Pine weevil attack

Pine weevils gnaw forest plants to death

The pine weevil is a serious pest in the forest. The insect principally attacks young and susceptible coniferous plants. It does this by gnawing away the thin bark. Without its protective bark, the plant dies.

The pine weevil has to be stopped. Otherwise, more than 80 per cent of the plants can die within three years following the planting of new forest. It is therefore important to protect the plants from the pine weevil’s jaws. This is particularly critical during the first two years after planting. Significant amounts of bark can be gnawed away in each hectare of forest land. On average, each pine weevil eats 23 mm2 of bark a day in the summer.

The pine weevil is a costly pest for the forestry industry. Replanting forest is expensive. And damaged forest grows poorly. It has been estimated that the pine weevil causes damage worth hundreds of millions of Swedish kronor to the forestry industry. Every year.

Pine weevils increasing in number

The pine weevil is a beetle that is approximately one centimetre in length. From a biological perspective, it belongs to the weevil family and the Hylobius genus. There are many different types of pine weevil. When we talk about the pine weevil in Sweden, we are usually referring to the most common species, Hylobius abietis, or the large pine weevil.

The pine weevil has an extended head, called a snout. It is this that gives the insect its Swedish name. The large jaws are located at the end of the snout. Using these, the weevil can gnaw the thin bark on conifers to obtain food.

Pine weevils swarm in early summer. They fly in their thousands, seeking out freshly felled forest with their excellent sense of smell. Here they find the roots of dead conifers, which serve as food for the weevils’ larvae. The felled area is like a large underground nursery. The following year, if they do not choose to overwinter for a year, the adult pine weevils crawl up out of the ground and start to eat. Their favourite food is young forest plants that have been planted in the clearing. As an adult, the pine weevil lives for 1–2 years, although it can survive for up to four years.

The pine weevil can be found right across Sweden, although it is most common in the provinces of Götaland and Svealand. The number of pine weevils is increasing in the north due to the warmer climate.