Effects of decontamination of eggs and y-irradiation of provisions on alfalfa leafcutterbee (Megachile rotundata) larvae
G Douglas Inglis; Mark S Goettel; Lynne Sigler; Joseph Borsa
Methods for axenic rearing of alfalfa leafcutter bee (Megachile rotundata) larvae were investigated. Gamma irradiation at a dose of 15 kGy prior to egg placement effectively sterilized provisions, and larval development on these provisions was not significantly different from larval development on untreated provisions, measured by time to defaecation, spinning of cocoons and prepupal weights. On a sterilized artificial diet, prepupae were significantly heavier and times to initial spinning and termination of cocoon construction were significantly longer than when larvae were reared on natural provisions. Surface treatment of eggs with buffer and 0.3% dry chlorine (sodium dichloros- triazine trione) decreased the incidence of micro-organisms on eggs by 11.1 % and 56.4%, respectively. Treatment of eggs with 0.5% and 0.3% dry chlorine increased mortality by 51 % and 27%, respectively, relative to eggs treated with buffer. When eggs were treated with 0.3% dry chlorine prior to placement on y-irradiated provisions, fungi and bacteria in the frass averaged 0.83 ± 0.43 and 2.15 ± 0.56 log colony forming units/g; these populations were 99.9% and 99.2% lower than microbial populations in the frass of larvae reared on untreated provisions. Percentage reductions of microbial populations in frass of larvae reared from eggs treated with dry chlorine were similar to those in frass of larvae reared from eggs treated with buffer alone. The presence of bacteria in the frass of larvae maintained on y-irradiated provisions was attributed to inadequate decontamination of eggs.