Borers are among the most destructive pests in the garden, hiding under bark, attacking edibles, ornamental plants, flowers, shrubs and trees. Boring into the plant leaves and stems, or roots. They destroy water and sap-conducting tissues within the plants.
Borers can be found in many insect groups and usually will develop into either beetles or moths.
Squash Vine Borer (Melittia cucurbitae)
The Squash Vine Borer is a diurnal (active during the day) species of Sesiid moth, native to North America but is found mostly east of the Rocky Mountains. The moth is often mistaken for a bee or wasp because of the way it moves and the bright orange hindleg scales.
The adult is about 1/2-inch long with an orange abdomen with black dots. The first pair of wings is metallic green while the back pair of wings is clear. The back wings are folded at rest and cannot be seen clearly.
The adult moth emerges from a cocoon in the ground and lays its eggs on the stems near the base of the plant in late spring or early summer. The eggs are flat , brown, and about 1/25-inch long.
In about a week, fat, white caterpillars with brown heads that are about one inch long, hatch out and tunnel into the stems of plants to feed. They cause sudden yellowing and wilting of all or part of a squash vine, eventually killing the plant.
The caterpillars feed for about four to six weeks, then exit the stems and burrow into the soil to pupate until the next summer.
To find the caterpillars that are causing damage cut open the wilted stem lengthwise and you will find a sawdust-like frass (droppings) and usually one or more caterpillars.
The squash vine borers prefers squash but will sometimes feast on other vine crops including:
- Winter squash
- Summer squash
The deep south usually gets two generation per year, while the north will get only one generation per year.
You should start checking your plants the last week of June. You can detect these borers by the buzzing noise they make when they fly, or you can fill a yellow container with water. The adults are attracted to yellow and will fly to the container and fall into the water becoming trapped.
Controlling Squash Vine Borer
- Clean and dispose of any plants killed by squash vine borers.
- Use floating row covers over your plants when they start to vine, or when you see a squash vine borer adult. Keep them covered for about two weeks. Uncover so bees will be able to pollenate plants. Don’t use row cover if cucurbits were planted in the same area the previous year. This is because the squash vine borers overwinters in the soil near their host plants and could be trapped under the row covers.
- Crop rotation helps to minimize the borers. You can accomplish this by planting in a different area each year or alternating seasons when growing cucurbits.
- Pesticides such as carbaryl, permethrin, bifenthrin, and esfenvalerate can be used, treating every 7-10 days. Always follow label directions attached to the container you are using. Also, before using the pesticide, be sure you can treat the fruit or vegetable with the pesticide and determine how long it is before you can consume the crop.
Peach Tree Borer (Synanthedon exitiosa)
The Peach Tree Borer is a species of moth in the family Sesiidae, and are native to North America.
The adult female peach tree borer is a metallic blue-black moth with an orange band around its’ abdomen. It has opaque forewings and clear hindwings. The male is smaller and has yellow stripes.
The adults emerge in early summer, the female begins to lay as many as 400 eggs on the trunk of the tree near the soil or in the soil against the tree. The eggs take 10 days to hatch.
The larvae are white to a light tan or brown color and are usually about one inch or more. Despite their size, they are seldom seen as they bore into the tree beneath the bark, entering the cambium layer and making tunnels filled with frass (droppings) and destroying the trees vascular system.
It’s in the larvae or caterpillar stage they do the most damage to trees by boring into the bark at or near ground level. The first indications are small piles of sawdust around the base of the tree. Sometimes a gummy sap oozes from the holes.
The peach tree borer will also infest the trees listed below:
- Flowering Cherry
Young trees are the most vulnerable.
You will find peach tree borers mainly in California but can occur wherever peaches grow.
Controlling Peach Tree Borers
- Borers are most vulnerable at the surface before they bore into the tree so clear any eggs found around the surface or just under the soil against the tree. Use a sharp object and poke any holes in the tree where larvae may be to crush the eggs. Also clear away soil from around the tree and if you find any eggs in the soil crush them as well, taking care to not harm the tree.
- Take care of trees with proper water so they stay healthy and strong. This will help deter infestations.
- Use pheromone traps to capture the adults.
- Use neem oil in the highest recommended concentrations around the crown of the tree and about 6-12 inches up the trunk. Saturate both the bark and the soil.
- Citrus extract sprays will repel the adults and discourage egg laying. Spray the tree crown and trunk just ahead of the moth hatching.
- BT. (Bacillus thuringiensis), a naturally occurring soil bacteria, will disrupt larvae and kill them. Spray BT. directly into borer holes after clearing as much of the frass as possible.
- Surround WP, a powder made of kaolin clay. Coat the base of the tree, the trunk up to 12 inches, and exposed roots with this paste.
- Spray the pesticide spinosad on the tree trunk and into the borer holes. Pesticides can kill beneficial insects and bees so you should use pesticides as a last resort.
- Apply beneficial nematodes in the spring and fall. They attack the eggs, larvae, and pupae stages. Also the nematodes keep working throughout the season.
- Beneficial insects such as the parasitic wasp can help control by parasitizing the visible eggs and just hatched larvae before they move into the tree.
- Attracting birds to your garden, such as woodpeckers can reduce numbers of borers by eating the larvae on and the under bark.
European Corn Borer (Ostrinia nubilalis)
The European Corn Borer, also known as the European Corn Worm, or European high-flyer is a moth of the family Crambidae and can be found throughout the Northern and Eastern sections of the United States, as far west as Montana and as far south as northern Arkansas.
These borers overwinter in the larval stage, pupate and emerge as adults in early to late spring.
The adult female moths deposit clusters of about 15 to 20 creamy white eggs on the undersides of leaves. The oval, flattened, egg darkens to orangish tan color with age.
The pinkish-gray or light brown larvae has a black head, yellowish brown thoracic plate and a body marked with round dark spots on each body segment. They feed on the leaves and tassels of corn plants then, as they mature, they burrow into the stalk and ears of corn leaving behind holes filled with a sawdust-like frass (droppings). A sign of their presence is a small “shot hole” in the leaves.
The European corn borer will also feed on other plants including:
- Lima Beans
- Grain corn
- Several weeds
There can be one to four generations per year depending on the climate and region you live in.
Controlling European Corn Borer
- Beneficial insects and bugs such as Ladybugs or green Lacewings.
- Attracting birds such as the woodpecker and the yellow shafted flicker have been known to eliminate 20% to 30% of overwintering larvae.
- Capture the adults with a black-light trap or a Pheromone-baited water trap, which seems to be the most effective in attracting the moths.
- Insecticides can be applied to plants usually when the tassels begin to form up until the corn silks are dry.
- Clear away any debris from site and till the area in the spring and late fall.
- BT. (Bacillus thuringiensis) can be effective on the European Corn Borer.
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With the tips and information from above you should be able to spot, control, and destroy any borers you find in your yard. To see several images of different species of borers check them out here!