Investigating the Citrus Aphid Species in Zhejiang, China: Morphometric Analysis and Genetic Distinctions

Aphids (Hemiptera: Aphididae) are well-known agricultural pests, affecting global crop production both through direct feeding and as the vector of multiple plant viruses. The classification of citrus aphid species was outdated and limited within the Zhejiang Province, China. A comprehensive investigation was conducted to determine the aphid species associated with citrus cultivars from 2019 to 2024. The present study included an analysis of occurrence rate, ecological contexts, and microscope slides photographs of apterous viviparous female, along with the key morphometric parameters such as body length, antenna, rostrum, hind tarsus, cauda, and siphunculi. Our morphological and molecular data revealed five species in this particular citrus region. Among the identified species, Aphis (Aphis) gossypii Glover and A. (A.) spiraecola Patch were the most prevalent, followed by A. (A.) craccivora Koch, A. (Toxoptera) citricidus (Kirkaldy), and A. (T.) aurantii Boyer de Fonscolombe. Furthermore, the genetic variation among aphid clades was assessed using Kimura 2-parameter (K2P) model. The results showed that citrus aphid species exhibits low intraspecific genetic variation and high interspecific genetic variation. Although the morphometric parameters of these aphid species are relatively similar, they can be distinguished through extensive morphological characteristics and cytochrome c oxidase subunit I (COI) fragment. Additionally, this study also addresses the historical and current distinctions among A. (A.) spiraecola and A. (T.) citricidus. These findings will significantly contribute to the ongoing research and management of citrus aphids in citrus plantations.