Spatiotemporal Dynamics and Outbreak Risk of Apolygus lucorum in Semi-Arid Wine Grape Regions: An Analysis Based on...

Apolygus lucorum is a major piercing-sucking pest in viticulture, yet its seasonal dynamics and outbreak risk in semi-arid wine-grape regions remain insufficiently understood. This study was conducted in a semi-arid wine-grape region of northwestern China during the 2024-2025 growing seasons. Adult density was monitored at 150 fixed sampling points across five landscape units. LOWESS-based phenological staging, stage-specific spatial interpolation, and an XGBoost-SHAP framework integrating meteorological, topographic, and grape phenological predictors were used to characterize spatiotemporal patterns and key predictors. A. lucorum density remained low in May, increased from June to July, peaked during August-September, and remained relatively high in October, with higher overall abundance in 2025 than in 2024. Spatial analyses revealed marked heterogeneity among landscape units, with high-density patches shifting across years and phenological phases. The XGBoost model showed good predictive performance, with an R² of 0.878 on the independent test set and a mean GroupKFold cross-validation R² of 0.869 ± 0.014. SHAP analysis identified grape phenology, elevation, relative humidity, sunshine duration, and temperature as the leading predictors of model-predicted density. PDP and ICE analyses showed higher predicted counts during later phenological periods, at lower elevations, and under higher relative humidity, particularly around 55%. Two-dimensional PDPs further indicated that high predicted densities mainly occurred under combinations of higher relative humidity, later phenological timing, moderate-to-high temperature, longer sunshine duration, and lower elevation. These findings provide a scientific basis for implementing precision-integrated pest management strategies in semi-arid viticultural regions, where monitoring relative humidity during critical phenological windows can serve as an early warning indicator for impending outbreaks.