Variations in the relative abundance of hemipteran species in different seasons and stages of rice growth depending on weather variations

Abstract

Rompin has played an active role in Malaysia's rice production for several decades. However, it also faces a threat, particularly from the hemipteran insect pests. There is limited documentation on the abundance of these insects and their relationship with climatic factors. Therefore, this study aimed to determine the abundance of hemipterans in different growth stages and to understand the effects of climatic factors on their population in rice fields. The study was conducted in farmers' rice fields in Rompin, Pahang, Malaysia, during the main and off-season rice planting. Sweep nets, yellow sticky traps, and yellow pan traps were utilized in each plot. Trapped insects were identified based on the rice planting seasons and growth stages. The trends of climatic factors such as rainfall, temperature, light intensity, and wind speed were analysed and correlated with insect abundance. A total of 23,023 individuals belonging to eight families and eleven species of the hemipteran order were recorded. Nine of these species were pests, namely Leptocorisa oratorius, Recilia dorsalis, Nephotettix virescens, N. nigropictus, Amaurochrous dubius, Nilaparvata lugens, Sogatella furcifera, Nezara viridula, and Scotinophara coarctata. The remaining two species were predators, Cyrtorhinus lividipennis and Polytoxus fuscoviftatus. R. dorsalis, N. lugens, S. furcifera, and A. dubius were found in significantly higher numbers and exceptionally high during rice's late vegetative and early reproductive stages. The maximum temperature significantly increased during the main season, while wind speed increased dramatically during the off-season. Wind speed significantly correlated with N. virescens, S. furcifera, L. oratorius, and A. dubius. On the other hand, rainfall exhibited a significant correlation with L. oratorius. Various pest species and their high populations in this study pose a significant threat to plants due to their preferences for different plant parts and strata.