Is there a relationship between the density of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) and Aphis gossypii Glover (Hemiptera: Aphididae)? Spatial analysis of moth-aphid abundance across cotton fields located southeast of the Caspian Sea

Abstract

The cotton bollworm (CBW), Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), and cotton aphid (CA), Aphis gossypii Glover (Hemiptera: Aphididae), are two cotton pests that are commonly found throughout the world. A weekly sampling program was established to determine the spatial distribution of A. gossypii and H. armigera in cotton fields. Spatial associations with each other and/or with climatic factors including the aerosol index of Sentinel-5, evapotranspiration of MODIS, and precipitation were determined. Sampling was performed simultaneously in all 63 grid-fields at weekly intervals. Pest density maps and analyses of pest density associations were produced with Spatial Analysis by Distance IndicEs (SADIE). Lloyd's Mean crowding, Morisita's coefficient of dispersion, and Fisher's indexes of aggregation showed significant aggregation patterns for both pests. Using the SADIE method, 𝐼𝑎 ≥1 for both pests were significantly (P < 0.01) aggregated over the sampling period. The association matrix showed a significant correlation for both pests in terms of aerosol index (-), precipitation (+), and evapotranspiration (+) but not for moth density-rainfall. Therefore, providing honeydew by Aphid cotton, aided 1st and 2nd generation of cotton bollworms to regulate their population. The positive and negative associations between aphid density and dust index variables may potentially act as an alarm for monitoring the cotton bollworm moth, particularly in cotton fields southeast of the Caspian Sea.