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In This Issue:
A) Soybean Herbicide Carryover Into Wheat
B) Wheat Planting Date: Not Too Early, Not Too Late
C) Corn Harvest Losses And Grain Drydown Rates
D) Adult Rootworm Survey Data Accumulating
E) Bean Leaf Beetle Problem Declining
F) Potato Leafhopper Activity Continues
With the dry weather this season there is a possibility of herbicides carrying over and causing injury to this Fall's wheat crop. Any area receiving lower than normal rainfall for the growing season needs to be concerned as to what fields should be planted to wheat. Any field that had Scepter, Squadron, Detail, Steel, Canopy or Canopy XL applied are the fields most likely to have a problem, however other products can not be ruled out as being a problem in the extremely dry areas of the state. Canopy and Canopy XL will be more of a problem than usual on soils with pH's of 6.8 or greater. Fields with a pH of 5.9 or less may also be more of a problem than with normal rainfall for Scepter, Squadron, Detail or Steel. In areas of below normal rainfall, wheat should not be planted after the use of Command as more injury than normal will occur.
The best way to avoid wheat injury in these fields is to not plant wheat, but that may not be practical. Any area receiving very little rain may want to perform a bioassay of the field prior to planting wheat, regardless of the herbicide that was used, other than Roundup Ultra. To perform a bioassay, collect two to three gallons of soil from areas in the field most likely to cause a problem. These areas are the driest parts of the field, or areas of pH extremes. In no-till and chiseled fields, collect soil to a depth of three inches. In conventionally tilled fields, collect soil to a depth of six inches. Collect the soil from a single area and collect two to three samples per field. At the same time collect soil from the same field or close proximity of similar soil type that has not been treated with any herbicides. This soil will serve as a check for germination and amount of growth of the crops that you plant in it. Put each sample in a container so that the soil is at least three inches deep. Then plant at least 10 and no more than 20 seeds of corn and wheat into rows. At three to four weeks after planting observe the plants in the soil treated with herbicide and compare it to plants in the soil without a herbicide to determine how much injury has occurred. The best measurements to evaluate are as follows:
Bioassays are not 100% accurate, but it is the best test method in determining whether or not to plant wheat. The corn will be more sensitive than the wheat to most herbicides, so make a final decision based upon the wheat. If slight injury occurs one recommendation is to plow the field to a depth of 10 inches to bury and mix the herbicide residue. If severe injury occurs, do not plant wheat into the field. The soil samples need to be collected as soon as possible, so the plants have enough time to grow to be evaluated properly. For more information about herbicide carryover read pages 9 and 10 in the Weed Control Guide for Field Crops.
Choosing the correct time to plant wheat in Ohio is truly a balancing act. The goal is to plant late enough to avoid insect and disease problems that occur in September, but we want the young wheat plants to grow big enough in the fall to survive the winter. Ideally, plants should have developed two to three tillers, each with three leaves before winter dormancy for best over winter survival.
Wheat growers have traditionally planted after the Hessian Fly Safe date for their location or county. This date ranges from September 22 for the most northern counties to October 5 for the most southern counties. This date is not an absolute date, it is more like a rule of thumb. In years with cold temperatures in September the actual date wheat could be planted could be a little earlier, but during years with warm fall temperatures the actual planting date may be later to avoid damage. However, this date is based on long term averages. The Hessian Fly Safe date is based on timing of when Hessian fly adults are no longer around to lay eggs on emerging wheat seedlings. If the adults find early planted wheat and lay eggs on the seedlings, Hessian Fly larvae overwinter on wheat plants and feed on developing plants in the spring causing severe lodging or premature stem death. We have not seen a severe outbreak of Hessian fly in Ohio for many years because most growers have been strict about planting after the Hessian Fly Safe date. However, we have seen low levels of infestations in some early planted fields.
Delayed planting of wheat also limits infections from several different diseases. Most important is Barley Yellow Dwarf. Barley Yellow Dwarf is caused by a virus carried by aphids. Aphids travel on wind currents from the South and land on early emerging wheat in Ohio. The aphid can transmit the virus to wheat plants within the first few hours after it lands on the plants. Infected plants turn yellow or have yellow leaves in the spring. In planting date field trials at Hoytville, Barley Yellow Dwarf reduced yield by 22% in plots planted 10 days before the Hessian Fly Safe date as compared to plots planted on Fly Safe Date. Additionally, foliar diseases like powdery mildew, Stagonospora leaf blotch and leaf rust can infect wheat if planted too early. Giving these fungal pathogens an early start in the fall can increase the potential for more severe problems in the spring if they overwinter on the wheat plants.
There has been considerable research on the effect of planting date on wheat yields in the past and only a few studies that are relatively recent. As most farmers understand, each year is different since seedling emergence depends on soil moisture and temperature. Thus, planting date recommendations are based on averages across years. In Ohio, under conventional tillage, yields are generally better when wheat is planted from 5 to 15 days after the Hessian Fly Safe date, but under no tillage, wheat yield is generally better if planted on the Hessian Fly Safe date to 10 days after this date.
