C.O.R.N. Newsletter 2006-17

Dates Covered: 
June 12, 2006 - June 20, 2006
Editor: 
Greg LaBarge

Armyworm Problems

Authors: Ron Hammond, Bruce Eisley

We continue to get numerous reports of armyworm problems, mostly from wheat fields. Remember to use a threshold of 6 or more larvae per foot of row or if head cutting is occurring. Note the maturity of the wheat and the size of the larvae. If the wheat is starting to mature and larvae are mostly full grown, armyworms will soon be pupating or moving out of wheat into nearby fields where a problem could occur in edges of corn fields. Thus, not only should wheat be scouted, but nearby corn fields should be watched. Also remember that armyworms tend to be more active at night or on very cloudy, hazy days. In wheat fields during the day, they will tend to stay hidden either at soil level underneath residue or plant material. In corn, you will often find them hidden in the whorls. If treatment is deemed necessary in wheat, remember to check the preharvest interval with insecticides (http://ohioline.osu.edu/b545/pdf/b545.pdf). The interval ranges from 7 to 30 days for the various materials labeled for armyworm control on wheat. For corn, see http://entomology.osu.edu/ag/545/cicaw.pdf for a list of insecticides.

European Corn Borer (ECB) in Corn

Authors: Bruce Eisley, Ron Hammond

European corn borer moths are being caught in pheromone traps throughout Ohio and with some corn fields approaching mid-whorl stage, fields should be inspected for possible economic infestations of 1st brood ECB. Fields that are nearing the mid-whorl stage should have the whorl area inspected for early signs of larval activity. Egg masses may be found on the underside of corn foliage if one searches long and hard. If whorl injury (shot holes and window-pane feeding) appears abundant, then about 20 plants should be inspected at 5 locations in the field to determine the proportion of stand exhibiting whorl injury. In the inspection process, a number of whorls should be pulled and opened to determine presence or absence of ECB larvae. When larvae are found, the average number of larvae per plant may be estimated based on the proportion of stand exhibiting whorl injury and the proportion of injured plants actually having larvae present. If the number of larvae found exceeds an average of one or more per plant, more than 75% or more of the stands shows whorl feeding and the larvae have not yet begun to burrow into the stalks, then the infestation may warrant a rescue treatment.
Pictures of early ECB feeding injury can be found at: http://ohioline.osu.edu/icm-fact/images/23.html and http://ohioline.osu.edu/icm-fact/images/24.html. Additional information about ECB can be found in a fact sheet at: http://ohioline.osu.edu/ent-fact/0015.html and insecticides labeled for ECB control can be found at: http://entomology.osu.edu/ag/545/ciecb.pdf.

Control of Common Pokeweed in Corn and Soybeans

Authors: Mark Loux

Common pokeweed is becoming more prevalent in Ohio crop fields, due to widespread use of reduced tillage practices, and the fact that it is inherently difficult to control with herbicides. While some perennial species have become less of a problem due to the use of glyphosate in Roundup Ready crops, reducing pokeweed populations has proven to be more difficult. Pokeweed is inherently difficult to control due to its perennial life cycle and ability to regrow from a well-established root. Successful control during the growing season depends upon use of the appropriate herbicide(s), herbicide rate and timing, and spray boom height. Pokeweed can be fairly large at the time of postemergence herbicide application, and the spray boom should be high enough to ensure coverage of the entire plant with spray. Be aware that the proper boom height for pokeweed may increase the potential for spray particle drift, and it may be necessary to raise the boom only in areas where the common pokeweed plants are present.

In non-GMO corn, the best control is usually results from a combination of the full rate of an ALS-inhibiting herbicide (Spirit, Beacon, Exceed, Permit, or Equip) with Distinct at 4 oz/A or dicamba at 6 to 8 oz/A. Apply when pokeweed plants are at least 8 inches tall, but before 24 inches tall. A second application or row cultivation with wide sweeps may be necessary for complete control. Other herbicides with significant activity include NorthStar, Yukon, Callisto, dicamba (1 pt/A), and Distinct.

In non-GMO and non-STS soybeans, the best control option is Synchrony XP at 0.38 oz/A plus Harmony GT at 1/24 oz/A plus MSO at 1.0 %v/v. This can cause significant soybean injury but will provide greater activity than Synchrony XP alone. In STS soybeans, use Synchrony XP at 0.75 oz/A with MSO, and consider adding additional Harmony GT to increase control.

In Roundup Ready II corn, apply glyphosate at 1.1 lb ae/A when pokeweed are in the bud to flower stage for a single application. Where two postemergence glyphosate treatments are planned, apply 1.1 lb ae/A when the pokeweed plants are 12 to 24 inches tall and make a second application after 12 inches of regrowth. The same recommendation should be effective in Roundup Ready soybeans. However, if using the single application strategy in soybean, the 1.5 lb ae/A rate will provide more effective control. The effectiveness of pokeweed control with glyphosate is tied very closely to rate and timing, so multiple applications of at least 1.1 lb ae/A will typically provide more effective control than a single application.

