SOLVING SUMMER ANTHRACNOSE CONTROL

Dr. Frank Wong, University of California-Riverside Extension plant pathologist, is on a mission. His goal: to find better fungicide alternatives for summer control of anthracnose on annual bluegrass that lend themselves to summer stress management programs.

“In California, we have a lot of Poa annua greens,” says Dr. Wong. “Poa can do very well, but definitely needs protection from summer diseases, especially anthracnose.

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“We specifically focused on the mid-summer treatments because we currently don't have a lot of chemical options during this time period,” he explains. “We need to expand our choices and look for stronger alternatives to maintain high-quality turf during summer conditions.”

He points out that issues with resistance and other concerns curtail the use of many currently available treatments. Chemical control options for anthracnose are limited in some locations in California during the mid-season period of June to September. Sterol biosynthesis inhibitor (SI) fungicides are effective against anthracnose. However, concerns regarding potential plant growth regulator (PGR) effects at high rates prevent them from being used regularly under high temperature conditions. Resistance to strobilurin [QoI] compounds and benzimidazole fungicides has plagued some locations, and chlorothalonil use is limited to 26.4 ounces of active ingredient per 1,000 square feet annually.

Last season, Wong's trials included 24 combinations of products currently labeled or pending registration for anthracnose control. Laid out in three replicated 3- × 4.5-foot plots on a mixed annual bluegrass and creeping bentgrass green at Round Hill Country Club in Alamo, Calif., the plots were mowed at 0.125 inches five days a week and irrigated daily according to evapotranspiration needs. The turf, which received three applications of an SI fungicide prior to the first experimental treatment, was anthracnose-free and healthy at the time of the first preventive treatment.

Six applications of the treatments under investigation were made throughout the season beginning June 17, at approximately 14-day intervals. Anthracnose pressure was not noted until mid July, with levels eventually reaching 50 percent within untreated check plots. An accidental application of 2 ounces of an SI fungicide and 3.67 ounces of Daconil Ultrex per 1,000 square feet was made to the entire green on July 26. The experimental treatment scheduled for the first week in August was cancelled, with treatments beginning again in mid-August. Even with the unscheduled fungicide application, there were clear differences between the experimental treatments.

The study yielded “interesting results,” Wong says. “We found some very good and promising materials with potential for integration into summer stress management programs.”

The plant pathologist points to treatments containing Chipco Signature fungicide as “impressive control agents. Mixes containing Signature performed very well overall,” he explains. “Depending upon the tank mix partner used, control effectiveness on anthracnose was 90 to 98 percent.”

In fact, a mixture containing 4 ounces of Chipco Signature 80 WG plus 0.33 ounces of Medallion WG provided the best anthracnose prevention overall.

“Tank mixes of Signature with Medallion, Daconil or 26GT provided very good control,” he continues. “I have to admit I was somewhat surprised at the control we received. But these tank mixes were very effective in these tests.”

He adds that because the experiments were placed on a green that was still in play but scheduled for renovation later in the season, the results of the experiments reflected real life playing conditions. “This was a unique opportunity,” he explains. “Superintendent Troy Flanagan gave us a lot of freedom to allow for damage to occur since there was to be renovation on the course that would allow the damage to be repaired before an upcoming fall tournament. It definitely presented one of the best ways to put the treatments to the test and was a great help in this research.”

Wong is looking forward to additional, expanded trials with the product and mixtures. “Our data is preliminary and we need to gather field data from various locations and study the treatments under diverse conditions,” he notes. “But, from what we've seen to date, Signature treatments are good candidates for inclusion in summer stress management programs.”

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