Browsing by Subject "soybean aphid"
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Item Incorporating host-plant resistance into soybean aphid integrated pest management.(2017-09) Hanson, AnthonySoybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), originally from Asia, is an invasive pest of soybean in North America that can damage resulting in up to 40% yield loss. Currently, foliar insecticides such as pyrethroids and organophosphates are used to control soybean aphid. Soybean resistant to soybean aphid also has been found (i.e., Rag genes), but these traits are not commonly available from seed suppliers. The following chapters focus on research identifying: soybean aphid resistant germplasm and genetic loci to increase the availability of soybean aphid resistance varieties, insecticide resistant field populations of soybean aphid, and how use of current insecticides may interact with host-plant resistance.Item Management options for insecticide-resistant soybean aphid: Effectiveness of a novel insecticide and implementation of host plant resistance(2019-04) Da Silva Queiroz, ObirataneaManagement of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae) is threatened by a limited number of insecticide groups and evolution of resistant to one of the commonly used groups (i.e., pyrethroids). There is a need to evaluate additional chemical and non-chemical tools for management of soybean aphid. Using a leaf-dip bioassay, susceptibility of several populations of soybean aphid to afidopyropen was assessed during 2017 and 2018. Variation in susceptibility was found among populations with concentrations of afidopyropen necessary to kill 50% of a population (LC50) for soybean aphid adults ranging from 0.0013 to 0.40 mg a.i. per liter. A greenhouse experiment and field experiments were used to assess movement and spatial pattern of soybean aphid on aphid resistant plants with Rag genes. More movement of soybean aphid was found in aphid-resistant varieties (i.e., Rag1, Rag1+Rag2) than aphid-susceptible soybean. However, under field conditions, the spatial patterns of soybean aphid in plots with susceptible, Rag1 or pyramided Rag1+Rag2 varieties were all aggregated and did not differ among varieties in vegetative and reproductive growth stages. In addition, three-years of field experiments were used to access compatibility of aphid-resistant soybean with several non-target herbivores. Plant genotype affected seasonal abundance of bean leaf beetle (Cerotoma trifurcata Forster), potato leafhopper (Empoasca fabae Harris) and green cloverworm (Hypena scabra Fabricius). This thesis provides essential information for growers and scientists to incorporate these additional management tools into soybean aphid management programs.Item Transgenerational Fecundity Compensation And Post-Parasitism Reproduction By Aphids In Response To Their Parasitoids(2017-03) Kaiser, MatthewIncreased reproductive effort by organisms in response to attack by consumers (‘fecundity compensation’) is well documented in both plants and animals, though most examples only involve direct compensation by the individuals exposed to consumers. In Chapter 1, I used the parasitoid wasp Lysiphlebus orientalis Starý & Rakhshani (Hymenoptera: Braconidae) and the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), to determine whether reproduction by parasitized aphids can lead to fecundity compensation. Although parasitism by L. orientalis strongly decreased fecundity for parasitized aphids, offspring of parasitized aphids reproduced at a greater rate at maturity than did the offspring of non-parasitized aphids. Also, parasitized aphids contained fewer but larger embryos developing within them. The presence of these larger embryos may explain how the offspring of parasitized aphids can produce more progeny with no apparent reduction in progeny quality. Mature and nearly mature A. glycines successfully reproduced after parasitism, a prerequisite for transgenerational fecundity compensation, and L. orientalis showed a preference for these age classes of aphids as hosts when foraging. This work is the first known demonstration of transgenerational fecundity compensation in an animal. In Chapter 2, I demonstrated that L. orientalis is able to suppress caged populations of A. glycines in spite of transgenerational fecundity compensation by parasitized aphids. Aphid populations exposed to parasitoids were driven to extinction within, on average, 8 or 11 weeks depending on the starting density of parasitoids. I also showed that transgenerational fecundity compensation has a relatively minor impact on modeled A. glycines populations. Instead, direct reproduction by parasitized aphids, as well as parasitoid host-stage preference, had stronger impacts. Finally, in Chapter 3, I showed that transgenerational fecundity compensation is not limited to the A. glycines – L. orientalis association, as it also occurs when Aphis craccivora Koch (Hemiptera: Aphididae) is attacked by both L. orientalis and Lysiphlebus fabarum (Marshall) (Hympenoptera: Braconidae). I also found that L. orientalis may prefer slightly older A. craccivora hosts than L. fabarum. These results indicate that while transgenerational fecundity compensation may be an interesting and novel physiological phenomenon present in multiple aphid-parasitoid associations, it may be relatively inconsequential for populations of aphids and their parasitoids.