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. 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 studied in the systems we are studying, with the exception of Axiom #169. The herbicides allow us to integrate with cultural tools to enhance economic viability and reduce the impact of ventenata.

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.

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:Impact of ventenata on ecosystem services within CRP.

Accomplishments/Milestones

Current practices and our current work towards changes in management continued with additional outreach meetings in Idaho (Salmon, Grangeville, Nampa, Lewiston, Orofino, Greencreek, Plummer, Moscow) and Enterprise, Oregon. The meetings have emphasized to us the importance of grazing management, soil fertility and harvest practices (Timothy). Leaving sufficient forage in the field to enhance competition is critical, as is ensuring a cutting height of four inches. Fertility needs to be timed so that potassium and phosphorus are applied in late summer or early fall with nitrogen applied in spring. 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.

The current distribution of ventenata includes most of eastern Oregon, some of eastern Washington and all of northern Idaho (Figure 1). As the distribution expands, we find greater need for the outreach component of our project and a keen interest in the research we have been engaged in through the Western SARE-funded project. The areas impacted include the areas targeted with this grant but also include a growing number of rangeland communities that are used for both livestock grazing as well as conservation objectives. Much of our work applies to that system, and we are partnering to address this additional dimension.

Included in our educational program is an electronic presentation that can be tailored to specific audiences and is included with our report. The electronic presentation is annotated so it can be used by others familiar with our work but not directly involved.

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. Ventenata germination was sampled along with environmental data. Emergence patterns were similar across production systems, with one hay production area with lower and slower emergence of ventenata seedlings (Figure 2). Preliminary analysis of degree day models is currently being conducted. We found emergence occurring after available soil moisture levels reach 8%, corresponding to approximately one inch of rainfall in the late summer to early fall (Figure 3). We now know that pre-emergent herbicides could be applied when nearly an inch has been received in an area, allowing timing to maximize effectiveness of a pre-emergent application. The information also allows farmers and ranchers to schedule fall applications of herbicides to our degree day model, starting the model once one inch of precipitation has been received.

In addition to soil moisture, we also know the minimum and maximum soil temperatures where germination will take place. We found a minimum temperature at 7 C, and we found that above 27 C germination also did not occur (Figure 4). If fall rains do not come and temperatures fall below 7 C, then delaying post-emergent applications would avoid applications made to seedlings prior to emergence. Emergence ranges from about one hundred up to nearly 2,000 seedlings per square meter (Figure 5).

Our nitrogen cycling study has been initiated, but we do not have results to share. Increasing amounts of litter were placed on the surface of small plots and will be followed in the 2013 field season (Figure 6).

IPM field experiments have been initiated: prescribed burning, litter manipulation, grazing to a predetermined utilization rate, hay harvest to a prescribed height of four inches and fertilization treatments timed to forage physiology have all been applied. Of note, Timothy in the four-inch cutting height for hay was noticeably greener (new leaf growth), even in late summer, suggesting the hay may have greater competitive ability in spring and summer. Each study is done in both low infestation sites (Figure 7) and high infestation sites (Figure 8).

Initial forage samples have been taken and will be compared with samples taken this summer. No analysis of forage data will be initiated until the 2013 forage production season to allow response to treatments to be compared with pre-treatment forage data.

We have noticed that litter enhances germination and survival of ventenata. We have found that litter covering at least 50% of the soil surface increases survival of ventenata. Without litter, the number of ventenata seedlings decreased by 80%. Litter management likely will play a role in managing for reduced infestations of ventenata (Figure 9).

The Conservation Reserve Program (CRP) was designed to place highly erodible farm fields into perennial grass to protect the soil resource. In addition, CRP also has other services it supplies that include wildlife habitat. High infestation levels of ventenata likely reduce plant diversity and subsequently diversity of other organisms as well. We are testing to see if lower insect abundance and diversity have an impact on cavity nesting birds. Our sites are colonized primarily by swallows, and we have followed growth and development of birds in low and high ventenata areas (Figure 10). Nest success was low (25% nest failure) when ventenata infestation was high when compared to low infestations. In addition, the eggs laid that resulted in a bird that left the nest was 79% for low ventenata and on 48% for high ventenata cover (Table 1).

• Figures and Tables of Accomplishments
• Master Educational Powerpoint for Ventenata Outreach

Impacts and Contributions/Outcomes

We will be able to report more on outcomes and impacts in our final report. Notable in our current report are:

1) increased costs of production because of ventenata,
2) regional economic impacts are significant,
3) importance of litter to increase ventenata survival,
4) an interest in diverse methods for control, which bodes well for our integrated pest management approach,
5) reduced nest success for cavity nesting birds.

As we complete our education and research program we will document additional impacts of our program.

Collaborators: