Graduate Thesis Or Dissertation
 

Elicitors: A Novel Tool for Controlling the Colorado Potato Beetle Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae)

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  • Over the last several decades, potato production has increased globally as it has been recognized as an important component to improving food security. However, potato production has been continuously challenged by pests. Current pest management practices rely heavily on chemical pesticides. Unfortunately, the overuse of pesticides can be harmful to the environment as well as the health of agricultural workers. Over-reliance on pesticides can also create problems with resistance. Hence, there is a need for more effective, selective, and less harmful options. Chemical elicitors, which are molecular signals that induce plant defenses, are commercially available as plant growth regulators. In recent years, elicitors have been used to successfully control pathogens. However, elicitors’ impact on insect pests has proven more complex and variable than reported. The Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is potato crops' principal defoliator. This pest has a nearly global distribution and can significantly impact potato yield if left uncontrolled. Current management practices in the U.S. rely heavily on the use of neonicotinoids. However, populations of L. decemlineata in the eastern U.S. have displayed resistance to this mode of action since the early 2000s; western U.S. populations are still susceptible to this pesticide mode of action. Modern research efforts have focused on improving host resistance and using chemical ecology to control L. decemlineata. Chapter 2, entitled “Effects of Elicitors on Plant Host Selection by Adult Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae)” evaluated how jasmonic acid (JA) and salicylic acid (SA) type elicitors affect host selection of adult beetles. Prior studies have illustrated how JA-type elicitors may induce a volatile profile in plants that is attractive to adult beetles. Thus, the aim of this study was to determine the host selection of L. decemlineata adults to 4-week-old greenhouse-grown ‘Russet Burbank’ plants sprayed with commercially available JA and SA-type elicitors using a y-tuber olfactometer. This study provides evidence that the JA-type elicitor Blush 2X increases the attractiveness of ‘Russet Burbank’ potato plants to L. decemlineata adults while the SA-type elicitor, Actigard 50WG, may act as a repellent. Chapter 3, “Impacts of Elicitors on Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) Larval Fitness” evaluated the effects of elicitors on the defoliation rate, weight gain, excretion rate, and developmental time of L. decemlineata larva. This study was conducted at two plant phenological stages with signal interference (aphids ±) to help explain the factors that influence the variability of elicitor efficacy observed in other cropping systems. This study provides evidence for the mechanisms in which foliar applications of elicitors can significantly impact L. decemlineata larval fitness. Furthermore, this study highlights the significance of plant phenology and signal interference (aphids ±) on the efficacy of elicitors. Surprisingly, this study also provides evidence that aphids induce systemic changes in plants that impact the fitness of L. decemlineata. Overall, results from this study provide evidence that elicitors can be integrated into pest management programs to control L. decemlineata. However, field studies are warranted to confirm bioassays and greenhouse results. Furthermore, molecular analysis of the underlying interactions between elicitors and signal interference from host plant recognition of multiple classes of biotic threats is recommended to fully utilize this potential management tool.
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  • National Institute of Food, and Agriculture National Needs Graduate and Postgraduate Fellowship Program (Award #2021-38420-34064)
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