Morphology and bionomics of Aphis gossypii (Hemiptera: Aphididae) on Chinese wolfberry (Lycium barbarum)
YAN Lin 1,*, GUO Rui2, LI Ya-Juan1, LI Lin-Lin1, WEI Qiong-Ru1, HAN Yun-Bang1, LIU Meng-Yao1, MA Xiu-Lian1
(1. Department of Grassland Sciences, Collage of Agriculture and Animal Husbandry, Qinghai University, Xining 810016, China; 2. Housing and Urban and Rural Construction Bureau in Changwu County, Xianyang, Shaanxi 713600, China)
Abstract 【Aim】 The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is an important widely dispersed agricultural pest with a wide host plant range. In recent years, it was found that Chinese wolfberry (Lycium barbarum L.) is heavily damaged by A. gossypii as a new host plant. L. barbarum mostly cultivated in the west of China is a rare traditional medicine and food, and the life cycle of A. gossypii on L. barbarum is still unclear. In this study, the biology and bionomics of A. gossypii on cultivated L. barbarum were studied in order to provide data for forecasting and managing A. gossypii on L. barbarum. 【Methods】 The morphological characteristics, developmental duration, life cycle, host plants, habits, population dynamics and natural enemy species of A. gossypii on cultivated L. barbarum plants were investigated under the field conditions in Qinghai Province. 【Results】 Both the nymphs and adults of A. gossypii directly damage Lycium host by sucking the cell sap from shoots, leaves, flowers and fruits. Population outbreaks of this pest lead to huge yield losses and dramatic quality decline of L. barbarum fruits. A. gossypii on L. barbarum host has six aphid types, i.e., virginoparae (apterous and alate parthenogenetic viviparous females), winged gynoparae, sexuparae (alate male and oviparous apterous female) and fundatrix, with significantly different external morphological characteristics which can be used to distinguish different life stages of this aphid. The original host for the aphid is Lycium vegetation. This aphid is polyvolitine (10-16 generations/year) in Qinghai-Tibet Plateau. The diapause eggs overwinter on trunk and twig of Lycium plants, and the fundatrix emerge from eggs in the next April. Apterous parthenogenesis aphids were often observed in early May, whereas winged aphids occur in June and migrate in Lycium fields. The viviparous stage ranges from May to September, and virginopara begin to produce sexual winged female aphids, alate males and apterous oviparous females. Mating and copulating, and oviposition on trunk and twig of Lycium plants were often observed in October. A. gossypii has four nymphal instars on Lycium plants. The average nymphal durations last 10.22±3.32 and 9.55±2.53 d, the average adult longevities are 10.10±1.07 and 8.97±1.34 d, the average entire life spans 20.32±6.31 and 18.52±4.51 d, and the average fecundities 17.86±5.66 and 15.33±3.76 nymphs per female for apterous and alate virginoparae, respectively. The main predators and natural enemies for A. gossypii include Hippodamia variegata (Goeze), Coccinella septempunctata L., Chrysopa formosa Brauer and Aphidius sp. in Lycium fields. 【Conclusion】 A. gossypii has a holocyclic life cycle on Lycium host. Its body size on Lycium host is bigger than that on other host plants, total developmental duration longer and fecundity less. Its population quantity on Lycium host has two peaks in August and September, respectively, instead of one peak on other hosts in May to June as found in the previous research. These differences may be related to the ecological adaptability of A. gossypii to Lycium host and the Qinghai-Tibet plateau environments. However, the adaptive mechanisms need further exploration.