Evaluation of Bacillus thuringiensis var israelensis as a larvicide for Musca domestica, formulated as poultry food additive

PEDROZO, FLORENCIA; VALDEZ LA HENS, DANAY; SEMORILE, LILIANA; MAFFIA, PAULO CÉSAR

Mar del Plata

Congreso; X Congreso Argentino de Microbiología General (SAMIGE).; 2014

The health pest infestations caused by domestic fly (Musca domestica) is a serious problem around poultry facilities. In these facilities, laying hens are kept in cages while feces accumulate for a long period of time and fly larvae reproduced in this substrate. The aim of the present work is the development of an effective larvicide against domestic fly larvae, based on Bacillus thuringiensis varisraelensis (Bti) which produces dipterans toxic crystals during sporulation. This biological larvicide will be incorporated into a specific formulation as a poultry food additive, in order that the spores or vegetative cells of Bti are consumed and excreted, preventing the fly reproduction. After molecular identification only one isolate was positive for the presence of cry genes and the extracted plasmid matched the pattern of Bti. The extraction and purification of the toxic crystals of Bti wereobtained and preliminary toxicity tests were carried out in mosquito larvae. The maximum dilutionthat retains toxic activity was found to be 1:1.000.000 of the purified crystals. Alumninosilicates likebentonite and zeolite was found to be capable of adsorbing viable spores of Bti but it showed noeffective toxic activity in aqueous solution against mosquito larvae. For the domestic fly larvaetoxicity assay, ten larvae at stage 3 were tested with our Bti crystal formulation, commercial Btiformulation and water as negative control. At this growth stages larvae were not affected either in itssurvival nor its development to adult flies. However when larvae at stages 1 and 2 where used, Btishowed a high toxic activity (mortality > 90%)