Population Dynamics of Major Pests and Their Natural Enemies in Next Generation Dryland Rice across Different Altitude in Yunnan

Purpose This study aimed to investigate the effect of altitude on the population dynamics of major pests and their natural enemies in next generation dryland rice (NGDR) in Yunnan, providing a basis for precise strategies make for pest control.

Methods Systematic surveys were conducted in NGDR demonstration areas at three altitudes (1388, 1680, and 1983 m) in 2024 in Kafang Town, Gejiu City, Yunnan Province. The population dynamics of major pests (Sogatella furcifera, Cnaphalocrocis medinalis larva, Mythinma separata larva, and scarab beetle and its larva, white grubs) and natural enemies (spiders, Cyrtorhinus lividipennis, etc.) were investigated. The effect of altitude and temporal niche characteristics were analyzed.

Results The population of S. furcifera followed the order of high-altitude>low-altitude>mid-altitude. The highest C. medinalis larva population was at mid-altitude, followed by low- and high-altitude. The highest M. separata larva population was at high-altitude, followed by low- and mid-altitude. The population densities of both adult scarab beetles and their grubs were significantly higher at mid-altitudes than at either high- or low- altitude sites. In low-altitude areas, the natural enemy complex was dominated by C. lividipennis, chrysopids (lacewings), spiders, and asilid flies (robber flies), whereas at mid- and high-altitudes, the dominant natural enemies comprised C. lividipennis, spiders, meloid beetles (blister beetles), and chrysopids. The population peaks of C. lividipennis coincided with those of the S. Furcifera at all altitudes, with the highest temporal niche overlap values (0.1910-0.4561), indicating a close following relationship.

Conclusion Altitude significantly influences the population sizes and occurrence dynamics of major pests and natural enemies in NGDR. However, the fundamental ecological relationships between pests and their natural enemies remain consistent across altitudes. Regionalized pest management strategies should be developed based on pest occurrence characteristics at different altitudes, leveraging the natural control provided by indigenous natural enemies.