Two plant immune inducers achieve comparable field control of the rice stem borer through distinct physiological...

Plant immune inducers are promising tools for sustainable pest management because they influence both target pests and natural enemies. Previous studies showed that ATL (3% amino-oligosaccharide +3% Alternaria tenuissima activating protein) attracts the egg parasitoid Trichogramma japonicum, whereas AOS repels the parasitoid, although neither inducer directly affects adult behaviour of the rice stem borer (RSB, C. suppressalis). Whether these contrasting ecological effects influence field efficacy and larval physiology has remained unclear.

Field experiments demonstrated that AOS + T. japonicum and ATL + T. japonicum reduced whitehead incidence caused by RSB to 10.89% and 9.67%, respectively. AOS significantly prolonged RSB larval development, reduced pupal weight, extended adult longevity and increased mean generation time from 29.53 to 32.14 days, whereas ATL had relatively weaker effects. Neither inducer significantly affected the RSB's intrinsic rate of increase (r), finite rate of increase (λ) or net reproductive rate (R_₀). Relative fitness was 0.88 for AOS and 0.85 for ATL. AOS reduced RSB's relative consumption rate by 38.3% and approximate digestibility by 24.4%. Enzyme assays showed that AOS initially increased total protease and α-amylase activities at 48 h, followed by suppression below control levels at 96 h. AOS transiently inhibited glutathione S-transferase activity of RSB and suppressed peroxidase activity, whereas ATL mainly affected peroxidase. Despite their contrasting physiological effects on RSB larvae, both inducers ultimately achieved comparable levels of field suppression against RSB.

Although AOS and ATL provided comparable field control of RSB, they acted through distinct mechanisms. AOS mainly was associated with stronger physiological suppression on RSB larvae despite repelling parasitoids, whereas ATL combined weaker larval effects with enhanced attraction of T. japonicum. © 2026 Society of Chemical Industry.