PRUSSIC ACID is often a problem in forage sorghums after a stress event such as frost.  I don’t think we had the freezing temperatures last week to freeze the plants.   But there may have been pockets in fields that did receive some frost damage.

Forage sorghum, sorghum-sudan, and sudangrass all have the potential to produce prussic acid poisoning in livestock.  If the frost is light and only kills the upper few leaves, the plant may attempt to regrow by putting out a new shoot from the base of the plant.  This new regrowth is most often where the prussic acid concentration can occur.

The regrowth after cutting or grazing is also of concern.  New, young shoots are very high in prussic acid potential.  Leaves contain twice as much prussic acid as stalks.

Prussic acid is the same as hydrocyanic acid (HCN), says Peter Jeranyama, SDSU Extension Forages Specialist.  “The toxifying action of prussic is almost immediate and death can occur within 15 to 20 minutes.  In general, cattle and sheep are more susceptible to prussic acid poisoning than horses and swine,” said Jeranyama.

Large amount of prussic acid may be released in a short period of time when sorghum plant tissue is injured by wilting, freezing, cutting, trampling.  The forage sorghums tend to be highest in prussic acid potential, followed by sorghum-sudan hybrids, then sudangrass, which is usually safe.

Wilting the forage for five to six days before feeding helps reduce its concentration, and makes it a safer feed for cattle.  Feeding green chop to cattle is usually safer than grazing as the prussic acid concentration is diluted more in the entire plant as compared to selective grazing of just the young leaves by the animals.

Stop in or give me a call at 589-3531 if you would like more information.

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RECENT RAINS are providing us an opportunity to get another punch on perennial noxious weeds.  The key for a successful fall program is to have adequate active growth.  Your best bets are with roadsides and areas that were mowed, grazed pasture and range, after small grain or silage harvest, and areas like CRP that were clipped during the summer season.   Fall is usually the best time to treat tree plantings and fencelines.

Spot treatments for small area will cost more, but give 80-95% reduction.  Tordon and 2,4-D are a good combination this time of year.  525 – Noxious Weed Control provides a lot of good information on control of a variety of perennial and biennial weeds.  Copies are available at our office.

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LAWN WEEDS like dandelion, white clover, plantain, and creeping jenny are actively growing now.  Herbicide applications in the next week or two should give excellent results on these tough to control perennials.

We sometimes recommend application after the first light frost to reduce risk of injury to other plants in the yard.  However it does not have to get below 32 degrees to be effective.

If there is heavy leaf cover from fallen leaves, raking the leaves before spraying greatly improves effectiveness.