For Release January 23, 2005

Asian Soybean Rust Update

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

Roughly two months has passed since the US Department of Agriculture announced that soybean rust had been found in the United States. Since that initial find in Louisiana, the rust has been found in about two dozen counties in nine states, the closest being the Bootheel region of southeastern Missouri. There is no doubt, in most of our minds, that soybean rust will arrive in Kansas this year and a good chance it will be found in Geary County. But don't give up growing soybeans just yet!

The potential for damage from soybean rust is huge. Based on where the disease showed up in November, it is set to explode right into the heart of the soybean belt. Regional losses of 50% have been predicted with nationwide losses of 10% . But fortunately for Kansas, we have several things working in our favor.

First of all, like all rust diseases, soybean rust needs green living tissue to overwinter on. It doesn't have to have soybeans to overwinter, it is successful at overwintering on many legume crops including the widespread kudzu on which it was found growing in late November in Florida. But it is generally felt that the disease is most likely to overwinter in southern Florida and the southern tip of Texas. Interestingly, the disease was not found last fall in either of these two locations. So most likely, the disease will have to develop in the south and blow in with warm moist winds.

Soybean rust prefers moderate temperatures and higher humidity. By the time enough of the disease gets rolling in the south, it may be too hot and dry for it to get established in much of Kansas. However, a repeat of 2004's cooler than normal and wetter than normal June and July and we could be staring straight down the barrel of a rust explosion. It is generally felt that we are more likely to see soybean rust develop late in the season when most soybean fields are starting to shut down and die down anyway.

The Environmental Protection Agency has already started registering fungicides for the certain need during the coming growing season. None of the current soybean varieties have any genetic resistance to soybean rust. The Ag Research Service branch of USDA has been doing fungicide trials in South Africa and South American since 2001 to get a handle on treatment programs. Early detection is going to be very critical as this disease can explode rapidly. Under heavy soybean rust pressure, two or three applications of fungicide were required for protection. In most cases an application at flowering was followed by an application 20 days later, If this becomes necessary, expect an increase in production costs of $25 to $30 per acre.

For the 2005 crop season, I wouldn't change any production plans. But it will be very important for all of us to be scouting fields on a regular basis as the season moves along. I expect that we'll have plenty of warning to be on the lookout for the disease as it heads north. Walking fields twice a week may be warranted as we head into critical periods. I'll be having a meeting in February to provide soybean producers with information on how to scout fields, what to look for and what the treatment options are IF treatment becomes necessary.

We've had a lot of years with soybeans that were fairly trouble free. Changes in the farm bill and the advent of Roundup tolerant soybean varieties have tripled soybean acres in the past 15 years. Now we get to pay the price for the popularity of soybeans. And a year from now, we'll unfortunately know a lot more about soybean rust than we do now!

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