C.O.R.N. Newsletter 2006-24

Dates Covered: 
July 31, 2006 - August 8, 2006
Editor: 
Jim Skeeles

Look at all the Problems

Authors: Anne Dorrance, Pierce Paul

There are lots of tracks in soybean fields and airplanes flying this summer applying fungicides across the state. We’ve both walked several fields last week and unless our hand lenses are broken, we are not finding economic levels of the diseases nor insects. However, we have found a few exceptions. Gray leaf disease levels were relatively high (10% of the leaf area on the leaf below the ear leaf) on a susceptible hybrid which had just flowered. This field will most likely see a benefit from sprays. Next year, a hybrid with higher levels of resistance to gray leaf spot would be a more economical choice. Frogeye leaf spot, at moderate levels, was found in another field. We do not have any data in Ohio for the best timing, severity levels that trigger spraying, or which varieties have the best resistance. However, we did have a few fields last year, planted to varieties that were super susceptible that got hit fairly hard. The majority of the acres had one or 2 lesions per 100 plants, these fields were NOT affected by frogeye. Interestingly, in one of our study plots we were rating the disease levels, but the insect damage was twice the threshold. This happened to the folks in Georgia last year, one of the rust plots was damaged by an insect before the rust ever got started. The bottom line is to scout the fields, if there are no lesions, leaf spots or insect damage, we have never been able to demonstrate any economic benefit under Ohio conditions in applying these materials.

Soybean rust is moving in Florida. Several more soybean sentinel plots now have soybean rust present in them. This hot weather, if it reaches the south, will delay things again, but otherwise we should expect to see an increase in rust finds over the next two months. This is too late to affect our crops, but it will be interesting to follow the course that this fungus takes over the next few months. These will be good lessons for the future. In Ohio, no rust was found in any of the sentinel plots scouted last week but bacterial blight, brown spot and a few frogeye leafspot lesions were found. In addition, areas of the state with historically prevalent SDS were also negative for any symptom development. Symptoms similar to SDS at this time of year can also be caused by Phytophthora root rot and triazole injury.

Soybean Aphid Update

Authors: Ron Hammond, Bruce Eisley

We continued to visit fields the past two weeks to determine the current levels of soybean aphid in Ohio. After much sampling, we still are finding relatively few aphids, although numbers have increased slightly. Although a few more soybean rust sentinel plots have aphids, they also remain at low levels. These findings of very few aphids are again common to surrounding states. Continue keeping abreast of the situation in this CORN newsletter, and hopefully within a few more weeks, we will be home free.

Soybean Defoliators

Authors: Ron Hammond, Bruce Eisley

We are getting reports from around Ohio of defoliation occurring on soybeans that is reaching levels of concern, with three insects causing the majority of the leaf feeding. First generation bean leaf beetles are present, with most of their actually feeding occurring on the new leaves that are still developing. As these leaves finish expanding, the leaves appear riddled with holes. Thus, this type of feeding gives the top portion of the leaf canopy a riddled affect. This insect is also the only one of the three that tends to be at similar densities across a field. The next pest of concern is the Japanese beetle. As with the bean leaf beetle, most of its feeding is also on the top leaves in the canopy, although the Japanese beetle feeds mainly on older leaves. However, Japanese beetles congregate in a grouping behavior, so you usually find them in patches of numerous beetles with significant feeding rather than spread throughout the field. The third defoliating insect present now are grasshoppers, which tend to gather mainly at the field edges.

Because of the varied feeding and location habits of these insects, growers need to scout the entire field rather then just the field edges, and examine random locations rather than just spots where feeding is extremely heavy. When sampling, you want the areas not being fed on to have as much chance as being in your sample as the heavy defoliated areas. During the reproductive stages the soybeans are currently in (R2-R5), the level needed for treatment is around 15% over the entire plant. Thus, the whole plant should be pulled from the soil to take a defoliation reading, rather than just looking at the top of the plant canopy where most feeding is probably taking place. Often that top canopy feeding, while heavy, only reaches 3-5% defoliation when the entire plant is taken into consideration.

