Stripe Rust Update, June 18, 2010

Rust Update, June 18, 2010

By Dr. Xianming Chen, Washington State University

Stripe Rust of Wheat

As winter and spring wheat crops are progressing, fungicide application for control stripe rust on winter wheat crop has almost reached the end and has started on spring wheat crops in most areas of the Pacific Northwest.  The winter wheat crop ranges from heading (Feekes 10.1) to soft dough stage (Feekes 11) and spring wheat crop ranges from mid jointing (Feekes 6) to flowering (Feekes 10.5) depending upon locations and planting dates.  Stripe rust is everywhere.  Some fields of winter wheat which has not been sprayed have 100% incidence (percentage of plants infected) with about 20 to 80% of severities (percentage of leaf area infected).  For such fields, yield loss could reach up to 20%, considering the intermediate reactions.  We have not found completely susceptible crops of winter wheat in commercial fields, but in experimental fields.  Highly susceptible reactions are easily found in commercial fields of spring wheat.  Based on the rust situation and weather conditions so far and predicted for next two weeks, a highly susceptible crop of either winter or spring wheat could easily have yield loss of more than 60%. Now, we have reached the critical time for fungicide application on spring wheat crop.

Based on our data in the past and field data and observations in this week, the following commonly grown spring wheat cultivars are susceptible:  Hank, Hollis, Bullseye, Zak, Eden, Macon, Tara 2002, Nick, Westbred 926, and Scarlet, etc. are either moderately or highly susceptible.  Fungicide application should be considered when rust is seen in these fields.  Louise, Alpowa, JD, Alturas, Whit, Babe, Buck Pronto, Otis, Clear White, Patwin, Solano, Expresso, Wakanz, Lassik, etc. are either resistant or moderately resistant. Fields of these cultivars may not need to be sprayed.   As we have observed, cultivars can react differently in different areas as rust races and environment conditions (mainly moistures and temperatures) can be different from one area to another. Therefore, it is important to check your fields to determine spray or not spray.

This year, black telia pustules of stripe rust are very common, especially on the lower leaves had early infection, due to the wet weather conditions and particular races.  When rust infection reaches to the telial stage, damage has occurred already, and generally no further damage will occur for the crop.

Head infection by stripe rust is common this year.  Damage by head infection is relatively low compared to leaf infection.  Head infection usually occurs on susceptible cultivars.  However, few cultivars can be infected on head, but leaves are resistant. Generally, when head infection occurs, it is too late to use fungicide. 

In contrast to most other areas of the PNW, southern Idaho has had very late appearance of stripe rust.  According to Dr. Jianli Chen and Dr. Juliet Windes, stripe rust was reported on spring wheat Ulturas in Burley, Idaho, but has not been confirmed.

Nationally, stripe rust has been reported from the south to north and from west to east in all major wheat growing areas and severe in many states, such as California, Oregon, Washington, Texas, Louisiana, Arkansas, Oklahoma, Kansas, and Nebraska.  Stripe rust has also been reported in Ontario, Canada.

High-temperature adult-plant (HTAP) resistance has been working in the PNW, but not to their full levels under the cool and wet conditions so far.  There is no a clear cut off point of either temperature or plant stage for HTAP resistance to work or not work.  It is a quantitative effect of cultivars (level of HTAP resistance) interacting with temperature and plant stages.  The higher level of HTAP resistance, the earlier in the growth stage and/or under the lower a temperature range does it work.  It is in a relative sense in comparison with a highly susceptible reaction (just vigorously sporulating rust pustule, no necrotic stripes).  Many fields of cultivars with moderate levels of HTAP resistance look very bad this year, but we have not seen such cultivars becoming completely susceptible. Cultivars with single effective all-stage resistance genes, combination of all stage resistance genes, high-level of HTAP resistance, and combination of effective all-stage resistance and HTAP resistance genes have held well this year.

Barley Stripe Rust

Stripe rust is till very low on barley in commercial fields.  Most of checked barley fields were rust free.  We found stripe rust on a couple of spring barley entries in our nurseries in Lind (Adams County), WA. 

Wheat Leaf Rust

Wheat leaf rust was found in the Variety Trials at the Lind Experiment Station only on a hard red winter wheat cultivar, Declo.

In a field of hard red winter wheat cultivar Farnum, between Pasco and Connell (Franklin County) WA, leaf rust had severities of 5 to 40% and more than 20% incidence.  Rust occurred very early from lower leaves and has mostly turned to black telia. Stripe rust in this field is very low.  The crop reached late dough stage.  The leaf rust damage is limited as the crop had well filled grains.  Leaf rust (uredinial stage) was also found in a neighboring field of hard red winter wheat Bauermeister at very low incidence level (<1%). In this field, stripe rust of resistant reactions was common.     

