pest is most active. We would recommend delaying planting until the beginning of July.
- Even with this delay, there are plenty of days left in the year for the plant to mature and produce fruit. In fact, it is likely you will get much more fruit long-term since the plant will most likely live longer. In our trials, delayed planting of winter squash resulted in no reduction in quantity or size of total fruit.
Preventative Barrier
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Vine Wrap Method
- Wait until the vine of your plant is strong enough to be handled. Depending on the plant, this may be just before transplanting or soon after.
- Lightly wrap stretchy medical gauze over the vine, starting from where the roots begin (often below the soil line) and continuing up to the first set of leaves. This will allow air to move in between the plant and the outer protective layer
- Bury the stem so that half of the stem covered with gauze is in the soil and half is out. The idea is to provide a physical barrier for the larvae to enter the stem.
- Wait until the vine of your plant is strong enough to be handled. Depending on the plant, this may be just before transplanting or soon after.
Step 1
Before transplanting, loosely wrap the stem of the zucchini plant with stretchy medical gauze. Start from the soil line and continue up to the first set of leaves. This will allow airflow next the stem while expanding as the plant grows.
Step 2
Plant your zucchini slightly deep so that the bottom of the foil is covered by soil. Periodically check the gauze to ensure it remains in place. If you notice the plant’s stem being cut off, reapply the gauze, making sure to keep the bottom of the gauze covered by soil.
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Row Cover
- After transplanting, cover your plant with row cover and anchor it down in the corners. This will act as a barrier keeping all insects away from your plant. However, depending on your plant, it may need to be removed to allow for insects to pollinate the flowers. Consult the page of the plant you’re growing for more information.
Insecticide Injection
- Find the hole (or holes) in the stem where the SVB larva has entered.
- Fill a long-needle syringe with Bacillius thuringiensis for caterpillars.
- Inject the BT into the holes in the stem, preferably the holes at the highest point of the stem so that the fluid can flow easier into the plant. The goal is to get the insecticide into the center void in the stem where the SVB larva lives.
- Closely monitor the holes for an increase in the sawdust-like plant material. If you continue to see new damage 3 days later, inject BT into the plant again.
- After 3 days of no new damage, wrap the stem with gauze to protect the plant from the open holes in the stem.
Step 1
Fill the syringe with Bacillius thuringiensis for caterpillars. Flexible plastic needles can make maneuvering the tip inside of the stem a bit easier.
Step 2
Inject the BT into the stem until you see it coming out of other holes in the stem.
Physical removal
- Regularly check your plants for signs of holes and sawdust-like frass. When you see either, carefully slice into the plant with a razor blade along the length of the vine where you see the frass. Make a small incision at first and enlarge as needed
- Carefully pull the slit open and look for the SVB larva. Use tweezers to remove the insect and destroy it. There may be multiple larvae in the vine at different locations, so multiple incisions may be necessary.
- Wrap the plant with medical gauze to protect the incision from the elements. Not wrapping the plant will likely result in the plants death.
- Contact us for help in removing the SVB
NOTE: Because the SVB lives within the plant’s stem, insecticidal sprays are ineffective against the larva. DO NOT SPRAY THE PLANT WITH ANYTHING. IT WILL NOT WORK!
