At this point in the season, small grain farmers have won or lost the battle with Italian ryegrass. But all may not be lost. Harvest weed seed control can be implemented to reduce the soil seed bank, leading to success in future years. Recently, in Texas, Dr. Muthukumar Bagavathiannan’s team was able to reduce the Italian ryegrass soil seed bank in wheat by integrating herbicides, harvest weed seed control (HWSC), and delaying tillage.
In this four-year study conducted in Texas and Arkansas, with Dr. Jason Norsworthy, Italian ryegrass control was evaluated using both a standard herbicide (Prowl applied as delayed PRE) and a diversified herbicide program (Axiom plus Zidua applied EPOST in late fall followed by Axial XL in spring). Within both herbicide programs, HWSC (in the form of narrow windrow burning) was compared to a no HWSC treatment. To increase seed predation after harvest, disking was delayed for a month after wheat harvest to expose weed seeds to predators.
At the end of the 4-yr experiment, results showed that HWSC combined with the diverse herbicide program provided greater Italian ryegrass control than other treatments, and a steep reduction in the soil seed bank. In plots with the standard herbicide program (without HWSC), approximately 60 ryegrass seedlings were observed in a 10 sq. ft area, which was reduced to about 8 seedlings/10 sq.ft when HWSC was used, an 87% reduction in ryegrass densities. In addition, the delayed disking strategy further reduced seedling densities (5 seedlings/10 sq.ft) as a result of seed predation. When HWSC was combined with a diversified herbicide strategy, ryegrass densities were <1 seedling/10 sq.ft. Therefore, it is very evident that the use of HWSC in combination with herbicides considerably reduces Italian ryegrass infestations, which will protect wheat yields.
Researcher: Muthukumar Bagavathiannan, Texas A&M University
Video: Claudio Rubione, University of Delaware