Penetration of deltamethrin in micro-emulsion formulation after injection in wood

In the Netherlands (and some other European Countries) the remedial treatment of Death watch beetle is stil) a problem. This is because the larvae of this insect pen-etrate the centra) heartwood of mainly large Oak beams. The heartwood is difficult to treat. The preventive treatment of wood boring insects has only recently been per-mitted in the Netherlands. Since 1989 injection of insecticides is recommended by the Dutch Association of Pest Control Companies (in Dutch this is the NVO for short. and member of CEPA). New methods of treatment are expected from the use of water-dilutable insecticides, for example deltamethrin in a micro-emulsion formulation. At this moment, this deltamethrin micro-emulsion is the only water-dilutable insecticide for use on wood with a registration in the Netherlands. TNO has measured the differente in penetration after injection of wooden beams of both deltamethrin in organic solution and deltamethrin in the water-soluble micro-emulsion. This work was part of a government project to study potential reduction in emission of organic volatiles (KWS 2000, see IRG/WP 94-20030). Results on European Oak show a better penetration of deltamethrin from the micro-emulsion formulation compared with the organic solvent formulation. Better results were obtained from high pressure injection than low pressure. Results indicate that most redistribution of deltamethrin occured short)y after injection. From these results, the number of injection points for remedial treatment of Death watch beetle in Oak can be reduced by using deltamethrin in a micro-emulsion.