Matacil insecticide spraying, pollinator mortality, and plant fecundity in New Brunswick forests
Exposure-cage trials in spruce–fir forest near Doaktown, N.B., Canada, showed that Matacil aminocarb insecticide, applied for control of spruce budworm, increased mortality rates of several types of solitary bees and syrphid flies, although previous studies had found no effect on bumblebees. Of two plant species predominantly pollinated by the sensitive pollinator taxa, one (Maianthemum canadense Desf.) showed significantly reduced fecundity in sprayed areas. The other (Cornus stolonifera Michx.) tended toward reduced fecundity in sprayed areas, although this trend was obscured by great within-treatment variability. Cornus canadensis L., which is visited by bumblebees as well as by the smaller, Matacil-susceptible insects, showed no reduction of fecundity in sprayed areas. This study generally supports the practicality of assessing plant risk a priori by considering (i) the breeding system, (ii) the flowering phenology, (iii) the effective pollinators, and (iv) the known susceptibility of the pollinators to the spray agent in use.