# Temperature Changes Affect the Vulnerability of Cotton Bollworms, Helicoverpa armigera (Hübner)

## TL;DR

This study shows how temperature changes affect cotton bollworm populations in different regions, helping improve pest management strategies.

## Contribution

The study identifies region-specific temperature factors influencing Helicoverpa armigera populations, revealing divergent climatic vulnerabilities.

## Key findings

- Warmer winters reduced bollworm populations in Bachu but increased them in Maigaiti.
- Summer temperatures above 33°C suppressed populations in some regions.
- Climate warming extended the bollworm's active period, increasing population size.

## Abstract

The cotton bollworm (Helicoverpa armigera), a globally distributed agricultural pest, severely damages crops and, as a poikilotherm, is highly sensitive to climate change—yet the link between its susceptibility and climatic shifts remains poorly understood, hindering integrated pest management (IPM). We analyzed long-term H. armigera population data and meteorological records from Maigaiti, Bachu (southern Xinjiang), and Shawan (northern Xinjiang) to clarify its response to temperature variation. The results showed H. armigera populations increased overall, with reduced interannual fluctuations. The main meteorological factors influencing the interannual population changes of H. armigera in Maigaiti, Bachu, and Shawan were Tmax difference in winter, Tmin difference in May, and Tmin difference in July, respectively. Higher winter temperatures (especially February) lowered the spring population sizes. Warmer winters reduced Bachu’s annual population significantly, increased Maigaiti’s markedly, and raised Shawan’s non-significantly. Summer temperatures >33 °C suppressed populations, while phenological shifts boosted them. These divergent regional responses reflect varying climatic vulnerability in H. armigera populations, providing insights for targeted IPM.

The cotton bollworm, Helicoverpa armigera (Hübner), a cosmopolitan agricultural pest, inflicts severe impacts on global agriculture. As a poikilotherm, it was highly susceptible to climate change, yet critical gaps persist in understanding how its sensitivity interacts with climatic shifts—knowledge essential for integrated pest management (IPM). We, therefore, analyzed H. armigera’s susceptibility to temperature variations using long-term pest population and meteorological data from Maigaiti and Bachu Counties (southern Xinjiang) and Shawan County (northern Xinjiang). The results showed H. armigera populations increased overall, with reduced interannual fluctuation magnitude. The main meteorological factors influencing the interannual population changes of H. armigera in Maigaiti, Bachu, and Shawan were Tmax difference in winter (98.0%), Tmin difference in May (80.7%), and Tmin difference in July (99.4%), respectively. Higher winter temperature (particularly February) reduced the spring population sizes across all three regions, with only the population in Bachu showing a significant correlation. For annual populations, warmer winter caused a significant decline in Bachu, a marked increase in Maigaiti, and a non-significant rise in Shawan. Summer temperature below 33 °C boosted populations in all regions; above 33 °C, the Maigaiti population declined non-significantly, while the Bachu population dropped significantly. Climate warming advanced the pest’s first appearance, delayed its disappearance, and extended its active period, increasing population size—a trend projected to intensify in the future. Maigaiti and Shawan populations were governed by Tmax in winter and Tmin in July, respectively, whereas the Bachu population was constrained by temperature differences during multiple key growth and development periods throughout the year. These divergent regulatory patterns and climatic responses reflect varying vulnerability levels, providing a theoretical basis for targeted H. armigera control.