eUpdate 06/28 / 2013 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, 785-532- 7105 [email protected], Jim Shroyer, Crop Production Specialist 785-532-0397 [email protected], or Curtis Thompson, Extension Agronomy State Leader and Weed Management Specialist 785-532-3444 [email protected]. 410 Extension Agronomy
Transcript
eUpdate
06/28/2013
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, 785-532-7105 [email protected], Jim Shroyer, Crop Production Specialist 785-532-0397 [email protected], or Curtis Thompson, Extension Agronomy State Leader and Weed Management Specialist 785-532-3444 [email protected].
1. Conducting germination tests on this year’s wheat seed ................................................................................. 3
2. Keys to having quality wheat seed ............................................................................................................................ 5
3. Corn leaf diseases in Kansas ......................................................................................................................................... 7
1. Conducting germination tests on this year’s wheat seed
Some producers may be anxious this year to find out the germination percent of the wheat they harvest, to see if it will make suitable seed. If they do a home germination test too soon after harvest, they will be shocked at the low germination percent. That’s because wheat has a post-harvest dormancy requirement (some varieties more so than others). Even high quality seed will not germinate right after harvest in most cases. For the first several weeks after harvest, it’s important to make sure the wheat is pre-chilled before taking a germination test. Any reputable seed lab will do that on a routine basis. Producers testing their seed at home should also pre-chill the wheat by putting it in the refrigerator at about 40 degrees for 5 days and then moved to room temperature for an additional 5-7 days. If the seed is not pre-chilled, producers should wait a month and a half after harvest before testing for germination. There is some difference among varieties regarding how long their summer dormancy requirement is and even that can vary from year to year. Hard white wheats with poor sprouting tolerance, for example, have almost no summer dormancy requirement. They will germinate almost as soon as the seed is harvested. Other varieties have a relatively long summer dormancy requirement, and may not germinate well for five or six weeks after harvest unless the seed is pre-chilled. Unfortunately, there is no routine testing of varieties for their summer dormancy requirement, so we have no way of knowing which varieties will germinate shortly after harvest and which will take a longer period of rest. By Labor Day, all varieties will have lost their summer dormancy and should germinate unless the seed is defective in some way. In addition, if seed is tested soon after harvest, it would still be a good idea to test again prior to harvest to be sure the germination has not been compromised due to heating or insect damage. If there is any question about the viability of the seed, it is well worth the $15 it costs to have the seed tested for germination by a professional seed laboratory. This is especially true in areas where there was freeze damage, severe drought, a rain delay at harvest, or scab. To the untrained eye, seeing some amount of shoot and root development would seem to be sufficient proof that the seed is in good condition. But that alone does not always mean you have a seedling that will develop into a healthy plant. A trained laboratory analyst evaluates each seedling to be sure that all essential parts exist and have sufficient development at the end of the test to, in fact, establish a normal, healthy plant.
