Number 142 May 30, 2008

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1 Number 142 May 30, Wheat disease update 1 2. Causes of white heads in wheat 2 3. New web site for Soil Testing Lab 4 4. Agronomy Field Day in Manhattan: August 22, Wheat disease update Leaf rust had been slowed by approximately two weeks of dry weather, but the risk of diseases has increased as frequent rains have returned to Kansas during the past week. The greatest risk of disease now appears to be in eastern two thirds of the state, where leaf rust has been active since early April. The disease was at low levels on the uppermost leaves in parts of southcentral and central Kansas before the rains started last week Friday (May 23). The severity of leaf rust on the upper leaves is likely to increase significantly over the next few weeks as the new infections become visible. Susceptible varieties such as Jagger, Jagalene, and Overley are most at risk. Fungicides are now longer an option in these areas because the crop is beyond the flowering stages. All fungicide labels prohibit application once flowering is complete. The amount of yield loss from leaf rust will depend on how quickly the disease increases. Yield losses will be reduced if the crop can make it to the dough stages of development before the rust becomes severe on the upper leaves. Overley has the best chance of outrunning the disease this year because the races that can overcome its resistance tend to arrive later. Fields that received a fungicide recently should still receive some protection from the residual activity of the chemical. Most fungicides remain active for about 2 to 3 weeks and vary with product and the rate of application. Leaf rust will begin to increase in these fields, but it will take the disease longer to build up to damaging levels. This delay in disease development will help preserve yield. Wheat in northcentral Kansas is still at moderate risk for the development of disease. 1

2 Leaf rust has been very slow to develop in many fields near Beloit and Bellville and appears to be restricted to the lower canopy. Wheat in this part of the state is heading and flowering, and it seems likely that the rust will not arrive in time to cause significant yield losses. Some seed fields might still benefit from a fungicide treatment, but most grain production fields may not need a fungicide application. Head scab may be a disease to watch for in these areas. Head scab is favored by frequent rainfall and moderate temperature just before and during flowering. You can check the disease prediction tools for head scab at to help evaluate the risk on your area. The fungicide Proline would be a good choice if you feel the risk of head scab is high. I have observed very low levels of leaf rust in western Kansas, and I believe the risk of yield loss from leaf diseases is minimal. -- Erick DeWolf, Extension Plant Pathologist dewolf1@ksu.edu 2. Causes of white heads in wheat There have been many reports of white heads in the wheat crop this year. Sometimes the white heads are just single tillers scattered throughout part or all of a field. And sometimes the white heads occur in small to large patches. Is it due to freeze injury? Hail damage? Scab? Something else? There are many causes of white heads. Here are some of the most common causes and their diagnosis. * Premature dying (hot dry winds, drowning, etc.). As wheat begins to mature, plants in some areas of the field may have an off-white color similar to take-all. This is premature dying, which could be due to hot dry winds, drowning, or some other stress. The pattern of off-colored heads will often follow soil types or topography. The grain will be shriveled and have low test weight. * Head scab. When there are periods of rainy weather or sprinkler irrigation applications made while the wheat is flowering, some heads may become infected with Fusarium head blight and turn white. The heads of some red-chaffed varieties, such as Overley, turn a darker red when infected with scab, but the heads of many varieties turn white. Often, only the upper half of the head is white. Head scab is most common where wheat is grown after corn, or after a wheat crop that had head scab the previous year. * Take-all. This disease often causes patches of white heads scattered throughout the field. It occurs most frequently in continuous wheat, and where there is a moderate to high level of surface residue. To diagnose take-all, pull up a plant and scrape back the leaf sheaths at the base of a tiller. If the base of the tiller is shiny and either black or dark 2

3 brown, it is take-all. All tillers on a plant infected with take-all will have white heads. Plants will pull up easily. * Dryland root rot (also known as dryland foot rot). This disease, caused by the Fusarium fungus, causes white heads and often turns the base of the plants pinkish. As with takeall, dryland root rot causes all the tillers on an infected plant to have white heads. This disease is usually most common under drought stress conditions, and is often mistaken for either drought stress or take-all. The photos below were taken during the week of May 27-30, 2008, in Meade County. Figure 1. White heads resulting from dryland root rot. Photos by Jim Shroyer. Figure 2. The inside of the stem will usually have a pinkish growth on wheat infected with dryland root rot. 3

