Squash vine borer on Plants

Symptoms

The first thing you are likely to notice is a plant that wilts. The wilting comes from stems that are blocked internally, which stops water flowing to the rest of the plant. The blockage sits inside the stems, not on their surface.

A second sign shows on the outside of the stems. You may see greenish or orange material that looks like sawdust. This sawdust-like material is called frass, and damage from boring insects may appear this way.

Wilting and sawdust-like frass on the stems are the two symptoms recorded for this problem. Larvae feeding inside the stems block the water flow that the plant needs. If you notice either sign, check the base of the plant, where the eggs are laid.

Causes

The damage has two causes: adult moths laying eggs and larvae feeding in the stems. The adult moth lays eggs at the base of host plants in early summer. Females lay these eggs at the base of susceptible plants.

The larvae feed inside the stems. Their feeding blocks water flow to the rest of the plant and causes the plant to wilt. That is why the wilting you see is a sign of damage inside the stem.

The base of the plant is where the eggs are laid, so that is the place to begin your checks. Monitoring in June and July is important, and early summer is when the moth lays its eggs.

Diagnosis

Wilting is one symptom of this problem, but it is not the only one to look for. The second symptom is greenish or orange sawdust-like frass on the stems. If you see frass on the stems along with the wilting, boring insects are a likely cause.

Start at the base of the plant, since that is where the females lay their eggs. Look along the stems for the greenish or orange frass. Frass on the stems points to larvae feeding inside them.

Timing is another clue, because the adult moth lays eggs in early summer. Monitoring in June and July is important, so those are the months to inspect your plants closely.

A plant that wilts with no frass on its stems does not match both symptoms recorded here. In that case, the wilting alone is not enough to name this problem. The cause described here is blocked water flow inside the stems, caused by larvae. That cause sits within the stem itself, so the stem is where the evidence will be.

Treatments

Every method listed for this problem is either cultural or organic.

Monitor the garden in June and July, since catching the moths early is important for control. Consider a second planting of vegetables in early July, if your growing season is long enough. That timing falls after the moths have laid their eggs. A second planting depends on your growing season being long enough.

Remove and destroy crops affected by the insect. Do not put them in the compost pile. Affected crops should be destroyed rather than composted. Keep the garden weeded to limit places for insects to hide. Practice crop rotation as well. Crop rotation is the last cultural step in the list.

The organic method is a moth trap made from a yellow-colored container. Set it out in mid-June, filled with water and a drop of dish soap. The container needs only a drop of dish soap in the water. The moths are attracted to the yellow, fly in, and become trapped in the water. Mid-June falls inside the June and July monitoring window.

The trap is for mid-June, and the second planting is for early July. Early July is the time for a second planting of vegetables. No chemical treatment is documented for this page.

Prevention

The adult moth lays eggs at the base of host plants in early summer, and monitoring in June and July is important. Catching the moths early is important for control. Eggs are laid at the base of susceptible plants, so the base is the part of the garden to watch.

A garden kept weeded gives insects fewer places to hide. Practice crop rotation along with weeding. If your growing season is long enough, a second planting of vegetables in early July comes after the moths have laid their eggs.

Remove and destroy crops the insect has affected, and keep them out of the compost pile. A yellow container of soapy water set out in mid-June traps moths that fly in.

Plants most often affected

No plant page in this build records this problem yet.