Larvae are often gregarious, and sometimes there can be major outbreaks, thus these wasps can be major forest pests at times.

Larvae feed on lichens as well as herbaceous and woody plants , and some species are forest pests.

International regulations and wood packaging standards exist to control the spread of forest pests and timber diseases.

It has also been introduced to New Zealand, Tasmania, and Brazil to help control horntail forest pests.

It is considered a forest pest, because its larvae feed on the leaves of young Dryobalanops lanceolata.

In their native habitat, all Amylostereum species have a minor importance as forest pests.

The diet of the Hoopoe includes many species considered to be pests by humans; for example the pupae of the processionary moth, a damaging forest pest.

It is a very important forest pest in Taiwan, with outbreaks occurring every five to 10 years.

Introduced forest pests are also a huge problem.

They also eat spruce budworm, a serious forest pest, during outbreaks.