C.O.R.N. Newsletter 2007-34

Dates Covered: 
October 8, 2007 - October 15, 2007
Editor: 
Curtis E. Young

Soybean Aphid Update

Authors: Ron Hammond, Bruce Eisley

This past week we sampled buckthorn for the presence of soybean aphids beginning their cycle of overwintering. This is the time that winged adult females fly to buckthorn and produce more aphids prior to males arriving which is then followed by mating. After that, overwintering eggs are laid. At all locations we sampled (Wood, Marion, Wayne, Ashland, and Franklin Counties) we found few soybean aphids. At most, we found 2 leaves with small colonies on them. The significance of these low numbers point to the possibility that, even though we did not have the large populations anticipated this past summer, we might still be in for a low aphid year in 2008. However, before we make any predictions for next year, we need to hear about observations from other states, especially from those locations farther to our north. We still think that Ohio's economic soybean populations come from the north. Stay tune to the CORN newsletter throughout the winter for further updates.

Western Corn Rootworm Variant Sampling

Authors: Bruce Eisley, Curtis Young, Ron Hammond

Personnel from Ohio State University Extension continued to sample for adults of the first year corn variant of the western corn rootworm (FYWCR) in soybean fields for the tenth year. Although data from the entire 2007 rootworm trapping program are still being assembled, we have preliminary data. So far, we have 26 of 93 fields reported that have reached or come very close to the threshold of 5 adult beetles per trap per day, which compares with last year when we had 23 of 88 fields reaching similar levels. Most of these fields are still in the northwest and west central portion of the state, from Fulton County down to Darke County and as far east as Crawford County. Thus, this year has seen populations similar to what we saw last year. Fields reaching threshold numbers will need a preventive treatment for rootworm if corn is planted into these fields next spring.

The distribution of the FYCRW variant is not uniform across the area where threshold populations are regularly found. Several surveyed fields in the same county where several fields exceeded threshold did not reach more than 3 beeltes/trap/day during the entire six week trapping period. Thus, blanket recommendations for large areas are difficult to make at this time. However, decisions need to be made for the coming growing season. Some factors to take into consideration include: proximity to surveyed fields that exceeded threshold; proximity to current year's corn fields; hybrids planted in the nearest corn fields; amount of CRW activity in current corn fields; amount of lodged corn due to CRW feeding observed; and past history of CRW activity in fields to be planted to corn. If near one of the areas where the rootworm variant was trapped in higher numbers, you might want to consider treating your first year corn. If trapped fields in your area were not at threshold (still the majority of fields surveyed), you should consider not treating. You can contact the extension educator for the situation in your area. In the future, the best method to make these treatment decisions is to employ the sticky traps in soybean fields to be planted to corn. These traps should be run for a minimum of three weeks making sure the traps are in the fields during mid July through early August. It would be better to run them longer.

Another Late Season Rust Find in Nebraska

Authors: Anne Dorrance

The USDA soybean rust map (http://www.sbrusa.net) continues to monitor movement of rust and as predicted more counties were turned red last week. Rust was identified in soybean fields and kudzu patches in Alabama and Arkansas. The most interesting finds were in two counties in Nebraska and one county in northeast corner of Kansas. In all cases soybean rust is being found at very, very low levels, a few pustules on a few leaves (1 or 2 out of 100) in the whole field, literally the needle in the haystack. This northward movement is the result of mid-season build-up in Texas then subsequent storm movement later in the season up through Oklahoma, Kansas, Missouri and Iowa. The hot dry weather does appear to have delayed this movement until the later part of the season. At this point, the soybeans are reported to be in late R6 and R7 growth stages and no fungicides are recommended. The search at this point is an academic one, to continue to support model development for next year.

Think About Your Water Management Needs Now!

Authors: Larry Brown

Soon harvest will be completed, and then it is time to start thinking about your water management needs for the coming growing season. As the combine moves across the field you may become aware of problems with your field's drainage system, i.e., maintenance, areas where further drainage improvements are needed, areas where the crop was severely drought-stressed and yields greatly reduced. It is important to address these types of problems sooner than later.

1. Maintenance

Make notes on locations in your field where the drainage system needs some attention. Look for subsurface drainage as well as surface drainage problems; i.e., blow-outs, ponded water, excessive erosion and gullying. Blow-outs may be common on fields where the older "tile" system has broken-down, silted-in, etc., and/or the drainage laterals were not installed "on-grade." Blow-outs are cause for concern for two reasons - crop production and water quality. If blow-outs are present, then the subsurface drainage system is not functioning properly, and any crop yield advantages from drainage may be greatly reduced or eliminated in affected in parts of the field. From a water quality standpoint, surface waters that enter the blow-out may transport sediment and soil-absorbed nutrients and pesticides from your field directly to ditches or streams. Therefore, timely repairs will have a double positive impact. Blow-outs should be properly repaired, and right after harvest is as good a time as any to make the necessary repairs. As some blow-outs may occur due to poor installation practices, new drains may have to be installed. If excessive erosion or gullying is evident, think about changing your tillage system to minimum tillage, and installing a grass waterway along the flow paths through eroded areas.

2. Additional drainage? Consider economics, rotations, etc.

In addition to maintaining your subsurface drainage system, now might be the right time to think about additional drainage needs. If your combine is equipped with a yield monitor, you may be able to see the crop yield variability resulting from less than adequate subsurface drainage. The addition of new drainage laterals installed between "older" laterals might partially address the yield variability issue, if the cause is excessive water in the crop root zone, and depending on soil type. Or, it maybe a totally new system is needed.

Before adding subsurface drains, do the economics. We have observed areas in Ohio where the existing drain spacing was 60 feet, and two new laterals were installed between each pair of older laterals (new spacing is 20 feet). Unless crop prices dramatically increase and are sustained over a number of years, it is difficult to see the change to a 20' drain spacing is a good economic decision, compared to a completely new set of laterals at a 50' spacing. Our modeling results suggest that for a Hoytville silty clay soil, only a 4% corn yield increase may be realized by the 20' spacing compared to the new 50' spacing.

Another option for improving corn and soybean yields over the long haul is to consider crop rotation. From our OARDC research in Wood County on Hoytville silty clay soil, we observed an average 22 bu/ac yield increase in corn from a corn/soybean rotation (drain spacing 50') over 12 years compared to continuous corn for the same conditions. The associated soybean average yield increase was 5 bu/ac.

3. Drainage and Conserving Water?

If your crops were impacted by drought conditions on subsurface drained field this past year, it might have been possible to save a little of the drainage water that went right down the drain early in the growing season. As we have discussed in past issues for this journal, Drainage Water Management (controlled drainage) might help save an inch or two of drainage water that might subsequently help crops during drier periods. Essentially by managing and controlling the elevation of the subsurface drainage system outlet, some drainage water can be conserved. The practice is site-specific, and will not be appropriate for all subsurface drained fields in Ohio. We have recently installed Drainage Water Management practices on several sites, to demonstrate how water conservation can be accomplished, that water quality benefits can be realized, that crop yield improvements are possible, and that the practice is economical.

Professor Larry C. Brown can be reached at 614-292-3826, or brown.59@osu.edu.

Archive Issue Contributors: 

State Specialists: Ann Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel and Bruce Eisley (Entomology), Larry Brown (Agricultural Engineering) and Peter Thomison (Corn Production). Extension Educators: Harold Watters (Champaign), Howard Siegrist (Licking), Roger Bender (Shelby), Glen Arnold (Putnam), Ed Lentz (Seneca), Wes Haun (Logan), Bruce Clevenger (Defiance), Mark Koenig (Sandusky), and Curtis Young (Allen).

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.