BIOLOGICAL-CONTROL OF POTATO BEETLE, LEPTINOTARSA-DECEMLINEATA SAY (COL, CHRYSOMELIDAE) IN NORTHERN LATIUM, CENTRAL ITALY

The results are reported of a biological control experiment carried out on Leptinotarsa decemlineata Say, in potato fields in the Northern Latium region in 1990. In this region the growing of Solanum tuberosum L. has a great economic importance. The biological material used for the experiment was Hymenoptera, Eulophidae Edovum puttleri Grissell and the microbiological insecticide Bacillus thuringiensis subsp. tenebrionis. The results evidenced the following: E. puttleri is not able to limit the number of eggs of L. decemlineata to acceptable levels (about 11% parasitized eggs). The combined use of a.m. parasitoid and B. thuringiensis subsp. tenebrionis produced very significant results both in terms of mortality rate of young larvae (1st + 2nd instar) caused by the bacterium - equal to 79.4 and 99.5 respectively for one and two treatments - and in terms of yield, which was observed to be 35 % higher than in the non-treated control. In the light of the present experiments, the utilization of B. thuringiensis subsp. tenebrionis is recommended on larger areas and in different environments.