Effect of planting mixed crops of resistant and susceptible soybeans on crop damage by Spodoptera litura and the population dynamics of key soybean pests
Author of the article:SHEN Fang-Yuan；ZHANG Yi-Fei ；XIAO Zi-Jin；LI Li-Kun；WEI Yong-Ji；YIN Yue；CHEN Fa-Jun
Author's Workplace： Insect-information Ecology Laboratory, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China; Guangdong Key Laboratory of Sugarcane Improvement & Biorefinery, Guangdong Bioengineering Institute (Guangzhou Sugarcane Industry Research Institute), Guangdong Academy of Sciences, Guangzhou 510316, China
Key Words：seed-mixed sowing; soybean yield; insect; population dynamics; community diversity; ecological control
Abstract：
[Objectives] Crop diversity can be used to control the occurrence of insect pests, thereby increasing yields and reduce pesticide use. [Methods] Soybean varieties with high resistance (cv. Lamar; R), medium resistance (cv. ZD35; M) and high sensitivity (cv. JLNMH; S), to Spodoptera litura were planted together, and in isolation, to investigate the effects of crop diversity on soybean yield; i.e. we compared the yield from R, M and S monocultures to mixed RM, RS, MS and RMS crops. The population dynamics of key pests (S. litura and Megacopta cribraria) and insect community diversity in these different crops were also assessed to determine the optimal cultivar diversity with respect to effective ecological control of insect pests and soybean production. [Results] There was no significant difference in the number of individual pests per 100 plants between RM, RMS, and R crops, and there was also no significant difference in individual pests per 100 plants between RM and R crops, all of which had significantly lower pest numbers than other crop types. Insect community diversity (H) and evenness (E) of insects in mixed crops were all significantly higher than those in monocultures, but there were no significant differences in these indices between RM, RMS and R crops. Moreover, the community richness (D) of insects in RM and RMS crops were all significantly higher than those of other crops, whereas the reverse was true for community dominance (C). Furthermore, the grain weight per 100 plants for RM and RMS crops was significantly higher (42.86%-192.27%) than for other crops, except for the R monoculture. The RM crop also had the highest 1000-grain weight of all crop types from 4.46% to 29.31%. [Conclusion] We conclude that the abundance of key insect pests were significantly lower in RM and RMS crops, whereas insect community diversity, evenness and dominance and soybean yield, were all higher. Consequently, we recommend jointly sowing soybean cultivars with both high and moderate resistance, or with high, moderate and high sensitivity to insect pests, to enhance both the ecological control of insect pests and soybean production.