Toxicity of delta-phenothrin and resmethrin to non-target insects.

BACKGROUND: The susceptibility of adult house cricket, Acheta domesticus (L.), adult convergent lady beetle, Hippodamia convergens (Guérin-Méneville), and larval fall armyworm, Spodoptera frugiperda (JE Smith), to resmethrin and delta-phenothrin synergized with piperonyl butoxide (PBO) was evaluated in a laboratory bioassay procedure. RESULTS: The 1 day LC(50) values for resmethrin + PBO were 23.2, 32.08 and 307.18 ng cm(-2) for A. domesticus, H. convergens and S. frugiperda respectively. The 1 day LC(50) values for delta-phenothrin + PBO were 26.9, 74.91 and 228.57 ng cm(-2) for A. domesticus, H. convergens and S. frugiperda respectively. The regression relationship between species mortality and concentration explained 51-81% of the variation for resmethrin + PBO and 72-97% of the variation for delta-phenothrin + PBO. The LC(50) values decreased with time for these insecticides for all surrogate species. In terms of sensitivities among the insects to resmethrin + PBO and delta-phenothrin + PBO, A. domesticus was most sensitive, followed by H. convergens and then S. frugiperda. CONCLUSION: The results indicate that resmethrin + PBO was generally more toxic than delta-phenothrin + PBO. Based on the results, A. domesticus seems to be a good surrogate species for estimating potential non-target terrestrial insect impacts from exposure to pyrethroids used in public health applications.

Semiochemicals to enhance herbivory by Diorhabda carinulata aggregations in saltcedar (Tamarix spp.) infestations.

BACKGROUND: Semiochemicals for monitoring, attracting or repelling pest and beneficial organisms are increasingly deployed in agricultural and forest systems for pest management. However, the use of aggregation pheromones and host-plant attractants for the express purpose of increasing the efficacy of classical biological control agents of weeds has not been widely reported. Therefore, we conducted field-based assays to determine if a specialized wax-based matrix impregnated with an aggregation pheromone of the northern tamarisk beetle Diorhabda carinulata (Desbrochers) or host-plant volatiles could increase the efficacy of D. carinulata. RESULTS: The aggregation pheromone and host-plant volatiles were formulated for field application using a wax-based matrix. Reported release rates suggest that this matrix is a viable formulation for enhancing D. carinulata aggregations under field conditions. Pheromone-treated saltcedar plants (Tamarix spp.) not only had higher densities of adult and larval D. carinulata, but also sustained greater levels of foliar damage than control plants. Increased damage from the focused feeding of D. carinulata caused an increase in foliar dieback and decrease in live canopy volume of semiochemical-treated plants. CONCLUSION: Field deployment of these semiochemical formulations could be useful in directing populations of D. carinulata for increased impact on Tamarix spp. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Comparing ecological risks of pesticides: the utility of a Risk Quotient ranking approach across refinements of exposure.

Environmental risk assessment of pesticides and other chemicals often uses the Risk Quotient (RQ) method to characterize risk quantitatively. An RQ is calculated by dividing an environmental exposure value by a toxicity end-point value. Tier 1 RQs, which are characterized by highly conservative toxicity and exposure assumptions, are used primarily for screening out negligible risks in regulatory decision making. It has been argued that the tier 1 RQ approach is valuable for making direct comparisons of quantitative risk between pesticides. However, an outstanding question is whether relative risks among pesticides would change if refinements of exposure are incorporated into the RQ calculations. This study tested that hypothesis. Aquatic ecological risk assessments were conducted for 12 herbicide and 12 insecticide active ingredients used on agricultural crops in the USA. The pesticides were chosen because surface-water monitoring data for them were available as part of the United States Geological Survey's National Water-Quality Assessment Program (NAWQA). Ecological receptors and effects evaluated were aquatic non-vascular plants (acute risk), aquatic vertebrates (acute risk) and aquatic invertebrates (acute risk) for the herbicides and aquatic vertebrates (acute and chronic risk) and aquatic invertebrates (acute and chronic risk) for the insecticides. The data indicate that there were significant statistical correlations between numerical rankings of tier 1 RQs and RQs using refined environmental exposures. The results support the hypothesis that numerical ranking of RQs for the purpose of comparing potential ecological risks is a valid approach because the rankings are significantly correlated regardless of the degree of exposure refinement.