C.O.R.N. Newsletter 2005-31

Single Rust-Like Fungal Spore Found in Spore Trap

Authors: Anne Dorrance

There have been many initiatives this year that were implemented to determine how best to track and monitor the movement of soybean rust. Recently, we deployed spore traps from Syngenta to assist in monitoring for soybean rust. Spore traps have been placed in two locations, with a third to begin this week. A glass slide is placed in the trap, which has a coating of Vaseline to catch the spores. These slides are then sent to a lab that specializes in this type of identification. The glass slides are then examined for spores. The difficulty is that spores of rust of several species look similar. This is a tool to help indicate that rust-spores maybe present and scouting intensity should increase. The use of spore traps were very helpful in Alabama, where spores were found 2 weeks prior to the first few pustules identified in the sentinel plot. However, Kentucky has been getting consistent positive finds for rust like spores in their traps for the past month, but they have yet to find soybean rust in any field or sentinel plot.

Our first slide, from Northwest Branch near Hoytville is positive for 1 rust spore. The traps were deployed after Hurricane Katrina and the trapping began Sept. 9th. I collected leaf samples from this area and we did not find active rust pustules on the 13th. If this is a soybean rust spore, it is unlikely that any lesions resulted last week, due to hot dry temperatures. Crops in the northern part of the state are maturing very rapidly. In addition, late planted soybeans (double crop) are also maturing very fast, so there is very little likelihood to have any damage. So what does finding a rust-like spore mean? It means we look and search. Even if this occurred during the normal growing season, we would not call for sprays, until we actually found some pustules in our sentinel plots. These are great tools to have as we continue to familiarize ourselves with this pathogen.

Finally, are you curious if Hurricane Katrina brought soybean rust to your fields? If so, then bring soybean leaves to the Firebaugh Building at Farm Science Review. We will be there to examine leaves. Collect leaves from green soybean plants from the low to mid-canopy. Focus on areas in fields that tend to be protected from wind and hold moisture longer. For the survey we will need the following information: county and growth stage. Only samples from Ohio should be brought to Farm Science Review, Indiana samples should be submitted through Purdue’s diagnostic clinic.

Tell CORN About Your Summer Experience with Aphids and Weed Control

Authors: Greg LaBarge

CORN readers please let us know what your experience was this past summer with soybean aphid and weed control issues. A survey that asks some questions related to these two summer problems and a few other issues can be found at the following link: http://www.zoomerang.com/survey.zgi?p=WEB224LWXVCMXN. The survey will only take a few minutes but provide us with valuable information on the extent of spraying for soybean aphids in Ohio and some weed control issues. The results of the survey will be used to direct research and educational activities. We will share the results in a future newsletter. The survey will be open for the next two weeks but we hope you can take time today to share your experiences with us!

Management Guidelines for Ohio Wheat Growers

Authors: Pierce Paul, Jim Beuerlein, Patrick Lipps, Edwin Lentz

As we approach the beginning of the wheat-planting season, wheat growers in Ohio need to make a few very important management decisions to increase their chances of having a successful wheat crop. Adequate and timely management are the keys to a successful crop. High yields and low cost of production are necessary for wheat to be a viable economic partner in Ohio. This can be achieved if the following management guidelines are followed:

1) Select the right variety. Select high-yielding varieties with high test weight, good straw strength and disease resistance. Do not jeopardize your investment by planting anything but the best yielding varieties that also have resistance to the important diseases in your area. Depending on your area of the state, you may need good resistance to powdery mildew, Stagonospora leaf blotch, and/or leaf rust. Avoid varieties with high susceptibility to Fusarium head scab. Plant seed that has been properly cleaned to remove shriveled kernels and treated with a fungicide seed treatment to control soil- and seed-borne diseases.

2) Plant at the right time. Plant after the Hessian Fly Safe date for your county. This date varies between September 22 for northern counties to October 5 for the southern-most counties. Planting within the first 10 days after this date insures the proper planting time to avoid serious insect and disease problems including Hessian Fly, aphids carrying Barley Yellow Dwarf Virus, and several foliar diseases. Planting before this date has lowered yield by 7 to 20% in research trials due to disease and insect problems. On the other hand, planting late (generally after Oct 20 in northern Ohio) can reduce the number of primary tillers that develop in the fall and increases the risk of cold temperature injury.

