Bio-Control of Plumeless Thistle

Final Report for FNC93-030

Project Type: Farmer/Rancher
Funds awarded in 1993: $3,644.00
Projected End Date: 12/31/1995
Matching Non-Federal Funds: $1,825.00
Region: North Central
State: Nebraska
Project Coordinator:
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Project Information


Objective: to control Plumeless Thistle with biological control so I don’t have to use chemicals that (you need to use yearly) do not provide long-term sustainable control of my noxious thistles.

My farm has a 7-year crop rotation that includes about 90 acres of alfalfa that stands for 3 years. My crop rotation is corn, grain sorghum, corn, oats as a nurse crop for alfalfa, and 3 years of alfalfa. These are all grown without the use of chemicals. The use of winter rye would give me another cutting of quality alfalfa to sell. I also have a ewe/lamb operation and finish out the lambs, and a cull cow/calf operation; buy breed cows in November-December, calf in March-April, sell cows in August and most calves in September then repeat it again.

Sustainable Practices
- Ridge till-minimum tillage for corn, milo, soybeans for 25 years
- V plow to kill alfalfa by under cutting it for 10 years
- Crop rotation corn, milo or soybeans, oats, alfalfa for 25 years
- Pasture rotation with 6 paddocks for 12 years

- Noah Poritz supplier of slide series, Rhinocyllus conicus, and Trichosirocalus horridus. He also provided life cycle on the many bugs. BioQuip Products supplier of cages.
- Dave Holshouser, Extension Weed Specialist; Keith Jarvi, Extension Pest Management; assisted in presenting 3 workshops, setting up cages, releasing of bugs, and present for tour and helped answer questions.
- Terry Gompert, Extension Educator; set up workshops in Knox and Holt Counties
- Michael Lechner, Extension Educator; set up workshop in Cedar County
- Bruce Ofe, Antelope County Weed Control Supt.; set up workshop for Antelope County
- Roman Wortmann, Cedar County Weed Control; assisting in releasing of bugs, farm tour, and educating neighbors about the bugs.
- Nebraska Sustainable Agriculture Society; published news release about project and tour date. NSAS newsletter article.

1. To control Plumeless Thistle with biological control. I would not have to use chemicals that (you need to use yearly) do not provide long-term sustainable control of my noxious thistles. These bugs are not commonly used on Plumeless Thistle. Using cages to monitor the bugs. To educate neighbors about the bugs, and how you need to work with their life cycle to get the bugs to procreate.
2. I am using Rhinocyllus conicus (seed head weevil) and Trichosirocalus horridus (rosette weevil) to control the thistles. I have also made releases in three cages so as to be able to watch the bugs and three other cages with no bugs to watch the thistles as they develop without the bugs.

We were able to see the effect of the seed head weevil on the tour (June 23, 1994), because they were on flowers on the thistles in the huts that had bugs in them, but two weeks later as the adult bugs were starting to die off the thistles came with their second flush of flowers. There were still plenty of bugs though to lay egg masses on these flowers. We got excellent control of the seeds and there were only 1 or 2 weevils per head because of the small head size.

Not too much is known about the rosette weevil in this region of Nebraska although a farmer from Bloomfield, Nebraska called me after reading about my project in the Norfolk Daily News and asked if I would come to his farm and help find the rosette weevil that he released 3 years ago, (that he could not find) although he said “I don’t know what to look for”. We were able to find some thistle rosettes that had the center eaten out, but found no larva as it was too late in the season to find them. A research paper from North Carolina states it may take 3 years before you may be able to detect them.

I helped with two workshops one each in Knox and Holt County’s in 1994. I was to help with one in Cedar County, but due to the death of my son-in-law I was unable to go, but Dave Holshouer and Keith Jarvi did use my slides. There were a total of 25 farmers at these workshops. One workshop at each of the Nebraska Sustainable Agriculture Society’s Western Conference (Ogallala) and their Annual Meeting (Columbus). There were 8 participants at Ogallala’s meeting and 10 at the Columbus meeting for my workshops. I also presented a workshop for the Antelope County Weed Control Authority at Neligh, Nebraska, by myself for 18 farmers. The Weed Control Authority sent letters to area farmers inviting them to the meeting. I also hosted a farm tour on June 23, 1994 to show the bugs, and to release the rosette weevil. There were 12 people here that evening. The number was small, but I consider it a big success because it was the first time in 15 year of hosting a tour that neighbors from as close as a mile away came to see what I was doing and asking questions to my face. We also served lunch. Due to my health I was unable to do any workshops in 1995 except for the NSAS annual meeting in Columbus, Nebraska. There were 20 farmers at this meeting. I will do further workshops as requested.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.