C.O.R.N. Newsletter 2006-10

Dates Covered: 
April 24, 2006 - May 1, 2006
Editor: 
Steve Prochaska

Don’t Delay Planting Corn

Authors: Peter Thomison

Last year’s experiences planting corn have weighed heavily on a lot of growers’minds. According to the Ohio Agricultural Statistics Service (USDA-NASS), as of April 23, 9 percent of the State's corn acreage had been planted compared to 48 percent last year and 17 percent for the five-year average. Due to favorable weather conditions, much of the corn crop was planted by April 22 in 2005. (NOTE: The recommended time for planting corn in northern Ohio is April 15 to May 10 and in southern Ohio, April 10 to May 10) This year, even though soils have been relatively dry in parts of Ohio (with April rainfall averaging as much as 2 inches below normal), some growers have been reluctant to plant as early as last year given what they experienced in 2005, i.e. slow, poor emergence and replanting. Many acres of early-planted corn were replanted due to injury from snow and freezing rains on April 22.

As we enter the last of week April, growers who may have limited corn planting thus far, should start planting in “earnest” and establish their corn crop as quickly as possible. There is no assurance that the relatively dry weather we’ve experienced up to this point will continue. Moreover, don’t forget years like 2002 when protracted wet weather kept us out of the fields throughout much of planting season, resulting in nearly half our corn planted after June 1. Also keep in mind that our highest corn yields statewide (2003 and 2004) were obtained in years when corn was planted earlier than normal.

During the two to three weeks of optimal corn planting time, there is, on average, about one out of three days when fieldwork can occur. This narrow window of opportunity emphasizes the need to begin planting as soon as field conditions will allow, even though the calendar date may be before the optimal date. There is a risk associated with early planting but remember that yield lost from planting too early is nearly always less than the loss when planting an equal period too late.


Wheat Scab Risk Prediction Tool And Wheat Update

Authors: Pierce Paul, Dennis Mills

Wheat Scab Risk Predicition Tool

The 2006 wheat scab risk prediction tool is now up and running, and is again available for use in 23 states, including Ohio. A few subtle but very important changes have been made to this tool in an effort to provide users with more information regarding the risk of scab occurring in the state. The model used in Ohio (the winter wheat model) remains the same in 2006; however, the sub-model for winter wheat planted into corn stubble is undergoing revision and will not be available this year. In addition to risk predictions based on actual weather conditions (the default risk map), the 2006 risk tool has been modified to provide predictions based on forecasted weather. Forecasted weather information will be used to generate risk maps that estimate risk 24 and 48 hours ahead of time. Another new feature of the 2006 risk tool is the inclusion of commentaries provided by your state extension specialist.

As the wheat growing season progresses, commentaries will be provided (below the risk map) and updated regularly to inform Ohio growers of the risk of Scab occurring in the state. These comments will serve to help users assess the risk of scab in their region of the state, based on the color patterns displayed on the risk map. Basic information on the use and interpretation of this risk tool will be provided. In addition to information on wheat scab, users will be provided with additional information regarding other wheat diseases, crop growth and development, weather patterns, and basic management recommendations for wheat diseases.

Wheat Update

Reports from across the state suggest that the 2006 wheat crop is in very good shape. Both late and regularly planted wheat seem to have recovered nicely from highly variable winter weather conditions. The crop is now between growth stages GS6 and GS7 (stem elongation), and if warm conditions persist, should be entering growth stage GS8 (flag leaf emergence) later in the week or early next week.

No major early-season disease problems have been reported. However, a few reports of purplish leaf discoloration were received from some parts of the state during the past week (and neighboring states), suggesting that some level of viral disease infection may have occurred in the fall and is now showing up as the wheat resumes growth. In addition to leaf discoloration, viral diseases often result in stunted plants with poor tiller development. However, since leaf discoloration and poor growth may also be the result of nutrient imbalances and varietal responses to environmental conditions, laboratory tests are needed in order to say conclusively that the observed symptoms are due to viral infection. Among the viral diseases known to affect wheat in Ohio at this time of the season and most likely to cause purple leaf discoloration is barley yellow dwarf virus (BYDV).

In general, weather conditions have been unfavorable for the development of wheat diseases, and for some diseases (such as wheat scab, powdery mildew, rust, and leaf blotches), it is still too early to say whether they are going to be a problem in 2006. Relatively warm, humid (or wet) conditions are needed for the growth and development of most disease-causing fungi. While temperatures have been fairly warm, the spring has in general been very dry in most parts of the state. However, since the forecast is for rain later in the week, weather conditions will likely become more favorable for fungal growth and disease development as the wheat crop enters GS8 (flag leaf emergence) and GS10 (boot stage). We will continue to monitor crop growth and weather conditions as the season progresses, and in subsequent articles, we will deal with scouting for wheat diseases and management recommendations.

For more information on wheat scab prediction and general wheat update visit the Fusarium Head Blight Prediction Center at http://www.wheatscab.psu.edu/ and the Ohio Field Crop Disease web site at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/

Don’t Forget Soybean Seed Treatments

Authors: Anne Dorrance

I’ve been working on some papers and finalizing plans for this year’s field studies and I was struck again how consistently higher yields from seed treated with fungicide are compared to the nontreated checks-- both statistically significant and at economical levels. Granted, many of you have seen the fields at Northwest branch, we irrigate within 3 days of planting to favor disease, but I still get reasonable yields (40 to 50 bu/A) planting at the end of May with old varieties. We do everything we can to favor the pathogen. Some characteristics of soils and production practices that have emerged over the years that may increase the chances that soybean fungicide seed treatments will pay for you are:

1. No-till, reduced tillage – we are finding in fields with a history of no-till >5 years, a larger number of pathogens in the seed beds. Since the soil is not turned over, pathogens will remain in the upper layers, this is especially important for the water molds, Pythium and Phytophthora.

