TOXICITY OF 4 FUNGICIDES TO THE PREDACEOUS MITE TYPHLODROMUS-PYRI (ACARI, PHYTOSEIIDAE)

A population of Typhlodromus pyri Scheuten in Burgundy, France, was te sted over a 4-yr period with 4 different registered fungicides applied at recommended field rates. Toxicities of these fungicides were found to be stable over the 4 yr except for that of dinocap. Dinocap (Karat hane LC, formulation with 73% phenylcrotonates, 5% nitrophenols, and 2 2% solvent, mainly xylene and impurities before 1994) was found to be toxic the Ist yr, became neutral in the field as early as 2nd yr, and showed reduced toxicity (at the normal dose of 525 ppm) over the 4-yr period. This reduction of susceptibility was confirmed in a laboratory resistance test. A selection process for resistance to this normally toxic fungicide seemed to be in progress.