Detecting and controlling pests on trees: effective measures to protect your trees

Tree pests can really be a nightmare. The key to effective pest control and protecting the tree is early detection. Since a tree weakened by pests is also more susceptible to fungal or bacterial diseases, the problem often does not occur alone.

A possible pest infestation situation – what to do?

If you notice something wrong with your tree, the first thing you should do is determine if it is a pest infestation and if so, what type (you'll find out about some of these pests below). You can do this yourself, but if you're unsure, it's best to call a professional. 

It is also necessary to report pests such as the Japanese beetle (Popillia japonica), the Asian longhorn beetle (Anoplophora glabripennis) and the San Jose scale insect (Comstockaspis perniciosa). To do this, contact the appropriate plant protection service in your community or city administration.

Caution is better than indulgence

Even if there is currently no suspicion of a pest infestation, it is still a good idea to seek advice from a specialist. You can get information about the pests that could attack your trees. You can discuss preventative measures for trees in need of protection and get tips on proper tree care to promote vitality.
 

Climate change and rising temperatures promote pest spread 

As temperatures rise, the risk of pest infestation also increases. Insects swarm, breed, and lay eggs shortly thereafter. Damage to trees is also caused by the hungry larvae, not just the adult beetles or moths. Check your trees regularly from spring to early fall to identify infestations as early as possible.

Important: Infestations are not always caused by pests, other insects are sometimes involved too. But aphids, ants or mites do not usually threaten the vitality of an established tree. Even though bugs are annoying, they usually cannot harm a tree.

Wood-destroying insects, which breed directly in the wood and destroy the bark or even the wood core, pose the greatest danger.

The most important and dangerous tree pests in Germany:

Yponomeutidae (webworm)

Time of infestation: from June

A silvery-gray web in which they live covers the bare branches, twigs and trunks of the caterpillars of the webworm species, which completely eat the leaves of infested trees. Although infestations of webworms do occur, most trees usually recover.

Oak processionary moth (Thaumetopoea processionea L.)

Time of infestation: from May 

This moth has caterpillars that spread nests on the tree and eat entire branches bare. The majority of oak trees are able to recover from defoliation, but they only lose vitality with repeated infestations. Since the caterpillars develop fine poisonous hairs in the third larval stage that can cause severe allergic reactions in humans, it is important to get rid of them. Control is carried out by a pest expert.

Chestnut leaf miner (Cameraria ohridella)

Time of infestation: from mid-April

The eggs of the chestnut leaf miner lay on the leaves of the white-flowering horse chestnut. The larvae mine the leaves after hatching and ingest the chloroplasts, resulting in white stripes. These turn brown over time. If the infestation is severe, the entire leaf turns brown. In the middle of summer, the chestnut loses its leaves, which limits the possibility of photosynthesis.
 

Asian longhorned beetle (Anoplophora glabripennis)

Time of infestation: from June 

The eggs are laid by the female beetles mainly on the branches. After hatching, the larvae begin to eat wood and create boreholes with a diameter of up to three centimeters. They leave behind borer dust on the bark or at the base of the trunk. The tree withers, turns yellow and eventually dies. Your trees can also be affected by many other species of longhorn beetle.

Jewel beetles (Buprestidae)

Time of infestation: from May 

The beech jewel beetle, the pear jewel beetle and the pine jewel beetle are examples of beetle species that lay their eggs on the bark or in cracks in the bark. The larvae feed on the outer layers of tree tissue and create feeding tunnels. The larvae cause a lot of damage to trees and it is possible that entire tree sections die. Jewel beetles prefer weakened trees and it is often difficult to detect an infestation.

Weevils (Curculionidae)

Time of infestation: from May

Some species of the weevil family, including the beech jumping weevil, the black vine weevil and the bark beetle, often develop well hidden. The damage can occur either underground, in the bark or in the sapwood, depending on the beetle species. The beetles lay their eggs there. The larvae feed on the roots, the bast or destabilize the wood by creating breeding tunnels.

How can I protect the trees from pests? 

Unfortunately, it is not always possible to spot serious tree pests with the naked eye. Experts are required to identify and control some pests. You should consult with your local conservation authority before proposing any control measures.

In general, we recommend controlling pests only in an environmentally friendly manner and preventing infestation if possible.

Preventive measures:

– Protecting the tree bark from cracking: You can use a white paint to prevent cracks in the bark caused by frost. Therefore, the tree is not as susceptible to pest diseases.

– Closing tree wounds: Wound balms specifically for trees are used to treat cuts or injuries on trees and to promote natural healing. 

– Create a habitat for beneficial insects: There are many native wildflowers in a natural garden in which beneficial insects can live. Parasitic wasps, ladybirds, etc. assert themselves as natural enemies and keep a pest population in check.

– Attaching glue rings: Glue rings protect fruit trees, but also deciduous trees such as lime, oak and maple from aphids, ants and winter moths. 

– Pheromone traps: The attractants attract and hold male insects. These simple traps, which are species-specific, reduce the reproduction rate and thus the pest infestation

In conclusion, early detection and control of pests is crucial for the health and longevity of your trees. Regular checks, preventative measures and the use of natural methods will not only help keep pests under control, but also protect the ecosystem. If you are unsure or suspect a serious infestation, it is advisable to seek professional help. This will ensure that your trees remain healthy and vital in the future.