A Mixed Bag for Stripe Rust & Eyespot with Tim Murray

Leaf with stripe rust pustules and a few isolated pustules of leaf rust.

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For questions or comments contact Tim Murray by email at tim.murray@wsu.edu, by phone (509) 335-7515, or Twitter @WSUWheatDoc.

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Episode Transcription:

[ Music ]

Drew Lyon: Hello. Welcome to the WSU Wheat Beat podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. In each episode, I speak with researchers WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production. If you enjoy the WSU Wheat Beat podcast do us a favor and subscribe on iTunes or your favorite podcasting app and leave us a review while you’re there so others can find the show too.

[ Music ]

Drew Lyon: My guest today is Tim Murray. Tim is a professor, an extension plant pathologist who has been on the WSU faculty since 1983. Prior to joining the extension Small Grains team in 2013, he taught introductory plant pathology. His research program focuses on integrated control of wheat diseases. Especially eyespot, Cephalosporium stripe, speckled snow mold, soilborne wheat mosaic, wheat streak mosaic and others. Hello Tim.

Tim Murray: Hi Drew.

Drew Lyon: So, Tim all though we’re still in the midst of winter as we’re recording this, a lot of growers are beginning to think about spring fieldwork. Especially down in the lower rain fall parts of the state. Disease is one of those considerations. What do you think growers should be thinking about now relative to spring field work for wheat disease?

Tim Murray: Well one of the things they’re probably thinking about most relative to disease is the stripe rust. And we’ve had several years in a row where stripe rust has been our major disease concern in the spring. We always think about stripe rust because fall infection and winter survival are important for determining how much disease is likely to occur this spring. The other disease that I start thinking about is eyespot. It’s another foliar disease. Also dependent on fall and winter conditions to determine how severe it’s going to be and the other disease for which we spray a fungicide as one of our control measures. So, stripe rust and eyespot are I think what are on most people’s minds or should be.

Drew Lyon: As we move into the spring. So, as you said every year’s a little bit different because every winter and fall is different. So, what do we know about stripe rust at this stage of the game?

Tim Murray: Well, it’s been kind of a mixed bag for stripe rust this year. 2018 fall conditions were very dry. You’ll recall we had very little rain during the summer. In general, seeding was late or if seeding was early there wasn’t enough moisture to get the crop up. So, emergence was late. And neither of which of those is favorable for stripe rust infection. Stripe rust depends on infecting that winter crop in the fall so that it can survive through the winter. Nevertheless, Dr. Chen’s group out surveying last fall did find some fields in Grant County that had very low amounts of stripe rust. A few pustules in a field he told me. So that seems to be at the low end of the spectrum. But not unusual for this time of the year. What we know about the stripe rust fungus is that survival depends on winter conditions and especially winter temperatures during December, January, and February. So, if temperatures are really cold, 5-degrees Fahrenheit, or less that’s going to reduce survival of the rust but still allow survival of the crop. So far, I think most people realize that our temperatures in December and up until now in January have been probably average or above average and not, certainly not cold enough to affect the survival of the rust. Dr. Chen, as we’re recording this, just released his first stripe rust update of the season this past week. And he is calling for about normal range of stripe rust this year. Now that’s dependent mainly on his models looking at temperature. I think because of the dry fall conditions we’re probably looking at something less than what would be normal for his predictions. But that said you know we’re going to have to monitor temperatures and the crop going forward to see where the stripe rust ends up because we’re still as we speak very early into the season. Things could turn around and become very favorable for the rust or conversely, they could remain cool and dry and not favorable for the rust.

Drew Lyon: So, given that statement what kind of recommendations can you make to growers at this time about stripe rust and what they should be doing. Anything out of the normal or just the things you would normally suggest growers do?

Tim Murray: Well I think our recommendations are really the same as they have been and growers who’ve listened to us know that we always recommend as the first line of defense planting a disease resistant variety. If you look at the Washington State Crop Improvement Association Seed Buyers Guide for winter or spring crops, try to pick a variety that is rated four or less. That means it’s either resistant or moderately resistant and varieties that have that rating should not need fungicide application during the year. Now it’s still early enough with us with spring seeding not having taken place yet for growers to think about variety selection for a spring crop. So, think first and foremost about that resistant variety. For winter crop it’s obviously too late. Crop is already in the ground. If you’ve got a variety that is resistant or moderately resistant, good job. You probably are not going to have to worry about saying fungicide for rust. If you have one that’s rated more susceptible than a four, then our recommendation is always to get out and monitor the crop. Get out and look to see if you can find those stripe rust pustules in the crop. And the recommendation is that if you have about three to five percent of the plants with actively sporulating pustules that’s the threshold for thinking about fungicide application. And if you reach that threshold you need to act quickly because the rust can develop very quickly. So, it’s not if you see that threshold, don’t wait around to make a decision whether you’re going to spray fungicide or not.

