Minor levels of leaf rust showing up now in Louisiana wheat

Stephen A Harrison, LSU AgCenter small grain breeder, reported late last week that there had been one report of minor levels of leaf rust on wheat in Louisiana.

“I have not heard any reports that would justify a fungicide application,” he reported in a memo sent to Extension agents. “I think we are weeks away from considering any kind of control measure. The warm weather we had the first half of January has pushed wheat along and is a contributing factor in the early development of leaf rust.”

Harrison also reported:

Oat stem rust turned up at the Ben Hur Farm in Baton Rouge in mid-fall and has continued to develop slowly. “ I first noticed oat crown rust at this site around January 10, and this has really exploded, with ideal temperatures for development and lots of free moisture. We have had a lot of cloudy weather and rainfall since mid-December and wheat around the state is suffering some from waterlogging and lack of sunshine, particularly on heavy and poorly drained soils. It is certainly a good year to have wheat on raised beds.”

Waterlogging is very evident. “A lot of wheat is pale and hungry.” Several weeks of dry weather would improve the appearance of this wheat, he added. “Growers may be justified applying a little nitrogen early this year to help green those fields up and get the wheat back on track. Topdress nitrogen applications should start going out in south Louisiana in early February, between leaf elongation and appearance of the first node. Given how wet our soils are it might be wise to fly on a split application. We have just about completed weed control activities in our nurseries at Winnsboro and Baton Rouge. Wet fields have made herbicide applications difficult. We will start topdressing as early as next week if weather permits.

Weed control, particularly Poa annua, has been a concern. “It has been too wet for many growers to get in the field, and much of the Poa is heading out. The dollarvalue of controlling Poa is questionable once it starts to head out. It is very hard to kill at that stage and will die pretty soon anyway.”

Cold weather is coming. “It is going to get cold again Sunday night, with temperatures in the 25-28 F range for north Louisiana and just a little warmer in south Louisiana. It has been pretty warm lately, and wheat is a little tender. But I do not expect any significant damage to occur. The majority of our wheat is too young for 26 F to cause significant damage. There may be a few fields that were planted too early have jointed out. These could suffer some damage but also have lots of time for secondary tillers to compensate.”

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