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Background Broflanilide has been registered in China for control of Lepidoptera and Coleoptera pests, and it is widely used to control the target pests on lethal and sublethal levels. Therefore, lethal and sublethal effects of broflanilide to the common cutworm (CCW) Spodoptera litura Fabricius, a representative lepidopteran pest in agricultural crops, were examined to explore its ecological influence to pests in this study. Results To F0 , broflanilide had little influence on hatchability of eggs, but significantly reduced the survival rate of neonate. The lethal activity of broflanilide to 3rd instar larvae and adults was 0.13 mg/kg (LD50 ) and 3.59 mg/L (LC50 ) respectively at 48 h. After treated by sublethal dose (LD10 and LD30 ) of broflanilide, the duration from 3rd to 6th instar larvae and the mean fecundity of reproductive females were significantly increased, but the pupation rate, weight of pupae, and life cycle rate were significantly decreased. In F1 , the duration of F1 larvae and the doubling time was prolonged, whereas the rates of pupation and the life cycle were decreased by 14.92% and 18.00%, respectively. The intrinsic rate of increase, finite rate of increase and net reproductive rate of sublethal group were lower than the control group. The relative fitness of F1 treated by LD10 and LD30 was 0.81 and 0.66, respectively. Conslusion Broflanilide not only has highly lethal activity, but also suppresses the population growth and the progeny of CCW, which is a critical factor for guideline of its usage in the field. This article is protected by copyright. All rights reserved.

BACKGROUND AND PURPOSE Fluralaner is a novel isoxazoline insecticide with broad insect spectrum, and mainly acts on the insect GABA receptor with unique binding action, but its molecular interaction with insect GABA receptor has not been deeply identified on molecular level according to its selectivity between target (insect) and non-target (mammal) organisms. EXPERIMENTAL APPOACH The potential binding residues (I258T and L275I in TM1; V288I, M298N, G303N and A304S in TM2; G3’M/S, A327S, G336N, M338I and A339F in TM3; M473V and I477D in TM4) were predicted by SYBYL-X 2.1 software, and verified respectively by the site-directed mutagenesis and two-electrode voltage clamp (TEVC) technique. KEY RESULTS In the 11 predicted amino acids, the G3’M has the strongest ability to reduce the sensitivity of recombinant rice stem borer RDL homomeric channel to fluralaner. Compared with the wild-type (WT)-RDL, the G3’M mutation almost completely abolish the binding of fluralaner and avermectin, but not fipronil on recombinant homomeric channel of RDL from several orders of insects in vitro. In addition, the M3’G on rat Mus musculus β2 improved the sensitivity of recombinant heteromeric Mmα1β2-M3’G channel to fluralaner. Our results demonstrated that the glycine at the third position of TM3 determines the action of fluralaner and should be the binding site of fluralaner with RDL. CONCLUSION AND IMPLICATIONS These results would contribute to understanding the molecular interaction of fluralaner with RDL homomeric channel and may be used to guide future modification of isoxazolines to achieve highly selective control of pests with minimal effects on non-targeted organisms.

The fall armyworm (FAW) Spodoptera frugiperda (Lepidoptera: Noctuidae) is a severe agricultural pest, which has invaded into China in 2019 and caused heavy damage to maize. The γ-aminobutyric acid receptor (GABAR)-targeted insecticides including broflanilide, fluralaner and fipronil exhibit high toxicity towards lepidopteran pests. However, whether they could be used for control of FAW and their possible mode of action in FAW remain unclear. In this study, broflanilide, fluralaner and fipronil exhibited high oral toxicity in FAW larvae with median lethal dose (LD50) values of 0.677, 0.711, and 23.577 mg kg−1 (active ingredient/ artificial food), respectively. In the electrophysiological assay, fluralaner and fipronil could strongly inhibit GABA-induced currents of homomeric FAW resistance to dieldrin 1 (RDL1) receptor with median inhibitory concentration (IC50) values of 5.018 nM (95% confidence interval (CI) 2.864–8.789) and 8.595 nM (95% CI 5.105–14.47), respectively, whereas broflanilide could not. In addition, the cytochrome P450 (P450), glutathione-S-transferase (GST) and carboxylesterase (CarE) activities were positively response to broflanilide, P450 and GST to fluralaner, and GST and CarE to fipronil, respectively, compared with those of control. In conclusion, we firstly reported a notable insecticidal activity of three representative GABAR-targeted insecticides to FAW in vivo, and in vitro using electrophysiological assay. The GST is the primary detoxification enzyme for three tested insecticides. Our results would guide the rotational use of GABAR-targeted insecticides in field.

