Comparative Toxicity of Acaricides to Honey Bee (Hymenoptera: Apidae) Workers and Queens

Abstract

Acaricides are used to treat honey bee (Apis mellifera L.) colonies to control the varroa mite (Varroa destructor Anderson & Trueman), a worldwide threat to honey bee health. Although acaricides control a serious honey bee parasite and mitigate bee loss, they may cause harm to bees as well. We topically applied five acaricides, each with a different mode of action, to young adult queen and worker bees to generate dose-response curves and LD50. Twenty-four hours after treatment, queens were found to be three times more tolerant of tau-fluvalinate and six times more tolerant of thymol than workers when adjusted for body weight differences between workers (108 mg) and queens (180 mg). Queens survived the highest administered doses of fenpyroximate (1620 μg/g) and coumaphos (2700 μg/g) indicating that queens are at least 11-fold more tolerant of coumaphos and at least 54-fold more tolerant of fenpyroximate than workers. However, queens treated with as little as 54 μg/g of fenpyroximate exhibited reduced survival over 6 wk after treatment. Amitraz was the only acaricide tested for which queens were not more tolerant than workers. The striking difference in acaricide tolerance of queen and worker honey bees suggests physiological differences in how the two castes are affected by xenobiotics. D A H L G R E N E T A L . , J O U R N A L O F E C O N O M I C E N T O M O L O G Y1 0 5 (2 01 2 ) 2 Keywords: Varroa destructor, pesticide, Apis mellifera, miticide, queenThe eusocial honey bee lives in a colony in which a single mated queen is mother to thousands of semisterile female workers. Genetically identical female eggs may develop into either a queen or a worker depending only on their diet. Queen and worker larvae receive different diets (Beetsma 1979), with queen larvae receiving a blend of larval food that includes the protein royalactin that results in a faster growth rate, larger body size, and increased ovary development (Reginato and Cruz-Lamdim 2003, Kamakura 2011). Adult workers and queens differ physiologically in their energetic and metabolic requirements, their susceptibility to pathogens, and the circulating proteins found in the hemolymph (Chan et al. 2006). Despite pronounced differences between the castes, there is little information on how queens and workers differ in their tolerance of pesticides in general, or to the in-hive acaricides used by beekeepers to control the ectoparasitic mite Varroa destructor Anderson & Trueman.The widespread distribution of Varroa mites poses a global threat to honey bee colony health (Sammataro et al. 2000). Varroa mites weaken the hive by consuming hemolymph from pupal and adult bees and by transmitting viruses that may increase colony susceptibility to both abiotic and biotic environmental stressors (Shen et al. 2005). Many honey bee colonies infested with Varroa mites perish without beekeeper intervention (Kraus and Page 1995, National Acad. of Sciences [NAS] 2007). While labor-intensive alternatives to chemical control exist (Sammataro et al. 2000) many beekeep...

Socially responsive effects of brain oxidative metabolism on aggression

“…We treated 7-d-old adult worker bees with two insecticides known to inhibit OX (16)(17)(18) and assayed aggression levels 24 h later. Bees were topically treated on the thorax because previous studies showed that such treatments reliably reach the brain (19).…”

Developing an in vivo toxicity assay for RNAi risk assessment in honey bees, Apis mellifera L

“…Hives were treated 3 times in the spring and one time in the fall with Terramycin™ (Pfizer, New York, NY) for bacterial brood diseases. Varroa mites were controlled with Mite Away Quick Strips (NOD Apiary Products, Ontario, Canada) in April 2012 and with Thymol as Apiguard™ (Vita, Basingstoke, United Kingdom) in September 2012 (Dahlgren et al, 2012).…”

“…Adult bioassays were performed using methods described by Dahlgren et al (2012). Briefly, late-stage capped brood frames were collected and placed in an incubator at 34 °C, 90% RH and 24 h darkness.…”

“…Briefly, late-stage capped brood frames were collected and placed in an incubator at 34 °C, 90% RH and 24 h darkness. Newly emerged adult bees were brushed from frames daily into screened wooden cages (9 × 10 × 18 cm), provided with a 1:1 sugar-water solution and returned to the incubator (Dahlgren et al, 2012). Three to four day old adult workers were anesthetized with carbon dioxide and 20 bees per treatment per replication were placed in wax-coated paper cups (177 cm 3 ; Solo S306, Highland Park, IL).…”

“…Three to four day old adult workers were anesthetized with carbon dioxide and 20 bees per treatment per replication were placed in wax-coated paper cups (177 cm 3 ; Solo S306, Highland Park, IL). Cups were covered with cotton cheesecloth and secured with rubber bands (Dahlgren et al, 2012). Adults were exposed to the same treatments as larvae: untreated diet, GFP 10 μg/adult, D. v. virgifera vATPase-A at 1 and 10 μg/ adult, and A. mellifera vATPase-A at 1 and 10 μg/adult dsRNA.…”