Friday, March 30, 2012

Update on Wheat Pests

From Dr. Tisserat:

More information on some potential insect/mite problems on wheat. 

Dr. Frank Peairs  indicates that ‘ Brown wheat mite is fairly widespread where it was not limited by extended snow cover.’   Chris Stallman reports that the mite infestations in certain parts of Cheyenne and Kiowa counties are severe.

Frank also mentioned that  ‘ Reports of some army cutworm activity are more frequent than they have been for the past few years.  Russian wheat aphid has been reported from the west slope, but so far does not seem abundant in the east.’ 

Bob Hammon from the Western Slope has also indicated that he is seeing a lot of wheat curl mites now.  And just a reminder that the Diagnostic Clinic is performing wheat virus tests to growers again this year.  If you see mites or aphids, and notice symptoms on your wheat, please send them in to the Clinic for screening. 

Wheat Disease Update

From Dr. Ned Tisserat:

The very warm weather will be speeding up the development of the wheat crop in the state.   Because of the dry March, I don’t expect that there is much disease activity, at least not in dryland wheat.   Some of you may be thinking of applying a fungicide along with the herbicide application at tillering as ‘insurance’ or for other reasons (plant health).   In my opinion, unless you know there is active disease (rust, Septoria, powdery mildew) in the field, a fungicide application at this stage is NOT warranted .  Our research trials have not shown any benefit of these early treatments in the absence of disease.   Remember, every time you make a fungicide application, you are potentially selecting for pathogens that are insensitive to that fungicide, whether the chemical is a strobiluron or triazole.   The risk of shifting the pathogen population to one that is insensitive to the fungicide is small, but real.   For example, we now have fungal pathogens resistant to strobilurons in many crops (sugar beet, apples, soybeans, even wheat in the UK). And once that shift occurs, it appears to be permanent (i.e. there is little or no cost to the pathogen).  Let’s save these fungicides for when we really need them. 

Stripe rust has been reported in Kansas ( Manhattan and Wichita) and Oklahoma, but not in any regions closer to Colorado (see Kansas report below).   It is still advisable to keep a close watch on the developing crop for stripe rust.

The following is from Erick DeWolf, Extension Specialist, Kansas State University.

The wheat crop in Kansas ranges between the jointing to boot stage of growth.  I suspect some wheat in Southeast Kansas is already be heading.  This is 2 or 3 weeks ahead of normal crop development.  Weather forecast for the next 3 days indicates that temperatures will remain warmer than normal with high temperatures consistently in the 80's and low temperatures in the 50's for much of KS. Weather forecast for the next 3 days indicates that temperatures will remain warmer than normal with high temperatures consistently in the 80's and low temperatures in the 50's for much of KS.

Stripe rust was observed in Sedgwick County (South Central, KS) yesterday (March 28).  Gary Cramer, Extension Agent for Kansas State University, reported the find.  Gary indicates that low levels of stripe rust in the mid canopy of a production field west of Wichita.  The wheat in this field was near flag leaf emergence at the time stripe rust was detected.  The grower indicated that this field was planted with the variety "Everest".  Everest was considered moderately resistant to stripe rust in 2010 when KS experienced a severe epidemic.   My discussion with Bob Bowden, USDA wheat rust specialist here in Manhattan, suggests that Everest often develops some symptoms of stripe rust but the reaction type has been moderately resistant in previous years.  I will do additional scouting and checking for infections this next week.

Leaf rust was  detected in research plots near Manhattan (Northeast, KS) today (March 29th).  The incidence of leaf rust was very low (<1%) in these plots. The wheat in this field was at flag leaf emergence and leaf rust was found in the mid-canopy.  The infection was on an older variety "2137" that is known to be susceptible to leaf rust. 

 No reports of stem rust to date in Kansas.

 Severe tan spot was reported in Riley county( Northeast, KS), and powdery mildew continues to increase in many areas.

Aphids are present at considerable numbers in Southeast Kansas and have also been observed near Manhattan.