Drew Lyon: So, some of these recommendations can growers find that information on this Wheat and Small Grains website? Do you have that on some of your?

Tim Murray: Yeah. It’s there. We have, in fact we have a table that has a list of fungicides that are used for, especially for foliar diseases, the rusts. There are several different fungicides that are registered for stripe rust control. I guess the one thing to remember with these fungicides is that most of them have a growth stage restriction. So most of them are going to cut off at anthesis growth stage 10.5.4 on the feekes scale. But you need to double check the label before you make that application. There are a couple of materials that actually have a pre-harvest interval of 30 days pre-application or application 30 days before your harvest. And so, depending on where you’re at in the season, make sure you know if there is that restriction. Dr. Chen will tell you that he doesn’t recommend fungicide applications after anthesis because he just doesn’t think there’s a return on the investment.

Drew Lyon: Okay enough damage has been done.

Tim Murray: That’s right. You’re not going to recover from damage that’s done at that point.

Drew Lyon: Okay. So, the other disease you mentioned was eyespot. What do we know about eyespot so far this year?

Tim Murray: Well, a lot of the conditions that favor stripe rust also favor eyespot. And the fall weather and so forth winter temperatures are going to also influence eyespot. Again, the dry fall conditions, the late seeding or late emergence in general will have reduced the potential for eyespot this year. That said, again, the mild temperatures that we’ve had in December and January have allowed the wheat to probably start growing out there in some parts of the state. And so, the crop be you know as advanced as it would have been had it emerged earlier in the season. Moisture was a little limiting this year but we did get some pretty good rains through November and so I have no doubt that the eyespot fungus is out there and going and if you’ve planted a resistant variety again as with stripe rust you are in good shape. And there’s a lot of varieties that have good eyespot resistance. If you’ve planted a susceptible variety where similar to what we talked about with stripe rust, get out and monitor your crop to see whether you’ve got enough disease to make it worthwhile to spray. How do you know when that happens? Well, what we recommend is you get out, you collect at least 50 stems, take them someplace where you can wash them off and strip the outer sheaths off, and if you can see five out of 50 that have recognizable eyespot on them that represents 10%, there’s probably another 10% out there that you can’t recognize. So that’s 20% and that’s the threshold for considering a fungicide application.

Drew Lyon: Okay and I assume the Washington Crop Improvement Association also lists varieties resistance to this disease as well?

Tim Murray: Yep, that’s right. The crop improvement, we update that every year after we evaluate new and upcoming varieties. So, there are ratings in there. I think on that rating scale Madsen is about a four. And so, if you have a variety there’s comparable to Madsen, you’re going to be in pretty good shape. There are about right now I think seven different treatments that are registered fungicide treatments registered for eyespot control. Many of them contain an older fungicide in them, Topsin M or thiophanate-methyl is the active ingredient. That’s the material to which we have resistance in the pathogen population in the Pacific Northwest. So that’s a consideration. There are some materials in there that don’t include that. If you’ve had or know that you’ve had a fungicide resistance problem in the past.

Drew Lyon: Okay and are these recommendations also, can growers find that on the Wheat and Small Grains website?

Tim Murray:  Yes, they can.

Drew Lyon: Okay.

Tim Murray: Yeah. We have got some of our presentations up there from the past where he can they can go in and look at recommendations for the threshold and the treatments that are registered as well.

Drew Lyon: All right Tim. We’re very early in the season but I think it is time to start thinking about it. I’m sure growers are as they come out of this winter meeting season, their minds are thinking about all they have to think about. We appreciate you bringing this to their attention. And I’m sure we’ll have you on again later this year as some of these things start to develop out there in the field.

Tim Murray: Okay. Great. Thanks Drew.

Drew Lyon: Thank you, Tim.

[ Music ]

Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcasting app. If you have questions or topics, you’d like to hear on future episodes please email me at drew.lyon That’s lyon@wsu.edu (drew.lyon@wsu.edu). You can find us online at smallgrains.wsu.edu and on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human and Natural Resource Sciences at Washington State University. I’m Drew Lyon, we’ll see you next time.