4 * Sharp eyespot. This disease is common in Kansas, but rarely causes significant yield loss. Sharp eyespot causes lesions with light tan centers and dark brown margins on the lower stems. The ends of the lesions are typically pointed. If the stems are girdled by the fungus, the tiller may be stunted with a white head. Each tiller on a plant may be affected differently. * Wheat stem maggot. Wheat stem maggot damage is common every year in Kansas, but rarely results in significant yield loss. It usually causes a single white head on a tiller, scattered more or less randomly through part or all of a field. If you can grab the head and pull the stem up easily just above the uppermost node, the tiller has probably been infested with wheat stem maggot. * Hail. Hail can occasionally damage just a portion of a head, and cause that damaged portion to turn white. * Freeze injury to stem or crown. Depending on the stage of growth at the time of a late spring freeze, parts or all of the heads may die and turn white. This is most often due this year to freeze injury to the lower stem, which then cuts off water and nutrients to the developing head. In years when the wheat is in the early heading stage at the time of the freeze, the freeze can damage the heads directly. Often, wheat on north-facing slopes, on ridge tops, or in low-lying areas will be most affected by freeze injury. When the crown is damaged by cold temperatures or a freeze, part or all of the tillers can die. If the tiller from a damaged crown forms a head, this head will almost always be white. The crown will have internal browning, and stands will usually be thinner than normal. -- Jim Shroyer, Extension Agronomy State Leader jshroyer@ksu.edu -- Bob Bowden, USDA Plant Pathologist rbowden@ksu.edu 3. New web site for Soil Testing Lab The K-State Soil Testing Lab has created a new and improved web site. A change in computer systems allowed the lab to add new information to the site while making it more user-friendly and informative. The new site went online the beginning of April, Web Manager Marsha Landis and her assistant Patricia Blocksome helped with design and development. The goal of the new design was to make the site easier to use. The site now is organized to guide different customers, such as farmers and agronomists, homeowners and researchers, to their specific needs. Each type of customer now has a different pathway to submit a soil test or leaf analysis. 4

5 We also wanted the site to be a source of helpful information for anyone with interests or concerns related to soil fertility and nutrient management. A publications section has been added to help answer questions about fertilizer recommendations, fertilizer applications, nutrient deficiency symptoms, nutrient management, and other subjects. This section will grow with time. In the future, information about research projects will also be accessible from the Soil Testing Lab home page ( This will hopefully be able to answer even more of our customers questions. A number of different groups use the Soil Testing Lab, such as County Extension agents, farmers, homeowners, golf course managers, and researchers from all over the globe. On the Web site, there are specific sections and forms for each type of client. For a producer who would like to send a soil sample: Starting from the home page, click on Farmer Samples in the left column; Click Soil Analysis that appears under that. The farmer (or Extension agent) can view the tests we offer and specific information about sample collection. The pdf document that is linked on the page is the order form for the sample. It includes a current price list. This form needs to be filled out completely, including information about the person submitting the sample, and sent to the lab. Results from the tests are sent to the producer, along with requested recommendations. If a county agent sends in the order form, the results are sent back to the agent, and he/she can make recommendations. For a homeowner needing a soil sample analyzed: Click Home Owner Samples; Then Soil Analysis. There are three different types of homeowner soil samples, which can be found under Sample Info: Lawn and Turf sample Flowers and Ornamentals sample Vegetables, Fruits and Nuts sample The appropriate information sheet can be filled out according to the type of area being sampled, then sent in to the lab. Golf course superintendents and contractors would also use the Home Owner section and would request a soil sample analysis using the Lawn and Turf order form. For researchers the process is similar: Click on Research Samples and go from there. There are two different forms in the research section, one for State of Kansas agencies, 5

6 and one for other agencies. Researchers can also request to have their sample sent back to them. Results are sent in a spreadsheet format through . The easiest way to get to the new Soil Testing Lab site is to start from the agronomy home page ( click Services in the left menu, then Soil Testing Lab. Any questions about the new site or the lab are welcome. Please call between 8 am and 5 pm, Monday through Friday, or me at the address below. -- Kent Martin, Soil Testing Lab Manager kentlm@ksu.edu 4. Agronomy Field Day in Manhattan: August 22, 2008 The Department of Agronomy s annual Field Day will be held August 22, 2008 at the Agronomy North Farm in Manhattan. The theme of this year s Field Day is: Agricultural Solutions to Global Change. A one-page flyer/poster about the Field Day is available for downloading at: We would encourage you to download this and post the flyers wherever you can to encourage producers to attend. The preliminary topics at this year Field Day are: 1. Bioenergy Production Systems a. Perennial native grasses b. Bioenergy cropping systems c. Energy crop processing 2.Greenhouse Gases and Climate a. Carbon sequestration b. Agricultural sources of CO 2 and N 2 O c. Meaurement of carbon loss and sequestration 3.No-till Cropping Systems a. Soil management b. Can cover crops suppress weeds? c. Cover crop species and mixtures d. Rotational oilseed crops for Kansas e. Herbicide-resistant sorghum 6

7 4.Water Quantity and Quality a. Improving water quality b. Irrigation water stewardship c. Cropping systems for water conservation -- Steve Watson, e-update Editor These e-updates are a regular weekly item from K-State Extension Agronomy and Steve Watson, Agronomy e-update Editor. All of the Research and Extension faculty in Agronomy will be involved as sources from time to time. If you have any questions or suggestions for topics you'd like to have us address in this weekly update, contact Steve Watson, swatson@ksu.edu, or Jim Shroyer, Research and Extension Crop Production Specialist and State Extension Agronomy Leader jshroyer@ksu.edu 7