C.O.R.N. Newsletter: 2017-09
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Facts about Early-Season Wheat Diseases
It has been cool, wet, and very humid so far this spring - perfect conditions for early season diseases like Septoria tritici blotch and powdery mildew to develop. Both of these diseases usually become established in the fall, thus getting an early start in the spring, particularly if winter conditions are mild. Here are a few more facts about Septoria tritici blotch and powdery mildew.
Septoria:
- Symptoms first appear on lower leaves (those close to the soil) as irregularly-shaped lesions with a tan center and yellowish margin. Under favorable conditions, lesions spread up the plant, taking on more of a rectangular appearance on upper leaves, without the clear yellowish margin. Stems may also be affects.
- The presence of distinct black dots or specks in the center of the lesions is the easiest way to tell Septoria apart from other diseases like Stagonospora leaf blotch and tan spot.
- Septoria is favored by cool, humid weather, with frequent rainfall (every 2-3 days). Rain splashes spores of the fungus from lower to upper leaves or to nearby healthy plants, causing the disease to spread quickly (within 7-14 days).
Read more about Septoria and other leaf blotch diseases of wheat at: http://www.oardc.ohio-state.edu/ohiofieldcropdisease/images/PLPTH-CER-07_Leaf_blotch_diseases_of_wheat_2016.pdf
Powdery mildew:
- As the name suggests, powdery mildew develops as white, powdery lesions (called pustules), beginning on the surface of lower leaves and stems. As the plant and lesions mature, pustules take on a grayish appearance, with distinct brownish-black dots.
- Powdery mildew is favored by cool, humid weather, and high nitrogen.
- Wheat tends to be most susceptible during rapid growth following spring topdressing.
Read more at: http://www.oardc.ohio-state.edu/ohiofieldcropdisease/images/PLPTH-CER-11_Powdery_Mildew_of_Wheat_2016.pdf
Yield loss and management:
The highest yield losses (due to small, light-weight grain or reduction in the number of heads in the case of powdery mildew) are seen in Ohio when susceptible varieties are planted and conditions remain cool and humid during grain development. Warm weather slows both powdery mildew and Septoria down.
Resistance is the best approach for managing Septoria and powdery mildew, but if your variety is susceptible, a fungicide application between flag leaf and head emergence will provide very good control. Most of the available fungicides are equally effective against both diseases. But scout fields before applying a fungicide to see if lesions are moving up the plant – in most years unfavorable hot, dry late-spring conditions provide the best control of Septoria and powdery mildew in Ohio, saving you the money.
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Soybean and Small Grain Research Report Available Online
The Soybean and Small Grain Crop Production Lab is pleased to present the first edition of the Ohio Soybean and Wheat Research Report: https://stepupsoy.osu.edu/sites/hcs-soy/files/Soybean%20and%20Wheat%20Trials%202016%203.pdf. This publication contains the final reports of soybean and wheat research trials conducted between 2012-2015 including high-input soybean production, soybean planting date x starter fertilizer, and wide-row wheat production. All research findings were originally published in peer-reviewed journals. Here, we present our research findings of our most recently published research in a concise manner.
For other useful soybean and wheat resources, see our recently updated website at: stepupsoy.osu.edu and follow us on Twitter @stepupsoy.
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Soybean Planting Date, Row Width, and Seeding Rate Recommendations
Over the past few years, with funding from Ohio Soybean Council, we’ve re-examined Ohio’s soybean planting date, row width, and seeding rate recommendations. Here are some things to keep in mind, as we approach planting:
Planting Date: Soybean planting date has a large effect on yield. Yield reduction as a result of late planting ranges from 0.25 to 1 bushel/acre/day depending on row width, date of planting, and variety. In southern Ohio, soybeans should be planted any time after April 15 when soil conditions are suitable. In northern Ohio, soybean planting can begin the last week of April if soil conditions are suitable. Soybeans should not be planted until soil temperature reaches 50 degrees Fahrenheit and moisture is present at planting depth. Planting too early (when conditions are not adequate) comes with risk such as damping-off, bean leaf beetle, and late spring frosts.
Row Width: In Ohio, most soybeans are grown in narrow rows: 7.5- or 15-inch row width. Soybeans grown in narrow rows generally produce more grain because they capture more sunlight energy, which drives photosynthesis. Row width should be narrow enough for the soybean canopy to close by flowering. With later planting dates, it is increasingly necessary to plant soybeans in narrow row widths to maximize yield.Seeding Rate: The effect of plant population on yield is very small over the normal range of seeding rates and for any particular set of conditions. For a crop planted before May 20 in narrow rows, final populations of 100,000 to 120,000 plants/acre are generally adequate for maximum yield. Final population is a function of seeding rate, quality of the planting operation, and seed germination percentage and depends on such things as soil moisture conditions, seed-soil contact, disease pressure, fungicide seed treatments, etc. In our research trials, we planted 140,000-150,000 seeds/acre in 15-inch row width and achieved final stands ranging from 109,000-147,000 plants/acre with an average of 132,000 plants/acre. Our seeding rate research is on-going with variable seeding rate trials being conducted this year.
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Alfalfa Weevil: An early-season pest
While most farmers are focused on getting corn and soybean in during the next few weeks, this is also the time to be aware of what alfalfa weevil larvae are doing in your forage. While February and March were warm, warmer weather on the horizon will give larvae a boost in their development. Scouting is essential to maintain a healthy alfalfa stand. Keep in mind that, while your alfalfa may be resistant to potato leaf hopper, it is NOT resistant to alfalfa weevil. As a reminder, alfalfa weevil scouting is accomplished by collecting a series of three 10-stem samples randomly selected from various locations in a field. Place the stem tip down in a bucket. After 10 stems have been collected, the stems should be vigorously shaken in the bucket and the number of larvae in the bucket counted. The shaking will dislodge the late 3rd and 4th instar larvae which cause most of the foliar injury. Close inspection of the stem tips may be needed to detect the early 1st and 2nd instar larvae. The height of the alfalfa should also be recorded at this time. Economic threshold is based on the number of larvae per stem, the size of the larvae and the height of the alfalfa. The detection of one or more large larvae per stem on alfalfa that is 12 inches or less in height indicates a need for rescue treatment. When alfalfa is between 12 and 16 inches in height, the action threshold should be increased to 2 to 4 larvae per stem depending on the vigor of alfalfa growth. When alfalfa is 16 inches in height and there are more than 4 larvae per stem, early harvest is recommended.
Crop Observation and Recommendation Network
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
Contributors
Disclaimer
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
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