Temperature and relative humidity influence Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) infestation and larval parasitoid activity in the tomato agroecosystems of the Niayes area, Senegal

<title>Abstract</title> <p> <italic>Helicoverpa armigera</italic> (Hübner, 1808) is a major tomato pest whose population dynamics may be influenced by climatic conditions and by the activity of its parasitoids. This study assessed the influence of temperature and relative humidity on <italic>H. armigera</italic> infestation and larval parasitoid activity in tomato crops in the Niayes area of Senegal. Field observations were conducted from April to July 2025 in 20 tomato plots, including 10 plots in the southern Niayes and 10 in the central Niayes. In each plot, 25 tomato plants were monitored at regular intervals to assess pest occurrence, incidence and infestation level. Larvae of <italic>H. armigera</italic> collected in the field were reared individually in the laboratory until death and adult or parasitoid emergence. Temperature and relative humidity were recorded using mini-weather stations installed in the study zones. The results showed that <italic>H. armigera</italic> infestation varied according to thermo-hygrometric conditions. Relative humidity was negatively associated with infestation, whereas temperature showed a weaker direct relationship but contributed to seasonal variation. Warmer and relatively drier conditions appeared more favourable to pest infestation. The parasitism rate was high, reaching 74.4% in the southern zone, 76.1% in the central zone and 75.2% overall. Temperature was positively associated with overall parasitism and with <italic>Cotesia vestalis</italic> (Haliday, 1834), whereas relative humidity was more closely associated with <italic>Meteorus laphygmarum</italic> Brues, 1926. <italic>Brachymeria</italic> sp. and Tachinidae were weakly represented. These findings highlight the importance of climate-pest-parasitoid interactions and support the integration of natural enemies into climate-informed pest management strategies. </p>