Bur Ragweed (Bursage) (Ambrosia grayii)

Description

A perennial, reproducing by underground root-stocks and seeds. Plant erect, 1 to 2 feet high, somewhat bushy, usually branching from the base and covered with fine, woolly hairs. The plant is purplish-white in appearance and grows from a well developed root system.

Leaves alternate, or opposite, broadly ovate, pinnately 3-5 parted or entire, long-petioled, dusty white in color. The end segment of the leaves much larger than the other segments.

Male flowers are in small drooping heads at the top of the plant and female flowers are in the axil of the leaves, usually one per leaf. Flowers in composite heads in short racemes. Seed cone shaped in heads 3-7 mm. long, with hooked spines or curved at tip. Seeds, September through November.

Prevention of Spread of Bur Ragweed

The occurrence of new infestations of bur ragweed can be reduced by cleaning harvesting and tillage equipment before leaving infested areas.

Bur Ragweed Control Practices

Control of bur ragweed shall mean preventing the production of viable seed and destroying the plant's ability to reproduce by vegetative means.

Cultural Control

Intensive cultivation following application of 2,4-D applied in the ester form in early summer (May 25 to June 20) gives good control. This is followed by seeding a winter small grain and the following year intensive cultivation is started immediately after harvest. Except for the first cultivation after harvest, 2,4-D may be substituted for some of the tillage operations provided soil moisture is ample, and bur ragweed is growing rapidly.

Rapid stand reduction can be obtained by using alternate crop and fallow, but one year of fallow followed by two small grain crops may be used.

Herbicides Approved for Controlling Bur Ragweed (Bursage)

The following herbicides may be used for cost-share with landowners. Other products labeled and registered for use on this noxious weed in Kansas may be used in accordance with label directions but are not available for cost-share. Be sure to follow all label directions and precautions. For additional information consult the current KSU publication of "Chemical Weed Control for Field Crops, Pastures, Rangeland, and Noncropland".

• 2,4-D LVE. Apply during fallow period. Apply during active growth at bud stage. Follow label directions and precautions.
  
  
• Dicamba + 2,4-D (Banvel + 2,4-D). See label for cropping limitations. Follow label directions & precautions.
  
  
• Dicamba (Banvel). For use on pastures, rangeland, cropland, and non-cropland. For suppression and top growth control. May injure cool season grasses. Follow label directions and precautions.
  
  
• Glyphosate + Dicamba (Roundup + Banvel + nonionic surfactant). Apply when plants are producing new growth initiated by moisture for at least 2 weeks and when plants are at or beyond flowering. Follow label directions and precautions.
  
  
• Picloram (Tordon 22K). Restricted Use Herbicide. Follow label directions and precautions.