Crop diversification as a method of managing the soybean aphid, Aphis glycines Matsumura
Author of the article:LI Xin-Min1** LIU Chun-Lai1 LIU Xing-Long1 WANG Ke-Qin1 WANG Shuang1 XIA Ji-Xing1LIU Yu1 YANG Fan1 SHAO Tian-Yu1 DING Jun-Jie2 SHI Xin-Rui3 XU Wei-Jun1***
Author's Workplace：1. Plant Protection Research Institute, Heilongjiang Academy of Agricultural Sciences, Harbin 150086, China;2. Jiamusi Sub-academy of Heilongjiang Academy of Agricultural Sciences, Jiamusi 154007, China;3. Mudanjiang Sub-academy of Heilongjiang Academy of Agricultural Sciences, Wenchun 157041, China
Key Words：Aphis glycines, natural enemy, population dynamics, crop diversity, control effect
Abstract： [Objectives] To determine the benefit of intercropping soybeans as a means of controlling the soybean aphid, Aphis glycines Matsumura. [Methods] Field surveys of the population dynamics of the soybean aphid, A. glycines and its natural enemies were conducted in 2009. A field experiment using cages artificially infested with 500 aphids per plant into which natural enemies were released was conducted to study the ability of indigenous predators to reduce the soybean aphid population. To study the influence of crop diversity on soybean aphids and their natural enemies, soybeans were intercropped with different crops at two sites inHeilongjiangProvince, early maturing potato atJiamusi, and Lagenaria spp., Cucumis melo，Nicotiana tabacum and Zea mays atMudanjiang. [Results] Aphids colonized soybeans in mid-late July, and infestation reached 100% after 3 to 5 weeks. The population peak occurred from late June to early August, and aphids began to disappear in early September. The dominant species of natural enemies were mainly lacewings, ladybugs and parasitoids. Releasing adult Harmonia axyridis and Chrysopa phyllochroma at a ratio of 700 aphids︰1 natural enemy, resulted in rates of soybean aphid decline of 54.78% and 78.79%, respectively after 7 days. In the fields intercropped with early maturing potatoes, natural enemies increased by 2.6 times 5 days after potatoes were harvested and the soybean aphid population decreased by 51.3% in intercropped fields compared to soybean monocultures. In soybean fields intercropped with different crops, the ratio of natural enemies to soybean pests was 1︰65.2 in soybean monocultures compared to 1︰26 to 1︰42 in intercropped fields and the soybean aphid population was 40.7% to 83.5% smaller in intercropped fields. [Conclusion] The soybean aphid population peak was on 3, August in 2009. The dominant species of natural enemies were mainly lacewings, ladybugs and parasitoids. In fields in which soybeans were intercropped with early maturity potatoes, some natural enemies migrated to soybean plants after the potatoes were harvested significantly reducing the population of soybean aphids. The ratio of natural enemies to soybean pests was much higher in soybean monocultures than in intercropped fields, suggesting that crop diversity can facilitate the bio-control of soybean aphids by their natural enemies.