1. Assessing the Impacts of Biological Control on Spotted Knapweed in Minnesota
Natasha Northrop
Minnesota Department of Agriculture
Legislative Commission on Minnesota Resources (LCMR)
Hello! My name is Natasha Northrop. I am part of the Weed Biological Control Program with the MN Dept. of Agriculture. I am here today to share with you our recent assessment of spotted knapweed biological control in the state of Minnesota.

2. Spotted Knapweed, Centaurea stoebe L. ssp
Spotted Knapweed, Centaurea stoebe L. ssp. micranthos (Gugler) Hayek (syn.=C. biebersteinii DC.)
Spotted Knapweed is an exotic terrestrial weed from Eurasia, and was first reported in the early 1930’s in Minnesota. It has a complicated scientific name as a subspecies of Centaurea stoebe, which I will not get into with our limited time. (Smile!) It has become a fairly common weed in many parts of the state along roads, railways, and other vectors that allow for transport of seed-infested hay and gravel. Knapweed seed is also picked up and moved by vehicles, logging equipment, and road construction vectors.

3. Spotted Knapweed
This highly invasive weed moves into and threatens pastures, grasslands, and prairie ecosystems, easily infesting disturbed areas and preferring well drained soils.

4. Spotted Knapweed Infestation
Spotted knapweed thrives by its ability to produce mass quantities of seed, and crowds out other vegetation by creating a monoculture. It’s self-proliferation is believed to be in part due to its production of allelopathic chemicals that alter the soil chemistry. As you can see from this infestation, if this was supposed to be a nice grassland for your cows to munch on, or a natural area, the carrying capacity as well as the biodiversity of the vegetation has been greatly reduced. Not much likes to feed on knapweed, and it’s toxicity causes intestinal problems in many ruminant animals.

5. Spotted Knapweed Biological Control Agents
Agapeta zoegana
Cyphocleonus achates
Larinus obtusus
Urophora quadrifasciata
As a less expensive and more environmentally sound alternative to using herbicides to control spotted knapweed, the USDA-APHIS-PPQ started releasing tested and approved biocontrol agents at infestation sites in MN in Since then, 11 bioagent insect species have been released in the state. In the year 2000, the program was turned over to the MN Department of Agriculture. We carried on with the program with the knowledge we had, but an evaluation needed to be done. We wanted to know what agents worked best, where all the biocontrol sites were, what agents were actually establishing in the field, or if this was even a viable pest management strategy. The plant being in the absence of those natural enemies is one reason exotic species can turn invasive in new territory. In theory, once established and at a critical mass in numbers and distribution, the introduced biocontrol will be a self-sustaining process that will bring the invasive species under an acceptable level of control, as it occurs in its native range. The invading weed will probably never be eradicated, but will instead become an integrated part of the plant community, much better than it invading and threatening the other vegetation.

6. LCMR* Research Project: Biological Control of Spotted Knapweed in Minnesota
My coworker Tony Cortilet obtained funding for a grant supporting an evaluation on spotted knapweed biocontrol through the State Legislature. It was a joint grant proposal with the Minnesota Department of Natural Resources, where they would evaluate potentials for biological control of Buckthorn.
*Legislative Commission on Minnesota Resources, now called the Legislative-Citizen Commission on MN Resources (LCCMR)

7. Goals of SK Biocontrol Research
- Increase MDA’s knowledge of spotted knapweed & biological control of this weed in Minnesota - status of most release sites was unknown.
- Define trends related to site characterizations that might affect biocontrol; define trends related to the invasiveness potentials of sites.
- Determine control impacts of bioagents.
- Develop protocols for future management decisions & best management practices.
The goals of the research were to increase our knowledge of the weed, evaluate the status of each biocontrol site, including bioagent establishment and impacts, and identify trends we saw along the way. All of this was in order to develop protocols for future management decisions and practices.

