Interaction of a bioherbicidal fungus and a phenoxy herbicide for controlling velvetleaf (Abutilon theophrasti)

Authors: Boyette, Clyde; Hoagland, Robert; Stetina, Kenneth - Ken

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2024
Publication Date: 5/6/2024
Citation: Boyette, C.D., Hoagland, R.E., Stetina, K.C. 2024. Interaction of a bioherbicidal fungus and a phenoxy herbicide for controlling velvetleaf (Abutilon theophrasti). Biocontrol Science and Technology. Vol.34(4), p.323-335. https://doi.org/10.1080/09583157.2024.2324396.
DOI: https://doi.org/10.1080/09583157.2024.2324396

Interpretive Summary: Velvetleaf (Abutilon theophrasti) is an invasive, problematic weed in corn, soybean, and cotton in the eastern and southern U.S. A single plant can produce up to 17,000 seeds that may persist up to 50 yrs. in the soil and emerge throughout the crop growing season when conditions are favorable. The success of velvetleaf as a weed is due to inadequate control, and "weedy" characteristics such as seed dormancy, the ability to germinate from deep in the soil, and tolerance to many herbicides used in corn and soybeans. These factors have led to a large seed reservoir in many areas where corn and soybeans are grown. The fungus Fusarium lateritium (FL) has shown potential as a bioherbicide for velvetleaf control of plants in the cotyledonary-to-first leaf growth stage with 12 h of dew. Greenhouse and field experiments were established to examine possible synergistic disease interactions with the herbicide 2, 4 - DB [4-(2,4-dichlorophenoxy)butyric acid; Butoxone®] that will improve the bioherbicidal potential of FL and to mitigate some physical and environmental restrictions (i.e., by controlling larger weeds with reduced dew requirements) that limit its utility as a bioherbicide. In greenhouse experiments, a synergistic herbicidal:bioherbicidal interaction occurred from sequential applications of 2,4-DB (0.02 kg a.e. ha-1) followed either immediately, or after 7 days, by FL at 1.5 x 106 spores ml-1. Infection and weed control were inhibited by tank mixtures of 2, 4 - DB and FL, and by sequential applications of FL followed by 2, 4 - DB. Similar results occurred under field conditions. These results suggest that timely applications of 2, 4 - DB followed by F. lateritium may provide effective control of velvetleaf.

Technical Abstract: The fungus Fusarium lateritium Nees ex Fr. (FL) has shown potential as a bioherbicide for velvetleaf (Abutilon theophrasti Medic.) control. However, to achieve optimum infection and weed mortality, bioherbicide applications must be applied to weeds that are in the cotyledonary growth stage, followed by a dew treatment of at least 16 h. Greenhouse and field experiments were established to examine for synergistic disease interactions with various chemical herbicides to improve the bioherbicidal potential of this fungus, and to mitigate some of the physical and environmental restrictions that limit the utility of this fungus as a bioherbicide. In greenhouse experiments, mortalities of 94% and 94% were recorded from sequential applications of 2,4-DB (0.02 kg ae ha-1) followed either 5 min after treatment, or after 7 days, by FL at 1.5 x 106 spores ml-1. Velvetleaf plants in the fifth-to-seventh leaf growth stage were infected and killed with < 8 hrs. of dew. Similar results occurred under field conditions. Infection and weed control were inhibited by tank mixtures of 2,4-DB and FL, and by sequential applications of FL followed by 2,4-DB. These results suggest that timely applications of 2,4-DB followed by F. lateritium may provide effective control of velvetleaf.