3) Use the correct seeding rate. Optimum seeding rates are between 1.2 and 1.6 million seeds per acre. For drills with 7.5 inch row spacing, this is about 18 to 24 seeds per foot of row with normal sized seed. When wheat is planted on time, actual seeding rate has little effect on yield, but high seeding rates (above 30 seeds per foot of row) increase lodging. There is no evidence that more seed is better, it only costs more money. For more information on seeding rates consult “Correct Wheat Seeding Rates Can Increase Profit” by Jim Beuerlein. C.O.R.N Newsletter 2005-29 (September 6, 2005 – September 12, 2005) available online http://corn.osu.edu/story.php?setissueID=102&storyID=605.

4) Plant seeds at the right depth. Planting depth is critical for tiller development and winter survival. Plant seed 1.5 inches deep and make sure planting depth is uniform across the field. No-till wheat into soybean stubble is ideal, but make sure the soybean residue is uniformly spread over the surface of the ground. Shallow planting is the main cause of low tiller numbers and poor over-winter survival due to heaving and freezing injury. Remember, you cannot compensate for a poor planting job by planting more seed; it just costs more money.

5) Fertilizer application. Apply 20 to 30 lb of actual nitrogen per acre at planting to promote fall tiller development. Wheat also requires at least 45 ppm of available phosphorus per acre in the soil to produce really good grain yields. If the soil test indicates less than 40 ppm, then apply 80 to 100 pounds of P2O5 at planting. Soil potassium should be maintained at levels of 135, 165 and 185 ppm for soils with cation exchange capacities for 10, 20, or 30, respectively. If potassium levels are low, apply 60 to 100 pounds of K2O at planting. In Ohio, limed soils usually have adequate calcium, magnesium and sulfur for wheat. Soil pH should be between 6.5 and 7.0 for eastern Ohio (6.0 and 7.0 for western Ohio).

The above recommendations may be fine-tuned by growers to fit their farming operation and soils. These guidelines are provided with the assumption that you are planting wheat in fields that are adequately drained and no tillage prior to planting. You can review more details on these, and other, research-based wheat management recommendations on-line at http://ohioline.osu.edu/iwy/index.html.

Evaluating Corn Hybrid Demonstration Plots

Authors: Peter Thomison

This is the time of year when corn growers visit and evaluate the numerous hybrid demonstration plots planted each year by seed companies and county Extension personnel, among others. When checking out these plots, it’s important to keep in mind their relative value and limitations, especially in a year like 2005 during which such diverse growing conditions occurred. Demonstration plots may be useful in providing information on certain hybrid traits, especially those that are usually not reported in state corn performance summaries. The following are some hybrid characteristics to consider while checking out hybrid demo plots.

PLANT/EAR HEIGHT. Corn reaches it maximum plant height soon after tasseling occurs. Remember that although a big tall hybrid may have a lot of "eye appeal," it may also be more prone to stalk lodging in the fall. Unless your interest is primarily silage production, increasing plant height should not be a major concern. Generally later maturity hybrids are taller than earlier maturity hybrids. Big ears placed head high on a plant translate to a high center of gravity, predisposing a plant to potential lodging. The negative effects of stalk rot on stalk lodging in the fall may be worsened by high ear placement.

STALK SIZE. Generally speaking, a thicker stalk is preferable to a thinner one in terms of overall stalk strength and resistance to stalk lodging. As you inspect a test plot, you will see distinct differences among hybrids for stalk diameter. However, also check that the hybrids are planted at similar populations. As population increases stalk diameter generally decreases.

LEAF DISEASES. During the grain fill period, leaf diseases can cause serious yield reductions and predispose corn to stalk rot and lodging problems at maturity. The onset of leaf death shortly after pollination can be devastating to potential yield, since maximum photosynthetic leaf surface is needed to optimize grain yield. Hybrids can vary considerably in their ability to resist infection by these diseases. Demonstration plots provide an excellent opportunity to compare differences among hybrids to disease problems that have only occurred on a localized basis. Look for differences in resistance to northern corn leaf blight and gray leaf spot.

STALK ROTS. Hybrids will likely differ widely when faced with strong stalk rot pressure. Begin checking plants in late August or about 6 weeks after pollination by pinching lower stalk internodes with your thumb and forefinger. Stalks that collapse easily are a sure indicator of stalk rot. Remember that hybrids with thicker stalks may be in plots having thin stands.

