No abstract

No abstract

No abstract

No abstract

The control of fall armyworm (Spodoptera frugiperda) populations involves the application of pesticides that cause several unwanted effects to humans and other animals, as well as to environment. Sodium chloride (NaCl) has been used in agriculture to potentiate the toxicity of pesticides. Here, the effects of NaCl on the viability of eggs, larvae, and pupae, as well as on development of S. frugiperda were evaluated. The treatment with 0.15 M NaCl caused a 35% reduction of egg hatching and the ingestion of artificial diet containing the salt caused mortality of caterpillars, pre-pupae, and pupae, as well as delayed the development of the insects. The larval, pre-pupa and pupa stages were elongated by about 2, 1 and 0.8 days, respectively. Additionally, significant reduction in pupae body weight was recorded in groups treated with NaCl at 0.62 mg/g and 3.12 mg/g. Despite these effects, NaCl ingestion did not affect the viability of adults and their reproductive performance. Food deterrent assay revealed that the salt acted as a phagostimulant agent. In conclusion, NaCl reduces the hatching of S. frugiperda eggs and damage the survival of carterpillars and pupae, as well interferes with insect development.

BACKGROUND Selective insecticides and insecticide‐resistant natural enemies are components of chemical and biological methods that can be compatible in an integrated pest management (IPM) program. Many insecticides that are labeled for treatment against insects in Brassica crops have lost their efficacy because of the development of resistance. However, natural enemies can provide an important role in regulating the population of these pests. RESULTS Survival of Eriopis connexa populations was >80% when exposed to insecticides, except for EcFM exposed to indoxacarb and methomyl. Bacillus thuringiensis, cyantraniliprole, chlorfenapyr and spinosad caused high mortality of P. xylostella larvae, but neither affected E. connexa survival nor its predation upon L. pseudobrassicae. Cyantraniliprole, chlorfenapyr, deltamethrin and methomyl caused high mortality of L. pseudobrassicae, but did not affect E. connexa survival nor its predation upon P. xylostella larvae. According to the differential selectivity index and the risk quotient, chlorfenapyr and methomyl were more toxic to P. xylostella larvae than to E. connexa, whereas indoxacarb was more toxic to E. connexa. CONCLUSION This study demonstrates that the insecticides B. thuringiensis, cyantraniliprole, chlorantraniliprole, deltamethrin, chlorfenapyr, spinosad, azadiracthin and spiromesifen are compatible with insecticide‐resistant adult E. connexa within an IPM program in Brassica crops. © 2023 Society of Chemical Industry.

The pupal parasitoid Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) parasitizes pupae of sugarcane stalk borers inside the stalk. Parasitoids currently used for applied biological control of sugarcane stalk borers target eggs and larvae, and T. howardi will add mortality to the pest stage with high survival. Nevertheless, insecticide applications required to control sugarcane borers and other sugarcane pests can affect T. howardi parasitism. Survival, walking, evasion and parasitism of T. howardi females were evaluated in response to the dry residue of insecticides from different chemical groups: chlorantraniliprole, bifenthrin, spinetoram, ethiprole, fipronil and thiamethoxam. Females of the parasitoid were confined on sugarcane leaves containing residues of the insecticides at 2, 24, 48, 72 and 96 h intervals after application, and survival monitored during the 96‐h period with subsequent determination of parasitism in the laboratory. Furthermore, female walking behaviour was observed individually using half‐treated arenas with insecticides. Chlorantraniliprole was compatible with T. howardi irrespective of residual intervals and studied variables. Other tested insecticides did not allow parasitoid survival up to 96 h of confinement on dry residues and, consequently, parasitism. Locomotory activity indicated that parasitoid females might avoid residues of spinetoram and ethiprole. Females were released in cages containing spinetoram and ethiprole‐treated sugarcane plants with the chance to move to untreated plants, parasitized pupae placed on either treated or untreated plants within a 24 h exposure period, which resulted in offspring production. Females observed for 10 min for walking behaviour in a half‐treated arena with chlorantraniliprole, ethiprole, fipronil, spinetoram, bifenthrin or thiamethoxam exhibited 100%, 73.3%, 70%, 66.7%, 10% and 0% survival after 24 h, respectively. Chlorantraniliprole was compatible with T. howardi through the bioassays conducted, and parasitoids showed the ability to parasitize their hosts on spinetoram‐ and ethiprole‐treated plants moving away from the treated environment.

Exposure of Eriopis connexa (Germar) to pyrethroid residues in agroecosystems has resulted in selection for resistance (R). Pyrethroid resistance allows E. connexa to survive lambda‐cyhalothrin applications. Following a field release of E. connexa, development of resistance in an incipient population may depend on three major factors such as the maintenance of: (i) selection pressure, (ii) frequency of mating with susceptible phenotypes (S) and (iii) differential reproductive performance due to the fitness costs associated with resistance. To investigate the potential effects of these three factors on the development of pyrethroid resistance by progeny of field released E. connexa, our experiments included panmictic mating between R and S phenotypes, followed by descendant rearing with and without insecticide selection pressure, reselection and determination of resistance levels. In addition, we measured the reproductive performance of the parental R and S phenotypes and their descendants to assess the cost of resistance after crossing and reselection. Survival of R × S descendants exposed to lambda‐cyhalothrin was reduced across successive generations in the absence of selection pressure, but still enhanced after four generations indicating the persistent presence of resistant phenotypes in the population. Under selection pressure with exposure to lambda‐cyhalothrin applied at label rates, descendant survival was >50%. Fecundity and survival were higher in the first‐generation of crossed R × S females, but higher fecundity was not sustained after reselection. Adults of the R population exhibited a fitness cost, reduced longevity, when compared to S phenotypes and R × S crossed populations. Therefore, resistance maintenance in E. connexa after release will depend on selection pressures imposed by insecticide exposure. In the absence of selection pressure, the phenotype for resistance was reduced, but not completely lost. Further, resistant phenotypes can be reselected following insecticide exposure and this can explain, in part, the high frequency of field‐evolved resistance to lambda‐cyhalothrin in E. connexa.