Chapter III-2 - Bacteria: Laboratory bioassay of bacteria against aquatic insects with emphasis on larvae of mosquitoes and black flies

Abstract

This chapter discusses laboratory bioassay of bacteria against aquatic insects with emphasis on larvae of mosquitoes and black flies. The bioassay of bacteria against larvae of most mosquito species is a relatively straightforward procedure. A number of factors, such as mosquito species and age, number of mosquito larvae per bioassay container, water quality and temperature, volume and depth of water, presence or absence of food and other particulates can significantly influence toxin activity and the results of bioassays. In addition to other susceptibility factors related to species, the feeding behavior of a particular species will influence the amount of inoculum with which the larvae will come into contact. The ITU ratings for Bacillus thuringiensis var. israelensis formulations as determined with mosquito larvae are often not correlated with activity against black fly larvae in laboratory bioassays nor under field conditions. It is suggested that once effective isolates are identified in laboratory bioassays, the most realistic evaluation of formulated bacterial microbial control agents will be under field conditions.