STALK LODGING/BREAKAGE. Perhaps as important as stalk rot resistance is the stalk strength characteristics of a hybrid. Sometimes, superior stalk strength will overcome the effects of stalk rot. If your variety plot is overcome with stalk rot in late August and early September, be certain to evaluate the stalk lodging resistance of the different hybrids. Demonstration plots also provide a good opportunity to evaluate another stalk related problem, green snap (a.k.a. brittle snap). Green snap damage in Ohio has usually been limited to localized areas where severe windstorms occur prior to pollination. Although green snap is not a major problem in Ohio, as it is in the western Corn Belt, there are differences in susceptibility among hybrids that growers may want to consider to avoid risks. Because damage from European corn borer (ECB) and western corn rootworm (WCRW) can be very localized, strip plot demonstrations may be one of the best ways to assess the advantages of Bt corns.

HUSK COVERAGE/EAR ANGLE. Hybrids will vary for completeness of husk coverage on the ear as well as tightness of the husk leaves around the ear. Ears that protrude from the husk leaves are susceptible to insect and bird feeding. Husks that remain tight around the ear delay field drydown of the grain. Hybrids with upright ears often associated with short shanks may be more prone to ear and kernel rots that those ears that point down after maturity. Last year we experienced major problem with Diplodia ear rot in many fields and Gibberella ear rot appeared to be more common than normal. Under certain environmental conditions, some hybrids are more prone to drop ears, a major problem if harvesting is delayed.

The following are some additional points to consider during your plot evaluations:

1. Field variability alone can easily account for differences of 10 to 50 bushels per acre. Be extremely wary of strip plots that are not replicated, or only have "check" or "tester" hybrids inserted between every 5 to 10 hybrids. The best test plots are replicated (with all hybrids replicated at least three times).

2. Don't put much stock in results from ONE LOCATION AND ONE YEAR, even if the trial is well run and reliable. This is especially important this year given the tremendous variability in growing conditions and crop performance across the state. Don't overemphasize results from ONE TYPE OF TRIAL. Use data and observations from university trials, local demonstration plots, and then your own on-farm trials to look for consistent trends.

3. Initial appearances can be deceiving, especially visual assessments! Use field days to make careful observations and ask questions, but reserve decisions concerning hybrid selection until you've seen performance results.

4. Walk into plots and check plant populations. Hybrids with large ears or two ears/plant may have thin stands.

5. Break ears in two to check relative kernel development of different hybrids. Use kernel milk line development to compare relative maturity of hybrids if hybrids have not yet reached black layer. Hybrids that look most healthy and green may be more immature than others. Don't confuse good late season plant health ("stay green") with late maturity.

6. Differences in standability will not show up until later in the season and/or until after a windstorm. Pinch or split the lower stalk to see whether the stalk pith is beginning to rot.

7. Visual observations of kernel set, ear-tip fill ("tip dieback"), ear length, number of kernel rows and kernel depth, etc. may provide some approximate basis for comparisons among hybrids but may not indicate much about actual yield potential.

Diagnostic Tent Available at Farm Science Review

Identifying weeds, diseases, and insects are important skills that continually need to be updated. Attendees at Farm Science Review will have the opportunity to enhance their diagnostic skills by working one-on-one with specialists at the Agronomics Crops Team Diagnostic Tent at Farm Science Review. The Diagnostic Tent is located at Kottman and Friday in Alumni Park.

Some of the features at the Diagnostic Tent include: Troubleshooting Ear Abnormalities with Peter Thomison, Weeds with Jeff Stachler, Diagnostic Scope/Videoscope with Nancy Taylor, Ag Answers, Precision Pumpkin Planter, and SPAD meter use with Robert Mullen.

In addition to the Diagnostic Tent feature, be sure to stop by the Soybean Rust display at the Firebaugh Building.

Admission to Farm Science Review is $5 in advance from most Ohio agribusinesses and all county offices of Ohio State University Extension; $8 at the gate. Children 5 and under admitted free. Farm Science Review is sponsored by The Ohio State University's College of Food, Agricultural, and Environmental Sciences: Resident Instruction Programs, OSU Extension and Ohio Agricultural Research and Development Center.