SUSCEPTIBILITY OF 2 STRAINS OF AMBLYSEIUS-ANDERSONI CHANT (ACARI, PHYTOSEIIDAE) TO DITHIOCARBAMATE FUNGICIDES

The effect of five fungicides on adult female mortality, fecundity, eg g hatch and on larval mortality was examined in the laboratory using a fungicide-susceptible and a fungicide-resistant strain of the predace ous phytoseiid mite, Amblyseius andersoni Chant. The combined effect o f each fungicide was compared using a coefficient of toxicity computed using the above four toxicity factors. The susceptible and resistant strains were most affected by the bidithiocarbommate fungicides mancoz eb, metiram and propineb. Ziram and dithianon had little effect on the S strain and ziram had little effect on the R strain. The toxicity of dithianon was not tested using the R strain. A resistance factor (LC( 50) R strain : LC(50) S strain) of 6.13 for mancozeb was estimated for the R strain. Mancozeb resistance was a heritable trait and was prima rily associated with the adult female.