Modeling Emergence of Annual Bluegrass (Poa annua L.) in Hybrid Bermudagrass [C. dactylon (L.) Pers. x C. transvaalensis Burtt-Davy]

Author

Dallas Rose Taylor, University of TennesseeFollow

Date of Award

5-2021

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

Dr. Timothy J. Brosnan

Committee Members

James T. Brosnan, Lawrence J. Steckel, Brandon J. Horvath, Thomas C. Mueller, Jerome F. Grant

Abstract

Annual bluegrass (Poa annua L.; ABG) is a troublesome weed of turfgrass systems. A model to predict ABG emergence patterns could aid in timing measures to control ABG. Field research was initiated in January 2019 at the East Tennessee AgResearch & Education Center (ETREC) (Knoxville, TN) to better understand environmental conditions associated with ABG emergence. Plots (1 m²) included both hybrid bermudagrass [C. dactylon (L.) Pers. x C. transvaalensis Burtt-Davy, cv. ‘Tifway’, at a 1.5 cm cutting height] and bare soil. Emerged ABG inside a 1000 cm² area in the center of each plot was counted weekly for 10 months; during June and July ABG was counted biweekly. Sensors in each plot captured air temperature data on 15-minute intervals. Air temperature data were expressed as cooling degree days accumulated after 21 June (i.e., the summer solstice) using a 21 C base temperature (CDD_21C). Python (v.3.8.7) was used (post-hoc) to fit non-linear functions to ABG emergence and CDD_21C data collected in 2019; models were then tested for validation in 2020. Fluctuations in CDD_21C accounted for ≥ 82% of the variance in yearly cumulative ABG emergence at ETREC over two seasons. Although ABG emergence was first noted at a similar CDD_21C benchmark each year (12 CDD_21C in 2019 and 8 CDD_21C in 2020), a yearly cumulative emergence model underpredicted 50 and 75% emergence in 2020. Peak ABG emergence occurred during a 4-week period in both 2019 and 2020; however, the timing of this 4-week period varied over years. Future research should be conducted using the 24-month dataset generated herein to develop new ABG emergence models using both CDD_21C and rainfall accumulation.

Recommended Citation

Taylor, Dallas Rose, "Modeling Emergence of Annual Bluegrass (Poa annua L.) in Hybrid Bermudagrass [C. dactylon (L.) Pers. x C. transvaalensis Burtt-Davy]. " Master's Thesis, University of Tennessee, 2021.
https://trace.tennessee.edu/utk_gradthes/6208