In controlling Helicoverpa armigera (Hübner) with the braconid parasitoid Habrobracon hebetor (Say), evaluating insecticide efficacy and compatibility is essential.
This study investigated the effects of sublethal concentrations of matrine and neemarin ingested by H. armigera larvae on H. hebetor developing on them, to assess their compatibility for potential integration into IPM programs.
Bioassays were performed on third-instar H. armigera larvae reared on an artificial diet, and sublethal concentrations (LC 10 , LC 20 , and LC 30 ) were determined.
Overall, matrine and neemarin at LC₁₀ and LC₂₀ exerted only limited adverse effects on H. hebetor, whereas LC₃₀ resulted in marked reductions in fecundity and other demographic traits.
Therefore, the use of these compounds in IPM programs targeting H. armigera should be restricted to lower concentrations, with careful consideration of their sublethal impacts on parasitoid performance.
Integrated pest management (IPM) relies on the compatibility of multiple control strategies. In controlling Helicoverpa armigera (Hübner) with the braconid parasitoid Habrobracon hebetor (Say), evaluating insecticide efficacy and compatibility is essential. Botanical insecticides may provide a safer alternative to synthetic chemicals due to reduced non-target effects. This study investigated the effects of sublethal concentrations of matrine and neemarin ingested by H. armigera larvae on H. hebetor developing on them, to assess their compatibility for potential integration into IPM programs. Bioassays were performed on third-instar H. armigera larvae reared on an artificial diet, and sublethal concentrations (LC 10 , LC 20 , and LC 30 ) were determined. Treated larvae were exposed to parasitoid pairs, and population parameters of the F₁ generation were analyzed. Both insecticides at sublethal concentrations significantly reduced female longevity (from 18.35 days in the control to 14.33 and 14.45 days at LC₃₀ of matrine and neemarin, respectively) and total fecundity (from 121.24 to 68.57 and 63.75 eggs per female at LC₃₀). However, the intrinsic rate of increase (r m ) and net reproductive rate (R₀) in matrine treatments and at LC₁₀ and LC₂₀ of neemarin did not differ significantly from the control. Only at the highest neemarin concentration (LC₃₀) showed a significant reduction in rm observed (0.18 vs. 0.21 day⁻¹ in the control), while other key population parameters showed no significant differences. Overall, matrine and neemarin at LC₁₀ and LC₂₀ exerted only limited adverse effects on H. hebetor, whereas LC₃₀ resulted in marked reductions in fecundity and other demographic traits. Therefore, the use of these compounds in IPM programs targeting H. armigera should be restricted to lower concentrations, with careful consideration of their sublethal impacts on parasitoid performance.
