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, have pastures or 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. 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 web site. 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 surviving 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. Discovery of herbicides effective on V.dubia are not part of this project but are an important component to an IPM approach, and several herbicides have been identified as effective within each of the production systems targeted by this research and education effort.

Objectives/Performance Targets

Education

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

Current practices that control ventenata were discussed at four meetings in Oregon (Jordan Valley, Heppner, Pendleton and Hood River); two meetings in Washington (Yakima and Spokane) and four meetings in Idaho (Moscow, Plummer, Boise, Cambridge). Building awareness for the problem and the possible solutions will continue to stress the importance of management of ventenata and will focus attention to solutions through use of our decision tools as they develop. Currently we have a set of practices that are helpful for management, and those practices will help in development of decision tools with stakeholders.

Research

RO1: Predict ventenata seed germination and seed set using a degree-day model approach.

Accomplishments/Milestones

In summer 2011, research plots for the degree-day model and nitrogen budget were established at two sites in each of four perennial grass production systems at a regional scale (Table 1). Ventenata germination was sampled five to seven times, and environmental data were collected from established weather stations throughout the fall growing season at each site. Preliminary analysis of degree day models is currently being conducted.

Table 1. Field sites for development of regional degree day model and nitrogen budget.
Site Location Lat/Long Production System
Moscow, ID N46.7784°, W116.917° Conservation Reserve Program
Worley, ID N47.4372°, W117.025° Conservation Reserve Program
Troy, ID N46.7748°, W116.687° Pasture
Cusick, WA N48.2868°, W117.302° Pasture
Harvard, ID N46.9332°, W116.669° Timothy Hay
Cusick, WA N48.2940°, W117.317° Timothy Hay
Anatone, WA N46.1052°, W117.104° Rangeland
Enterprise, OR N45.4318°, W117.331° Rangeland

RO2: Define impact of ventenata within a whole-farm system nitrogen (N) budget.

Accomplishments/Milestones

Initial ventenata control treatments were also initiated within nitrogen budget plots. Nitrogen budget experiments will commence spring 2012.

RO3: Determine crop competitiveness (yield) response to alternative management strategies.

Accomplishments/Milestones

A series of field studies were initiated in fall 2011 to support the development of IPM strategies. Six selective herbicides (sulfosulfuron, imazapic, rimsulfuron, flufenacet + metribuzin, propoxycarbazone and imazapic + glyphosate) were tested at a pre- and post-emergent fall timing for ventenata control at four CRP sites and one rangeland site (Table 2). Treatments will be evaluated in spring 2012. Results will be communicated in extension materials, and the most efficacious control treatment will be used in combination with cultural or mechanical control methods in IPM field trials starting in summer 2012.

Table 2. Site locations of ventenata control trials
Site Location Lat/Long Production System
Moscow, ID N46.7784°, W116.917° CRP – Intermediate Wheatgrass
Moscow, ID N47.4372°, W117.025° CRP – Smooth Brome
Grangeville, ID N45.9396°, W116.060° CRP – Timothy
Fenn, ID N45.9396°, W116.243° CRP – Intermediate Wheatgrass
Anatone, WA N46.1052°, W117.104° Rangeland – Bluebunch Wheatgrass

IPM field control trials will include cultural or control trials, such as prescribed burning or grazing, for the management of ventenata litter. It has been postulated that ventenata litter dynamics creates a positive feedback for ventenata recruitment and development. An undergraduate research project was initiated in fall 2011 at a local research station to investigate the effect of ventenata litter on germination and development. Ventenata seed was sown into potted native soil and subjected to four litter treatments (0, 5, 10 and 20 g per plot), which is correlated to foliar cover (0, 33, 66 and 100%). Soil moisture and temperature probes were installed in pots to measure the effect of litter on these environmental characteristics. Pots were sampled three times during the fall growing season and will continue to be monitored through the spring of 2012. Germination rate, survival and growth were significantly greater at the two highest litter treatments, which suggest that ventenata litter exceeding 50% cover may increase fitness of ventenata at the critical stage of germination and fall growth. These results highlight the importance of identifying appropriate litter management techniques with an IPM strategy.

Accomplishments/Milestones

Economics

Growers in the Anatone and Moscow areas were surveyed, either in person or via telephone, on their experiences with damages caused by ventenata infestations and the costs they incurred using various control measures in crops and pasture. In some cases pastures, grass or hay crops had to be taken out and re-established. Various chemical treatments were used as well, with varying success. Pasture stocking rates were cut by half or more in some areas due to ventenata damage.

Damage to timothy hay, an important export crop in the northern counties, can be particularly costly. Timothy is typically a 10-year stand. In infested areas, ventenata is killed with Roundup and then the area is reseeded to an annual crop like triticale or bearded barley. Typically, the highest quality timothy sells for $230 per ton while contaminated timothy sells as feeder hay for $55 to $85 per ton (2011 prices). Contaminated areas have to be baled separately to prevent contamination of the clean hay. Ventenata infestations require a great deal of extra management.

Grass stands have also been affected by ventenata infestations. The stand life for hay such as brome, timothy and bluegrass is reduced, from eight to ten years to four or five years. Ventenata damage to bunchgrass pastures is worse than for seeded pastures, with a 50% to 75% average reduction in the stand. Ventenata damage is worse in stands that are continually harvested compared to pastures that are also grazed. Typically, pasture is not treated as it is hard on the grass and it is too expensive. Using triple the usual seeding rate and increasing fertilizer rates from about 50 lb N per acre to 70 or 80 lb per acre is one approach for addressing ventenata problems. Prowl H2O works well, but it limits cropping options as it is only supposed to be used on alfalfa/grass mixtures, and this treatment must be continued or the problem will resurface. Growers may have to quit raising alfalfa/grass mixes due to limits on what can be used for weed control.

Survey

A survey was sent to 1,200 producers in northern Idaho and eastern Washington. Five hundred sixty-three individuals returned completed surveys. Forty-one respondents stated they were no longer farming. The final adjusted response rate (AAPOR2) was 49.1%. The primary crops grown by the producers surveyed were wheat, alfalfa and grass hay. A significant number of producers also had pasture for cattle, pasture for horses or land in CRP. Just under half of respondents (49 percent) stated they had seen or heard of the grass Ventenata, and 40 percent of respondents had seen it growing. Of those that had seen it growing, 83 percent had seen it growing on their farm. Fifty-seven percent of individuals who had Ventenata on their property stated that Ventenata control on their property was “very important” and an additional 35 percent stated it was “somewhat important.” Farmer practices will be summarized and used to inform the IPM decision tool research and development. Data important to the economic analysis also were collected and those will be used this spring to gain additional insight into the economic impacts of ventenata. Further, the initial survey will serve as a baseline for our evaluation of the research and extension program.

Impacts and Contributions/Outcomes

• Outreach has raised awareness, and farmers and ranchers identify Ventenata dubia as important to manage in their production systems.

Collaborators: