Ecological Dynamics and Management of Citrus Psylla Diaphorina citri Kuwayama (Hemiptera: Psyllidae) Under Semi-arid Conditions in India

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a key citrus pest in India, and an important vector of Huanglongbing. This study characterized the seasonality and population dynamics of D. citri in Kinnow mandarin orchards in south‑western Punjab in relation to weather variables and host phenology conducted between 2012-2018. Adults were present almost year‑round, surviving winter in the adult stage within the canopy, while nymphs occurred primarily during two major flushing periods: early February to April and August–September, with the first flush supporting the highest populations. Population build‑up peaked in the 13th standard meteorological week (56.36 ± 2.05 nymphs and 32.46 ± 2.49 adults per 10 cm twig). Optimal conditions for proliferation were maximum temperatures of 21.69-37.87 °C, minimum temperatures of 7.30–20.53 °C, and relative humidity of 63.90–92.66% (maximum) and 19.53–54.22% (minimum). A multiple‑regression prediction model incorporating temperature, humidity, radiation and wind speed explained 67% of the variation in D. citri populations (R² = 0.67). Among citrus cultivars, lemon, sweet lime and Kinnow mandarin were the most preferred hosts, whereas Early Gold and Mosambi were moderately infested. Chemical control trials achieved 30.72-82.90% nymph reduction 14 days after treatment, with thiamethoxam (12.6%) + lambda‑cyhalothrin (9.5%) most effective, followed by beta‑cyfluthrin (8.49%) + imidacloprid (19.81%), flonicamid, thiamethoxam and imidacloprid. Biopesticides including Beauveria bassiana (1.15%, 1×10⁸ CFU mL⁻¹), Verticillium lecanii (1.15%, 1×10⁸ CFU mL⁻¹) and horticultural mineral oil provided 47.86–52.23% reduction while remaining relatively safe to natural predators. Overall, D. citri population dynamics were strongly shaped by climatic conditions and host phenology, and both newer insecticides and biopesticides offer effective management options compatible with natural enemy conservation.