Figure 1. Effect of poor seed quality on germination. The entire field was planted on the same day, but with two different seed lots. The seed on the right had been stored under extremely high temperatures, which reduced seed quality and resulted in low germination. Photo by Jim Shroyer, K-State Research and Extension. -- Jim Shroyer, Crop Production Specialist [email protected] -- Eric Fabrizius, Kansas Crop Improvement Association [email protected]
Producers should take care to plant the best quality seed possible this fall to get good emergence, early season vigor, and yield potential. It makes no sense to plant poor quality seed that will just create more problems next season. Certified seed, which has been professionally prepared, cleaned and tested for quality, is the best option. Buying certified seed will automatically take care of most of the concerns mentioned below about conditioning homegrown grain for seed. In addition, certified seed producers can apply seed treatments thoroughly and uniformly. Producers should order their seed as soon as possible. If producers plan to save part of this year’s grain crop back for seed, there are several steps they should take to condition it. One of the first things to do is make sure the grain is aerated in the bin. High-moisture weed seeds and foreign material can quickly heat up wheat in the bin, and reduce the potential seed quality of the grain. Wet grain can also harbor insects. Cleaning the grain is also important if it will be used for seed, and should be done as soon as possible after harvest. That way, producers can determine if they have enough seed to meet their needs. Cleanout may be especially high this year to get acceptable seed quality. Wheat should be cleaned with a 6/64 screen, if possible. If that cleans out far too much of the wheat, then a 5.5/64, or even a 5/64, screen will do. But no less than that. Cleaning wheat with less than a 5/64 screen will do little or no good. An air/screen cleaner (also known as a “fanning mill”) is the most common piece of seed cleaning equipment. If operated properly, an air/screen cleaner will remove all the weedy annual brome species, such as cheat and downy brome, from wheat. Gravity tables are excellent at sorting out the test weight difference in a lot of seed, but really depend on the air/screen cleaner to do the bulk of the cleaning job by first removing the trash, small seed, and weed seed. The gravity table then separates seeds that have similar width, but slightly different densities. In between the air/screen and gravity table, some facilities will use a length grader to separate jointgrass and or buckwheat, because they are similar in width to wheat. So having the wheat cleaned with an air/screen cleaner (and possibly a length grader if there is jointgrass or buckwheat contamination) is the most important step to take. A gravity table is a good piece of secondary equipment to help raise the test weight, if that is a concern. If there was rye or Italian ryegrass in the field, the wheat should not be planted back. In that case, it’s best to sell the wheat and take advantage of the current cash market for grain, then buy new seed. Producers should have the seed tested for germination by a reputable laboratory. The test costs about $15, and it is well worth it. Home germination tests are not as accurate and reliable. There’s no sense risking poor germination for lack of a $15 germination test.
If there was loose smut present in the field and producers are concerned about it, they should have the seed treated with a fungicide seed treatment. This should either be applied by a professional seedsman or with an auger-based system on-farm. Drill box treatments do not do an adequate job of coverage. -- Jim Shroyer, Crop Production Specialist [email protected] -- Eric Fabrizius, Kansas Crop Improvement Association [email protected]
There are several leaf diseases that can infect corn in Kansas in any given year. They can all be controlled with some combination of hybrid selection, tillage management, crop rotation, planting dates, or foliar fungicides. The primary corn leaf diseases of concern in Kansas are:
Anthracnose leaf blight
Figure 1. Anthracnose leaf blight. Photo courtesy of Ohio State University, ohioline.osu.edu/ac-
fact/0022.html Symptoms are tan, irregular-shaped lesions on the lower leaves as early as V3 to V4. Lesions may reach a half-inch in length, with a red, reddish brown, or yellow orange border. Anthracnose is most common in fields with old corn debris present. High temperatures and cloudy, rainy weather favor infection. Most occurrences of the disease are found in northeastern Kansas under no-till conditions. Resistant hybrids can be used to control this disease, but producers should be sure that the hybrid is resistant to anthracnose leaf blight, not just anthracnose stalk rot, since the two types of resistance are different. Producers can also help reduce this disease by using rotation or tillage to eliminate crop debris. Use of foliar fungicides to control early anthracnose has not been demonstrated to be profitable since hot weather alone usually checks the disease’s progress. Having anthracnose leaf blight has no bearing on the development of anthracnose stalk rot. The stalk rot infection enters the plant through the roots, not from leaf infections.
Figure 2. Common rust on corn. Photo courtesy of Iowa State University,
www.ent.iastate.edu/imagegal/plantpath/corn/comrust/0796.37comrust.html This disease is typically less serious in Kansas than the other leaf diseases. Symptoms are small, round to elongated pustules that start out golden brown then turn darker later in the season. Common rust pustules commonly form on both sides of the leaf and are sparser than those of southern rust. This disease can occur wherever corn is grown. Infection is favored by moderate temperatures (60 to 77 degrees) and high relative humidity (greater than 95 percent for at least six hours). Common rust is easily controlled by using resistant hybrids. Fungicides are not recommended for this disease alone since common rust causes only minimal yield loss.
Figure 3. Goss's wilt. Photo by Doug Jardine, K-State Research and Extension.
