Susceptibility of Megachile rotundata to insecticides used in wild blueberry production in Atlantic Canada

Abstract

The alfalfa leafcutting bee, Megachile rotundata (Fabricius), is a valuable wild and managed pollinator of lowbush blueberry (syn. 'wild blueberry', Vaccinium angustifolium Ait.), in Atlantic Canada. As some insecticides may present a hazard to pollinators, we assessed the susceptibility of M. rotundata to insecticides used or projected for future use in lowbush blueberry pest management. In topical direct contact bioassays, adults were susceptible to phosmet, spinosad, spinetoram, and deltamethrin. Based on findings from these laboratory studies, it appears that when used at recommended or projected application rates, each of these compounds poses a hazard to M. rotundata by direct contact. In a second experiment, eggs and larvae were collected in the field and their pollen provisions were treated with deltamethrin, flubendiamide, and spinetoram at field relevant concentrations. Larvae treated with deltamethrin and spinetoram in the laboratory either died before spinning a cocoon or, in the case of spinetoram, occasionally pupated without spinning a cocoon. Flubendiamide was not toxic to adult M. rotundata by direct contact and had no effect on larval survivorship, or time to complete cocoon spinning. Emergence after overwintering was relatively poor overall, but there was no effect of treatment. Based on these results, flubendiamide appears safe to use in the presence of M. rotundata, whereas the other insecticides we tested may pose a hazard.

Honey bee survival is affected by interactions between field-relevant rates of fungicides and insecticides used in apple and blueberry production

“…All compounds were tested at a field rate, with the exception of spinetoram, which was diluted below the typical tank-mix concentration. Field rates of this insecticide are lethally toxic to honey bees (Shimokawatoko et al 2012), bumble bees (Gradish et al 2012b), and solitary bees (Gradish et al 2012a) by acute oral and contact exposure. Spray of spinetoram is not permitted when honey bees are foraging, but bees could nonetheless be exposed to this insecticide post-spray.…”

The leafcutter bee, Megachile rotundata, is more sensitive to N-cyanoamidine neonicotinoid and butenolide insecticides than other managed bees

“…M. rotundata is one of the most economically important managed solitary bee pollinators worldwide 5 . This species is principally used as a commercial pollinator in alfalfa seed production (Medicago sativa), with secondary uses in the pollination of canola (Brassica napus) and lowbush blueberries (Vaccinium angustifolium) [5][6][7] .…”

Toxicity of organophosphorus pesticides to the stingless bees Scaptotrigona bipunctata and Tetragonisca fiebrigi

“…While chlorpyrifos has contact, oral and fumigant action (Fletcher and Barnett 2003), phosmet has a greater toxic effect on contact (Kovaleski and Ribeiro 2003). In a study of the effects of phosmet on the solitary bee Megachile rotundata (Fabricius), Gradish et al (2012) found that phosmet is highly toxic when applied topically.…”

“…Assays performed under laboratory conditions often overestimate the lethal effects of insecticides in the natural environment (Lourenço et al 2012). Furthermore, susceptibility in agricultural areas depends on other circumstances, including abiotic factors, pesticide degradation rates and bee behaviours (Gradish et al 2012). Nevertheless, Stevenson (1978) noted that a correlation exists between the relative toxicity determined on laboratory testing and the actual effects of pesticides on bees in the field.…”