2. Continuous soybeans or only corn-soybeans – another recent finding from the lab is an increase in the number seedling pathogens that are pathogenic on both corn and soybean seed and seedlings. This reduced number of crops per field and reduced tillage favors this increase in seed and seedling pathogens.

3. Poor drainage – fields with old tile lines or tiles spaced too far apart are also prone to seed and seedling diseases. This comes down to providing the most favorable environment for the longest period of time for the seedling pathogens. The longer the fields are saturated the more time these pathogens have to produce spores and infect the roots of the plants.

4. Old Rps genes for Phytophthora sojae. Occasionally we get some soybean seed in the state with Rps1a, this gene is no longer effective in most of our fields and the partial resistance (tolerance, field resistance) is what is protecting the plant through the season. The partial resistance component is not 100% effective until the plants are up and growing. We have shown over several years the added benefit of putting a seed treatment on when the partial resistance is the primary form of resistance in the plant.

If you have two or more of the conditions listed above in any of your fields, those would have the highest probability of a seed treatment preventing a replant situation but also increasing your yields overall.

Soybean Rust Update for April

Authors: Anne Dorrance

Sentinel plots across the south, Florida, Georgia, Alabama, Louisiana and Texas have been planted and reports are that “they are coming up nicely”. Reports from the sentinel plot coordinators in Florida and Georgia are reporting dry conditions. Layla Sconyers at the Univ. of Georgia is reporting that kudzu is greening throughout the state with south being the most advanced. No new finds on Kudzu as of (4/22/06). For Ohio several sentinel plots were planted this past week with more to go in next week.

Scout For Slugs

Authors: Ron Hammond, Bruce Eisley

Now is the time to begin determining your chances for slug problems. Population densities were average in many fields in the fall of 2005, suggesting that spring populations this year could be a concern if conditions are right. Corn and soybean growers who have had problems with slugs in the past should sample their fields over the next few weeks, checking numerous spots in their fields for eggs. Slug eggs are usually laid in batches of 3-5 and are found just at or slightly below the soil surface. Growers should move crop residue aside in an area about a foot square, and scrape the soil with a small knife or other instrument. The eggs will be round, slightly smaller than a BB, and usually clear to slightly opaque (see picture at http://entomology.osu.edu/ag/slugegg.htm . Although there are no thresholds as to what represents an economic problem, finding eggs in the majority of locations suggests a potential problem and a field that needs to be monitored closely. However, not finding any eggs is not a reason to forget that field. Egg sampling and knowing which fields have a higher damage potential will aid you in managing your slugs.

Alfalfa Weevil Update

Authors: Ron Hammond, Bruce Eisley

Two weeks ago we mentioned that it was time to begin scouting for alfalfa weevil in southern and central Ohio. With the continued warm weather, it is also time to sample in northern Ohio for signs of alfalfa weevil. Although we have not yet heard of any need for insecticide control, this is the time to be in your alfalfa fields checking for possible problems.

Fields should be scouted for weevil in all areas of the state and continued weekly sampling until at least the first harvest. Check for tip feeding by the larvae and if found, use the bucket method found in the newsletter two weeks ago or in the fact sheet on the web at http://ohioline.osu.edu/ent-fact/0032.html to sample the field. The fact sheet also contains information about the number of larvae and damage necessary to require treatment.

As we get farther into May and the alfalfa starts getting around 12-16 inches in height, growers should consider an early harvest rather than spraying. Over 16 inches, we would always recommend an early cutting. In those fields which are cut early for alfalfa weevil, the regrowth should be checked to make sure weevils that are still alive do not prevent good regrowth.


Progress of Giant Ragweed Seedling Emergence

Authors: Brian Schuttte, Kent Harrison, Emilie Regnier

The progress of giant ragweed seedling emergence can be found on the Weeds Page on the Agronomic Crops Network website at https://agcrops.osu.edu/weeds/research/2006ragweedemergence.php
In addition, a forecast for future giant ragweed seedling emergence is presented. A description of the seedling emergence model and how it can be used for giant ragweed management was published in the C.O.R.N. Newsletter 2006-08.

Archive Issue Contributors: 

Ann Dorance, Pierce Paul and Dennis Mills (Plant Pathology), Mark Loux, Brian Schutte, Kent Harrison, Emilie Regnier and Jeff Stachler (Weed Science), Peter Thomison, (Corn Production), Bruce Eisley, Ron Hammond (Entomology). Extension Educators: Howard Siegrist (Licking), Harold Watters (Champaign), Glen Arnold (Putnam), Roger Bender (Shelby), Steve Foster (Darke), Steve Bartels (Butler), Steve Prochaska (Crawford), Bruce Clevenger (Defiance), Gary Wilson (Hancock), Tammy Dobbels (Montgomery), Todd Mangen (Mercer), Mark Koenig (Sandusky), Alan Sundermeier (Wood), and Keith Diedrick (Wayne).

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.