Stem Rust

No more news about stem rust since the last report on June 9 that rust on barberry plants was identified as stem rust in greenhouse testing.

Stripe Rust - Update, corrections and pictures!

Dr Chen updated and corrected his information from yesterday:

1. Three varieties should be changed: 
1. Goetze should be in the "should be sprayed" group.  Goetze has been severely damaged in western Oregon and showed a susceptible reaction in the Dayton Variety Trial.  
2. Varieties ORCL 103 and RJames  and maybe others should be put in the group of "either spray or not spray".  (Thank Art Swannack and Mike Mckinley for sharing their observations of these varieties.)

 

Stripe Rust Update, Dr. Chen

Stripe rust started earlier in the Milton Freewater, Walla Walla and Dayton (Columbia County)area than in other areas of the region this spring. Dr. Chen, WSU, was able to take preliminary notes in the variety trial near Dayton on June 7 and 8th.  Here are his observations and recommendations:

• Stripe rust reactions of the most of tested varieties were as expected with some exceptions.   
• Rod, SWW variety, had more susceptible plants than in the past, indicating a considerable proportion (estimated as 20%) of plants became susceptible.   
• Tubbs 06, SWW variety, became more susceptible than in the past a couple of years after the re-selection from ‘Tubbs’. 
• Lambert had very high severity (40-80%),even with a moderately resistant reaction.   
• The changes towards more susceptibility of these two varieties are not only due to the low temperature and high moisture conditions this year, but also possibly due to changes of races and their frequencies.

Based on Dr Chen notes in this variety trial and previous data, the unique weather conditions, and HTAP resistance has started kicking in, he is grouping the major varieties into the following three groups and rating the need to spray fungicide applications:

Varieties should NOT be sprayed:  Eltan, Madsen, Eltan/Madsen, Chukar, Finch, Skiles, ORCF-102, ORCF-103, Coda, Madsen/Rod, Legion, Bitteroot, Bruehl, Stephens, Brundage 96, Eltan/Tubbs06, KCF9002, RJames, Goetze, Goetze/Skiles, Cara, and George.

Varieties should be sprayed: AP Legacy, Salute, KCF9003, CDC Ptarmigan, Paladin, Eddy, Finley, Finway, and Buchanan.

Varieties can be either sprayed or not sprayed:  Tubbs 06, Simon, Xerpha, Rod/Tubbs 06, Rod, Lambert, Masami, WB-528, AP700CL, Farnum, and Bauermeister.  The difficulty to make a decision of spray or not spray for varieties in this group is due to the inadequate levels of HTAPWalla Walla, Columbia, and Garfield counties and southwestern Whitman County as rust severity has reached to significant levels and expected to increase more in another week or so.  In most of the other areas, rust levels are still quite low and we expect that HTAP resistance starts to work in most of these varieties as the weather is going to warm up next week.  The second consideration is the yield potential.  The higher yield potential, the easier to justify the cost of fungicide application.  A general guideline is that fields of 100 bushel per acre should move toward spraying as yield losses of such varieties may range between 5 to 15%. 

In addition to Tilt, Quilt, Quadris, Stratego, and Headline, Folicur can be used. 

Spring wheat has a much wide variation in growth stages, from tillering to flag leaf stage across the Pacific Northwest, particularly in Washington State.  Rust is in spring wheat fields, but in very low incidence and severity (less than 2%) in general.  If susceptible varieties (such as Scarlet, Hank, Nick, Eden, Westbred 926, Tara 2002, Jefferson) are grown, you may consider an early spray before rust reaches 10% severity or incidence as you may be able to use ground application in early stage.  If resistant varieties (such as Louise, Wakanz) are grown, fungicides may not be used you should not use fungicides.  Alpowa is in between and we hope its HTAP resistance starts working as the weather becomes warm.

Dr. Chen found a very low level of stripe rust on barley in a couple of fields in Whitman County, not warrant immediate spray.  People should check their fields for stripe rust and its increase.  If moderately resistant varieties (such as Baronesse and Bob), spray may not be necessary.  If other varieties (mostly susceptible) are grown, spray may be needed in a week or two when rust reaches about 10% severity or incidence.

Stem rust:  The rust samples we collected from barberry bushes in the Latah County Idaho and Whitman County, Washington last month have been identified as stem rust.  We couldn’t found any stem rust in the wheat fields nearby the barberry bushes in the Latah County today.  Rust reached last stages of aecial on the bushes. 

Stripe rust treatment options-Going Going GONE!!

