Common Pokeweed (Phytolacca americana L.) Management in Pennsylvania Field Crops
Open Access
- Author:
- Patches, Kelly Marie
- Graduate Program:
- Agronomy
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 02, 2014
- Committee Members:
- William Curran, Thesis Advisor/Co-Advisor
- Keywords:
- pokeweed
Phytolacca americana
corn
soybean
herbicide efficacy
emergence
glyphosate
conservation tillage - Abstract:
- Common pokeweed (Phytolacca americana L.) is a perennial broadleaf weed with a large persistent taproot that is also capable of abundant seed production. It has become a frequent problem in agronomic crops in Pennsylvania. Traditionally, plowing was used to manage pokeweed; however, the wide-spread adoption of conservation tillage, a decline in the use of soil residual herbicides, and a decrease in diverse cropping rotations may have allowed pokeweed populations to increase in recent years. This research was conducted in order to identify opportunities to better manage pokeweed in corn, soybean, and other Northeast U.S. cropping rotations and shows that an integrated approach which includes both cultural and chemical tactics enables successful management of pokeweed in conservation tillage systems. Experiments were conducted in order to investigate the biology of common pokeweed in order to better time control tactics. In a pokeweed seedling emergence timing experiment, seedlings emerged throughout the summer, but peak emergence occurred in mid to late May. By August, pokeweed seedling emergence ceased. Both above- and below-ground pokeweed biomass decreased with delayed emergence and plants which emerged in late July did not produce mature berries by the end of the season. Experiments were also conducted to assess herbicide efficacy on pokeweed control. In corn, glyphosate, plant growth regulators, and other herbicides provided at least 80% control in trials conducted over a 3-year period. In soybean, glyphosate provided the best control of pokeweed; all treatments including glyphosate provided at least 80% control, while non-glyphosate treatments provided less than 62% control. Other glyphosate experiments examined herbicide rate, nozzle selection, carrier volume, and application timing. Air induction and flat fan nozzles provided the same level of control and in one of two years, 93 L/ha carrier provided better control than greater carrier volumes. The highest rates of 1.27 and 1.73 kg ae/ha provided the best control 12 weeks after application (WAA), but at 44 WAA, there was no difference in control due to glyphosate rate. Glyphosate application after mid-June provided better control than earlier in the summer. Even though pokeweed is a challenging weed to control, the results from this research show that there are options for controlling pokeweed in Pennsylvania field crops. Understanding the emergence pattern and current herbicide options has provided insight on how to better time control tactics and reduce this problematic weed. In order to control pokeweed, an integrated approach must be taken. Crop rotation and selection and timing of herbicide application are important for effective control.