VIII SIMPOSIO INTERNAZIONALE ICPBR

HAZARDS OF PESTICIDES TO BEES

Bologna, 4-6 Settembre 2002

Metodologie dei test e studi sugli effetti dei pesticidi sulle api

A method to feed bees known amounts of pesticides

Edith Ladurner (1), Jordi Bosch (2), Stefano Maini (1) and William Kemp (3)

(1)Dipartimento di Scienze e Tecnologie Agroambientali, University of Bologna, Via Filippo Re 6, 40126 Bologna, Italy. E-mail: eladurner@entom.agrsci.unibo.it
(2) Biology Department, Utah State University, 5310 Old Main Hill, Logan UT 84322, USA
(3) USDA-ARS, Bee Biology & Systematics Laboratory, 5310 Old Main Hill, Logan UT 84322, USA

To study the effect of pesticides on bees in the laboratory, bees must be individually fed measured amounts of test solutions. We devised a method to feed bees individually, and tested it against two other available methods on three bee species, Apis mellifera L., Osmia lignaria Say and Megachile rotundata (Fabricius). Method 1. Film canister - bees were individually transferred to black film canisters with a small hole drilled on the side of the canister near the base. The test solution was pipetted onto a microscope slide next to the hole. Method 2. Glass vial - bees were individually transferred to 12-ml glass vials with plastic snap caps. The test solution was injected into a segment of plastic tubing, fitted snugly into the plastic snap caps. Method 3. Flower - a tiny ampoule, made of polyethylene tubing was inserted into the calyx of a flower, whose reproductive column had been previously removed with forceps. The test solution was pipetted into the ampoule. Flowers and bees were individually housed in ice cream cups covered with a lid. To facilitate flower manipulation, we used large flowers with open corollas (Prunus avium, Vinca minor and Convolvulus arvensis).

In all three methods, a 10 m L-drop sucrose test solution (25% vol.) was offered to the bee for one hour. We tested each method under four different light conditions: 1. Natural light – outdoors; 2. Artificial light – 15W Cool White Sylvania® fluorescent tube; 3. Light stimulating plant growth – 20W Gro-Lux/Aquarium Standard Sylvania® fluorescent tube; 4. Complete darkness.

A. mellifera workers were captured in the morning at the hive entrance and brought to the laboratory, where they were chilled for a maximum of half an hour at 4°C prior being assigned to the different feeding methods. O. lignaria and M. rotundata female cocoons were incubated until emergence. Upon emergence, females were starved overnight and then assigned (no chilling was necessary) to the different feeding methods. For each bee species, 20 individuals were tested with each feeding method (3) and light regime (4).

For all bee species, Method 3, the flower, was the most effective: 90-95% of the bees fed under natural light, 80-95% under artificial light, 75-100% under light stimulating plant growth, and 45-70% in darkness. Percent success was 0-60% with the glass vial method, and 0-50% with the film canister method.

In conclusion, Method 3, the flower with the polyethylene tubing insert, is a simple, yet superior, feeding device to very successfully feed bees known amounts of test solutions. Because a trained worker can prepare 100 test flowers in 40 minutes, and, because of its success rate, the method actually saves time and bees. This method could help standardize oral tests on the effect of pesticides on bees in the laboratory.