Contrasting effects of two pesticides on motile arthropods in a citrus orchard canopy

Abstract

Multidimensional Scaling (MDS) was used to assess the effects of two different pesticides on non-target motile foliage-dwelling arthropod communities that could be sampled by a portable suction system in a citrus orchard in the coastal region of New South Wales, Australia. Sprays of nC24 horticultural mineral oil (HMO) and an organophosphorous insecticide (methidathion) were applied at the level of whole blocks in the manner pertinent to successful control of (sessile) scale insects. The MDS model produced ordination figures for several sampling times before and after spray applications that showed that any effect of HMO was undetectable but methidathion was disruptive to the sampled motile foliage arthropod community for at least 18 weeks. This was confirmed with ANOVA of arthropod abundance. Thus if sprays were required several times per year it would be desirable to use HMOs to preserve biodiversity