C.O.R.N. Newsletter 2006-28

Frogeye Leaf Spot -- A Primer

Authors: Anne Dorrance

Reports have continued to come in this past week as more fields have been identified with very high levels of frogeye leaf spot. In some of these fields, and it is only some, the disease levels are very high and economic losses are possible. High is greater than 20% of the leaf area affected on all leaves from the mid-canopy to the top. The biggest drawback to all of this is that we do not have any economic thresholds for frogeye leaf spot on varieties grown in this region – nor for infections that come in this late in the season. Yield loss estimates range from 10 to 25% in more northern regions. Don Hershman from Kentucky was able to find some information from Tennessee – where 50% of the leaf area was affected – but there was only a 9 bushel yield loss.

What is frogeye? Frogeye is caused by the fungus Cercospora sojina. The lesions are typically less than one quarter inch in size and are gray in the center – surrounded by a reddish purple border. There is a very good picture on the soybean rust ID card or see the Plant Pathology website: http://www.oardc.ohio-state.edu/ohiofieldcropdisease/soybeans/frogeye.htm. This fungus is primarily a leaf pathogen but it can infect pods, stems and seeds. Seed transmission is possible, and severely infected seeds may be discolored and fail to germinate. Seedlings from infected seeds will be weak. This fungus can easily penetrate and infect new young growing tissue but does not easily cause infections on older tissues.

This disease is primarily managed with host resistance, but there are a few susceptible varieties out there this year. So our first goal is to get these through the season.

We have recommended that a few fields be treated, but these were approaching the 30% leaf area affected at the R3. This is a disease that southern soybean producers deal with on an annual basis and it is usually accompanied with a few other problems at the same time (Purple leaf and stem canker). The primary question that we are getting is – should producers still treat their fields? For those few fields that were planted with a highly susceptible variety….
1) If the disease is approaching 20% or more of the leaf area covered with lesions and the fields are between R3 and R5. I would recommend spraying. The only materials, however, are those with full Section 3 labels.

2) Louisiana has reported yield savings with a tank mix application of TopsinM (8oz) and Quadris (4 oz) applied at R3 and R6 under high disease pressure. Now an R6 application in Louisiana is much different than an R6 here, our R6 is good for 30 days and theirs can go for 45 to 60. If a field has a high level of disease (>50% leaf area affected), and it is in a low spot, or an area with heavy dews; and the field already has spray tracks in it; and the producer needs some high quality seed – a late spray – mid R5 – will not likely increase yield, but may save some on quality. Both Quadris and Headline have 14 and 21 day pre-harvest intervals, respectively. As you can tell I’m hesitant about this late application timing. If the area will be dry – it takes 9 to 12 days from infection to lesion formation – by that time most of the beans will be progressing rapidly towards maturity.

If the field is treated, be sure to leave untreated strips…. We really don’t have any data on this and this is a learning experience for all of us. Finally, there are only a few varieties that are getting hit hard and for the most part the great majority of fields have few if any frogeye lesions, thus we have a lot of resistance in our northern varieties. This problem will likely disappear once we stop growing these susceptible varieties.

Soybean Aphid August 28 Update

Authors: Ron Hammond, Bruce Eisley

With August coming to a close and soybeans in the late R5 or R6 growth stages, any threat from soybean aphid is coming to an end. We have had no reports of aphids reaching or approaching threshold this past summer in Ohio, and it is highly doubtful that they will be of any concern the rest of the summer. Our prediction for low soybean aphid numbers in 2006 appears to have come through! Any late planted soybean fields that still have seeds developing should still be watched, but most concern should now be on pod feeding by either bean leaf beetles or grasshoppers.

What is in store for 2007? At this time, it is still too early to say. However, based on the past 4-5 years, we could be in store for high populations and economic problems. We will be monitoring fall flights of adult aphids as well as aphid populations on buckthorn, the overwintering host, throughout the Midwest to determine the potential for higher numbers next year. Stay tuned to the CORN newsletter as well as our talks during the upcoming winter for our 2007 prediction!

Start Scouting for Wild Turnip in Forage Production

Last Spring wild turnip was reported as far west as Licking County and as far northwest as Richland County. Wild turnip, which we have also called birdsrape mustard, was first reported in Muskingum County about six to eight years ago. Since that time, it has spread throughout eastern Ohio and continues to spread north and west.

