Velocity kills Poa dead

EAST LANSING, Mich. - Managing Poa annua has traditionally been an inexact science, but researchers here at Michigan State University (MSU) along with chemical maker Valent USA, said they have discovered a postemergent herbicide that controls Poa and certain broadleaf weeds in bentgrass and ryegrass fairway turf.

“Velocity controls Poa,” said Jason Fausey, field market development specialist for Valent. “We are used to managing it, so this is a different approach.”

Valent acquired rights to Velocity in the turf and ornamental market from Kumiai Chemical. The Japanese chemical maker has rights to the agricultural market where the herbicide is currently registered for use on rice to control barnyard grass. Velocity’s active ingredient, bispyribac-sodium, inhibits the enzyme acetolactate synthase, which plants require to produce three key amino acids.

Valent submitted its approval package for Velocity to the U.S. Environmental Protection Agency in April. Company officials said Velocity’s low use rates, favorable toxicology profile and the fact that it is already approved for use in other markets should speed the EPA approval process.

Velocity is approved for use under special local needs in Georgia, Florida and South Carolina to control Poa annua in overseeded ryegrass fairways. A special local needs label for Michigan is currently pending.

Velocity has a wide application use since most courses across the country view Poa annua as a nuisance.

“Bentgrass and ryegrass are very tolerant overall,” Fausey said. “There is some potential for slight discoloration, but what we have seen is very slight.”

Poa annua, on the other hand, is not tolerant at all. Growth usually stops three to seven days after treatment and Poa annua turns yellow or brown within three to 14 days after treatment. It dies approximately 21 to 28 days following treatment.

Since Velocity effectively eliminates Poa annua, leaving bare earth behind, application rates and timing will depend on the goals of each individual course.

“A sober assessment of Poa populations is required,” said MSU research specialist Ronald Calhoun. “On the label it should say ‘Caution: this will work.’”

Initially, Velocity will be labeled for fairway use between June 1 and Sept. 1. For courses with a high percentage of Poa annua, Calhoun said two applications at a rate of 30 grams on Aug. 15 and Sept. 1 would be the best fit for most courses trying to control Poa annua in their bentgrass fairways. A late-season application allows for reseeding of bentgrass at a time when the level of play is lower.

According to Fausey, a new course that has 5 percent Poa annua can take more of a maintenance approach.

“A new course could go in with a higher rate at one to two applications a year and control Poa,” he said. “The percentage of turf that is removed will be filled in quickly so it won’t be as noticeable.”

RESEARCH ON GREENS APPLICATIONS ONGOING

Calhoun and Fausey are continuing research on how best to use Velocity on greens.

“We are taking more of a transition approach,” said Fausey. “We have had good results with low rate applications through the summer months and we are getting 50 to 60 percent control in the following year. But we need to do more research to get more comfortable with greens use.”

In addition to working on plots at MSU, Calhoun has been doing work with area golf courses to get a better sense of how effective Velocity is under the daily stress of traffic and compaction.

Research work on postemergent goose grass control and crabgrass control is also continuing.