This disease is caused by a bacterial, not a fungal, infection. Foliar symptoms are long, gray/tan lesions with wavy margins that follow the leaf veins. Within these lesions, dark green to black, water-soaked spots that take on the appearance of freckles usually appear and are an excellent diagnostic symptom (see left side of photo). When early season infection takes place (V4 – V6), the plant can become systemically infected. Systemically infected plants will have brown to orange colored vascular bundles in the stalk (see right side photo). Wounding from hail or sand blasting is usually required for infection to occur. This disease occurs primarily in northwest Kansas, northeast Colorado, and southwest Nebraska, but has begun to spread to other areas in recent years. It can be managed with resistant hybrids and crop rotation. Since the disease is caused by a bacterium, fungicides will not control the disease.
Figure 4. Gray leaf spot on corn. Photo by Doug Jardine, K-State Research and Extension.
Symptoms develop on the lowest leaves first and progress upward. The first symptoms are tiny lesions surrounded by a yellow halo. These eventually elongate into pale brown or gray rectangular lesions ranging from less than an inch to two inches in size. The entire leaves may become blighted. Gray leaf spot survives in infested plant debris on the soil surface. In Kansas, initial infections occur in late June and early July. Cloudy weather accompanied by prolonged periods of leaf wetness and high humidity favor disease development. Severe damage often occurs in low spots or in fields bordered by trees or streams where air circulation is poor. To control gray leaf spot, producers can use a crop rotation that is long enough to eliminate corn debris. Producers can also till under the old corn debris. There are many hybrids available with at least partial resistance. Producers can also use foliar fungicides when the economic threshold is exceeded. Application of a fungicide prior to full tasseling is not recommended as crop damage can occur prior to this stage of development.
Figure 5. Northern corn leaf blight. Photo courtesy of Iowa State University,
www.ent.iastate.edu/imagegal/plantpath/corn/northleafblight/ncorn_leaf_blight_0796_02.html Symptoms are gray, elongated lesions 1 to 6 inches long. The lesions appear on the oldest leaves first, and progress upward. Lesions may become tan as they mature. Northern corn leaf blight is most common in continuous corn where crop debris remains on the surface. Conditions that favor infection are temperatures of 65 to 80 degrees with extended periods of dew. There are many hybrids with resistance to northern corn leaf blight. Producers can also help reduce this disease by using rotation or tillage to eliminate crop debris. Symptoms could be confused with Goss’s wilt (see above). There will be no “freckles” within the lesion with northern corn leaf blight.
Figure 6. Southern rust on corn. Photo by Doug Jardine, K-State Research and Extension.
Southern rust pustules looks similar to common rust, but there are usually a lot more of them and they usually only occur only on the upper leaf surfaces. This often gives the upper leaves a dusty appearance. Southern rust does not overwinter in Kansas. Spores blow up from southern production areas in mid- to late-July. Warm, humid weather favors infection. Resistant hybrids are the best choice for management. If susceptible hybrids are planted late, and disease conditions are favorable, applications of a systemic foliar fungicide may be warranted.
Summary The following are leaf diseases that can occur in certain situations:
Continuous corn, with residue on the surface: All diseases Continuous corn, no residue on the surface: Common rust, southern rust Rotated corn: Common rust, southern rust
* The following lists leaf diseases according to the time of year they typically occur in Kansas:
1. (Earliest in the season) Anthracnose leaf blight 2. Common rust 3. Gray leaf spot
4. Comparative Vegetation Condition Report: June 11 – 24
K-State’s Ecology and Agriculture Spatial Analysis Laboratory (EASAL) produces weekly Vegetation Condition Report maps. These maps can be a valuable tool for making crop selection and marketing decisions. Two short videos of Dr. Kevin Price explaining the development of these maps can be viewed on YouTube at: http://www.youtube.com/watch?v=CRP3Y5NIggw http://www.youtube.com/watch?v=tUdOK94efxc The objective of these reports is to provide users with a means of assessing the relative condition of crops and grassland. The maps can be used to assess current plant growth rates, as well as comparisons to the previous year and relative to the 24-year average. The report is used by individual farmers and ranchers, the commodities market, and political leaders for assessing factors such as production potential and drought impact across their state. NOTE TO READERS: The maps below represent a subset of the maps available from the EASAL group. If you’d like digital copies of the entire map series please contact Kevin Price at [email protected] and we can place you on our email list to receive the entire dataset each week as they are produced. The maps are normally first available on Wednesday of each week, unless there is a delay in the posting of the data by EROS Data Center where we obtain the raw data used to make the maps. These maps are provided for free as a service of the Department of Agronomy and K-State Research and Extension. The maps in this issue of the newsletter show the current state of photosynthetic activity in Kansas, the Corn Belt, and the continental U.S., with comments from Mary Knapp, state climatologist:
Figure 1. The Vegetation Condition Report for Kansas for June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that photosynthetic activity continues to be greatest in the eastern areas of the state. Delayed planting has limited activity in Brown, Doniphan, and northern Atchison counties, while continued heat and drought has limited biomass productivity in the west.
