C.O.R.N. Newsletter 2005-27

Dates Covered: 
August 22, 2005 - August 30, 2005
Editor: 
Harold Watters

Managing Foliar Diseases with Fungicides in Corn

Authors: Pierce Paul, Patrick Lipps

The use of resistant hybrids is still the most effective, economical and widely recommended control measure for foliar diseases (such a gray leaf spot and northern corn leaf blight) of corn. However, if for some justifiable reason a susceptible hybrid is planted in an area or under conditions known to favor the development of these diseases, an early application of a fungicide may be warranted. Both the gray leaf spot and northern corn leaf blight fungi survive in corn residue left on the soil surface from the previous growing season. If a susceptible hybrid is planted in a reduced-tillage field and conditions are favorable for disease development (extended periods of high relative humidity and moderate to high temperatures), extensive blighting of leaves may occur prior to grain fill, leading to substantial yield reduction. To achieve the desired effect, fungicides should be applied at the right time.

The main goal of fungicide application is to prevent disease from spreading to the ear leaf and the leaves above the ear, since these leaves contribute a significant portion (about 75%) of the carbohydrates for grain fill. Applications should begin prior to tasseling when the first few lesions are observed on the leaves below the ear leaf. Fields should be scouted regularly to determine the appropriate time for fungicide application. Research has shown that two applications may be more effective than one at reducing the level of disease; however, more than one fungicide application is generally not economical. Yield increase is often not enough to offset the cost of two applications.

The following should be taken into consideration when making decisions regarding fungicide application:

1- Susceptibility and yield potential of the hybrid
2- The amount of disease in the field
3- The growth stage of the crop
4- Weather conditions
5- Fungicide and application cost
6- Grain price
7- Directions and restrictions on product label

Soybean Aphid and the Multicolored Asian Lady Beetle

Authors: Ron Hammond, Bruce Eisley

As we enter the last few weeks of the growing season, we are beginning to see large populations of the multicolored Asian lady beetle in many soybean fields feeding on aphids. Observations point to many new adult lady beetles as well as large numbers of pupae and larvae that are starting to pupate. Thus, we expect at least another generation of the beetles to occur which will further increase their populations by mid-September. We have seen this in each of the years that soybean aphids have been a significant problem.

What does this mean for soybean growers and the soybean aphid? Basically, nothing for this growing season. Aphid populations have, for the most part, reached their peak numbers and are either hold studying or beginning to fall. Damage has already occurred, or if populations were scouted and treated, they have been controlled. What the lady beetles will optimistically do, based on what we have seen for the past 4 years, is to reduce the numbers of aphids that will overwinter this coming winter and thus, greatly lowering the numbers of aphids next spring. As most growers are aware of, we have seen a 2-year cycle of aphid, one year where we have problems followed by a year without heavy aphid populations. We hypothesize that lady beetles help to produce this cycle, which will hopefully lead to low aphid populations next year. We will be gathering data this coming fall throughout the Midwest on the numbers of winged aphids, which we expect and hope will be very low. We will then use that information to make a prediction on soybean aphid problems for next year. Throughout the coming winter, we will be discussing that prediction during meetings and here in the CORN newsletter.

Although the multicolored Asian lady beetle will not have an effect this year for soybean growers, their larger numbers do mean a potential problem in the fall for fruit growers, grape production and wine producers, and later to home owners. At this time we are predicting significant numbers of the lady beetle this coming fall, similar to what we saw in 2001 and 2003. Thus, for those of you who experienced problems and concern with the lady beetles in those two years, we suggest preparing for another round of problems in the coming months!

Preparing Soils for Fall Seeded Alfalfa

Authors: Robert Mullen

An important consideration for fall seeding of alfalfa is ensuring that adequate soil nutrient levels are present to promote good growth this fall going into dormancy and good biomass accumulation in the spring. Soil testing is the best method to determine the nutrient supplying power of your soil, and hopefully it is a component of your management system. Soil testing can reveal if pH levels are optimum for alfalfa production and determine if phosphorus and/or potassium are sufficiently present.

