Abstract
The cotton aphid Aphis gossypii Glover is the main aphid pest in cotton fields in the Yangtze River Valley Cotton-planting Zone (YRZ) in central China. Various natural enemies may attack the cotton aphid in Bt cotton fields but no studies have identified potential specific top-down forces that could help manage this pest in the YRZ in China. In order to identify possibilities for managing the cotton aphid, we monitored cotton aphid population dynamics and identified the effect of natural enemies on cotton aphid population growth using various exclusion cages in transgenic Cry1Ac (Bt)+CpTI (Cowpea trypsin inhibitor) cotton field in 2011. The aphid population growth in the open field (control) was significantly lower than those protected or restricted from exposure to natural enemies in the various exclusion cage types tested. The ladybird predator Propylaea japonica Thunberg represented 65% of Coccinellidae predators, and other predators consisted mainly of syrphids (2.1%) and spiders (1.5%). The aphid parasitoids Aphidiines represented 76.7% of the total count of the natural enemy guild (mainly Lysiphlebia japonica Ashmead and Binodoxys indicus Subba Rao & Sharma). Our results showed that P. japonica can effectively delay the establishment and subsequent population growth of aphids during the cotton growing season. Aphidiines could also reduce aphid density although their impact may be shadowed by the presence of coccinellids in the open field (likely both owing to resource competition and intraguild predation). The implications of these results are discussed in a framework of the compatibility of transgenic crops and top-down forces exerted by natural enemy guild.
Highlights
The widespread adoption of insect-resistant genetically modified (GM) Bt cotton has led to decreased use of chemical insecticides and enhanced biocontrol services provided by natural enemies in Northern China [1,2]
Aphis gossypii accounted for 85.1% of total pest insects recorded; the other three main pest species were the leafhopper Empoasca biguttula Shiraki, the whitefly Bemisia tabaci Gennadius and the common cutworm Spodoptera litura Fabricius (Lepidoptera: Noctuidae)
Our study demonstrated the contribution of natural enemies on cotton aphid population growth in Bt+CpTI cotton field
Summary
The widespread adoption of insect-resistant genetically modified (GM) Bt cotton has led to decreased use of chemical insecticides and enhanced biocontrol services provided by natural enemies in Northern China [1,2]. The Yangtze River Valley Cotton-planting Zone (YRZ), which located in central China, is one of the largest cotton-growing regions nationwide [3] In this region, several insect-resistant GM cotton cultivars, notably the transgenic cotton that combines the two genes Cry1Ac (Bt endotoxin) and CpTI (Cowpea Trypsin Inhibitor), have been widely adopted during the past decade [4,5,6]. Various studies have documented top-down forces regulating herbivore populations and crop biomass yield [12,13,14,15] and identified key natural enemies of predators involved in pest suppression in specific crops [14,16,17,18]. Studies documenting top-down forces in agroecosystems are crucial for developing effective IPM programs
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
