Understanding the Black Locust Beetle

The black locust beetle is a fascinating insect that's often misunderstood.

It's a type of longhorned beetle, specifically the Megacyllene robiniae species.

These beetles are known to infest black locust trees, which is how they got their name.

The black locust beetle is native to North America, where it can be found in a wide range of habitats.

It's a relatively small beetle, typically growing to about 1 inch in length.

The black locust beetle's larvae feed on the sapwood of black locust trees, causing damage to the tree's bark.

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Adult black locust beetles are active from late August to October, feeding on goldenrod pollen in the morning hours.

They can be seen searching for egg laying sites on the trunks of black locust trees, often in crevices and around wounds on living trees.

The female beetle deposits her eggs in these crevices, which hatch into larvae that bore into the inner bark and construct small hibernation cells.

Newly hatched larvae spend the winter in these cells, emerging in the spring as the leaf buds begin to swell.

As the larvae grow, they enlarge their tunnels to the exterior, pushing out frass and eventually emerging as adults in the summer.

The adult beetles are about 3/4 inch long and have a distinctive jet black background color with bright yellow bands. They closely resemble the painted hickory borer, but are active in the fall instead of the spring.

Their legs are reddish and antennae are moderately long and black. The third band on the wings is W-shaped, which is a notable characteristic.

Full grown larvae are legless, white, robust, and about 1 inch long. They are quite large and noticeable in their environment.

Locust borer adults have brightly colored yellow markings and are about 19 mm (0.75 inch) long. They also have reddish legs.

Larvae are white and do not have legs.

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Adult beetles can be found feeding on goldenrod pollen early in the day during the late summer and fall. They're particularly active in the morning hours, which is a great time to spot them if you're out and about.

Adult beetles are also found on black locust tree trunks searching for egg laying spots, which are deposited in crevices in the bark and around wounds of living trees. This behavior is a key part of their life cycle.

After hatching, larvae bore deeper into the bark where they hibernate throughout the winter. This is a clever strategy, as it helps them survive the harsh winter months.

As leaf buds swell the following spring, larvae bore deeper into the wood where they continue feeding and maturing. This is a critical time in their development, and they need to be able to adapt to their surroundings.

Maturing larvae enlarge the holes and push out frass (dried insect feces). This is a sign that they're getting close to emerging as adult beetles.

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To control the locust borer, certain sprays can be applied to trunks and larger limbs until wet, with a repeat application in 10 – 14 days.

These sprays kill larvae as they enlarge galleries under the bark. Old black locust trees with dying tops should be removed, as they can serve as a reproductive hot spot for the borer.

Trees should be cut when borers are dormant and peeled or burned to kill locust borer larvae.

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Trees under environmental, drought, or nutritional stress are most likely to be attacked by the beetle.

Low-vigor trees, damaged trees, and trees under environmental, drought, or nutritional stress are most likely to be attacked.

Trees less than 6 inches in diameter are susceptible to attacks, while healthy trees larger than 8 inches in diameter are generally safe.

As young larvae bore into wood, they secrete a substance that stains the wood yellow, which radiates into the tissue and eventually turns the wood brown.

Early-season borer feeding often produces oozing sap and wet spots on the bark, making it a visible sign of the infestation.

Larvae produce coarse frass (sawdust-like excrement) in late summer, which is visible on the bark, and can be a sign of the infestation.

The tree grows faster in areas where the larvae have tunnelled, resulting in knotty swellings and a gnarled look.

Larval tunneling can result in broken and dead limbs, weakened trees, excessive sprout production, and even tree death.

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Chemical control is a viable option for managing the black locust borer, especially during the spring when buds are opening. Certain sprays can be applied to trunks and larger limbs until they're wet, with a repeat application in 10-14 days.

This method effectively kills larvae as they enlarge galleries under the bark. Old black locust trees with dying tops should be removed, as they can serve as a reproductive hot spot for the borer.

After removal, these trees should be cut when borers are dormant and peeled or burned to kill locust borer larvae.

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The black locust beetle is a longhorned beetle, classified by its extremely long antennae. These beetles are often found in black locust firewood.

Locust borers can be found in black locust firewood, and their damage is seen long before any beetle is discovered: small, pencil lead-sized holes in the wood and sawdust so fine it feels like flour or talcum powder.

To avoid accidentally bringing these beetles into your home, store firewood indoors for as short of a period as possible before burning, and don't let it touch the ground.

The locust borer is a type of beetle that's native to eastern North America. It's a relatively small beetle, about 3/4 inch long, with yellow stripes and black body.

The locust borer's host plant is the black locust tree, and it doesn't damage other closely related locust trees. However, it can still cause problems if you're trying to grow black locust trees in your area.

Drought-stressed trees and trees lacking sufficient soil nutrients are more susceptible to locust borer attacks. This means that if your black locust trees are already under stress, they're more likely to be damaged by the locust borer.

Here are some common symptoms of a locust borer infestation:

These symptoms can help you identify if your black locust trees have been infested by the locust borer. If you suspect an infestation, it's a good idea to consult with a professional for guidance on treatment options.

The Locust Borer is a longhorned beetle with extremely long antennae, and its adults are very colorful with a black and yellow striped pattern.

This beetle often inhabits dead and dying locust trees, which is why you're likely to find it in firewood made from black locust.

To avoid bringing these unwanted critters into your home, it's best to store firewood indoors for as short a time as possible before burning, especially if the wood is near an outside wall of the house.

Locust borers can be a problem if the firewood is not handled correctly, so make sure to stack it where the heat of the sun can contribute to moisture loss and don't let it touch the ground.

Newly cut wood usually takes six months to season, or age, to dry out enough for burning, which is a good time to check for any signs of locust borer damage.