Effect of pheromones, plant volatiles and spinosad on mating, male attraction and burrowing of Cadra cautella (Walk.) (Lepidoptera: Pyralidae)

Authors: SAMMANI, A.M.P. - Rajarata University Of Sri Lanka; DISSANAYAKA, D.M.S.K. - Rajarata University Of Sri Lanka; WIJAYARATNE, L.K.W. - Rajarata University Of Sri Lanka; HETTIARACHCHI, S. - Rajarata University Of Sri Lanka; BAMUNUARACHCHIGE, T. - Rajarata University Of Sri Lanka; Morrison, William - Rob

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2020
Publication Date: 11/28/2020
Citation: Sammani, A., Dissanayaka, D., Wijayaratne, L., Hettiarachchi, S., Bamunuarachchige, T.C., Morrison III, W.R. 2020. Effect of pheromones, plant volatiles and spinosad on mating, male attraction and burrowing of Cadra cautella (Walk.) (Lepidoptera: Pyralidae). Insects. 11(12). Article 845. https://doi.org/10.3390/insects11120845.
DOI: https://doi.org/10.3390/insects11120845

Interpretive Summary: Mating disruption is a system of applying pheromones to disrupt the ability of males to locate females and reproduce, thus interrupting the life cycle. There are currently mating disruption systems for a select few moth stored product pests, including Cadra cautella, the almond moth. However, mating disruption has rarely been evaluated with other IPM strategies, such as the use of botanical oils or organic insecticides, including for effects on behavioral resistance such as burrowing to escape treatment. We found that the combination of botanical oils and the almond moth sex pheromone decreased the efficacy of mating disruption, while increasing the ability of males to locate female moths. We also found that exposure to the organic contact insecticide spinosad induced greater burrowing behavior by almond moth, which may be a form of behavioral resistance. The decreased efficacy of mating disruption when used with botanical oils suggests plant-based cues may support mate-finding by this moth species. Finally, our work supports the hypothesis that IPM different tactics may have interacting effects, and emphasizes the importance of taking a systems-level approach to assessing IPM tactic efficacy.

Technical Abstract: Mating disruption of Cadra cautella using its sex pheromone components, (Z, E)-9,12-tetradecadienyl acetate (ZETA) and (Z)-9-tetradecadien-1-yl acetate (ZTA), has been successful in the management of its populations. In addition, botanical oils have been extensively investigated in stored product integrated pest management, but their role as sources of plant volatiles to manipulate pest behavior has been underappreciated. Further, the effect of the synthetic sex pheromones on mating of C. cautella in the presence of plant volatiles (using botanical oils as surrogates) is still unknown. Spinosad used in food facilities effectively controls many stored-product insects, including C. cautella. But, if C. cautella larvae burrow into stores of food, they may escape the effects of contact insecticide treatments on the surface as well as monitoring and detection efforts. Importantly, the burrowing ability of C. cautella larvae and the impact of spinosad on that behavior remain unknown. Therefore, the objectives of the current study were to determine the effects of sex pheromone components ZETA and ZTA in the presence of plant volatiles (e.g. botanical oils) on the mating of C. cautella and the burrowing ability of C. cautella larvae in different types of flour treated with spinosad. In the first study, botanical oils (camphor, sandlewood, neem, cinnamon, citronella, and mee oils) were placed on the bottom surface of a cubicle with the pheromone deployed in the middle. The male and female moths were individually introduced into the cubicle. The mating status of female moths and male moth attraction to the trap were determined. The control experiments had only the botanical oils or pheromone. In the second study, the burrowing ability of C. cautella larvae through different types of flour was evaluated over 10 d. The flour in the treatments was sprayed with spinosad, whereas the controls were treated with water. The mating success was higher in the presence of botanical oils alone but declined with exposure to pheromone either alone or in combination with botanical oils. There was no difference in the attraction of males to traps in pheromone only or pheromone + botanical oil treatments. In spinosad-treated rice flour, mung bean flour and cowpea flour, C. cautella larvae burrowed more than their respective controls. In spinosad-treated flour, C. cautella larvae burrowed the greatest depth in rice flour, and the least depth in atta flour. We also found that spinosad altered the burrowing ability of C. cautella larvae in different types of flour. Thus, we conclude that the mating and burrowing of C. cautella is influenced by both its pheromone and by exposure to spinosad.