The Effect of Synergistic Compounds on the Susceptibility of Euschistus heros (Hemiptera: Pentatomidae) and Chrysodeixis includens (Lepidoptera: Noctuidae) to Pyrethroids

Abstract

The Neotropical brown stink bug, Euschistus heros (F.), and the soybean looper, Chrysodeixis includens (Walker), are key pests of soybean in South America. Low susceptibility to pyrethroids has been reported for both species in Brazil. Here, we evaluate the addition of synergistic compounds piperonyl butoxide (PBO) and diethyl maleate (DEM) to manage E. heros and C. includens with resistance to λ-cyhalothrin and bifenthrin. The LD50 of technical grade and commercial products containing λ-cyhalothrin and bifenthrin decreased against field-collected E. heros exposed to PBO and DEM relative to unexposed insects; synergistic ratios up to 4.75-fold. The mortality also increased when E. heros were exposed to commercial formulations containing λ-cyhalothrin (from 4 to 44%) and bifenthrin (from 44 to 88%) in the presence of synergists. There was also a higher susceptibility of field-collected C. includens to technical grade λ-cyhalothrin when PBO was used; synergistic ratio of 5.50-fold. High lethally of technical grade λ-cyhalothrin was also verified in the presence of PBO, with mortality increasing from 6 to 57%. Our findings indicate the potential utility of synergists in reversing the resistance to λ-cyhalothrin and bifenthrin in E. heros and C. includens and suggest a significant role of metabolic mechanisms underlying the detoxification of both pyrethroids.

Development and biological evaluation of nanoencapsulated‐based pyrethroids with synergists for resistance management of two soybean pests: insights for new insecticide formulations

“…This is due to effects of synergistic compounds reducing physiological detoxification process by enzymes from cytochrome P450 monooxygenases, which are the major ones responsible for the resistance of this species to pyrethroids. 9,15 Similar detoxification mechanism was also reported in S. litura and S. exigua in which the synergist PBO reduced the resistance to deltamethrin 20,23 and in H. armigera and Plutella xylostella increasing its susceptibility to deltamethrin and fenvalerate. 22,49 The synergist DEM also enhanced the susceptibility of S. exigua and S. litura to cypermethrin and deltamethrin, respectively, revealing that the high expression of glutathione S-transferases enzymes are involved with the resistance mechanism.…”

“…The high lethality can be explained by the reduction caused by synergists on the activity of detoxification enzymes including P450 monooxygenases and glutathione S‐transferases enzymes, confirming that these enzymes are mainly responsible for the metabolic detoxification of pyrethroids in E. heros from Brazil. Previous studies also demonstrated that the low susceptibility of this notorious soybean pest to BFT, LAM, methamidophos, endosulfan, and acephate was associated with high expression of α‐esterase, β‐esterase, and glutathione S‐transferases enzymes 13–15 . Similar resistance mechanism was reported in bed bugs of the genus Cimex (Hemiptera: Cimicidae), in which the detoxification of LAM and deltamethrin was associated with the overexpression of cytochrome P450 enzymes 47,48 .…”

“…These bioassays were performed using the methodology mentioned earlier, with the following doses and experimental design: (i) 2 μg BFT/mL and 0.64 μg LAM/mL – five replicates of five stink bugs/dose; and (ii) 1.6 μg BFT/mL and 0.89 μg LAM/mL – four replicates of 24 larvae/dose. Thirty minutes before exposure to commercial formulations containing BFT and LAM, stink bugs and larvae were treated with 2 μL of PBO or DEM applied in the dorsum, as described previously by Boff et al 15 …”

“…These bioassays were performed using the methodology mentioned earlier, with the following doses and experimental design: (i) 2 μg BFT/mL and 0.64 μg LAM/mL -five replicates of five stink bugs/dose; and (ii) 1.6 μg BFT/mL and 0.89 μg LAM/mLfour replicates of 24 larvae/dose. Thirty minutes before exposure to commercial formulations containing BFT and LAM, stink bugs and larvae were treated with 2 μL of PBO or DEM applied in the dorsum, as described previously by Boff et al 15 Concentration-mortality data were subjected to Probit analysis to estimate the 50% and 90% lethal concentration (LC 50 and LC 90 ) and respective 95% confidence intervals (CIs) using the PROC PROBIT procedure in SAS® 9.1. 36 The LC values were pairwise compared, being the significance declared if 95% CIs did not overlap.…”

“…18,19 Earlier studies indicated that the exposure of E. heros to PBO reduced its resistance to pyrethroids and neonicotinoids, and that DEM improved its susceptibility to acephate, suggesting that enzymes are responsible for the detoxification of these molecules. 14,15 Similarly, in lepidopteran pests such as Spodoptera litura F., Spodoptera exigua (Hübner), and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) a high susceptibility to pyrethroids was verified in the presence of PBO. [20][21][22][23] It was also reported that the synergist DEM reduced the resistance of S. litura and S. exigua to pyrethroids.…”