Don't plan your harvest strategies this year based on the average calendar dates for corn maturity in past years. Grain moistures may be considerably lower than you might expect. Grain maturation has been accelerated by warm, dry weather conditions. Moreover, premature plant death caused by severe drought has resulted in earlier than normal maturity and drydown. Since there is potential for corn stalk rots and lodging in some drought stressed areas of the state, grain yield could drop considerably if harvesting is delayed much beyond maturity.
The loss of one "normal" sized ear per 100 feet of row translates into a loss of more than one bushel/acre. In fact, an average harvest loss of 2 kernels per square foot is about 1 bu/acre! Keep in mind that most harvest losses occur at the gathering unit. An Ohio State study shows the range of visible corn harvesting losses by source (Table 1).
| Table 1. Corn Harvest Losses by Source (bu/acre) | |||
| Source | Low | Avg. | High |
| Preharvest | 0 | 0.35 | 2.44 |
| Gathering Ear | 0 | 0.50 | 4.00 |
| Loose kernel | 0.02 | 0.66 | 3.36 |
| Machine | 0.13 | 1.51 | 5.02 |
| Total crop loss | 0.17 | 1.86 | 7.47 |
From Gliem, J.A., R.G. Holmes, and R.K. Wood. 1989.
Current utilization and optimization of existing machinery technology
when harvesting feed grains. The Farm Income Enhancement Program.
OSU Dept. of Agric. Econ. and Rural Sociology.
Average gathering unit losses accounted for about a 1.2 bu/acre loss out of the total 1.5 bu/acre machine loss. This data indicates that approximately 80% of the total machine loss is caused by corn never getting into the combine.
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 (probably a week to 10 days earlier, respectively, for southern and northern Ohio). By early to mid-October, drydown 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- 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 generally average 10-15 GDDs per day. In October (as things cool down) 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 considerably from this pattern of drydown.
We conducted evaluations of corn drydown at the OSU-OARDC Western Branch Research Farm, near S. Charleston, OH in 1991 and 1992. In 1991, under warm, dry fall conditions, grain moisture loss per day ranged from 0.76 to 0.92%. Whereas under cool, wet fall conditions in 1992, grain moisture loss per day ranged from 0.32 to 0.35%. Grain moisture losses based on GDD ranged from 24-29 GDD/percent moisture (i.e., a loss of one percentage point of grain moisture per 24-29 GDD) in 1991, whereas moisture loss ranged from 20-22 GDD in 1992. The number of GDDs required to reduce grain moisture was lower in 1992 than 1991.
Results from the summer survey for first year corn rootworm (FYCRW) using yellow Pherocon II sticky traps in soybeans are beginning to accumulate. Based on initial returns, the pattern of western corn rootworm (WCR) activity in soybeans across the state is similar to that of the 1998 field season, but catches of WCR in traps are generally higher. As data is collected from extension agents, consultants and agri-business representatives, we should gain a fairly good picture on the spread of the FYCRW problem and the relative risk for potential rootworm injury in first year on a county by county basis.
Although bean leaf beetle (BLB) activity continues to be very heavy in many soybean fields across the state, dry weather is causing the problem to decline. Many fields are rapidly turning color and drying down causing BLB to search for greener pastures. Thus, if someone has a nice green field of soybeans next to a large field of soybeans drying down, they may want to monitor the BLB activity. The dry weather is also limiting the development of moldy seeds within damaged pods. As a result, one may have a high level of pod injury and not have much injury to the seeds. Although we did have a number of rainy periods during the past few weeks, each period of wetness has been followed by periods of hot and dry weather, which has limited seed deterioration.
If a field is found to have heavy BLB activity at this point in time, it is important to determine beetle activity (with a sweep net), determine pod injury (on a whole plant basis), and finally inspect the pods closely to determine whether there is very much fresh injury and whether the seeds are showing any signs of discoloration or mold.
A drive around the countryside clearly demonstrates that potato leafhopper (PLH) has inflicted significant injury on many alfalfa fields. PLH activity has continued to thrive under the current growing conditions and many fields would likely to have benefited from a timely treatment of the third cutting. In our alfalfa plots at the Western Branch Station, PLH adults and nymphs were present in high numbers in the untreated check plots during the past week.
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Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/
C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.
Contributors to C.O.R.N. this week include: State Specialists: Anne Dorrance (Plant Pathology), Pat Lipps (Plant Pathology), Peter Thomison (Hort and Crop Sciences), Hal Willson (Entomology), Ron Hammond (Entomology), and Jeff Stachler (Weed Science); District Specialist: Ed Lentz (Agronomy); Extension Agents: Extension Agents: Howard Siegrist (Licking), Steve Prochaska (Crawford), Clark Hutson (Seneca), Glen Arnold (Putnam), Roger Bender (Shelby), Barry Ward (Champaign), and Andy Kleinschmidt (Van Wert).
Editor: Andy Kleinschmidt Web Editor: Steve Lichtensteiger
Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
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