Toxicity Evaluation and Field Performance of Certain Insect Growth Regulators for Spodoptera littoralis Management in Cotton

Document Type : Original Article


1 Plant Protection Research Institute, Sabahia, Alexandria, Egypt;

2 Bioassay Research Department, Central Agricultural Pesticide Laboratory, Agricultural Research Center, Dokki, Giza,Egypt


Spodoptera littoralis (Boisd) (Lepidoptera: Noctuidae), management requires the implementation of effective and sustainable control strategies. In this study, we aimed to compare the insecticidal activity and field performance of four commonly used insect growth regulators (IGRs) against S. littoralis larvae for helping in decision making to get the most effective and sustainable pest management for S. littoralis under local condition. The tested IGRs included Benzoylphenyl ureas BPUs (Lufenuron, Chlorfluazuron, Diflubenzuron), and an ecdysone receptor agonist (Methoxyfenozide). Laboratory bioassays were conducted to determine the toxicity of these IGRs against 2nd and 4th instar of S. littoralis larvae. Lufenuron exhibited the highest toxicity, with the lowest LC50 values (0106 & 0.069 and 0.889 &0.453 mg\l) at 72 and 96h of exposure, respectively. Chlorfluazuron, Diflubenzuron, and Methoxyfenozide displayed relatively lower toxicity compared to lufenuron, as their toxicity indexes were (2.59, 1.99 and 4.50) refereeing to the lowest LC50 value of Lufenuron against the 2nd instar after 72h of exposure. Moreover, positive significant correlations were observed between the log LC50 values of each IGR and other tested ones (pairwise comparison) which alert the possibility of cross resistance between these IGRs. Field experiments were performed over two cotton seasons to assess the efficacy of the IGRs in reducing S. littoralis larval populations. All treatments resulted in a significant reduction in larvae compared to the control group. Lufenuron consistently demonstrated the highest initial efficacy (73.5 and 75.2%) and mean reduction (83.9 and 81.5%) after 15 days of treatment in both 2020 and 2021 seasons, respectively. In contrary, the lowest efficacy was recorded for Diflubenzuton with mean reduction (68.2 and 71.2) after 15 days of treatment in 2020 and 2021 cotton seasons, respectively. This finding highlights the importance of selecting IGRs with higher toxicity to achieve effective larval control. The work underscores the potential of lufenuron as a highly effective IGR for managing S. littoralis. Furthermore, our research emphasis the crucial of the continuous evaluation of IGRs efficacy and persistence as well as resistance and cross resistance to IGRs under local field conditions.


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