What is wild turnip? It belongs to the mustard (Brassicaceae) family and closely resembles canola, rape, or wild mustard, but usually has an enlarged root like a turnip. The scientific name for wild turnip has been reported as Brassica napus, but not all botanists agree with this classification. It is found in both hay and pasture fields. At this time of the year it has already or is in the process of germinating. It has become most problematic in fall seeded alfalfa fields. The cotyledons of this species are kidney-shaped just like wild mustard or radish, turnip, broccoli, or cauliflower in your garden. The true leaves are rather large like turnip with the leaf margin being smooth early and more deeply lobed later. The leaves have some hair that is thicker and more rigid than most species, making it rougher like a bristle. The plant will form just a basal rosette (leaves attached to a stem near the soil surface) of leaves from now until frost. Early next spring the plant will bolt (produce an obvious upright stem) and start to flower about mid-April. The flowers are a deep yellow color and rather large like canola. This type of a growth habit makes it a winter annual, therefore it can be present already, will continue to germinate, and seed production must be eliminated to have the maximum effect upon the wild turnip population.

Current research indicates the best way to control wild turnip in an alfalfa field (new or established) is to apply 2,4-DB at 1.0 lb ai/A (2 qt/A of Butyrac 200 or equivalent) or Pursuit at 1.08 oz/A plus 2,4-DB at 0.5 lb ai/A (1 qt/A of Butyrac 200 or equivalent) plus crop oil concentrate at 1 qt/A plus a nitrogen source at the recommended rate in the fall. Increasing the rate of Pursuit to 2.16 oz/A with 2,4-DB will provide the most broad-spectrum control and residual activity. These herbicides should be applied at the fourth trifoliate of seedling alfalfa or about one week after the last cutting in an established stand. Research plots were sprayed in late September, but too much competition with seedling alfalfa had already reduced the stand, so an application based upon the alfalfa stage is preferred. Be careful not to rely upon Pursuit only for control of wild turnip as resistant biotypes will be selected at some point in time.

In grass only pastures, current research indicates the best way to control wild turnip is to apply 2,4-D at 1.0 lb ai/A (1 qt/A for most formulations) plus nonionic surfactant (NIS), Ally at 0.2 oz/A plus NIS, or Crossbow at 1 qt/A in the fall. For the most economical and broad-spectrum control, apply 2,4-D at 0.75 to 1.0 lb ai/A (1.5 to 2.0 pt/A for most formulations) plus dicamba (Clarity, Banvel, etc.) at 0.5 lb ai/A (1 pt/A of most formulations).

Using Oilseed Radish as a Cover Crop

Authors: Alan Sundermeier

Now is a good time of year to consider planting Oilseed Radish as a cover crop on your farm. Oilseed radish belongs in the Brassicaceae plant family which includes cabbage, broccoli, and mustards. It is used in Canada and Michigan as a cover crop that establishes and grows quickly in cool weather. With a thick, deep taproot, oilseed radish can break up compacted soil layers and scavenge nitrates. The leafy topgrowth can produce up to 4 tons/ acre biomass. What is also appealing as a cover crop is that oilseed radish will winterkill at temperatures below 25 degrees F.

On-farm test plots located in Northwest and North central Ohio were planted in August and September in 2005. Following a manure application on wheat stubble or silage harvested areas, oilseed radish was shallow seeded at 10 lbs/acre. The 2006 corn was easily planted in these plots with no spring surviving plants. On-going testing will determine the amount of nitrate cycling this cover crop can achieve.

Liquid manure application with oilseed radish added in the tank is a new slurry seeding method that is being investigated. This will reduce trips over the field and provide nutrients and moisture for seed germination.

For more information on oilseed radish follow the cover crop link from Michigan State University at: http://covercrops.msu.edu.

Contact me at sundermeier.5@osu.edu if you are interested in on-farm testing of oilseed radish.

OSU Extension/GVM West Field Day, September 7

Authors: Steve Prochaska

The Ohio State University Extension/GVM West Field Day will be held Thursday, September 7, 2006 from 8:00 am to 3:00 pm at GVM West, 4341 Sandhill Rd, Bellevue, Ohio 44811.

The event will showcase the latest in innovative spray technology: Air Assisted Booms; Auto Steer; Light Bars; and Dual Product Fertilizer Application Demonstrations.

Also, presentations on Key Production Issues will be featured with Dennis Mills of Ohio State University sharing research data on Corn and Soybean Health Fungicide Applications and Jeff Stachler of Ohio State University discussing a farmer/dealer scenario of various crop weed control problems and solutions compatible to both farmer and the dealer.