Simple Summary The khapra beetle is defined as one of the most important quarantine pests globally, and fumigating by methyl bromide, one of the ozone-depleting substances under the Montreal Protocol, is a routine measure used for phytosanitary treatment. To protect the Ozone layer, an environmentally friendly measure is needed to be developed. The middle- to late-stage larvae and adults were treated with irradiation, modified atmosphere (MA) alone, and their combinations at room temperature of 24–26 ℃. As a result, late-stage larvae are determined as the most tolerant stage. Ionizing radiation was used to enhance the effects of 1% and 2% O2 MA treatments that the obvious synergistic effects are presented in all combinations, resulted in saving as high as 60% of the estimated exposure times comparing with MA treatment alone. A total of 111,366 late-stage larvae were exposed to a 1% O2 atmosphere for 14 or 15 days after a 200 Gy irradiation, resulted in no survivor in the validating tests. Therefore, the MA-irradiation combination treatment can provide quarantine security at a very high level, it may be combined with international transportation (train or sea container) to disinfest the commodities infested by khapra beetle and other stored products insect pests. Abstract The khapra beetle, Trogoderma granarium Everts, is defined as one of the most important quarantine pests globally, and fumigation with methyl bromide, an ozone-depleting substance, is a common phytosanitary measure currently used. The modified atmosphere (MA), irradiation, and their combination treatments of T. granarium larvae and adults were performed at room temperature (24–26 ℃) to develop an ecofriendly phytosanitary disinfestation measure and to shorten the exposure time and overcome treatment disadvantages of irradiation. Late-stage larvae are determined as the most tolerant stage resulted in large LT99.9968 values of 32.6 (29.2–37.5) and 38.0 (35.1–41.7) days treated under 1% and 2% O2 (with N2 balance) atmosphere, respectively. Ionizing radiation was used to enhance the effect of MA and the mortality was highly significantly affected by all the interaction effects, indicating that the synergistic effects present in all the combined treatments. The synergistic ratios, which is defined as the estimated lethal time for MA treatment (LD90, LD99, and LD99.9968), divided by that of combined treatment, were between 1.47 and 2.47. In the confirmatory tests, no individuals recovered from a sum of 111,366 late-stage larvae treated under 1% O2 atmosphere for 14- or 15-d after 200 Gy irradiation, which resulted in validating the probit estimations and achieving an efficacy of 99.9973% mortality at 95% confidence level. Therefore, these treatment schedules are recommended to disinfest T. granarium infecting commodities for phytosanitary purposes under the warehouse, MA packaging, or in combination with international transportation by train or sea container.

Ionizing radiation creates free radicals, the effect of which is enhanced by the presence of oxygen, a low oxygen level produces radioprotective effects for insects compared with irradiation in ambient air. Modified (controlled) atmosphere packaging is used for maintaining quality and shelf-life extension, therefore, treatment efficacy may be affected, and there is a need to determine the critical O2 levels that may cause radioprotective effects. Late third-instar Bactrocera dorsalis (Hendel) larvae were irradiated in bags filled with ambient or low-oxygen air (0%, 2%, 4%, 6%, 8% O2) and were exposed to radiation doses of 8 to 64 Gy with intervals of 8 Gy. Efficacy was measured by the prevention of adult emergence. Dose&ndash, response data on mortality (failure of adult emergence) were analyzed via two-way ANOVA (analysis of variance), ANCOVA (analysis of covariance), and probit regression. The difference in radiotolerance was only significant in 0% O2 atmospheres through two-way ANOVA, therefore, the 95% confidence limits (CLs) of lethal dose ratios at LD99 were used to determine significant differences between treatments at different O2 levels. The differences in radiotolerance were significant in 0% and 2% O2 but insignificant in 4%, 6%, and 8% O2 environments when compared with radiation in ambient air. The critical threshold of radioprotective effects for late third-instar B. dorsalis larvae is an O2 level of &ge, 4% and &lt, 6%, but a maximum radiation dose of 14 Gy can compensate for this effect during phytosanitary irradiation treatment.