C.O.R.N. Newsletter 2006-33

Dates Covered: 
October 3, 2006 - October 9, 2006
Editor: 
Andy Kleinschmidt

Western Corn Rootworm Sampling in Soybean in Ohio, 2006

Authors: Ron Hammond, Bruce Eisley, Curtis Young

Personnel from Ohio State University Extension continued to sample for western corn rootworm adults (WCR) in soybean fields for the tenth year. Data from the 2006 rootworm trapping program have been assembled. This is an overview of the results from that survey. Sampling was done using Pherocon® AM yellow sticky traps placed in 86 fields covering 25 counties. Six traps were placed in the soybeans on metal posts at canopy height and located at least 100 feet from the field edge and evenly spaced in the field. The traps were initially placed in fields in mid-July and removed in late August or early September. Traps were serviced once a week throughout the sampling period with a new, clean trap. After each trapping week, the numbers of beetles collected were summed and divided by the number of traps (6) and the number of days the traps were in the field resulting in the average number of beetles collected per trap per day.

A summary of the weekly catches of WCR adults per trap per day from the 2006 growing season can be found on the web at:
http://allen.osu.edu/ag/fycr2_6.htm

Research indicates that catches in soybean of 5 or more beetles/trap/day during any trapping week indicates a potential problem with rootworm in the field the following year.

The trapping data from 2006 had the following results from the 86 fields:

After rounding results to the nearest whole number, nineteen fields had an average of 5 or more beetles/trap/day and five fields had an average of between 4 and less than 5 beetles/trap/day. The rest of the fields were less than 4 beetles/trap/day.

Fields with 5 or more beetles/trap/day were in Allen, Champaign, Crawford, Defiance, Hardin, Miami, Paulding, Putnam and Van Wert Counties. Those fields between 4 and 5 beetles/trap/day were in Allen (1), Miami (1), Paulding (1) and Van Wert (2) Counties.

So What Does This Mean?

The trapping data from 2006 was at the highest level we have seen in the 10 years that trapping has been conducted. It is not difficult to make recommendations about the fields that were trapped in 2006 because, based on research, if a field has a beetle count of 5 or more beetles/trap/day during any trapping week, the field will need to be treated for rootworm if it is planted to corn in 2007 (see last weeks newsletter for treatment options http://corn.osu.edu/index.php?setissueID=155#A). Research would also suggest that fields with less than 5 beetles/trap/day during any trapping week should not need to be treated for rootworm if going to corn in 2007.

The problem becomes when a decision needs to be made about fields that were not trapped. We know that there are probably more fields that need to be treated and at the same time, fields that will not need treatment. Since there isn’t any way to predict which fields need treatment without trapping information, we would suggest that producers take into account several things before a decision is made about treatment needed on the field. Things that can be used to help make the decision are: 1) Are the fields located in a county with low or high counts in 2006? We cannot use a few trapped fields in a county to make countywide recommendations but it does give some idea of the level of rootworm activity in the area. 2) Has there ever been a problem with the western corn rootworm variant in the field in the past? 3) Were there any direct observations of root injury and lodging due to rootworm activity in your own adjacent corn fields during the 2006 growing season? 4) How wide spread was the injury and lodging within the fields? Was it a small localized spot or across the entire field? 5) Were there any severe weather events that could account for the observed lodging? 6) Did the lodging have a significant impact on yield or economic returns? 7) Since there are no rescue treatments for rootworm larvae, how much risk can be tolerated?

We also suggest if a field is treated for the western variant next year, that several untreated strips be left in the field. This will be the only way we can tell if the western variant is a problem in the field. Because of this continued concern with this insect, we urge growers to develop a sampling plan next year in their soybean fields, and to sample roots for feeding injury in their first year corn for the presence of the western variant.

Extension personnel participating in this statewide effort: Curtis Young, Bruce Eisley, Ron Hammond, Andrew Kleinschmidt, Bruce Clevenger, Glen Arnold, Greg Labarge, Jim Lopshire, Mark Koenig, Harold Watters, Roger Bender, Florian Chirra, Susan Couser, Alan Sundermeier, Jerry Mahan, John Smith, John Hixson, Steve Ruhl, Gary Wilson, Steve Foster, Ed Lentz, Tony Nye, and Steve Prochaska.

Effects of Harvest Delays on Corn Performance

Authors: Peter Thomison, Allen Geyer, Rich Minyo

Harvest delays expose a corn crop to less favorable weather conditions, as well as wildlife damage. Additional losses may occur when ears on lodged plants come in contact with wet soils and surface residues resulting in development of ear rots. Ear rots reduce grain quality and lead to significant dockage when the grain is marketed. Some ear rots produce mycotoxins, which may cause major health problems if fed to livestock.

We recently completed a study that evaluated effects of four plant populations (24,000, 30,000, 36,000, and 42,000 plants/A) and three harvest dates (early-mid Oct., Nov. and Dec.) on the agronomic performance of four hybrids differing in maturity and stalk quality. The study was conducted at three locations in NW, NE, and SW Ohio over a three year period (2002-2004) for a total of eight experiments. The following lists some of the major findings from this research.

KEY FINDINGS

1. Results showed that nearly 90% of the yield loss associated with delayed corn harvest occurred when delays extended beyond mid-November.

2. Higher plant populations resulted in increased grain yields when harvest occurred in early to mid-October. Only when harvest was delayed until mid-November or later did yields decline at plant populations above 30,000/acre.

3. Hybrids with lower stalk strength ratings exhibited greater stalk rot, lodging and yield loss when harvest was delayed. Early harvest of these hybrids eliminated this effect.

