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

Microencapsulated fenitrothion and chlorpyrifos ethyl on Apis mellifera L.; a synopsis of research carried out on apples

Gino Angeli, Michele Berti and Diego Forti

Agronomy Institute of San Michele all’Adige (Tn), Italy. E-mail: gino.angeli@ismaa.it

Laboratory and field trials have been carried out to evaluate the side effects of the microencapsulated insecticides Fenitrocap, IPM-400 (a.i. fenitrothion) and Pyrinex (a.i. chlorpyrifos ethyl) on Apis mellifera L.. Preliminary analysis of the characteristics of microencapsulated insecticides show the following aspects: the average size of capsules diameter was 12.9 micron for IPM400/Fenitrocap and 9.8 for Pyrinex; with regard to <10 micron class, the highest number of capsules is obtainable. The drift of capsules (IPM400) in the air was observed up to 15 m distance from the treated orchards; furthermore the spore-traps indicated that the capsules remained in the air for about 7 hours after the treatment. On microscope slide the persistence of IPM400 and Pyrinex microcapsules was detected within 18 days after treatment whereas on treated vegetation it was observed up to 12 days after treatment. When there was no blooming in the field, the treated microcapsules were not attractive towards foraging honeybees. The pollen collected by foraging honeybees became contaminated by microcapsules only when the bees foraged on flowers previously sprayed with the microencapsulated formulations. When the bees foraged on treated flowers, capsules could be detected in their digestive apparatus up to 14 days after the treatment.

In laboratory foraging honeybees have been exposed to Fenitrocap and Pyrinex by ingestion and topical treatments, and regression line and LD50 have been accordingly determined. Field investigations have been conducted applying the microencapsulated insecticides on a Phacelia tanacetifolia crop before and during blooming, and on an apple orchard with and without mowing before treatment and with and without a repellent.

In laboratory exposure to the encapsulated formulations Fenitrocap and Pyrinex has resulted to be less toxic both topically and by ingestion compared to the exposure to an emulsifiable fenitrothion formulation. Open field applications of insecticide on P. tanacetifolia crop have shown that adult honeybees mortality rate was lower before blooming whereas during blooming it was higher than usual only within 48 h after treatments. Field investigations on apple orchards treated with IPM400 and Pyrinex have shown a remarkable adult mortality and the reduction of some productive parameters only when lawn was blooming. Further field investigations on apple orchards treated with microencapsulated and a repellent during blooming are discussed.