Squash Vine Borer Management Strategies
This insect overwinters as a pupa, typically emerging as adults in mid-to-late June. The black and orange to red moths will lay eggs throughout July and August. The eggs are oviposited individually or in small groups on the stem of the host plant just above the ground surface. The eggs can take up to a week to 10 days to hatch. After hatching, the larvae enter the stem of the host plant, leaving a small hole surrounded by frass – a telltale sign. The larvae will feed while tunneling through the plant stems for about one month. This injury will cause wilting or sudden collapse of the leaves where the feeding occurs. Once the feeding is complete and they are ready to pupate, the larvae will burrow into the soil and spin a cocoon. They will remain in the soil until the following June.
Squash vine borers are challenging to prevent or manage. Once the larvae invade the stem, it is difficult to treat squash vine borers. Check your squash for the presence of adult borers starting the last week of June.
There are two methods for detecting squash vine borer adults. Watch for their activity in the garden. These moths are easily noticed as well as heard (buzzing noise) when they fly.
Use a container (e.g. pan, pail, bowl) colored yellow and filled with water. Squash vine borer adults are attracted to yellow. They will fly to the container and be trapped when they fall into the water. Place traps by late June, checking your traps at least once a day. Promptly pull and destroy any plants killed by squash vine borers.
Once the presence of squash vine borers is confirmed, pick one of the methods to control their population. Plan your planting schedule carefully. Plant vine crops that are usually not attacked by squash vine borers, such as butternut squash, cucumbers, melons and watermelons, as trap crops. Plant a second planting of summer squash in early July. These plants will mature after adult borers have finished laying eggs and will not suffer any damage.
Use a physical barrier by placing floating row covers over your vine crops when they start to vine (or for non-vining varieties, starting late June or early July) or when you first detect squash vine borer adults.Keep the barriers in place for about two weeks after the first adult borer has been seen.Secure the row covers in a way that prevents adults from moving underneath it. Caution: Do not use floating row covers anytime crops are flowering. This prevents bees from pollinating your vegetables.
If your crop is still successfully attacked by borers, you can try to kill the borer inside the vine. Keep in mind that you may not be able to save the plant. As soon as wilting is noticed, use a sharp knife to cut a slit in the affected stem. Slice carefully up the vine until you locate the borer (or borers).
Once you have killed any borers with the tip of the knife, mound moist soil over the cut area and keep this spot well watered. New roots may grow along the cut stem, allowing the plant to survive. Practice rotation to minimize this issue by planting cucurbits in different areas of your garden (if possible) or alternate seasons when you grow cucurbits.
If pesticides are needed, spray or dust the stems at their base.Start treatments when vines begin to run (or the last week of June or early July for non-vining varieties) or when the first adult borers are detected. Repeat in 7-10 days. Two applications help manage most squash vine borer adults. For more thorough coverage, continue treatments at 7-10 day intervals until the end of July. Common names of active ingredients effective against squash vine borers are: carbaryl, permethrin, bifenthrin and esfenvalerate.
Be sure that the fruit/vegetable you wish to treat is listed on the label of the pesticide you intend to use. Also be sure to observe the number of days between pesticide application and when you can harvest your crop.