Maintaining an optimum soil pH can ensure good growing conditions for the seeded crop. While it is a little late to apply lime for alfalfa seeded this fall (we recommend application and incorporation about 6 months prior to seedling), if soil pH is a bit low you can supply some now to make an adjustment to soil pH. If soil pH is low (<6.0) and lime was applied a little late, application of a small amount of nitrogen may be beneficial (only about 10 lb N/acre). This might encourage crop growth which may be limited due to poor nodulation caused by acid soil conditions.

If phosphorus and/or potassium are shown to be deficient by soil test, application of these fertilizer materials should be made. Specific rates of application based on soil test can be found in the Tri-State Fertilizer Recommendations (http://ohioline.osu.edu/e2567/index.html). For no-till seeding, it is past the optimum time for phosphorus and potassium application (we recommended application about six months prior to seeding), but if needed applications can still be made.

Remember, soil test should be an integral part of your management strategy, and proper fertilization can ensure good productivity from your fall seeded alfalfa next spring.

Corn, Soybean, Wheat and Alfalfa Field Guide

Authors: Dennis Mills

The updated 2005 version of this color pocket field guide is now available at county Extension Offices. It has been designed by the 16 authors as a reference to be used by scouts, agents, consultants and farmers. The guide contains over 200 pages of information on insect, disease, and weed management along with fertility and additional useful agronomic information on corn, soybeans, wheat and alfalfa.

Indiana and Ohio CCA Program at the Farm Science Review

Authors: Harold Watters

Attending the Farm Science Review is an old tradition in Ohio. This year we want to encourage you to attend the Farm Science Review to do more than just see large equipment and talk with seed sales representatives. Ohio State University in cooperation with Purdue University will be presenting a Certified Crop Adviser program at the Review, to include crop updates from the growing season and hands on participation in evaluating applied treatments. We will have a very good update on Asian soybean rust from two state authorities. And with the price of nitrogen fertilizer increasing and the concern for water quality, we will also be able to discuss management practices to better manage this important crop input.

Program:
Soybean Rust: Indiana & Ohio Respond and A Review of 2005
- Anne Dorrance, OSU Plant Pathologist
- Greg Shaner, Purdue Plant Pathologist

Nutrient management: Efficiency and Water Quality
- Robert Mullen, OSU Soil Fertility Specialist
- Nathan Watermeier, OSU Geospatial Extension Specialist

Manure Application: Water Quality, Needs and Efficiency
- Brad Joern, Purdue Agronomist
- Jon Rausch, OSU Ag Engineering

Diagnosing Kernel Set & Grain Fill Problems in Corn
- Peter Thomison, OSU Corn Specialist
- Bob Nielsen, Purdue Corn Specialist

We are planning a program to start at 8AM on Wednesday of the Farm Science Review, September 21st, and end at noon with a lunch. Wednesday is the big day for attendance so we thought providing a lunch would help you with planning your activities for the rest of the day at the Review. During lunch you will have time for interaction with other CCAs and time to ask questions of the state specialists. After lunch you can spend the rest of the day making those important visits to the field demonstrations or talking with on-site exhibitors.

For the CCA continuing education credits, meal, a parking pass, a ticket to the Farm Science Review and access to some of Indiana and Ohio’s best state specialists, we will charge $70. Registration is limited to 120, please register by September 7th. To register click on “CCA College” at the OSU Extension Agronomic Crops Team Website - https://agcrops.osu.edu/, on the Purdue Crop Diagnostic website - http://www.agry.purdue.edu/DTC/ or by calling (419) 466-4145 (T & M Registration Services).

Archive Issue Contributors: 

Anne Dorrance, Pat Lipps, Dennis Mills and Pierce Paul (Plant Pathology), Ron Hammond and Bruce Eisley (Entomology), Robert Mullen (Soil Fertility) and Mark Loux and Jeff Stachler (Weed Science). Extension Agents: Keith Diedrick (Wayne), Howard Seigrist (Licking), Glenn Arnold (Putman), Roger Bender (Shelby), Harold Watters (Champaign), Gary Wilson (Hancock), Dusty Sonnenberg (Henry) and Steve Foster (Darke).

About the C.O.R.N. Newsletter

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.