FIELD AND LABORATORY TRIALS ON THE USE OF HOST TREE MONOTERPENES AGAINST PINE PROCESSIONARY CATERPILLARS

Secondary plant compounds have recently become the focus of interest in developing environmentally sustainable methods for arthropod control, also against Thaumetopoea pityocampa (Denis & Schiffermüller), the most common and harmful lepidopteran in Mediterranean pine forests. Various monoterpenes in pine needles play a primary role in the tree’s defense mechanisms and may be employed in control experiments against the Pine Processionary Caterpillar. Two monoterpenes, limonene and -pinene were used in field and laboratory tests in 2002 and 2003 to evaluate their effect on the survival and development of II and III instar larvae. The substances were applied in two ways: in an aqueous emulsion sprayed on pine needles used by the larvae to feed (both in the field and in the laboratory); or left to evaporate inside the rearing cages, in the laboratory tests. When used as fumigants, both caused virtually total larval mortality, while the mortality of larvae that fed on treated needles was very low, except in the case of the field experiment. Sprayed β-pinene and limonene showed a negative effect on the development of the II and III instar larvae, as a result of measuring larval weight.