The willow borer is considered a pest not only in the forest but also in home gardens because its caterpillars attack weak trees and cause them to die. However, in this article you will learn how you can recognize and combat willow borer caterpillars!
What do the willow borers and their caterpillars look like?
The adult willow borer is a large, grayish moth with a wingspan of 7 to 8 cm. The caterpillar is 9-10 cm long, pink to brownish-red and has a light abdomen. The head is black and has strong cheeks. It secretes a strong smelling substance (leather or wine body odor) from glands near the mouth.
The moths feed on nectar and do no harm. The caterpillars, on the other hand, feed on living wood from many different deciduous trees (not just willows). By opening the wood to oxygen, the caterpillars create a habitat for fungi that can significantly worsen the damage.
The willow borer's life cycle lasts at least two years, depending on conditions. The adult moths fly and mate in July and August; then the females lay their eggs on the bark of weakened deciduous trees. The young caterpillars gnaw into the wood and create tunnels that protrude slightly upwards directly under the bark. The next spring they gnaw their way into the wood and create finger-thick tunnels all the way to the heartwood. They overwinter there and pupate the following spring.
How can you recognize the caterpillars of the pest?
Willow borer caterpillars attack older and already diseased trees, to which they can pose a danger. How can you identify the damage caused by willow borer caterpillars? Their holes are irregular in shape and usually run along the tree trunk. The tunnels dug can be up to one meter long and up to two centimeters in diameter. The holes are often infected with fungal growth, which further weakens the tree. If the infestation is severe, there is a risk that the entire tree will die. Reddish colored dust and excrement are often found at the base of the infected tree.
- Notice: The willow borer feeds on nectar and does no damage. On the other hand, the caterpillars feed on live wood in many different types of deciduous trees. In addition to willows, they also use poplars, birches, black alders and apple and pear trees as a source of food. By opening the wood to oxygen, the caterpillars create an environment for fungi to grow, which can greatly increase the damage.
The activity of the willow borer caterpillars can be recognized by the typical vinegar smell that surrounds the tree. If the infestation is severe, you can hear the crackling noises of the caterpillars as they feed from inside the tree. Sometimes the willow borer caterpillars can also be seen moving along the bark. The willow borer caterpillars are not poisonous.
- Notice: If a strong, healthy tree has been attacked by the willow borer, you can usually be reassured about what happens next. As a rule, they have a strong self-regulation system that ensures that the willow borers lose interest in drilling wood.
Fighting willow borer caterpillars – How can you do it?
There is no chemical pesticide against the willow borer available on the market yet and should not be used due to the consequences for the environment. However, the following control methods are climate and environmentally friendly, but still very effective, especially in combination.
Control willow borer caterpillars by pruning: The first and most important step in the event of a willow borer infestation is to cut off the affected parts of the plant. If the infestation is severe, a chainsaw can make it easier to remove the bark. Infected branches should be cut off with pruning shears. If they have already dried up, the cut should be made directly into the healthy part. Cut plant parts should be burned or disposed of in a lockable container to prevent pests from returning to the garden.
Fight willow borer caterpillars with Quassia soap broth:
- Soak 250 grams of quassia shavings in two liters of water for 12 hours.
- After soaking, bring the solution to a boil and simmer for about 30 minutes.
- Then strain out the shavings and let the broth stand.
- Dilute the decoction with ten times the amount of water
- Heat 500 grams of soft soap in a liter of water and let it dissolve.
- Add the dissolved soft soap to the diluted broth.
- Pour the Quassia soap broth into a spray bottle and spray the affected tree generously with it.
Frequency of application: Every other day for ten to 14 days
- Notice: Useful insects that are valuable to nature can also be killed when they come into contact with the broth. Quassia should therefore only be used with caution and care!
Skewer with wire: Some hobby gardeners appreciate this control measure, for others it is too unsafe. For this method, a long wire is inserted into the feeding tunnels to impale the willow borer caterpillars there.
How can you control other pests in the garden without chemicals – tips, strategies and recipes you can use immediatelycan be found here!
