We get more questions about grassburrs or sandburs than all other topics combined. They
have been around for at least 70 years and probably longer. The numbers seem to increase almost every year. The drought of 2011 seemed to kick start the explosion of grassburr numbers. The increase of fertilizer prices over the years with a corresponding decrease in the amount of fertilizer applied has made the problem even worse. The expense of treating for grassburrs with products that do not perform up to customer expectations has also limited the number of acres treated.
Factors outside of the producer’s control can limit grassburr control. 2021 was a prime example of that. Fifteen inches of rain in May leached much of the chemical below the root zone.
There are two classes of grassburrs, annual and perennial. Annuals come up from seed every year and perennials come from a root that lives year around. Perennials are much more difficult to control. The grassburr seed is viable for approximately ten years and may lie dormant for several years before germinating.
There are two types of chemicals that aid in grassburr control. Preemergent herbicides work by limiting the germination of grassburr seed and generally need to be applied twice a year for the best control. Postemergent herbicides attempt to control grassburrs that have already germinated and emerged. Postemergents work better on grassburrs that are less than two inches tall and have no effect on grassburrs that have already germinated. Most producers don’t notice grassburrs until they have a head on them which greatly reduces control. We recommend postemergent products as a rescue treatment because they only work on plants that are up and growing and have no residual.
Remember, the best grassburr control program starts with a good fertility program.
The following are options for preemergent control of grassburrs.
4 ounces of Panoramic in early February. The cost is about $14.25 per acre applied.
3 ounces of Rezilon in March. The cost is $33 per acre applied.
4 ounces of Panoramic in February followed by 3 ounces Rezilon in June. Cost is $47.25 applied
3 ounces of Rezilon in March followed by 3 ounces Rezilon in June. Cost is $66 per acre applied
The first two options may or may not last full season. Last year neither lasted full season because of the heavy rains in May.
When looking at price only, the Panoramic looks very good. It has one major drawback. In some instances, it can stunt your first cutting of hay. Many hay producers don’t even consider this product because of the risk of severe stunting.
Supplies of Panoramic and Rezilon should be adequate. Prowl supply and pricing is uncertain.
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