8. Research Methods:
1) Obtain USDA-APHIS-PPQ Release, Monitor, & Harvest Biocontrol Records; combine with MDA Records (2004)
2) Characterize each biocontrol site (2004)
a) visit each site once during growing season
b) topography, soil type, ownership, land use, etc.
c) delineate knapweed infestation area = acreage
d) vegetation observations; % knapweed cover (est.)
e) bioagent presence (sweep netting)
3) Revisit 10 sites w/high bioagent recoveries/combos (2005)
a) sample each site three times over growing season, more detailed vegetation sampling
b) use random transect sampling within delineated infestation areas
Our research methods were as follows: The first objective of the grant was to obtain all PPQ data, including release, monitor, and harvest records, combine it with any MDA data, and organize it into a database. Then, in the growing season of 2004, each site was visited and characterized by ownership and land use as well as various geographical, landscape, and soil parameters. The infestation at each site was to be delineated, the knapweed % cover estimated, and other vegetation recorded. Lastly, bioagent presence was taken through sweep net sampling through the vegetation. The next season in 2005, sampling occurred at 10 sites that had high bioagent recoveries and combinations in The sites were sampled 3 times over the growing season. This time, more rigorous vegetation and bioagent sampling was done using random transects within the infestation delineations created the year before.

9. Advanced Technology in the Field
All data was taken electronically through a Mobile Weed Mapping System developed by MDA, using a handheld iPAQ Pocket PC with ArcPad and a fully integrated Bluetooth Wireless GPS. Data forms were created specifically for each piece of data you wanted to collect.

10. 2005 Transect Sampling
quadrate data= # knapweed stems, ht. of 5 random stems, # rosettes, # flowers, # seed heads, % knapweed bloom, % cover (knapweed, other forbs, grasses, bare ground, etc.)
1 transect =
1m2 quadrate drop
+ sweep set (25 sweeps)
+ 1m2 quadrate drop
I wanted to use this slide to take a closer look at the transect sampling. We took vegetation data within these meter-squared quadrates at random points, and used this sweep net method to collect the bioagents.

11. Identified Biocontrol Release Sites with GPS Data
So here’s what we found! By the end of 2004, 103 sites were sampled, most of them residing (POINT) in the metro and this NorthWest Central part of the state. Some of the sites were no longer accessible or were obviously no longer suitable biocontrol sites due to various factors. But we learned that there were many established field insectary sites that were collectable for redistributing agents to new sites.

12. Bioagent Species and Releases in Minnesota, 1991-2004
Biocontrol Agent
Order
Family
Method of Damage to SK
Released
Agapeta zoegana
Lepidoptera
Cochylidae
Root Borer (L)
1,717
Bangasternus fausti
Coleoptera
Curculionidae
Leaves/Rosettes (A), Seedhead (A/L)
2,975
Chaetorellia acrolophi
Diptera
Tephritidae
Seedhead (A/L)
1,340
Cyphocleonus achates
Leaves/Rosettes (A), Root Borer (L)
3,745
Larinus minutus
61,646
Larinus obtusus
3,519
Metzneria paucipunctella
Gelechiidae
5,470
Sphenoptera jugoslavica
Buprestidae
100
Terellia virens
600
Urophora affinis
108,550
Urophora quadrifasciata
41,400
Urophora spp. mix*
565,663
(A)=Adult Stage
(L)=Larval Stage
Total:
796,725
We found out where and when all of these 11 different bioagent species were released, and in what kind of numbers and combinations. The Urophora seedhead gall flies were released in the largest quantities. The Larinus species were second highest in release numbers. Overall, there were 4 species of flies, 2 moths, 4 weevil species, and a very small number of buprestid beetles released. They each specialized in some method of damage to the spotted knapweed. There have been around 800,000 bioagents released total.
*Release consisting of mixtures of U. affinis and U. quadrifasciata.

13. Peak Emergence Chart of Recovered Spotted Knapweed
Bioagent Species at 10 Biocontrol Sites in MN, 2005
These are the 6 bioagents we were able to recover, and that we think are well established and seem to do well in Minnesota’s climate. In addition to the seedhead agents I’ve already mentioned, the root-boring weevil Cyphocleonus achates, and the root-boring moth Agapeta zoegana were also recovered. Sampling for all of these agents over time during the 2005 season allowed us to create a peak emergence chart, so we’ll know the best time to collect them, specifically in our state, when planning to redistribute them to other sites.

14. Obstacles to Drawing Solid Conclusions About Trends & Impacts of Biocontrol on Spotted Knapweed in MN
No Pre-release data
no Knapweed density, stem counts, rosette counts, etc. before biocontrol.
no records of other vegetation present at beginning of invasion or before biocontrol.
In general, what was the site like before biocontrol?
Now we at least have baseline data to compare new data to in the future.
High variability between the many unique sites
both in site characteristics and the agent combinations and numbers released; few trends could be identified across sites within any parameters.
indicates sites have to be treated on a site-by-site basis.
Unfortunately, there was no data taken before biocontrol releases, so we had nothing to compare the data we just obtained to. This made it difficult to draw solid conclusions about the impact the biocontrol was having. ?What was the knapweed and vegetation like before biocontrol? And now what is it like years after releases? Now, we at least have baseline data to compare new data to in the future Also, there was high variability from site to site in their characteristics as well as their biocontrol species combinations, and numbers released. With the sites being so unique in so many ways, few trends could be identified across biocontrol sites in our analysis. This indicated sites needed too be treated on a site-by site-basis.