Warrior on Soybeans

Authors: Ron Hammond, Bruce Eisley

In a newsletter article in early June, we mentioned that Warrior received a new label with a reduced PHI, or preharvest interval, for soybeans. As we are into the later reproductive stages of soybeans where insect defoliators are causing the major concern and PHIs have to be taken into consideration, we again wanted to mention this change in label. The new PHI for Warrior on soybean is 30 days, down from the 45 day PHI that was on the previous label. This change gives the grower approximately two weeks longer in which this material can be used.

Wheat Stubble Management Reminder

Take advantage of weed control opportunities in wheat stubble, especially perennial species for those individuals growing non-GMO soybeans! Most of the state has received plentiful rainfall since wheat harvest, allowing germination of new weeds including some winter annuals. This has also delayed mowing of wheat stubble to suppress summer annual seed production. There is still time to mow the wheat stubble if perennial weed control is desired, but time is quickly fading. Mowing should be done by the end of the first week of August and absolutely not past the 15th. This will allow perennial weeds to regrow to a size large enough for maximum control. All perennial species should be at least 8-10 inches tall before applying herbicide and some, such as Johnsongrass should be at least 24 inches tall before applying herbicide to maximize control.

Perennial weed species are the most difficult to control and wheat stubble is an ideal habitat to control almost all perennial species. The best way to maximize control of perennials is to mow the wheat stubble low to the soil before early August to allow maximum regrowth before applying herbicide in either mid-September to early October before a frost or after a frost in mid- to late October. The proper time to apply herbicides will depend upon whether a warm-season species, such as Johnsongrass, common pokeweed, or hemp dogbane are present or a cool-season species, such as quackgrass, Canada thistle, or dandelion are present.

If summer annual weeds are your target then tillage or an application of glyphosate plus 2,4-D ester will control most plants. Apply the glyphosate plus 2,4-D ester combination as soon as possible if it has not been done already. Apply to as small of weeds as possible. Apply the glyphosate at 1.5 pounds acid equivalent/ acre and the 2,4-D ester at 0.5 pounds active ingredient/A (1.0 pt/A or 0.67 pt/A depending upon formulation).

2006 Ohio Wheat Performance Trial Results

Authors: Jim Beuerlein

2006 test results for 58 soft red winter wheat varieties and one soft white winter wheat variety will be available later this week at: https://agcrops.osu.edu/ and http://www.ag.ohio-state.edu/~perf/ On the internet sites, any column of data can be sorted by clicking at the top of the column, which makes it easy to arrange varieties in order by any characteristic for comparison purposes.

Depending on variety and test site, yields varied between 60.7 and 96.9 bushels per acre, and average test weight ranged from 56.1 to 60.1 pounds per bushel. Yield differences between test sites were due primarily to the length of the grain fill period and disease level and the reaction of each variety to various diseases is included in the report. The average heading date was five days earlier than in 2005 and 2 days earlier than normal. Average plant height was two inches shorter than normal.

Variety selection should be based on disease resistance, average yield across test sites and years (tables 2 & 3 of the report), winter hardiness, test weight and standability. Soft white winter wheat and hard red winter wheat should never be mixed together or be mixed with soft red winter wheat because they have very different flour characteristics and end uses. Mixing of different classes of wheat destroys their unique utility, makes them unacceptable for quality premiums and reduces their usefulness to animal feed only.

Archive Issue Contributors: 

State Specialists: Ann Dorrance and Pierce Paul (Plant Pathology), Jeff Stachler (Weed Science), Ron Hammond and Bruce Eisley (Entomology) and Robert Mullen (Soil Fertility). Extension Educators: Howard Siegrist (Licking), Harold Watters (Champaign), Glen Arnold (Putnam), Roger Bender (Shelby), Steve Foster (Darke), Steve Prochaska (Crawford), Greg LaBarge (Fulton), Mike Gastier (Huron), Mark Koenig (Sandusky), Jim Skeeles(Lorain), Gary Wilson (Hancock), Jonah Johnson (Clark), Ed Lentz (Seneca) 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.