Arrest® - Postemergence Herbicide greatly improves quality and longevity of forage plantings

W. Carroll Johnson, III

“To our mothers, wives, and children who must surely have wondered how grown men could become so enraptured with weeds" *

Sethoxydim (Arrest®) is a postemergence graminicide – a herbicide that controls emerged grasses.  Sethoxydim was registered in 1983 for use on soybean and cotton.  Later, other crops were added to sethoxydim registrations.  Sethoxydim products have recently been packaged and marketed for small acreage specialty crops.  An example is Arrest®, a sethoxydim product registered for use on forage legume plantings.

Many consider sethoxydim-containing herbicides like Arrest® to be indispensable tools for managing food plots.  These herbicides consistently control emerged annual and perennial grasses, with minimal phytotoxic effects on broadleaf crops.  Arrest can be used on most broadleaf forages including clover, alfalfa, Brassica, chicory, and forbs.  While these herbicides are simple to use and nearly foolproof, there are recurring questions that need to be answered.

How does Arrest® kill grasses?  The foliage of grasses quickly absorbs Arrest® and other postemergence graminicides.  Once inside the leaf, Arrest® is translocated through the vascular system of the grasses and accumulates in growing points.  Growing points can be in the above ground buds and, in the case of perennial grasses, in the underground growth buds.  Growing points are more numerous in large weeds than in small weeds, thus making large grasses difficult to control. Arrest® inhibits amino acid synthesis in the growing points of grasses, thus symptoms are first seen in the growing points, not in the whole plant.  While visible symptoms are slow to develop, the growth of treated grasses ceases long before symptoms are expressed.

The accumulation of Arrest® in the growing point of grasses is not particularly efficient, thus weed control efficacy is largely dependent on environmental conditions that favor herbicide absorption, treating small grasses, using an appropriate rate, following adjuvant recommendations (as stated on the label), and thorough spray coverage.  If any of these conditions are compromised, weed control efficacy will be reduced, although Arrest® and other postemergence graminicides are among the most consistent herbicides available.

How can I tell if Arrest® is working?  Beginning about five to seven days after Arrest® treatment, an unfolded leaf blade in the whorl (growing point) can be easily removed, showing a brown, partially decayed base of the leaf blade (Figure 1).  This is typically the first symptom of Arrest® activity on grasses.  These symptoms progress to yellow leaves, beginning with the growing point and spreading to the entire plant (Figure 2a).  After about 14 to 21 days, the entire plant essentially melts away (Figure 2b).

Does a crop oil concentrate need to be used with Arrest®?  This is a confusing issue, since there are differing adjuvant recommendations among sethoxydim herbicides.  A crop oil concentrate helps postemergence herbicides penetrate the leaf cuticle.  Arrest® does not need a crop oil concentrate adjuvant since there are surface active agents included in the commercial formulation and the Arrest® use rate is increased as further compensation.  This is useful to the customer by not having to procure another product.  It should be noted that other sethoxydim herbicides may not be formulated the same as Arrest® and require a crop oil concentrate for maximum efficacy. The often stated phrase - “follow the herbicide label” – is the solution to the confusion.  

How long does Arrest® need to stay on a plant to protect from wash-off?  Arrest® is quickly absorbed by grasses giving the herbicide excellent protection from wash-off.  Arrest® is adequately absorbed one hour after application.  As with any herbicide, avoid applying Arrest® if rainfall is imminent or during droughty conditions.  A weed scientist’s cliché is worth remembering:  “If conditions are good for plant growth, then conditions are good for herbicides”.

How is Arrest® used for perennial grass control?  This is a common question—from the South on johnsongrass, to the North and Mid-west on quackgrass.  A key fact to remember is that perennial grasses propagate by seed and overwintering vegetative structures (roots, rhizomes, tubers, and stolons).  Vegetative structures tend to re-sprout, guaranteeing the need for multiple applications of Arrest® per year for acceptable control.  Once it warms in the spring and perennial grasses begin sprouting from the overwintering structures, the first application of Arrest® needs to be made.  Subsequent applications should be timed according to re-growth, which can be two to four weeks after the initial application.  When treating perennial grasses with Arrest®, use the high end of the rate range.

This entire regime will likely need to be repeated the following season.  This is due to perennial grass seedlings sprouting from dormant seed and continual re-sprouting from the surviving vegetative structures.  It is safe to say that perennial grasses are a pest you learn how to manage the best you can and accept a few survivors.  While perennial grasses are difficult to manage, Arrest® makes the job possible.

Several years ago, I wrote an article in Whitetail News on grass control with sethoxydim herbicides.  In that article, I presented a brief history of sethoxydim, including a personal recollection of the reaction of North Carolina peanut growers in 1982 the first time they saw sethoxydim demonstrated in research plots.  This herbicide was a major developmental breakthrough in weed control technology and in the peanut farmer’s eyes – a miracle.  Without a doubt, Arrest® is a valuable weed control tool for managers of food plots, just like it is for peanut farmers.  The grass control Arrest® provides will greatly improve the quality and longevity of forage plantings.

As with any herbicide, read and follow all instructions on the herbicide label.