April 29, 2011 Pest and Disease Update

From Ned Tisserat: I am forwarding some information from Kansas and Oklahoma on the status of wheat pests.    I really have nothing to report yet from Colorado.  The recent rains may start to trigger some foliar diseases, but the very dry fall and winter pretty much has kept diseases in check.  I also have not heard reports of much virus disease development, but to be honest, the crop is developing slowly, at least in the northeast.  If any of you have noted anything unusual please let me know.  

Wheat Disease Update – 29 April 2011
Bob Hunger, Extension Wheat Pathologist
Department of Entomology & Plant Pathology
Oklahoma State University

Oklahoma:  Barley yellow dwarf definitely is the most prevalent disease across Oklahoma.  Dr. Brett Carver (OSU wheat breeder) observed widespread BYD symptoms in breeder plots across northern Oklahoma.  The same is true here around Stillwater and to the west of Stillwater.  Around Stillwater and west to Marshall, wheat is past flowering with berries being fully formed to milky.  The nearly 2 inches of rain this past weekend likely will start some foliar diseases, but the only place I could find significant leaf rust in trials around Stillwater was in a strip of Jagalene that was planted early last fall.  This strip, which has leaf rust in the 25-65% range on the flag leaves, was also hit hard with powdery mildew and BYD.  Scattered leaf rust pustules can be found in susceptible varieties in other fields/plots.  In the diagnostic lab over the last week, samples have been diagnosed with brown wheat mite damage (southwestern, OK), with wheat streak mosaic virus, high plains virus, Triticum mosaic virus (panhandle), and with BYDV (northeastern OK).  Rick Kochenower (Area Res & Extn Spec – Panhandle) confirmed that only virus diseases such as BYD, WSM, etc. are appearing in the panhandle.

Reports/excerpts of reports from other states:
Texas (Rex Herrington, Research Associate, Texas A&M, College Station), 23-Apr:  On Saturday the 23rd, I stopped by our McGregor TX nursery, and found numerous single pustules of wheat stem rust on leaves in the McNair 701 trap.  Wheat leaf rust is much lighter than normal, due to the drought.  This is a dryland nursery, and is extremely drought stressed.

Texas (Dr. Yue Jin, USDA-ARS Research Scientist, Cereal Disease Lab, St. Paul, MN), 28-Apr:
Rust survey report from southern TX
        This is the first time for CDL staff to conduct rust survey trips in Rio Grande Valley since the early 1990s.  Dr. Goolsby, an entomologist at ARS Weslaco, hosted me during my surveys on April 20-21.  Dr. Goolsby is very knowledgeable on this unique and diverse agriculture system in Rio Grande Valley.  He has worked in this region for a number of years.
        Wheat stem rust
Stem rust was found on emmer, barley and triticale plants used in windbreaks of watermelon fields in Rio Grande Valley in southern TX.  According Dr. Goolsby, there are about 35000 acres of watermelon planted in this region, thus acreage of small grain cereals as windbreaks is substantial.  Varieties of these small grains planted in the windbreaks were unknown.  Majority of the fields were emmer only, some fields with emmer and barley alternating, and a few fields with triticale only. Windbreaks were generally planted in November last year.  As of mid April, barley plants were over-matured (dried up), emmer was at late milk to soft dough stages, and triticale was from flowering to early milk.  The barley and emmer appeared to be resistant to stem rust race(s) present in those fields as majority of plants were free from stem rust.  Infected emmer and barley plants were sparse and infections ranged from trace up to 20% in severity.  The triticale was highly susceptible with stem rust severity up to 80S.
        Wheat leaf rust
        Common wheat was not observed as a windbreak in the lower Rio Grande Valley (near McAllen) but an awnless variety of common wheat was observed as windbreak in a watermelon field near Laredo.  Leaf rust was not observed on this common wheat or on emmer and triticale in the lower Rio Grande.
 
Kansas (Dr. Erick De Wolf, Wheat Plant Pathologist, Kansas State University), 27-Apr:  The wheat in southeastern and south central Kansas is beginning to head out.  The growth stage of wheat in other areas of the state ranges between the boot and jointing.  Most areas of the state have been very dry this season and these dry conditions appear to be slowing the development of most fungal diseases. I continue to find low levels of leaf rust in central Kansas despite these dry conditions.  Most recently, I found leaf rust in Sumner county, which is just south of Wichita in south central Kansas.  The incidence of leaf rust was less than 1% but the disease was present on the flag-1 leaves.  I have not been able to find stripe rust or stem rust to date in Kansas.
Other diseases: Parts of southeastern Kansas have received frequent rains this week, which may increase the risk of Fusarium head blight (FHB) in this region.  Maps of FHB risk in Kansas and other states can be found on-line at: http://www.wheatscab.psu.edu/riskTool_2011.html.
        Severe powdery mildew has been reported in southeastern Kansas, and I observed mildew in demo plots near Wichita. Barley yellow dwarf also appears to be common in many areas of Kansas this spring, but I will need to do some additional surveys to determine how wide spread this viral disease may be.

Nebraska [Dr. Stephen Wegulo, Plant Pathologist, University of Nebraska, Lincoln), 27-Apr:  Yesterday I surveyed wheat fields in southeastern Nebraska (Saunders, Lancaster, Gage, Saline, and Jefferson Counties).  Wheat was just starting to joint in most of the fields I visited.  According to a report by the Nebraska Wheat Board which referenced a USDA source, wheat jointed statewide was 10% on April 25.  Dry conditions before mid April and lower than normal temperatures in March and April slowed wheat development somewhat.  Much needed rain over the last two weeks has considerably improved the wheat crop condition.
        I found disease only at Mead in Saunders County.  Leaf spots were starting to develop and powdery mildew was evident in the lower canopy.  There was a low incidence (less than 1%) of barley yellow dwarf.  I did not find any rust diseases.

Arkansas (Dr. Gene Milus, Small Grains Pathologist, University of Arkansas) 28-Apr-2011:  Wheat growth stages in Arkansas range from soft dough in the south to flowering in the north. Our drought ended quickly with up to 15 inches of rain during the past 6 days. The southeast corner received the least rain at 2.5 inches. Some wheat has been damaged by wind, rain, hail, and/or flood. More flooding is likely as rivers, creeks and ditches back up. Stripe rust is the most prevalent disease, but still at low levels. Temperatures are still favorable for stripe rust (upper 30s last night in Fayetteville). There is concern about scab, but none has been reported at this time. Septoria has been reported to be moving up plants but is still only at mid canopy. There have been reports of BYD from all across the state, but incidence and severity appear to be low. No new reports of leaf rust. No report of stem rust.

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