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Musk Thistle Management Action List

Collage of thistles.

Calendar of thistle and Weevil Activity



Musk thistle head weevil overwinter in rosette

Plant: thistle rosettes Thistle rosettes in poor healthThistle rosettes with inside damage.

 Rosette weevil larval damage can be detected in the thistle rosettes.



Biennial musk thistle begin to emerge.   These plants will not begin their reproductive (bolting) until next spring.

Biennial musk thistle




Thistle that have overwintered begin their upright reproductive growth (bolting).

Now is the time to control problem areas with herbicides

A thistle plant. A bug on a thistle. A bug.


Now is the time to control problem areas with herbicides
Two people applying herbicides to thistles.




Purple to red flowers  indicate musk thistle is in full bloom.

Head and rosette weevil adults emerge and feed on thistle. Head weevils are laying eggs.  Collect weevils now for redistribution in other fields.



  Head weevils are feeding on the seeds in thistles heads.

A pink thistle. Head weevils are feeding on the seeds in thistles heads


July / August  

Musk thistle seeds are being dispersed by the wind.

Musk thistle seeds being dispersed by the wind.

An empty pupae chamber.Head weevil pupae and empty pupae chambers can be found in the thistle heads.  New adult weevils have moved into the ground until spring.  If at least half of the thistle heads in the fields have four to six pupae per head, there will be enough adults to collect and in the spring. 



Annual musk thistle begins to emerge. these plants will not flower until the spring.

Annual musk thistle.



Rosette weevils are laying eggs on the thistle seedlings 



Musk thistle overwinters as a rosette.

Musk thistle overwinters as a rosette.



Rosette weevils (eggs , larva, adults) and adult head weevils are hibernating until late February.



Table 1 Herbicide recommendations for control of invasive thistles in Oklahoma.

(Recommendations for controlling Thistles)

  Pasture and Range Rate Expense Levelb Fall - rosette Spring - rosette
Pasture and Range          
  2,4-D Amine 1 to 2 quarts/acre $ M M
  GrazonNext® 1.2 to 2.1 pints/acre $$ B-M-S B-M-S
  Grazon P+D 2 to 4 pints/acre $$$ B-M-S B-M-S
  Weedmaster® 1.5 to 2 pints/acre $$ B-M B-M
  Escort® 1 oz./acre $$$$   S
  Transline® 0.7 to 1.4 pt./acre $$$$   M
  Vanquish® 1 to 2 pt./acre $$$$   S

a 2,4-D, GrazonNext®, Grazon P+D and Weedmaster® are labeled for pastures and rangelands. Escort®, Transline® and Vanquish® are labeled for non-cropland. Grazon P+D is a restricted use pesticide. Read labels for specific information and guidelines prior to using the product.

b Check your dealer for updated prices.

c Control includes killing the actively growing plant and preventing it from producing seed. Best results are obtained with spring applications, so that fall and spring emerging seedlings are actively growing at the time of treatment. B = bull thistle, M = musk thistle and S = Scotch thistle.

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