Major pests and insects which cause diseases in trees

Just like human, trees which have not been taken good care of, are prone to diseases and pest infestations. Good care of trees means that they are timely pruned, appropriately trimmed, well sprayed, and properly checked for any other sign of disease.

The most common pests include,

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These are larvae of various plant chewing insects, wasps, or beetles. They mostly invade weak or young trees and usually feed unnoticed from inside the roots, barks as well as the trunk. They eventually lead to inhibited food and water flow in the plant and if not controlled can lead to eventual death of the tree.

The main signs of attack are saw dust like materials coming from the bark; it may also appear swollen and calloused. The twigs and leaves also start to get discolored and eventually falls off and dies.

The best control mechanism is to ensure that you maintain good health in your trees by fertilizing, mulching as well as the use of proper pruning practices. These beetles lay their eggs on open areas of the bark of a tree.

Balsam woolly Adelgid

These exclusively feed on coniferous plants. They pierce the hemlock and Abies trees respectively. Hemlock is not a commercial tree but is mostly grown for aesthetic purposes or forms food to wild animals. They are shade tolerant trees, and this makes them the right target for the soft-bodied aphid-like insects.

Use of pesticides can control infestations. Invasion is exhibited by the presence of large cotton masses on twigs and bases of hemlock needles. The main issue is that the cotton like covering is resistant to pesticides and you may be required to spray severally.

You can also try using insecticidal soaps as well as horticultural oils. Another natural source being used to eradicate these insects is breeding of Sasajiscymnus Tsuga and Laricobius Nigrinus beetles which exclusively feed on these aphids.

Emerald ash borer

These mostly invade the ash trees. The undeveloped beetle larvae feed on the bark of the tree. An infected tree may start dying from the top downwards. Eventually, the leaves change color and fall prematurely.

Ash trees are the most ones affected by these larvae, and they spread very fast since their eggs hatch only 10-days after being laid. The larvae also take one to two years to develop and in all this time it is still burrowed in the tree.

Pesticides and insecticides should be used when you see the slightest invasion on an ash tree. The greatest challenge in controlling the emerald ash beetles is their mobility as they can migrate from one area to another and return when the chemical effect meant to kill them settles down.

Gypsy moth

It lays eggs on hardwood trees and when the larvae hatch they proceed to feed on the tree. Excess infestation on a tree can cause eventual drying of the tree.


The best sure way to ensure your trees are protected is to exercise proper tree maintenance practices.

  • Ensure proper trimming and pruning
  • Avoid inflicting wounds on trees.
  • Disinfect the soil before planting trees.
  • Spray pesticides and insecticides if you see any signs of aphid’s infections
  • Cut off and burn affected parts of the leaves and branches.