Sclerotinia sclerotiorum Bio-Control Plots

Matt Schuster, Minidoka County Extension Educator

Reid Smith, Minidoka County Weed Superintendent

October 18, 2001

 

Plots were established and treatments applied on April 11, 2001.  Two sites were established on federal land.  One site was established on Jackson Island, which belongs to the Bureau of Land Management.  The site was established on Cape Hawley, which belongs to the Bureau of Reclamation.  Both sites have a problem with Canada thistle, and because of their location or regulations, cannot easily be sprayed with herbicides.

 

Both sites were set-up in a completely randomized design with three treatments and five replications.  Plots measured 2 meters by 2 meters.  Treatments included a control, 40 grams of S. sclerotiorum, and 160 grams of S. sclerotiorum per plot.  S. sclerotiorum inoculum is packaged as a dry product and treatments were applied (or sprinkled) in uniform manner.

 

Temperature:                35-37oF

Humidity (%):               73%

Soil temp (4”):              41oF

Cloud cover (%):          95%

Time:                            Jackson Island   9:30am

                                    Camp Hawley   10:30am

Precipitation:                 0.15” (April 11-12)

Wind speed:                 Jackson Island   1-5 mph

                                    Cape Hawley   5-10 mph

 

Plant counts were taken 6, 14, 28, 84, and 142 days after application.

 

Results

Treatments of S. sclerotiorum did not differ, or had more Canada thistle than the control, at both sites.  By 142 DAT, the 160 g/m2 treatment had 15% less Canada thistle than the control, but the 40 g/m2 and the control were essentially the same at the Jackson Island site.  However, the treatments at Jackson Island were not significantly different from one another for any evaluation date.  At the Cape Hawley site, both S. sclerotiorum treatments had higher populations of Canada thistle compared to the control.  However, only the last evaluation date showed a significant difference from the control.  At both sites, the 40 g/m2 treatment had the highest population of Canada thistle at each evaluation date after 28 DAT.

 

One possibility for the poor performance of the S. sclerotiorum may have been the result of the painted lady butterfly (Vanessa cardui), which is a thistle-eating butterfly that did an excellent job of controlling Canada thistle.  The Magic Valley had a significant infestation of these insects during the spring of 2001.  Therefore, that information needs to be considered when evaluating the results of this study.

 

See Results

 

Jackson Island Plot Layout:

200 N 500 E (on island)

Rupert, ID  83350

North
 
 


(­ River)

11

 

160 grams

12

 

40 grams

13

 

Control

14

 

40 grams

15

 

160 grams

6

West
 
 


Control

7

 

160 grams

8

 

40 grams

9

 

40 grams

10

East
 
 


Control

1

 

40 grams

2

 

Control

3

 

160 grams

4

 

Control

5

 

160 grams

South
 

 

 

 

Cape Hawley Plot Layout:

350 N 100 W

South
 
Rupert, ID  83350

 

11

 

160 grams

12

 

Control

13

 

160 grams

14

 

40 grams

15

 

Control

6

East
 
 


160 grams

7

 

40 grams

8

 

40 grams

9

 

Control

10

West
 
 


Control

1

 

40 grams

2

 

Control

3

 

160 grams

4

 

40 grams

5

 

160 grams

North
 
(ßHighway)