Insect pests of trees

In the last 50 years insect pests of conifers have declined but insect pests of deciduous trees have increased. This is the result of the change in the composition of Dutch forest.

Trends

From the top 10 of insect plagues in the Netherlands it can be seen that insect pests of conifers have declined but insect pests of deciduous trees have increased. This is related to the increase in deciduous trees in Dutch forests and the dwindling area of young coniferous stands. The insect species responsible for infestations between 1950 and 1970 are nearly all species that live on softwood, like the common pine sawfly. Post 1980, the pest species live mainly on deciduous trees (for example, the two-spotted oak borer).

Since1946, 350 insect species have been recorded as pests in the Netherlands. The top 10 gives only the most common. In 2000 these were (starting with number 1): the horse-chestnut leaf miner, the oak procession moth, horse-chestnut scale, goat moth, Dutch elm beetle, woolly beech aphid, spindle ermine moth, green oak tortrix moth, bird-cherry ermine moth and two-spotted oak borer.

Pest insects often cause economic damage to crops and trees. Insect infestations in forests are a natural phenomenon that is aggravated by the planting of monocultures. But given that forest management is now aimed at producing more mixed forest and thus at reducing the monocultures, it is expected that the plagues will become less severe.