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Date: May 14, 2007
Source: The Hays Daily News, Kansas [edited]
<http://online.hdnews.net/content/news/wheat051407.shtml>

High winds brought a quick halt to last-gasp attempts to protect this year's [2007] wheat crop from leaf rust, a disease brought on by this year's abundant moisture. While that moisture is making the prospects of a bumper crop -- at least in the western third of the state -- a distinct possibility, it is also bringing with it difficulties that are sure to rob some of the yield potential from this year's crop.

Strangely enough, Kansas State University wheat breeder, Joe Martin, said he's already seeing signs of drought stress, even though the soil is full of moisture. "I'm afraid what we've got is a wheat crop that is used to three-quarters of an inch [2cm] of rain every week," he said. Less than that fell in the Hays area last week [7-13 May 2007], even though the rest of the state was inundated by floods.

The 2007 wheat crop is also struggling with wheat streak mosaic, a disease spread by the wheat curl mite. [There are also a few] fields that are suffering from both wheat streak mosaic and the relatively new _Triticum mosaic virus_. Together, those 2 viruses can decimate a crop. "The plants are dying," Martin said of fields that are battling both diseases. "That's what happens. [With] both of these viruses together, [the plant] will probably die off before it matures." But there's still plenty to learn about the disease, he said, including exactly how it is spread or what effect it might have on the future of the wheat industry. "I'm not sure how important this virus will be in the long run," Martin said.

Until the [strong winds started], it was leaf rust that was a concern. Crop experts, however, say it's simply too late to do anything now in the area.
In the Plainville area, there had been plans to even apply to wheat fields a fungicide by ground sprayers -- an exceptionally uncommon practice this late in the season -- to bring leaf rust to a halt, but the warmer temperatures hurried along the crop, pushing it into the flowering stage -- the last point when fungicides can be applied.

Likely, however, wheat fields in far north west Kansas might be seeing some application of the chemical to halt the spread of leaf rust. It's an expensive proposition, however, costing anywhere from USD 20 to USD 25 an acre (0.4 hectare) for the farmer. Leaf rust, Martin said, can reduce yields by about 30 per cent.

Spraying should have started about 3 weeks ago, said aerial applicator John Werth. "The conditions were right with the weather," he said. Now, it's too late. "Somebody wasn't on their toes," he said of taking steps to get the fields sprayed. As a result, he added, some of the fields are hurting.
"Some of it is in really sad shape," Werth said of wheat fields in the McCracken and Bison areas. There, farmers were hoping to harvest 50 to 60 bushels (1.36-1.64 metric tonnes) of wheat. Now, he said, they will be lucky to get 25 bushels (680 kg) an acre. Some of those fields, Martin said, might be taking [the 3 diseases]: leaf rust, wheat streak and triticum mosaic -- 'trim-v' as it's generally called in the industry.

Spraying for leaf rust is supposed to take place once the flag leaf emerges and up until the plant starts flowering. That happened over the weekend
[12-13 May 2007] and so the spraying will stop. The idea of the timing, Werth said, is to allow at least 45 days from the time of spraying until harvest. In addition to the leaf rust, Martin said there have also been some fields that are showing stripe rust. "It looks like leaf rust is going to win," he said, adding that stripe rust likes cool weather.

Midland Marketing agronomist, Lee Niblock, said farmers in the Plainville area had been spraying, and continued to do so until the heat advanced the crop. What effect the rust will have is uncertain because there's no way to tell what the weather will do. "The weather from here on is going to decide that," he said.

[byline: Mike Corn]

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[The main rust diseases on wheat are: leaf (brown) rust caused by the fungus _Puccinia triticina_ (formerly _P.
recondita_ f. sp. _tritici_) stripe (yellow) rust caused by _P. striiformis_ stem (black) rust caused by _P. graminis_.

The fungal spores are spread mainly by wind dispersal and with infected plant material. Rust management can be used at key decision times defined by the growth stages of wheat to reflect the changing risk as the season unfolds.

_Wheat streak mosaic tritimovirus_, genus _Potyviridae_ is spread by the wheat curl mite _Aceria tulipae_. It can also be mechanically transmitted and seed transmitted at a very low level. It infects wheat, maize (some cultivars), grasses, and also oats and barley in experimental inoculations.

_Triticum mosaic virus_ is an as yet unclassified virus in the genus _Potyviridae_. It was discovered very recently (2006) in the Hays area in wheat cultivars developed for their resistance to _Wheat streak mosaic tritimovirus_.

Each of the 4 pathogens alone can cause serious losses to wheat crops, thus a combination may indeed prove devastating.

Pictures:
Leaf rust symptoms
<http://www.hgca.com/hgca/wde/IMAGES/brown%20rust1.JPG>
Stripe rust, leaf symptoms
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>
Wheat streak mosaic virus, leaf symptoms <http://www2.dpi.qld.gov.au/images/8658.jpg>
Wheat curl mite
<http://www.nwroc.umn.edu/Cropping_Issues/2006/Issue8/wht_curl_mite.jpg>
Links:
Information on wheat leaf rust
<http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=1138>
Information on wheat stripe rust
<http://www.oznet.k-state.edu/path-ext/factSheets/Wheat/Wheat%20Stripe%20Rust.asp>
and
<http://www.ars.usda.gov/Main/docs.htm?docid=9918&pf=1&cg_id=0>
Description of wheat growth stages
<http://extension.oregonstate.edu/catalog/html/em/em8578/>
Information on rust management
<http://www.arableds.co.uk/wdm/>
<http://www.grdc.com.au/>
_Wheat streak mosaic tritimovirus_ taxonomy and description <http://image.fs.uidaho.edu/vide/descr888.htm>
Wheat streak disease information with pictures <http://plantpathology.tamu.edu/Texlab/Grains/Wheat/wsmv.html>
Wheat streak disease fact sheet
<http://www.agric.wa.gov.au/pls/portal30/docs/FOLDER/IKMP/PW/PH/DIS/CER/FS005_2003.PDF> 

Triticum mosaic virus preliminary taxonomy and description
<http://taxon.molgen.mpg.de/gettaxon?taxid=431317>
News story on recent discovery of the novel triticum mosaic virus <http://www.wkarc.org/news/ARCH_WheatVirus.htm>
General information on wheat diseases and pathogens <http://www.apsnet.org/online/common/names/wheat.asp>.  - Mod.DHA

Kansas is a Midwestern state in the central United States. It can be located on the map at <http://www.census.gov/geo/www/us_regdiv.pdf> . - CopyEd.MJ]