Background: The cotton leafworm, Spodoptera littoralis (Boisd.), is a serious economic pest in Egypt. Pest control depends mainly on chemical control with several pesticides include conventional and modern insecticides. Comprehensive analysis of pesticides impacts needs to investigate sublethal effects in addition to lethal effect. Results: In the current study, the leaf-dip bioassay method was used to evaluate emamectin benzoate (EMB) sublethal concentrations. Results showed that EMB proved high toxicity against S. littorals with LC₅₀ value of 0.019 mg liter⁻¹. Life table analysis showed that treatments with LC₅ and LC₁₅ prolonged larval period, mean longevity of males and females, mean generation time (T), doubling time (DT), adult preovipositional period (APOP), and total preovipositional period (TPOP) compared with control. On the contrary, net reproduction rates (R₀), intrinsic rates of increase (r), finite rate (λ), fecundity, gross reproductive rate (GRR), and relative fitness were decreased compared to control. Conclusions: The current study clarified that sublethal concentrations of EMB induce adverse effects and suppress the population growth of S. littorals. Our results would be useful to assess the overall effects of EMB on S. littorals and can contribute effectively in pest management.

Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) is a major economic pest attacking a variety of crops in Egypt and other Mediterranean countries. S. littoralis has developed resistance to both traditional and novel insecticides. The current study investigated S. littoralis resistance to indoxacarb regarding inheritance mode, realized heritability (h²), and fitness costs. An indoxacarb-resistant strain (Indoxa-SEL) was obtained by selecting a field strain with indoxacarb. Indoxa-SEL strain outperformed the susceptible one (Indoxa-S) by 29.77-fold after 16 consecutive generations of selection. Based on the LC₅₀ values of the progenies of reciprocal crosses F1 (R♂ × S♀) and F1ʹ (R♀ × S♂), S. littoralis resistance to indoxacarb was found to be autosomal and partially recessive. Chi-square tests for goodness-of-fit between observed and expected mortalities of self-bred F₁ and resistant strain reciprocal crosses revealed that the resistance was controlled by multiple genes. The resistant strain had a relative fitness of 0.80, with significantly increased total preovipositional period of females, egg, larvae, pupae, preadult, adult, and total longevity period. The estimated realized heritability value in the Indoxa-SEL strain was 0.21. The current study will contribute to sustaining indoxacarb efficacy and designing effective resistance management programs against S. littoralis.

The cotton aphid, Aphis gossypii is an economically significant insect pest infesting various important crops and vegetables. The neonicotinoid, acetamiprid was recommended against aphids with excellent results. Resistance emergence and environmental pollution makes acetamiprid a favorable alternative to conventional insecticides. The aims of the present work were to predict acetamiprid resistance risk in A. gossypii, investigate cross resistance to other tested insecticides and explore acetamiprid stability in the absence of selection. A field-collected population from Sharqia governorate, Egypt was selected with acetamiprid. After 16 generations of selection, there was a 22.55-fold increase in LC 50 and the realized heritability (h 2) of resistance was 0.17. Projected rates of resistance indicated that, if h 2 = 0.17 and 50% of the population was killed at each generation, then a tenfold increase in LC 50 would be expected in 12.2 generations. If h 2 was 0.27 then 7.63 generations would be needed to achieve the same level. In contrast, with h 2 of 0.07 it necessitates about 30 generations of selection to reach the same level. Cross resistance studies exhibited that the selected strain showed obvious cross resistance to the other tested neonicotinoid members, moderate cross resistance to alpha-cypermethrin and no cross resistance to pymetrozine. Fortunately, resistance to acetamiprid in the cotton aphid was unstable and resistance reverses the nearby susceptible strain throughout five generations without exposure to acetamiprid. Our results exhibited cotton aphid potential to develop resistance to acetamiprid under continuous selection pressure. The instability of acetamiprid makes A. gossypii amenable to resistance management tactics such as rotation with pymetrozine.

The cowpea aphid, Aphis craccivora (Koch), is a significant agricultural pest that globally affects numerous crops, leading to substantial yield losses through both feeding and the transmission of viral diseases. Flupyradifurone has an excellent safety profile and a unique mode of action; resistance to flupyradifurone has been reported in certain aphid species. In the current study, the cross-resistance and resistance mechanisms of A. craccivora to flupyradifurone were investigated. The results revealed that A. craccivora developed a resistance ratio (RR) of 46.6-fold as a result of laboratory selection for 28 consecutive generations. In the flupyradifurone-resistant strain (R-strain), metabolic enzyme determinations indicated significant increases in cytochrome P450 monooxygenase, esterase, and glutathione S-transferase activities. Moreover, quantitative real-time PCR (RT-qPCR) revealed the differential expression of CYP6DA2 and CYP380C6, with CYP6DA2 being upregulated, suggesting its pivotal role in flupyradifurone resistance. Molecular docking studies demonstrated a stronger binding affinity of flupyradifurone to CYP6DA2 than to CYP380C6, further supporting its involvement in detoxification processes. The findings also highlighted moderate cross-resistance to malathion, underscoring the need for insecticide management to mitigate the evolution of resistance. This study provides critical insights into the biochemical mechanisms underlying flupyradifurone resistance in A. craccivora and emphasizes the importance of developing effective resistance management strategies for pest control.