During orchard pollination studies in California, we observed dramatic changes in nesting and foraging behavior of Osmia lignaria Say (Hymenoptera: Megachilidae) after sprays with tank mixtures containing fungicides. A characteristic pattern of postspray events observed includes
erratic behavior and interrupted foraging and nesting activity for several days. In an effort to determine whether fungicidal sprays were disruptive to bee foraging and thus to pollination, we exposed O. lignaria females nesting in field cages planted with lacy scorpionweed,
Phacelia tanacetifolia Benth (Hydrophyllaceae), to selected spray mixtures normally encountered in California orchard production systems: iprodione (Rovral), propiconazole (Orbit), benomyl (Benlate), and captan (Captan 50 WP); the surfactant Dyne-Amic, alone and mixed with Rovral; and
the tank mixture IDB (Rovral + Dyne-Amic + the foliar fertilizer Bayfolan Plus). An additional cage sprayed with an equal volume of water acted as control, and a cage sprayed with the insecticide dimethoate as a toxic standard. For each female O. lignaria, we recorded
time spent inside the nest depositing pollen-nectar loads, foraging time, cell production rate, and survival. All females in the dimethoate treatment died postspray + 1 d. Before death, some of these females behaved similarly to our previous orchard observations. A high proportion of
females in the IDB cage were inactive for a few hours before resuming normal foraging and nesting activity. No lethal or behavioral effects were found for any of the other compounds or mixtures tested. Our results indicate that the fungicide applications that we tested are compatible with
the use of O. lignaria as an orchard pollinator.
Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.