Semester

Fall

Date of Graduation

2020

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Plant and Soil Sciences

Committee Chair

Yong-Lak Park

Committee Member

Cynthia D. Huebner

Committee Member

Insu Hong

Abstract

Persicaria perfoliata (L.) H. Gross (Polygonaceae; Mile-a-minute weed) is a rapid-growing invasive vine introduced from eastern Asia to northeastern United States in the 1930s. This vine has been invaded in disturbed areas and reforestation sites in 15 states in the U.S. and forms dense, monocultural patches that may inhibit natural forest regeneration. To control this weed, a host-specific biocontrol agent, Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) has been released in the P. perfoliata invaded states in the U.S. during the past 15 years. Currently, R. latipes is released by hand to the invaded area where the presence of the weed is readily detected. However, the hand-release method is not applicable to weed patches located in hard-to-access areas. Moreover, successful management of a target invasive species using biocontrol and/or other methods may not lead to recovery of native species. Understanding the plant composition of invaded sites prior to management may prevent invasion of other exotic weeds currently present in lower abundance. This study was conducted to improve weed management of P. perfoliata using UAS for spatially-targeted release of R. latipes on P. perfoliata patches in hard-to-access areas and to evaluate the plant species composition of invaded sites to determine likely species assemblies and successional trajectories after removal of P. perfoliata.

First, we developed a spatially-targeted biocontrol strategy by using an unmanned aircraft system (UAS) for the detection of P. perfoliata and release of R. latipes. A rotary wing UAS was flown at 15 different altitudes to determine the detectability of P. perfoliata patches and, the presence of P. perfoliata was confirmed by a ground survey. In addition, we developed a new insect-release system that would be environmentally-friendly and easy to handle in the field. The release system that housed R. latipes for aerial release was 3-D printed with biodegradable polyvinyl alcohol (PVA), and tests were conducted to determine the ability of R. latipes to escape the pod and assess their post-release mortality and feeding ability of R. latipes. Persicaria perfoliata patches were readily detectable on the aerial images taken at ≤ 15-m flight altitudes. More than 98% of R. latipes (n = 118) successfully escaped from the release system within 24 hours after aerial deployment. There were no significant (P > 0.05) effects of PVA exposure on the mortality and feeding ability of R. latipes.

Second, we conducted a plant community survey on P. perfoliata dominated sites. We compared the species composition of P. perfoliata-dominated (dominated) patches and adjacent patches where P. perfoliata was not dominant (not-dominated) within an environmentally homogeneous site infested with P. perfoliata. This study was conducted in two invaded sites (JS and RV) in southwestern Pennsylvania. The relative importance of all vascular plant species (combined cover and frequency values), richness, diversity, and evenness were determined for each plot type. Significant differences in species composition in the two plot types were determined using nonmetric multidimensional scaling and a multi-response permutation procedure. Indicator species within the plot types were also calculated. There were a total of 36 and 26 plant species from the JS and RV sites, respectively. The dominated plots had lower species diversity and richness than the nondominated plots. The species compositions between the two plot types differed significantly, though site differences were stronger. In addition, an exotic invader, Microstegium vimineum, and native weed, Ambrosia artemisiifolia, were the most important species in the nondominant plots in JS and RV sites, respectively.

Those results of this study suggest that the comprehensive management including utilization of UAS as a site-specific deployment system of R. latipes and understanding potentially coexisting native and exotic plant species within the P. perfoliata invaded sites will help successful control of the target weed and restoration of invaded sites.

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