Abstract
Aphids are major pests of cotton crops in the Xinjiang Uygur Autonomous Region in China, and parasitoids are considered as important natural enemies in regulating aphid populations. However, information on aphid parasitoids in the Xinjiang cotton fields is limited, which hinders the study of aphid-parasitoid interactions and the application of conservation biological control against cotton aphids. In this study, a 3-year survey was conducted in a large geographical range that included three primary cotton planting areas in southern and northern Xinjiang. The population dynamics and the parasitism levels of an assemblage of aphids in the cotton fields were investigated along with the composition of the parasitoid community associated with these aphids. Aphid parasitization varied significantly within both years and seasons, with parasitism levels ranging from 0 to 26%, indicating that there is less effective biological control of parasitoids on aphids under field conditions. Among the primary parasitoids described, Binodoxys communis (Gahan) constituted 95.19% of the parasitoid species, followed by Praon barbatum Mackauer (3.15%), Trioxys asiaticus Telenga (1.01%) and Lysiphlebus fabarum Marshall (0.65%). Significant differences were found in the composition of the primary parasitoid species between the cotton seedling period (June) and the flowering period (July-August), and two more primary aphid parasitoids were found in the seedling period. Twelve hyperparasitoid species belonging to six genera were found in our study, of which Pachyneuron aphidis (Bouché), Syrphophagus species and Dendrocerus laticeps (Hedicke) were the dominant species. The composition of the hyperparasitoid community also differed significantly between the seedling and the flowering periods. The description of this parasitoid community-associated assemblage of aphids in cotton fields will facilitate the study of aphid-parasitoid interactions and promote the development of effective cotton aphid management strategies in Xinjiang.
Highlights
Cotton is one of the most economically important crops in China [1, 2], and the cotton industry is the mainstay of Xinjiang Uygur Autonomous Region, the main area of cotton production in northwestern China [1, 3]
We provide a description of the parasitoid community attacking an assemblage of aphids in cotton fields in Xinjiang Province, China
Yang et al [57] reported that among wasps emerged from mummies in northern China, B. communis accounted for most (>93%) of the primary parasitoids of A. gossypii
Summary
Cotton is one of the most economically important crops in China [1, 2], and the cotton industry is the mainstay of Xinjiang Uygur Autonomous Region, the main area of cotton production in northwestern China [1, 3]. Cotton production is limited by the damage caused by aphids and other pests. During the last 40 years, cotton aphids (especially Aphis gossypii Glover) have spread widely in Xinjiang, resulting in an increase in infected areas and great losses of cotton. Thereafter, aphids gradually spread to all cotton growing areas in Xinjiang. In northern Xinjiang, aphid-related losses of 30% were reported in 1994, and cotton production was only 56 kg per ha. In Aksu, an area in southern Xinjiang, aphids infested 13,800 ha of cotton in 2000 [5]. A. gossypii and other aphids are crucial pests of citrus, peach and many important greenhouse-grown vegetables, leading to great economic losses in agriculture [6,7,8]. High climatic adaptability, and high fecundity make aphids difficult to control
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