The most consistently effective strategy for controlling pokeweed is the cut-stump method. Cut the pokeweed stems off with a pruner or a sharp corn knife and apply concentrated (not diluted) herbicide to the cut surface until it begins to run off the cut surface. Glyphosate may be the most appropriate herbicide when using this method in a crop, but other non-crop herbicides are also effective in situations where they can legally be used. This method may not kill every plant, but can be considerable more effective than a single postmergence application.

Continued Soybean Stand Loss in Some Areas

Authors: Anne Dorrance

Stands of soybeans and corn are continuing to decline in some areas of the state. Some of these are associated with low areas, ponding in some fields. Others are where the fields have been saturated periodically over the last 4 weeks. There are several causes to stand loss, from the disease perspective, we’ve got flooding injury and the root rots. With flooding injury, sometimes the plants can recover, if the conditions favor new root development. Key symptoms of flooding injury are stunted, skinny plants and when you dig them up, the smell is fairly strong indicating decay. With root rots, the roots are pale to dark brown and the whole root is rotted including the root stele. Root rots will also be spotty, one to three plants, then skip some plants, then 2 to 3 more. All will be at various stages of decline. Pythium had been one of the primary disease causing agents this spring, but Phytophthora has also started. Susceptible varieties at NW branch are beginning to show symptoms.

Other than replanting, this is a good time to make some notes for next year. For flooding injury, these are the areas of the field where drainage improvements are needed. For seedling diseases, make notes of variety that was planted – gave you problems, double check the resistance package for Phytophthora that the variety had, did it have Rps1c or Rps1k or a gene stack and did it have partial resistance. Don’t forget to note the seed treatment package. Was the rate of Apron XL or Allegiance the high rate or the low rate. The length of time that these seeds have been in the ground is pushing our seed treatments to their limit, but from last years studies, we could still see an effect when flooding occurred 3 weeks after planting. Making some notes for improvements this year, will help getting off to a better start next year. Nothing like learning from the book of experiences.

Soybean Rust

Authors: Anne Dorrance

Georgia is still reporting dry conditions and no new rust pustules have been found. Two weeks from now will be the time to see if this latest storm will bring them any inoculum. Florida did find a few new pustules in kudzu. To date – none of the sentinel plots across the south east are positive. We’ve deployed two spore traps this week and will begin monitoring for spores. From the sentinel plots that were scouted in Ohio, brown spot is becoming more prevalent. It also seems to be favoring a couple of varieties over some others, so that is something to note in your fields as well. At this point, the risk of rust is very low for Ohio.

Ohio Farm Bureau Excellence in Crop Advising Award

Authors: Harold Watters


The OSU Extension Agronomic Crops Team works with Certified Crop Advisors (CCA) on a daily basis and together we serve the crop producers of Ohio. Many OSU Extension Agronomic Crops Team members are Certified Crop Advisors, but you can also find a CCA at your local co-op or ag supplier, as your seed dealer or as your independent crop consultant. The Ohio Farm Bureau began a program four years ago to recognize CCAs working with Farm Bureau members. Please consider your local CCA for the Excellent in Crop Advising Award.

The Ohio Farm Bureau Federation (OFBF) and the American Society of Agronomy’s (ASA) Ohio CCA Program are sponsoring one state award titled Excellence in Crop Advising. This is to recognize an individual that has performed superior service for farmer clients in nutrient management, soil and water management, integrated pest management and crop production. Each county nominee for the state award will receive a certificate, which will be presented by the county Farm Bureau at an appropriate county level meeting. The statewide Excellence in Crop Advising Award will be presented at the 2006 Farm Science Review. The state award includes a plaque, recognition in industry publications, and a $500 cash award from the agronomic industry. Nominations are due to OFBF by July 17, 2006. Click on the Ohio Farm Bureau website (http://www.ofbf.org/page/JHUD-6QAQ9K/?OpenDocument) for a description and a nomination form or contact Amy Hurst at 614-246-8262 or ahurst@ofbf.org.

Archive Issue Contributors: 

State Specialists: Ann Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Mark Loux and Jeff Stachler (Weed Science), Peter Thomison, (Corn Production), Ron Hammond and Bruce Eisley (Entomology). Extension Educators: Howard Siegrist (Licking), Harold Watters (Champaign), Glen Arnold (Putnam), Roger Bender (Shelby), Steve Foster (Darke), Steve Bartels (Butler), Steve Prochaska (Crawford), Bruce Clevenger (Defiance), Greg LaBarge (Fulton), Todd Mangen (Mercer), Mike Gastier (Huron), Mark Koenig (Sandusky), Jim Skeeles(Lorain), Gary Wilson (Hancock) and Keith Diedrick (Wayne)

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.