Can Sunspot Activity Affect the Population Dynamics of Cotton Bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)?

Whether there is a correlation between sunspots and an impact on insects has long been a subject of debate. As a worldwide pest, the cotton bollworm can feed on a variety of plants and cause great harm to agriculture. Clarifying the pattern of sunspots' influence on it is of great significance for the integrated management of pests. Therefore, we analyzed the sunspot data from 1989 to 2018, as well as the cotton bollworm data from three counties: Maigaiti and Bachu in southern Xinjiang (with 29 and 25 years of data, respectively) and Shawan in northern Xinjiang (with 23 years of data), China. The population size of cotton bollworms increased with the rise in annual mean temperature (<i>T</i>_mean) in the three regions. The impacts of sunspots on annual <i>T</i>_mean in Maigaiti and Bachu were not significant, while in Shawan, there was a lagged effect. Sunspot activity was significantly negatively correlated with the number of moths in Maigaiti and Shawan, while the influence of sunspots on the Bachu population exhibited a certain degree of lag. The fluctuation cycles of moth numbers in these three regions were not consistent with those of sunspots. In Maigaiti and Shawan, the increase in annual, monthly, and daily sunspot numbers was negatively correlated with the rise in annual, monthly, and daily moths captured, respectively, while in Bachu, they were positively correlated. The cycle of sunspots was not synchronized with the cycles of annual <i>T</i>_mean in the three regions. When the number of sunspots exceeded 100, the relative catch (RC) of moths rose in Bachu, while the RC of moths decreased in Maigaiti and Shawan. The RC of moths did not at all increase as the number of sunspots rose. The abrupt changes in the annual <i>T</i>_mean and moth numbers both occurred later than the abrupt change in sunspots, indicating that the influence of sunspots on them had a certain degree of lag and was not synchronous.