Performance of the predatory stink bug Arma custos against the tea tussock moth, Euproctis pseudoconspersa

• Provides the first evidence that Arma custos is a effective predator of the key tea pest Euproctis pseudoconspers a. • Both 4th and 5th instar nymphs of A. custos exhibited a Holling Type II functional response against the pest larvae. • The 4th instar nymphs displayed a higher attack rate and greater maximum consumption than the 5th instar • Field release of 4th instar nymphs at a 1:2 predator–prey ratio suppressed the pest population by 78.96% within seven days. • This study positions A. custos as a viable biocontrol agent for integration into tea IPM programs. The tea tussock moth, Euproctis pseudoconspersa , is a major defoliator in tea plantations, causing significant yield losses. Its urticating hairs also pose a health risk to harvesters, disrupting agricultural activities. Overreliance on chemical control of these pests has led to ecological disruption and pesticide residue issues, highlighting the need for sustainable control tactics within integrated pest management (IPM) frameworks. The generalist predatory stink bug, Arma custos , has demonstrated efficacy against various Lepidopteran pests, but its potential for controlling E. pseudoconspersa remains unexplored. In this study we evaluated the biocontrol potential of A. custos against 3rd instar E. pseudoconspers a larvae through functional response assays, intra-specific interference tests, and field trials. Laboratory studies revealed that both 4th and 5th instar nymphs preyed on E. pseudoconspersa larvae. The maximum daily consumption was similar between the two nymphal instars. Predation rates plateaued post-satiation with increasing prey density, while the proportion of consumed prey declined. Both nymphal instars exhibited a Holling Type II functional response. Fourth instars demonstrated a higher attack rate and a greater theoretical maximum daily consumption than 5th instars. Search efficiency decreased with increasing prey density but was consistently higher in the 4th instar. Intra-specific interference intensified with predator density, reducing per capita predation efficiency. In field trials in Weng’an County, releases of 4th instar nymphs at a 1:2 predator–prey ratio resulted in a significant reduction of the pest population, with control efficacy reaching 78.96% after seven days, a level comparable to conventional biopesticides. Our study demonstrates the significant potential of A. custosas a biocontrol agent against E. pseudoconspersa. The operational parameters defined here, including the superior predator stage and an effective release ratio, establish a foundation for its practical integration into tea IPM systems to reduce reliance on chemicals.