4. The greatest increase in stalk rot incidence came between harvest dates in October and November. In contrast, stalk lodging increased most after November.

5. Harvest delays had little or no effect on grain quality characteristics such as oil, protein, starch, and kernel breakage.

6. Delaying harvest until November decreased grain moisture content by 5.8% (from 23.8 to 18.0%). Further harvest delays achieved almost no additional grain drying.

The 2003 and 2004 growing seasons during which most of this research was conducted were extremely favorable for corn growth and yield. Record corn yields were achieved statewide. Due to stress conditions in 2006 in various parts of Ohio, stalk quality is probably inferior to those past two years. In some severely stressed fields, corn died prematurely in August and September and significant stalk deterioration has already occurred. Given the poor quality of corn stalks in many corn fields, it’s likely that we could expect greater stalk lodging with shorter harvest delays than the research above would indicate.

For more details concerning this study, including table summaries, check out
“Effects of Harvest Delays on Yield, Grain Moisture and Stalk Lodging in Corn”. C.O.R.N Newsletter 2005-34 (October 10, 2005 - October 18, 2005); available online at:
http://corn.osu.edu/story.php?setissueID=109&storyID=631

Winter Annual Weeds and Soybean Cyst Nematode

Authors: Kent Harrison, Mark Loux

Soybean cyst nematode (SCN) is the most economically important pathogen of soybean in the U.S. and is present in virtually all of the soybean-producing counties of Ohio. Foliar symptoms of SCN infection in soybeans may not be apparent during the growing season, and in fact many growers are unaware that their fields are infested with the root parasite. Symptoms of infection may not be evident even at moderate to high infestation levels, and the use of SCN-resistant soybean varieties is no guarantee against crop yield loss in heavily infested fields.

Winter annual weeds are a specialized group of plants that can emerge in the fall, then over-winter in a dormant state and complete their life cycle as temperatures warm up in the spring. Roots of some winter annual weed species serve as sites for SCN to feed, grow and reproduce in the absence of soybean. In addition, these weeds extend the period during which SCN can reproduce during the growing season, since SCN reproduction otherwise stops when soybeans usually reach full maturity in September. For example, recent research has confirmed that SCN can infect winter annual weeds in early fall and produce new egg-containing cysts before the end of October. This is a major cause for concern since these additional cysts mean higher egg concentrations in soil and a greater likelihood of significant crop damage the next time soybeans are grown in the field.

The following winter annual weeds have been identified as alternate hosts of SCN in Ohio: purple deadnettle, henbit, field pennycress and shepherd’s-purse. To view images of these weeds in the fall seedling stage, visit:
https://agcrops.osu.edu/weeds/WinterAnnualSCNHosts.htm

In Ohio, our greatest concern is with the first two weeds listed, purple deadnettle and henbit. These two species are the most prevalent in no-till corn and soybean fields, and both are strong hosts of SCN. Purple deadnettle and henbit usually begin emerging in August or early September and can continue to emerge through mid-October in most of the state, although the majority of seedlings tend to emerge before October 1. This year, our general observation is that maximum deadnettle emergence was delayed until mid-September, which presents a good opportunity to control it effectively in early October while seedlings are small and before SCN reproduction on the weeds can occur.

In SCN-infested fields, it is important to control purple deadnettle and henbit before sufficient time elapses for SCN to complete its life cycle and reproduce, typically 3 to 5 weeks after the weeds emerge. Delaying weed control measures beyond that period may be too late to prevent the deposition of new SCN cysts+eggs in the soil.

For the latest recommendations on fall herbicide treatments available for controlling purple deadnettle and other winter annual weeds, visit:
http://corn.osu.edu/story.php?setissueID=153&storyID=917

For additional information on weed hosts of soybean cyst nematode visit:
http://ohioline.osu.edu/agf-fact/0145.html

Cover Crop Demonstration

Authors: Alan Sundermeier

A cover crop demonstration will be held on Thursday, October 5, 2006, 9 - 11 am, at the Northwest Ag Research Station, near Hoytville, OH.

Topics scheduled to be covered include: “Is there a place in the crop rotation for cover crops?”, “What type of seed should be used?”, and “Can cover crops add soil fertility?”

Come and view cover crop research plots with: red clover seeded into wheat last spring, annual ryegrass variety comparison, late summer seedings of Oilseed Radish, oats, Cowpea, Winter Pea, and Cereal Ryegrass.

This demonstration is free and open to the public; no registration is required.

Directions: 4240 Rangeline Road, one mile east of SR 235 north of Oil Center road.

Sponsored by Wood & Henry County Soil & Water Conservation Districts, Ohio State University Extension - Wood County, Ohio Ag Research & Development Center

Call Alan Sundermeier at 419-354-9050 for more information

Archive Issue Contributors: 

State Specialists: Ann Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Peter Thomison, Allen Geyer and Rich Minyo (Corn Production), Ron Hammond and Bruce Eisley (Entomology), Kent Harrison and Mark Loux (Weed Science). Extension Educators: Curtis Young (Allen), Glen Arnold (Putnam), Roger Bender (Shelby), Todd Mangen (Mercer), Howard Siegrist (Licking), Steve Foster (Darke), Greg LaBarge (Fulton), Alan Sundermeier (Wood), Mike Gastier (Huron), Gary Wilson (Hancock), Steve Prochaska (Crawford), Ed Lentz (Seneca), Harold Watters (Champaign), Jonah Johnson (Clark), and Keith Diedrick (Wayne).

About the C.O.R.N. Newsletter

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.