15. Other Observations & Lessons Learned
Visible decrease in knapweed.
Urophora flies – they’ve established everywhere and can distribute on their own. We no longer put efforts into moving them.
Sites with a combination of root agents and seedhead agents seemed to give better control.
The trends we were able to identify from observations came to us as valuable lessons learned. Photos were a great source of impact feedback - pictures of many sites that were taken before and after biocontrol have shown visible decreases in knapweed. Also, we learned that the seed head flies are pretty much everywhere and doing well. We no longer put efforts into supplementing or moving them as they disperse easily on their own. A third trend we identified was that the best control comes when a combination of a root agent along with seedhead agents is used. Most sites just had seedhead agents prior to this research, and weren’t getting the results like this site (POINT TO PICTURE) that DID have a nice combination of the agents.

16. Best Biocontrol Impacts Observed =
Larinus spp.
Urophora spp.
Seedhead Agents +
Combating the weed from as many fronts as possible, from top to bottom, seedhead to root, using this combination hits the weed the hardest. Initially, there were more seedhead agents in supply when we were getting them from outside sources. Now that we have established field insectary sites for both seedhead AND root agents, we can readily collect and redistribute them. This should drastically improve impacts at sites where there were previously only seedhead agents.
Cyphocleonus achates
Agapeta zoegana
Root Agents

17. Other Benefits:
Minnesota Cooperative Weed Biological Control Project: MDA, USDA-APHIS, MN DNR, MN DOT, MN Association of County Ag. Inspectors, USFWS, University of Minnesota, Private Landowners.
Renewing and gaining new interest in the program, and regenerating communication and implementation between spotted knapweed biocontrol collaborators.
Collaborators were great source of impact feedback.
There are many other benefits that came out of this research. The MN Cooperative Weed Biological Control Project consists of a network of people who have been implementing and participating in the spotted knapweed biocontrol program for many years, from private land owners, to County Ag. Inspectors, to other agencies like the US Fish & Wildlife Service. This research has really helped renew and regenerate interest in the program, and has sparked new interests as well. Collaborators turned out to be our greatest source of impact feedback for this research project. They are the ones who have been observing their land since the releases. Many have reported a noticeable decline in knapweed using biological control, and many sites are considered controlled by it. Collaborators have been well educated and understand that the process requires patience, sometimes up to a decade on large sites to work. The program is getting positive feedback, and working together is what makes the program a success.

18. Research is a Work in Progress
-Based on observations, we can now make biocontrol recommendations.
-Data coming in later may modify these recommended practices.
-Also started a 7 yr. IPM project with MN DOT using biocontrol and herbicide in 2006 – we’ll see!
We still have a lot of work to do, and if the desired result isn’t yet occurring at a site, it still may need to be supplemented with the right agent combination. We continue to have a growing list of people who are eager to get the bugs. So this research continues to be a work in progress. Now, based on observations, we can now make experienced biocontrol recommendations. We are going to collect more data this summer, and as new observations and data are pulled in over time, we can modify our recommendations. We plan on trying to tease out more trends and correlations along the way. We have also started a 7 year IPM project with MN DOT using herbicide and biocontrol together, in hopes that control can be obtained faster using this regime.

19. For More Information Natasha Northrop, MDA Weed Biocontrol Program:
MDA Spotted Knapweed Biological Control
Video: Using Advanced Technology for Efficient Fieldwork
MDA Integrated Pest Management Program:
MDA Weed Mapping System & Viewer
Legislative-Citizen’s Commission on MN Resources
If you would like to learn more about this project, here is my contact information. There’s a great little video about the mobile weed mapping system on our knapweed page, where you will also soon be able to access a copy of this LCMR Report. There is our IPM program link, links to our Weed Mapping System and Viewer, and the LCMR.
I would like to acknowledge my coworkers Tony Cortilet and Monika Chandler for giving me opportunity, knowledge and guidance in getting my career going.