The Departments of Plant Pathology, Physiology, and Weed Science and Crop, Soil, and Environmental Sciences held their first joint graduate research symposium on Friday, February 10, 2017 at the Inn at Virginia Tech. With more than 30 student's sharing their research at the afternoon's poster presentation, two PPWS invasive plant students were among those earning top honors. Kara Pittman, crop weeds master's student, was awarded first place with her poster titled "Comparison of Rolled Cover Crop Mulch and Residual Fall Herbicides for Horseweed (Conyza canadensis) Supression". Invasive plant ecology doctoral student Rebecca Fletcher's poster "Is there Evidence For Fine-scale Habitat Specialization in an Invasive Weed?" placed third.
The goal of Kara Pittman's research is to assess cover crop combinations to evaluate which are able to supress horseweed, Conyza canadensis. "Horseweed is a problematic weed for Virginia growers because of its high level of seed production, multiple germination times throughout the year, and increasing cases of herbicide resistance," said Kara.
In this study, Kara discovered that cover crop mixtures which included cereal rye produced the best results in horseweed supression. Herbicide Valor® SX also exhibited results simular to the cover crop combinations. Implications from her research means growers can incorporate cover crops in horseweed suppression, thus benefiting the ecosystem while also adding biomass from cereal rye to suppress the weed.
PPWS doctoral student and Global Change Ph.D. fellow Rebecca Fletcher's work is based on the limited knowledge related to exotic plant response to fine-scale landscape heterogeneity. This study assessed the fine-scale, local adaptation of agricultural and non-agricultural populations of Sorghum halepense (Johnsongrass) collected through its invasive distribution. Research concluded no evidence of fine-scale, local adaptation, however data suggests home climate (precipitation) may have a noteworthy impact on Johnsongrass in the common garden.
Fine-scale, local adaptation could have important implications in invasive plant management. Rebecca and her colleagues' results showed non-agricultural populations grew just as well in the corn-competition treatment as in agricultural domains . These findings show suppression of populations along the borders of crop fields is likely important for controlling this species in managed agricultural systems, as these populations may be a large propagule source.
Kara Pittman received her bachelor's degree in Horticulture from North Carolina State University and is advised by crop weed extension assistant professor Michael Flessner. Rebecca Fletcher graduated from the University of Montana with a bachelor's degree in Biological Sciences and is advised by associate professor and ecological invasives expert Jacob Barney.