Amira Cornish & Aria Deluna – Proposal Seminar

Amira Cornish (M.S.)- Seasonality, Distribution, and Biological Control of Crapemyrtle Bark Scale, A New Invasive Threat in Tennessee (Advisor: Dr. Grant)

Crapemyrtle bark scale (CMBS), Acanthococcus (= Eriococcus) lagerstroemiae (Kuwana), an invasive pest from Asia, is a threat to the ornamental nursery industry, homeowners and landscapers in the U.S. Although feeding is not fatal to many crape myrtles, its effects on aesthetics impacts the sale (valued at >46 million annually) and popularity of crape myrtle in landscapes. This pest species has been found in numerous states, including Tennessee. Little is known about its state-wide distribution, life cycle, biology, natural enemies, and impact on crape myrtles. The purpose of this two-year study is to gain additional knowledge to mitigate CMBS before it becomes an economic barrier for crape myrtle production and growth. This pest was first found in Shelby County in Tennessee in late 2013; as of November 2019, CMBS had been documented in eight counties (six of these counties are in western TN) in Tennessee. It has now been found in three major metropolitan areas (Knoxville, Memphis and Nashville), and extensive damage is apparent in these areas. Biweekly sampling of CMBS suggests that the life cycle of CMBS in Tennessee encompasses eggs, four nymphal instars, and adult females (sessile) and winged males, with two or three overlapping generations per year. Overwintering populations of last-stage instar females, adult females, and pre- pupal/pupal males were found in mid-February. Populations of several species of lady beetles were found to reduce CMBS densities at some locations. This seminar will describe research plans to determine distribution, seasonality and life cycle of CMBS in Tennessee.

Aria Deluna (M.S.)- Development of a Method for Screening and Discovery of Insecticidal Proteins with New Modes of Action (Advisor: Dr. Jurat-Fuentes)

The Cry insecticidal proteins (IPs) from the bacterium Bacillus thuringiensis (Bt) produced in transgenic crops have controlled Lepidopteran pests of corn and cotton for >20 years with effectiveness and specificity. The biggest threat to the sustainability of Bt crops is the evolution of resistance in pest insects, which can result in economic losses of over $1 billion. The vast majority of Cry proteins follow a three domain (I to III) structure important for their mode of action. One of the key steps in the Cry mode of action is the recognition of receptors in target midgut cells, which is mostly controlled by domain II, although domain III has also been involved in some cases. The first goal in this project tests if domain III of the Cry1F IP produced in Bt corn and cotton contributes to binding specificity. I will test this hypothesis by producing individual Cry1F domains and testing their ability to prevent binding and toxicity of the full-length Cry1F toxin against larvae of the fall armyworm (Spodoptera frugiperda). The second goal of the project focuses on identifying IPs amenable for gene pyramiding to delay evolution of resistance to Bt crops. In this strategy, two or more Bt IPs recognizing distinct midgut receptors (different modes of action) are produced in the same plant, reducing selection pressure. I will test Cry IPs for activity against S. frugiperda and corn earworm (Helicoverpa zea) larvae as major pests targeted by Bt crops. Active IPs will then be tested for shared binding sites with Cry1F in S. frugiperda and Cry1Ac in H. zea. Results from this research will help establish the role of domain III in Cry1F binding and identify candidate IPs for pyramiding with Cry1F and Cry1Ac in Bt crops in controlling relevant pests of corn and cotton and delaying resistance.