Residues of Pesticides in Honeybee (Apis mellifera carnica) Bee Bread and in Pollen Loads from Treated Apple Orchards Maja Ivana Smodis ˇS ˇ kerl Æ S ˇ pela Velikonja Bolta Æ Helena Bas ˇa C ˇ esnik Æ Ales ˇ Gregorc Received: 21 November 2008 / Accepted: 30 April 2009 / Published online: 12 May 2009 Ó Springer Science+Business Media, LLC 2009 Abstract Honey bee (Apis mellifera carnica) colonies were placed in two apple orchards treated with the insec- ticides diazinon and thiacloprid and the fungicide difeno- conazole in accordance with a Protection Treatment Plan in the spring of 2007. Pollen and bee bread were collected from combs inside the hives. The residue of diazinon in pollen loads 10 days after orchard treatment was 0.09 mg/ kg, and the same amount of residue was found in bee bread 16 days after treatment. In pollen loads 6 days after application 0.03 mg/kg of thiacloprid residues and 0.01 mg/kg of difenoconazole were found on the first day after application. Possible sub-lethal effects on individual honey bees and brood are discussed. Keywords Insecticide Á Fungicide Á Analyses Á Diazinon Á Thiacloprid Á Difenoconazole Honey bees (Apis mellifera L.) collect nectar and pollen from flowers for their food and for brood development, so are useful for collecting material from the environment, and have been used to assess atmospheric and other types of pollution (Kevan 1999). Among the various routes of pesticide exposure for bees and other pollinating insects, pollen is particularly relevant, as the whole bee colony can potentially be exposed (Russel et al. 1998; Thompson and Hunt 1999). The safest time to apply pesticides in the field is thought to be during the night and early morning before bees are foraging. Another source of risk to bees is from treating a non-flowering crop when nearby cover crops, weeds and wildflowers are in bloom. These may be attractive nectar sources and may become contaminated by spray drift. A method for assessing the risk for honey bees from pesticide exposure via pollen was developed by Villa et al. (2000). Hazards of insecticides to honey bees have been reported in many studies (e.g. Koch and Weisser 1997; Villa et al. 2000; Waller et al. 1984; Schmuck et al. 2001; Bonmatin et al. 2003). Pollen loads have been ana- lysed for pesticide residues to monitor weakness of honey bee colonies (Porrini et al. 2003; Chauzat et al. 2006). Two organophosphate compounds, coumaphos and diazinon, were examined for effects of sublethal exposure on odour learning and generalization in honey bees by Weick and Thorn (2002) and effects of pesticides on honey bees and brood have been studied by McKenzie and Winston 1989; Papaefthimiou et al. 2002; Rosiak 2002; Gregorc et al. 2004; Silva-Zacarin et al. 2006. ‘‘Oleodiazinon’’ is a mixture of paraffin oil and diaz- inon, an organophosphorus insecticide and acaricide. It is used throughout the world to control a wide range of insects and mites on a range of crops and is toxic to honey bees. ‘‘Calypso’’ is an insecticide using thiacloprid as the active ingredient and is chemically related to imidacloprid, which has an effect on the hypopharingeal glands of worker honey bees (Smodisˇ S ˇ kerl and Gregorc, submitted for publication). Difenoconazole is used against pests on the apple and pear trees. In our survey, we made an attempt to detect possible residues of thiacloprid and difenoco- nazole in pollen loads and bee bread. We therefore per- formed an investigation in order to assess the level of residues in pollen collected by bees after application of the most commonly used pesticides in orchard areas; diazinon, thiacloprid, difenoconazole. We aimed to determine whe- ther properly applied pesticide treatments in the field can M. I. Smodis ˇS ˇ kerl (&) Á S ˇ . Velikonja Bolta Á H. Bas ˇa C ˇ esnik Á A. Gregorc Agricultural Institute of Slovenia, Hacquetova 17, Ljubljana, Slovenia e-mail: maja.smodis.skerl@kis.si 123 Bull Environ Contam Toxicol (2009) 83:374–377 DOI 10.1007/s00128-009-9762-0