Decrease in Apistan® efficacy used against Varroa disease in the honeybee (Apis mellifera)

Varroa disease is a very serious parasitosis of the bee, which induces important hive losses. Fluvalinate (Apistan®) has been one of the most widely used acaricides since 1989. In 1992, 1993 and 1994, ineffective treatments were observed in Italy and then France, and the hypothesis of a resistance was put forward. The therapeutic efficacy of fluvalinate was estimated in experiments performed in 1992, 1993 and 1994. Groups of colonies from different areas were thus treated for 32-34 d with 2 strips placed in contact with the cluster. Mite mortality was checked with fatted detector boards on hive bottom boards. A treatment with amitraz (Anti- Varroa Schering®) to determine the residual infestation of adult bees was performed the day following the strip withdrawal. Brood infestation was checked by examination of 100 capped cells, by entire brood hatching in an incubator, and by counting the mites on emerging bees. The results showed a decrease in efficacy in the Italian colonies in which fluvalinate therapeutic efficacy fell to 29.7% in 1994. The dosage of fluvalinate in the strips before and after treatment and their good positioning with regard to the bees did not allow us to incriminate a misuse of Apistan® strips. In France, the therapeutic efficacy will be examined at the Italian border during an investigation of all apiaries

Varroosis: demonstrating resistance of parasites to acaricides by means of the 'determination of mean lethal time' method

A simple method of evaluation of Varroa jacobsoni resistance to acaricides (amitraz, fluvalinate and acrinathrin) was developed by comparison of lethal times with a reference strain from CNEVA Sophia Antipolis. This method reproduced the field conditions of the bee colony and kept the host-parasite relationship. The acaricide was administered either as a small piece of plastic strip (Apistan®, Apivar®), or by impregnation of a piece of Whatmann paper no 3 with a known quantity of acaricide. The strip was stuck on the bottom of a Petri dish covered with a net. Five bees were put in contact with the acaricide for 2 hours (fig 1). After that, five mites were introduced onto the bees. The time for the parasites to fall off their host was determined and compared to controls without acaricide. According to the different varroa strains, the lethal time varied from 6-1218 min with fluvalinate. The highest lethal times were registered from mites coming from apiaries where treatments with Apistan® were ineffective (table I). A significant difference was noted with acrinathrin, coincident with the degree of resistance of the mites to fluvalinate. With amitraz, no difference was found. This simple method, named 'determination of average lethal time', can be applied to other acaricides and provide information on the development of resistance through time to beekeepers

Assignments of the chemical shifts of meso-phenyl protons and carbons of tetrakis-5,10,15,20 (a,b,a,b-ortho-amidophenyl)porphyrins

International audienc

Behaviour of imidacloprid in fields. Toxicity for honey bees

Following evidence for the intoxication of bees, the systemic insecticide imidacloprid was suspected from the mid nineties of having harmful effects. Recently, some studies have demonstrated that imidacloprid is toxic for the bees at sub-lethal doses. These doses are evaluated in the range between 1 and 20 µg kg−1, or less. It appeared thus necessary to study the fate of imidacloprid in the environment at such low levels. Thus, we developed methods for the determination of low amounts, in the µg kg−1 range, of the insecticide imidacloprid in soils, plants and pollens using high pressure liquid chromatography — tandem mass spectrometry (LC/APCI/MS/MS). The extraction and separation methods were performed according to quality assurance criteria, good laboratory practices and the European Community’s criteria applicable to banned substances (directive 96/23 EC). The linear concentration range of application was 1–50 µg kg−1 of imidacloprid, with a relative standard deviation of 2.9% at 1 µg kg−1. The limit of detection and quantification are respectively LOD = 0.1 µg kg−1 and LOQ = 1 µg kg−1 and are suited to the sub-lethal dose range. This technique allows the unambiguous identification and quantification of imidacloprid. The results show the remanence of the insecticide in soils, its ascent into plants during flowering and its bioavailability in pollens

A LC/APCI-MS/MS method for analysis of imidacloprid in soils, in plants and in pollens

Imidacloprid, the most used systemic insecticide, is suspected of having harmful effects on honeybees at nanogram per bee or at microgram per kilogram levels. However, there is a lack of methodology to detect imidacloprid and its metabolites at such low levels. We developed a method for the determination of low amounts of imidacloprid in soils, plants (leaves and flowers), and pollens by using HPLC coupled to tandem mass spectrometry (APCI-MS/MS). Extraction, separation, and detection were performed according to quality assurance criteria, to Good Laboratory Practice, and to criteria from the directive 96/23/EC, which is designed for banned substances. The linear range of application is 0.5-20 microg/kg imidacloprid in soils, in plants, and in pollens, with a relative standard deviation of 2.9% at 1 microg/kg. The limits of detection and of quantification are LOD = 0.1 microg/kg and LOQ = 1 microg/kg, respectively. For the first time, this study permitted us to follow the fate of imidacloprid in the environment. When treated, flowers of sunflower and maize contain average values of approximately 10 microg/kg imidacloprid. This explains that pollens from these crops are contaminated at levels of a few micrograms per kilogram, suggesting probable deleterious effects on honeybees