Determination of the LC50 in the mite Varroa jacobsoni of the active substances in Perizin® and Cekafix®N. Milani and G. Della Vedova
Dipartimento di Biologia applicata alla Difesa delle Piante, Udine University, Via delle Scienze, 208, 33100 Udine, Italy
Abstract - A bioassay has been developed to measure the toxicity of the organophosphorus acaricides, the active ingredients of Perizin® and Cekafix®, to the mite Varroa jacobsoni Oud. The distribution of the lethal concentrations was rather narrow (LC90/LC10~4). Slight, but significant and consistent differences (up to three times) were found among groups of mites taken from different brood stages; at 26 °C the toxicity was 1.2-2.7 times lower than at 32.5 °C; at a given concentration coumaphos was about twice as active as the active ingredient of Cekafix®. No increase in the LC50 to coumaphos of mites resistant to pyrethroids was noted. Varroa strains resistant to these acaricides were not studied.
Key words: Varroa jacobsoni / toxicity / resistance / coumaphos / organophosphorus acaricide