Phagostimulants enhancing the efficacy of Bacillus thuringiensis formulations against the giant looper, Boarmia (Ascotis) selenaria, in avocado

In both laboratory and field trials, as well as in semicommercial scale applications, the minimum concentration of Bacillus thuringiensis (B.t.) required to secure satisfactory larval mortality of Boarmia selenaria could be halved, from 0.5% to 0.25%, by addition of 1% of the commercial phagostimulant Coax. Another phagostimulant product, Gustol, was inactive. Coax did not attract caterpillars from a distance. However, individual, Coax-treated spots on the avocado leaf surface were consumed by the larvae to a significantly greater extent than control. The same difference in palatability was recorded when the spots were treated with a mixture of Coax and a B.t. formulation. This explains, at least partially, the aforementioned advantageous effects of Coax in practical control of the looper by B.t. .