Impact of Currently Used or Potentially Useful Insecticides for Canola
Agroecosystems on Bombus impatiens (Hymenoptera: Apidae),
Megachile rotundata (Hymentoptera: Megachilidae), and
Osmia lignaria (Hymenoptera: Megachilidae)
C. D. SCOTT-DUPREE,1L. CONROY, AND C. R. HARRIS
Department of Environmental Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
J. Econ. Entomol. 102(1): 177Ð182 (2009)
Pest management practices may be contributing to a decline in wild bee populations
in or near canola (Brassica napus L.) agroecosystems. The objective of this study was to investigate
the direct contact toxicity of Þve technical grade insecticidesÑimidacloprid, clothianidin, delta-
methrin, spinosad, and novaluronÑcurrently used, or with potential for use in canola integrated pest
management on bees that may forage in canola: common eastern bumble bees [Bombus impatiens
(Cresson); hereafter bumble bees], alfalfa leafcutting bees [Megachile rotundata (F.)], and Osmia
deltamethrin and spinosad were intermediate in toxicity, and novaluron was nontoxic. Bumble bees
were generally more tolerant to the direct contact applications ? O. lignaria ? leafcutting bees.
clothianidin was only 4.9 and 1.3? more toxic, deltamethrin was 53 and 68? more toxic to leafcutting
bees than to bumble bees and O. lignaria, respectively. Laboratory assessment of direct contact
may differ greatly depending on management practices. Research conducted using only honey bees
of their unique biology and differential susceptibility. Research programs focused on determining
nontarget impact on pollinators should be expanded to include not only the honey bee but also wild
bee species representative of the agricultural system under investigation.
bumble bee, alfalfa leafcutting bee, O. lignaria, insecticides, direct contact toxicity
(Free 1993, Allen-Wardell et al. 1998, Kearns et al.
bee (Apis mellifera L.) is generally regarded as the
most important bee pollinator (Allen-Wardell et al.
1998, Kearns et al. 1998, Delaplane and Mayer 2000,
important (Free 1993, Williams 1996, Kevan 1999,
Westerkamp and Gottsberger 2000, Kremen et al.
2002). There has been growing concern about sus-
pected declines in wild bee populations and the im-
plications for agricultural and natural ecosystems
and Phillips 2001, Klein et al. 2007, NRC 2007).
Wild bee declines have, in part, been attributed to
insecticide use (Kearns et al. 1998, Westerkamp and
Gottsberger 2000, Tasei 2002). Bees maybe uninten-
tionally exposed to insecticides during or after spray
application while foraging in crops and nesting in
insecticide residues in nectar and pollen from treated
crops. Wild bees are particularly vulnerable to foliar
insecticides because, unlike honey bees, nesting sites
cannot be moved or protected during spray applica-
tion (Tasei 2002), and different foraging behaviors
may bring wild bees into contact with insecticides
applied at times designed to reduce foraging honey
bee exposure (Corbet et al. 1993). Although there is
limited information on the toxicity of pesticides to
nontarget beneÞcial insects such as common eastern
bumble bees [Bombus impatiens (Cresson)] (hereaf-
ter bumble bees), alfalfa leafcutting bees [Megachile
rotundata (F.)], and Osmia lignaria Cresson com-
pared with honey bees (Tasei 2002), in recent years,
several studies have been conducted that focus on
et al. 2004, Morandin et al. 2005, Malone et al. 2007,
Abbott et al. 2008). Morandin and Winston (2003)
concluded that ?7 ppb of imidacloprid in pollen
1Corresponding author, e-mail: email@example.com.
0022-0493/09/0177Ð0182$04.00/0 ? 2009 Entomological Society of America
cally modiÞed canola and its effect on seed production.
Ecol. Appl. 15: 871Ð881.
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Received 2 July 2008; accepted 16 September 2008.
182JOURNAL OF ECONOMIC ENTOMOLOGY
Vol. 102, no. 1