Developing a Decision Support Tool for Ventenata IPM in the Inland Northwest

Developing a Decision Support Tool for Ventenata IPM in the Inland Northwest

Summary

Management of Ventenata dubia is gaining prominence as farmers and ranchers gain experience with the weedy grass. The majority of farmers and ranchers who produce alfalfa and grass hay, who have pastures or who participate in the Conservation Reserve Program consider it a very important problem for their production. Reports from producer meetings suggest that production of grass hay is reduced by as much as 50%, grass stand life is cut in half and foreign export of infested hay is not possible. Ventenata has caused farmers to change their practices and they are trying a diverse set of methods for control. The regional losses are $6.7 million and ripple effects in the economy pose a $22 million impact. In addition to economic effects, ecosystem services appear to be impacted, with nearly a 50% lower level of nest success for cavity-nesting birds within CRP.

Research sites have been located within the three-state region of Idaho, Oregon and Washington. The research will become the basis for a decision tool that will be delivered and downloadable from a website. Our work on the biology of Ventenata dubia demonstrated that seed life tends to be short, with most seeds gone in 18 months. But a tenth of a percent survived two years at one location. Seedling survival is enhanced when high levels of litter are present, suggesting litter management may become part of the final IPM approach. The herbicides LandMark, Outrider, Axiom and Plateau/Panoramic all have activity with labeled use in at least one system that we are studying, with the exception of Axiom. The herbicides allow us to integrate with cultural tools to enhance economic viability and reduce the impact of ventenata. Within CRP we have found that a fall or spring burn decreases ventenata when compared to the control and, when combined with the herbicide Outrider, most ventenata was removed.  In timothy hay we found that a harvest height of four inches improved competitiveness of timothy.  When combined with the herbicide Axiom, we had very good control.

Objectives/Performance Targets

Education EO: Involve stakeholders in production of ventenata IPM using a web-based, decision support tool (DST).

Research:

RO1: Predict ventenata seed germination and seed set using a degree-day model approach.
RO2: Define impact of ventenata within a whole-farm system nitrogen (N) budget.
RO3: Determine crop competitiveness (yield) response to alternative management strategies.
RO4: Determine impact of ventenata on ecosystem services within CRP.

Accomplishments/Milestones

In timothy hay, ventenata can be best controlled by harvesting timothy at 10 cm and integrating fertilizing with a fall herbicide application of flufenacet plus metribuzin. These treatments reduced ventenata biomass by 97% in high infestations (Table 1) and 88% in low infestations (Table 2) as compared to the 5 cm harvest height control treatment. Additionally, timothy yield increased by 50% as compared to the 5 cm harvest height control treatment (Table 3). In CRP, ventenata was best controlled when integrating prescribed burning with a fall herbicide application of sulfosulfuron. In high infestations spring prescribed burning decreased ventenata biomass by 95% (Table 4) and in low infestations fall prescribed burning decreased ventenata biomass by 94% (Table 5) as compared to the control treatments. The fall prescribed burning treatment increased perennial vegetation yield by 40% as compared to the control treatment (Table 6). Alternatively, rotary mow, sickle mow and remove and fertilize only treatments increased ventenata biomass.

Within our extension efforts we held 10 meetings and three field days. We updated the PNW Weed Management Handbook under the problem weed section for ventenata.

• Burning in CRP in low and high infestation levels of ventenata
• Integrating harvest height, fertilization and herbicide application for management of ventenata in timothy hay
• Accomplishment Supporting Tabular Results

Impacts and Contributions/Outcomes

Ventenata invasion into CRP is changing plant composition and diversity (Table 1), decreasing insect abundance (Table 2) and directly reducing tree swallow reproduction (Table 3). In highly infested CRP fields, there are 32% less tree swallows fledging as compared to fields with low infestations. Through time, aerial insect abundance decreases by 45% in high sites vs. low sites.

We will be conducting our post-project survey to assess outcomes of the project.  Anecdotal discussion with farmers suggest significant improvements in hay fields.  One farmer contacted Tim Prather and said that he was able to sell hay for $258 in 2012 when his neighbors, who had not been able to control ventenata, were selling at $60 to $70 per ton.

• Field Day Handout Detailing Ventenata Studies
• Impacts of ventenata in CRP

Collaborators: