Abstract:
Bathycoelia distincta is one of the most dominant stink bug pests associated with macadamia orchards in South
Africa. Understanding the toxicity and sublethal effects of insecticides on this pest is essential for its effective
management. This study tested four commercial insecticide formulations, consisting of one organophosphate
(acephate) and three pyrethroids (lambda-cyhalothrin, beta-cyfluthrin and tau-fluvalinate). The toxicity of these
insecticides and their behavioural effects on mobility were assessed. The sublethal effects of lambda-cyhalothrin on
the biological parameters of parent B. distincta (F0) and offspring generations (F1) were also determined by treating
B. distincta adults with sublethal concentrations (LC10 and LC30). In toxicity bioassays, acephate was more toxic to B.
distincta than lambda-cyhalothrin, beta-cyfluthrin and tau-fluvalinate. Behavioural changes were only observed in
bugs exposed to pyrethroids, resulting in an increase in the distance walked and decrease of angular velocity. In the
F0 generation, LC30 reduced the fecundity whereas the LC10 and LC30 accelerated development of the F1 generation.
These results suggest that pyrethroids may enhance the dispersal of this pest and stimulate the growth of offspring
populations. Further experiments should be conducted to confirm these results and understand the mechanism of
action of pyrethroids on B. distincta.
