Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Field pennycress is a new winter oilseed crop that will be used to produce sustainable aviation fuel. Little is known about how soil carryover of herbicides used in the preceding corn crop may affect pennycress growth and yield. Experiments were conducted to measure pennycress response to herbicides applied in the preceding corn crop, and simulated herbicide carryover in greenhouse bioassays. In the three years these experiments were conducted in Illinois, herbicide carryover from commercial products used in corn did not reduce pennycress yield. Greenhouse studies showed that a minimum interval of 15 to 120 days from the time of application would be required, depending on the specific herbicide, to avoid a reduction in pennycress growth. Data from these studies will allow herbicide manufacturers to begin the process of updating herbicide labels to allow pennycress planting at appropriate intervals after herbicide application.

Technical Abstract: Domesticated field pennycress is a winter annual oilseed crop intended for the production of sustainable aviation fuel. One production model envisions pennycress being planted immediately after corn harvest and being harvested in late spring prior to planting soybean. The objective of this research was to 1) evaluate pennycress stand and yield following field applications of common corn herbicides in the preceding corn crop, and 2) simulate herbicide carryover using preemergence dose-response bioassays on pennycress in the greenhouse. In field studies, commercial corn premixes were applied at 1X and 2X rates for in May and June. Corn was harvested as silage, and pennycress was drilled into the plots. Neither pennycress stand count nor seed yield were reduced by carryover from a single PRE or POST herbicide application. Similarly, adding atrazine to a tank-mix did not reduce yield. In average weather years, degradation processes in Illinois field soils with a history of atrazine use were adequate to minimize pennycress injury from most corn herbicides applied in May and June, even at 2X rates. In greenhouse dose-response experiments, herbicides were applied as single active ingredient products and as commonly-used commercial premixtures. Pennycress stand counts, dry weight, and injury ratings at 6 weeks after treatment were fit to a four-parameter log-logistic curve. Carryover of the Group 27 herbicide tembotrione caused greater than 10% dry matter loss at a dose equivalent to more than 7 half-life periods, while isoxaflutole, mesotrione, topramezone and tolpyralate caused less than 10% dry matter loss at doses equal to 4 half-life periods or less. Pennycress dry matter loss from commercial premixtures fell below 10% at doses ranging from 0.06X to 0.016X of the labeled rate. Although these data suggest that a period of 4 to 6 half-life intervals from applying herbicides in corn is adequate to avoid pennycress yield loss, labels of the products tested currently do not allow for planting pennycress within 4 months of application.