Commercial PAT credits and CCA CEUs will be offered. Registration is free and includes coffee, donuts and lunch, if you call GVM West at 1-800-848-8460. The complete program agenda and array of credits offered can be found at: http://crawford.osu.edu.

Certified Crop Advisor College at the Farm Science Review September 21

Authors: Harold Watters

Last notice! Many of you wanted to participate last year and we were not able to accommodate late registrants so here is your chance. Go to the website for more information and to register on-line: https://agcrops.osu.edu/Program%20Pages/FSRProgram.htm?PHPSESSID=dd4e64b3f1cee1a64ad0475a9c0a7330.

Program -
Thursday, September 21, 2006 - Registration deadline September 8th.
Time 8:00 a.m. – 12:00 noon. (followed by lunch)

1) Resistant Weeds - A creeping problem for Ohio and Indiana
- Jeff Stachler, OSU Extension Weed Scientist
- Bill Johnson, Purdue Extension Weed Scientist
2) Understanding Corn N rates for Ohio and Indiana
- Robert Mullen, OSU Extension Soil Fertility Specialist
- Jim Camberato, Purdue Extension Fertility Specialist
3) Soybean Management for Pod Fill
- Jim Beuerlein, OSU Extension Soybean & Small Grain Specialist
4) Water Holding Capacity for Manure Applications
- Jon Rausch, OSU Extension Ag Engineering
- Frank Gibbs, USDA, NRCS
- Brad Joern, Purdue Extension Agronomist

CCA-CEUs (approved for 1.0 CM, 1.0 PM, 1.0 NM, 1.0 SW)

Cost: $70 which includes:
• Hot breakfast buffet and box lunch
• Ticket for entrance to the Farm Science Review
• Additional tickets to the Farm Science Review are available for $5 when you register
• Registration is limited - logistics prevent us from accepting late registrations!
• You will receive your parking pass and entry ticket only if registered by September 8.
• There will be no on-site registration the day of the event.

Easy ways to register! Check or credit cards are accepted.
• Internet: Go online to https://agcrops.osu.edu, click on CCA College
• Request registration form: Call OSU Extension, Champaign County at (937) 484-1526
Hosted by the OSU Agronomic Crops Team, Contact: Harold Watters, OSU
Extension Champaign County (937) 484-1526 or by email: watters.35@osu.edu.

Corn Drydown

Authors: Allen Geyer, Peter Thomison

Dry weather across much of Ohio during the past 3 to 4 weeks has accelerated maturation in many corn fields. Corn will normally dry approximately 3/4 to 1% per day during favorable drying weather (sunny and breezy) during the early warmer part of the harvest season from mid September through late September. By early to mid October, dry-down rates will usually drop to 1/2 to 3/4% per day. By late October to early November, field dry down rates will usually drop to 1/4 to 1/2% per day and by mid November, probably 0 to 1/4% per day. By late November, drying rates will be negligible.

Estimating dry down rates can also be considered in terms of Growing Degree Days (GDDs). Generally, it takes 30 GDDs to lower grain moisture each point from 30% down to 25%. Drying from 25 to 20 percent requires about 45 GDDs per point of moisture. In September we average about 10 to15 GDDs per day. In October as temperatures drop, the rate drops to 5 10 GDDs per day. However, note that the above estimates are based on generalizations, and it is likely that some hybrids vary from this pattern of drydown.

Some past Ohio research evaluating corn drydown provides insight on effects of weather conditions on grain drying. During a warm, dry fall, grain moisture loss per day ranged from 0.76 to 0.92%. During a cool, wet fall, grain moisture loss per day ranged from 0.32 to 0.35%. Grain moisture losses based on GDDs ranged from 24 to 29 GDDs per percentage point of moisture (i.e., a loss of one percentage point of grain moisture per 24 to 29 GDD) under warm dry fall conditions, whereas under cool wet fall conditions, moisture loss ranged from 20 to 22 GDD. The number of GDDs associated with grain moisture loss was lower under cool, wet conditions than under warm, dry conditions.

Agronomists generally recommend that harvesting corn for dry grain storage should begin at about 24 to 25% grain moisture. Allowing corn to field dry below 20% risks yield losses from stalk lodging, ear rots, and insect feeding damage. This year growers should be prepared for localized root lodging and stalk lodging that may slow harvest and contribute to yield losses.