Pest Identification

Identifying different life stages

Large pine weevil eggs are oval (about 1 mm by 0.5 mm) and pearly white in colour.

Larvae are legless, curved and are cream with a light brown head capsule. Larvae measure up to 15 mm when fully mature.

Pupae have appendages, are colourless and measure between 8 and 10 mm in length.

Mature adult large pine weevil are black while younger adults are purple-brown, and each have patches of yellow/golden scales on the wing cases and thorax. The antennae, near to the end of the weevils snout, are elbowed. Adults can measure up to 15 mm.

Life Cycle

The eggs of the large pine weevil are mainly laid in late spring, within the bark of roots or stumps of dying or dead conifers. The practice of clear felling provide large pine weevils with an abundance of breeding sites, however in a standing forest breeding sites are limited by the lower availability of recently dead wood. Eggs are laid inside small notches that are made in the dead wood by the adult weevils just below the soil surface, and each female lays between one and five eggs. When larvae hatch they move lower in the soil profile and there undergo four larval moults. Larval development can take between one and five years depending on the climate however, given the relatively mild temperatures in much of Europe, 75% of adult emergence occurs within one year of egg laying (Bejer-Peterson et al, 1962).

Adults can live for up to four years, but hibernate underground when temperatures are lower than 8˚C, typically emerging in spring when temperatures exceed this value. Adults may live for up to four years and feeding damage may occur at anytime during the year when temperatures are warm enough for insect activity (typically March to November); however damage incidence tends to increase in the spring when adults emerge and before eggs are laid as many adults can emerge from each stump, which can result in very high population densities and therefore high levels of feeding damage, and in the late summer before adult hibernation.

Insect stage that causes damage

Adult weevils inflict feeding damage to the living bark of conifers and other woody plants. The stem of young trees, from the root collar up, may be attacked by adult pine weevils which remove patches of bark and phloem tissue, and this can girdle stems and cause plant death. The bark and needles of young shoots on more mature trees may also be attacked by adult large pine weevil.

When and where to identify

Adult large pine weevil population size on a site can be estimated using billet trapping when adults are active, which occurs when the temperature is over 8˚C (typically March to November in the UK & Ireland).

References

Bejere-Petersen B, Juutinen P, Kangas E, Bakke A, Butovitsch V, Eidmann H, Heqvist KJ & Lekander B (1962) Studies on Hylobius abietis L. I. Development and life cycles in the Nordic countries. Acta Entomologica Fennica 17:1-107.

Geographical location

The large pine weevil is widely distributed, and is considered a pest species in many European countries, whilst also occurring in Russia, China and Japan.

Damage

Timings

The stem of young trees, from the root collar up, may be attacked by adult pine weevils which remove patches of bark and phloem tissue, and this can girdle stems and cause plant death. The bark and needles of young shoots on more mature trees may also be attacked by adult large pine weevil. Feeding damage can occur at any time during the year when temperatures are high enough for insect activity (typically early March to November), however higher levels of damage may be seen in spring, before egg laying, and in the late summer before hibernation.

What and Where

Adult large pine weevil population size on a site can be estimated using billet trapping when adults are active (typically March to November in the UK & Ireland), and this can then be used to predict the loss of transplants that can be expected after replanting. Without control treatments, however, large pine weevil can commonly induce transplant losses of 90% or more.

Susceptible plant species

Adult large pine weevils feed on a wide variety of woody and herbaceous plants; however breeding sites are largely limited to the stumps and roots of felled coniferous trees. Subsequently, in areas that have been clear felled and restocked, the young trees are vulnerable to heavy feeding damage as adults emerge. Since multiple adults can emerge from single stumps, pest pressure can be severe.

Crops Affected by Red Palm Weevil

Adult large pine weevils feed on a wide variety of woody and herbaceous plants, including:

• Pines (e.g. Scots pine, lodgepole pine, maritime pine, eastern white pine)
• Spruces (e.g. Norway spruce, Sitka spruce)
• Larches (e.g. common larch)
• Douglas-fir
• Common silver birch
• Common beech
• Hazel
• Oak

The range of tree species affected by the large pine weevil includes almost all coniferous and some deciduous species, however Scots pine and Norway spruce are the pests favored food plants.

Nemasys^®C

Nemasys^®C is based on the beneficial nematodes Steinernema carpocapsae and provides control of the large pine weevil in plantation forestry.

Nemasys^®C contains nematodes in their vigorously infective juvenile stage. Once applied these nematodes seek out and control large pine weevil larvae. It is also able to control shore fly, codling moth and oriental fruit moth, as well as the caterpillars of a wide range of other Lepidopteran pests.

Nemasys^®C applied as a stump drench is effective in killing large pine weevil larvae, and by reducing the population of adults that subsequently emerge, can significantly reduce the feeding damage inflicted on young trees used in restocking.