Protection of conifer seedlings against Hylobius pine weevils

The objective is to identify a compound or a combination of compounds that acts as an antifeedant or repellent on pine weevils feeding on young conifer seedlings. The protection has to be long lasting, preferably remaining for growing seasons, and the compounds should, of course, not be hazardous to human health or to the environment.

Background. The pine weevils, especially Hylobius abietus, are the most important pest insects in Swedish forestry. Without control efforts up to 80% of spruce and pine seedlings may die because of weevils feeding on the bark. Until now the seedlings have been treated with the chemical insecticide permitrin, but from 2003 this will not be allowed any more. Thus, the forest regeneration can run into big problems, with higher costs as a result, if no efficient and environmentally acceptable plant protection method is developed soon.

Synthetic compounds. A large number of substances, acting as antifeedants, have been identified from various plant-insect systems. Several of these have been tested within the project, both in laboratory and in the field. Some of them have shown very promising effects and the efforts are now concentrated on making the effect lasting longer by using different dispensers, e.g. waxes.

Substances from non-hosts. The pine weevil is able to feed on several plant species, but some are less preferred. In the project we determine if there are certain chemical compounds in these plants that make them less palatable. If such compounds are identified, they could potentially be used for protecting the seedlings.

Applications. Currently field tests are in progress with the most promising substances with different formulations. The experiments are done at Asa experiment station in southern Sweden, where the pine weevil problems are most pronounced, and the results are compared with permitrin-treated and untreated seedlings. The durability of the protective effect is tested in long-term experiments. Patents have been filed for the most promising substance and its dispenser.

Place of research: Chemical ecology, Department of plant sciences, Swedish Univ. of Agricultural Sciences, Alnarp and Asa Experimental forest

Participating scientists: Fredrik Schlyter (project leader), Jan Löfqvist†, Elisabeth Marling, Per Månsson