Figure 2. Compared to the previous year at this time for Kansas, the current Vegetation Condition Report for September June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that much lower NDVI values are concentrated in northeast Kansas. In southwest Kansas the decrease is not as visible, since last year’s productivity was low as well. The biggest increase is centered around Saline County, where conditions this year have been much more favorable than last year.
Figure 3. Compared to the 24-year average at this time for Kansas, this year’s Vegetation Condition Report for June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that near-average conditions in the central portions of the state are bracketed by below-average values in the west and the northeast. Conditions are more likely to improve in the northeast, where excess moisture is the culprit than in the west, where persistent drought has severely compromised plant activity.
Figure 4. The Vegetation Condition Report for the Corn Belt for June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that overly wet soil conditions continue to have a negative impact in the eastern portions of the Dakota into Minnesota and Iowa. This is the first year since 1993 that Iowa reported corn still to be planted at this point in the season.
Figure 5. The comparison to last year in the Corn Belt for the period June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows the big contrast in years. In the northwestern areas of the region, cooler temperatures have moderated the drought impacts somewhat. Through the central portion of the region, cooler temperatures and wetter conditions have delayed vegetation. Last year, many locations reported vegetative development 4 to 6 weeks ahead of usual; this year development has been delayed by several weeks.
Figure 6. Compared to the 24-year average at this time for the Corn Belt, this year’s Vegetation Condition Report for June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that most of the region has close to normal photosynthetic activity. The center of the region has below-average biomass production due mainly to cool temperatures and saturated soils which have delayed planting. The impact of drought on vegetation has been pushed mainly to the south and west of the region. In western Kansas, drought impacts continue to be severe, with very little photosynthetic activity.
Figure 7. The Vegetation Condition Report for the U.S. for June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that much of the country has high photosynthetic activity. The lowest NDVI values are seen in the Southwest from Nevada to West Texas. In these areas, high temperatures and low rainfall continue to have a negative impact on vegetation. Along the northern portions of the Missouri River Basin into the Ohio River Basin, saturated soils continue to slow plant development. These impacts have lessened slightly in the last week as warmer, drier weather arrived.
Figure 8. The U.S. comparison to last year at this time for the period June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows that there is a very sharp gradient in the northern Plains. In the eastern parts of the Dakotas through Illinois, cool and wet weather is a marked contrast from last year. The result has been slower plant emergence. In the western parts of the Dakotas, temperatures and moisture have been closer to normal, favoring normal plant development.
Figure 9. The U.S. comparison to the 24-year average for the period June 11 – 24 from K-State’s Ecology and Agriculture Spatial Analysis Laboratory shows the sharp gradient between too much moisture and too little. Mason City, in northern Iowa, has had nearly normal temperatures for June and more than an inch above normal for June rainfall. In contrast, Dodge City, Kansas reports almost 4 degrees above-average temperatures and below-normal precipitation for June. -- Mary Knapp, State Climatologist [email protected] -- Kevin Price, Agronomy and Geography, Remote Sensing, Natural Resources, GIS [email protected] -- Nan An, Graduate Research Assistant, Ecology & Agriculture Spatial Analysis Laboratory (EASAL) [email protected]