A quick reminder that most fungicides for the treatment of stripe rust have a cutoff for treatment with either a stage of growth of Feekes 10.5 (full heading) and/or a pre-harvest interval of 35-40 days! Once the heads are flowering we have moved beyond 10.5.

Please check your product labels closely and don't push the treatment window!! We can not afford to have misapplications of fungicides in our wheat crops and the related potential for food safety concerns!

Reports continue to come in that stripe rust is being found on the flag leaves of varieties such as Tubbs 06, Skiles, Goetze, Rod, ORCF102, Xerpha and WEstbred 528 in Umatilla County and north into Walla Walla County, Washington, but our treatment window is going, if not gone in many areas near Pendleton.

Wheat Head Armyworm - larvae emerging

Wheat head armyworm adult moths (F. diffusa) are starting to emerge in increasing numbers, plus we are starting to find larva in Umatilla County. The following numbers are total moths collecting in our 25 sites. The largest numbers in individual traps were found near Holdman Rd, west of Kings Corner with 37 adults, and also south of Myrick with 21 adults. We expect about a 2-3 week delay between adults emerging and larva hatching. We will continue to keep posting numbers. If you desire more details about specific counts please call my office at 541-278-5403.

               Adults       Larva
14-Apr       0               0
21-Apr       4               0
28-Apr       7               0
5-May        1               0
12-May      17             1
19-May      157           2

Stripe Rust Infections Reaching Treatment Levels

STRIPE RUST CONTINUES TO INCREASE:
Stripe rust has been developing rapidly in Walla Walla and nearby parts of Umatilla County. Since the first observation by Xianming Chen in plots in Walla Walla on April 29, stripe rust has been reported to be widely spread. Plants of a field of ‘Declo’, a susceptible hard red winter wheat cultivar, were quite uniformly infected. Up to 20% incidence was reported in some fields grown with ‘Tubbs 06’ or a mixture of ‘Rod’ and ‘Tubbs 06’.
Dr. Mike Flowers reports significant infection in OSU trials in Hermiston, Pendleton, and Lexington.
Dr. Stephen Guy reported significant infection in one replication of ‘Lambert’ in the variety trial near Walla Walla. Some fields have been sprayed with fungicides in this region. Rust is developing in the Central Ferry area (Columbia County, southeastern WA). Based on Dr. Kim Campbell, ‘Xerpha’ (a soft white winter wheat with a moderate level of high-temperature adult-plant resistance) had infection type 5 and 10-20% severity. Rust has been reported in commercial fields in this area.
Stripe rust management in the PNW:
The current stripe rust situation is similar to what we forecasted in January, little bit more severe than last year, but should be less than 2005. The low temperature and high moisture conditions in the past several weeks and predicted for the next two weeks have been and will be favorable for stripe rust. Under such conditions, fields grown with susceptible cultivars (such as Declo, Buchanan, Finley, Finway, Palatin, and Eddy) should be sprayed. Depending upon locations, cultivars with low to moderate levels of high-temperature adult-plant resistance (such as Farnum, Xerpha, and Baurmeister) may need to consider spraying. Cultivars with high levels of resistance (such as Eltan, Madsen, Stephens, and many others) may not need to spray. Now is the critical time for growers in the Walla Walla, central WA, and nearby regions to check their fields and spray if necessary. Growers in the Palouse region (Whitman County of Washington and Latah county of Idaho) and further north should start to check wheat fields, and consider spraying if rust develops to 5-10% of severity. People also need to consider the fact that several cultivars (such as Tubbs, Tubbs 06, Brundage 96, and many others) are not uniformly resistant, susceptible plants can be found in these crops. Fields grown with such cultivars may need or not need spraying depending upon locations, and a 20% severity threshold may be used to make decision.

This report is based on information provided by Xianming Chen, WSU and Mike Flowers, OSU.

Wild weather and Stripe rust update

Weather is on everyone's mind in the West this week. Winds topped 102 mph on Rattlesnake Mt. in south eastern Washington and numerous reports of winds in the 50 mph range were reported on Monday in the Columbia Basin in Oregon. Snow in the foothills and frost the last two mornings in the valleys would to keep weather on our minds.
While late frosts can damage heads, for the moment cool temperatures are keeping the wheat crop looking good for the first week of May. As cool temperatures linger, we would typically expect to have one hot week in May, and so we know warm temperatures will eventally come, and if rains don't arrive with them, many of the shallow soil areas to run out of soil moisture in a hurry.
Cool temperatures have slowed wheat development may delay stripe rust development on susceptible varieties. Stripe rust was found in the Walla Walla area last week at very low levels, and growers should be scouting their fields to look for infection levels on suspectible varieties.