Chlorantraniliprole (Diamide insecticide) Effects on Predatory Beetle Function and Reproduction Tomato crops

Abstract

Anthranilic diamide insecticides are frequently incorporated into lepidopteran pest management programmes because they are considered more selective than many broad-spectrum compounds. However, relative selectivity does not guarantee ecological neutrality, particularly for ground-active predators that contribute to biological control through continuous foraging and movement. This study evaluated the acute and sublethal effects of chlorantraniliprole on field-collected predatory carabid beetles in tomato, using a randomized complete block design with four treatments: the recommended field rate (35 g a.i. ha⁻¹), a half rate (17.5 g a.i. ha⁻¹), lambda-cyhalothrin (25 g a.i. ha⁻¹) as a broad-spectrum positive control, and an untreated control. Acute mortality was recorded at 24, 48, and 72 h, while sublethal endpoints—feeding rate, locomotion, fecundity, and egg viability—were assessed through laboratory bioassays. At 72 h, cumulative mortality was 12.3% at the chlorantraniliprole field rate and 5.7% at the half rate, compared with 78.6% after lambda-cyhalothrin and 1.2% in the control. However, field-rate exposure caused substantial functional impairment among survivors: feeding declined by 37.6% and locomotion by 42.1% from baseline at 72 h, while fecundity was 28.3% lower than the control and egg viability fell from 91.7% to 82.4%. Lambda-cyhalothrin produced severe and persistent reductions across all endpoints, confirming assay sensitivity. These results demonstrate that chlorantraniliprole has a markedly more favorable acute toxicity profile than the pyrethroid, yet it is not functionally neutral; the combination of moderate mortality, reduced prey consumption, impaired movement, and decreased reproductive output can collectively weaken carabid-mediated biological control. Therefore, a mortality-only risk assessment would substantially overstate the compatibility of chlorantraniliprole with natural pest suppression. The study recommends that chlorantraniliprole be used within an integrated pest management (IPM) framework—triggered by scouting-confirmed pest thresholds, directed to the crop canopy, and accompanied by untreated refuge strips, drift reduction, and post-application monitoring of predator activity. Future compatibility trials should include behavioral and reproductive endpoints alongside mortality, and species-level identification of carabid assemblages is essential to account for differential sensitivity among taxa. While chlorantraniliprole is preferable to broad-spectrum pyrethroids when intervention is necessary, it should not be classified as harmless or applied prophylactically. Full population-level risk assessment requires multi-season validation, residue concentration monitoring, individual-level recovery tracking, and stage-structured modelling to quantify effects on predator recruitment and long-term pest suppression.