June 8, 2009
Continue Scouting for Black Cutworms
Some scattered black cutworm activity is being found in the area. A rescue insecticide treatment should be considered if about 2-3% of the plants are cut and the cutworms are less than ¾ inch long. This threshold can be adjusted somewhat with changing corn prices, corn plant stands, and expected corn yields. Erin Hodgson and Jon Tollefson have developed a spreadsheet in the ICM News article at http://www.extension.iastate.edu/CropNews/2009/0527hodgson.htm that can be used to fine-tune decision making on treating for cutworms. A higher threshold of about 5% has been used when most cutworms are over an inch long, since the cutworms should be about done cutting by then. Continue scouting until the corn is at V5 (five leaves completely emerged from the whorl). More information on scouting and treating for black cutworms can be found at http://www.ipm.iastate.edu/ipm/icm/2004/5-17-2004/bcwcutting.html.
With a producer and a dealer, I looked at several corn fields with armyworm damage and armyworms present at various sizes. All of the fields had a winter rye cover crop that had been killed with glyphosate shortly before planting. Armyworm moths are attracted to fields with grass such as winter rye or fields with grassy weeds. Large populations of armyworms can quickly defoliate fields, so fields that may have attracted the moths should be scouted. Many insecticides are labeled for armyworms. More information can be found at http://www.ipm.iastate.edu/ipm/icm/2004/6-14-2004/armyworm.html.
Stink bug damage (stunted plants with lateral shoots and holes in leaves) is also noticeable in some corn fields. Stink bugs are attracted to fields with a heavy infestation of winter annuals, such as pennycress, sherherds purse, etc., have grown well into the spring. There is no rescue as the damage has already been done See http://www.ipm.iastate.edu/ipm/icm/2002/6-24-2002/stinkbugtwist.html for more details.
Liquid Nitrogen & Post Herbicides on Corn
With the crazy nitrogen prices this spring, some may be using liquid nitrogen for the first time on emerged corn. UAN solutions can be broadcast over the corn, but some burning will occur and there can be some nitrogen lost due to volatilization if a rain doesn’t incorporate the N soon after application. Check herbicide labels before using the nitrogen solution for a carrier for an herbicide application. Almost all herbicide labels prohibit using nitrogen solution as a carrier after the corn has emerged. Severe injury can occur with some combinations when applied on emerged corn. See Mike Owen’s article for more information at http://www.ipm.iastate.edu/ipm/icm/2006/5-1/postemerge.html.
The recent wet weather and windy days have likely delayed some planned herbicide applications. Some corn is already too large to safely apply some postemergence herbicides. See Bob Hartzler’s recent article summarizing the maximum corn size for various corn herbicides at http://www.extension.iastate.edu/CropNews/2009/0602hartzler.htm.
Early June is usually a good time to spray for multiflora rose and Canada thistle. Roses should be blooming soon, if they haven’t started already. When the bushes are in full bloom is an ideal time to apply the foliar products, such as 2,4-D and Crossbow. Chaparral is a new product from DOW that contains the active ingredients from Milestone and Ally (Cimmarron), which performed as well or better than Crossbow in a trial last year in Cedar County. Some other possibilities for multiflora rose control can be found on the attached fact sheet based on work done in eastern Iowa.
No product will give 100% control of Canada thistle because of its extensive underground root system, but when the plants are pre-bud just starting to put on some buds is usually the best time to spray. Milestone and Forefront (Milestone + 2,4-D) have looked very good in eastern Iowa trials, as well as Grazon P + D. Trial results can be seen in the attached document.
Another weed I get questions on in wet years is equisetum (scouring rush, field horsetail, snakegrass, etc.). The vegetative stage looks like little Christmas trees and the reproductive stage is a hollow jointed stem. These plants date back to the dinosaurs so most herbicides have little effect on them. There are some products that work fairly well in non cropland, but there is not an easy answer in corn and soybeans. Roundup has no effect. Permit and Hornet have some activity in corn. Ken Pecinovsky had some luck with Liberty (Ignite) in 2007 in a trial at Nashua. Bob Hartzler has put out a recent fact sheet on the weed at http://www.weeds.iastate.edu/mgmt/2009/equisetum.pdf.
FOR YOUR CALENDAR
SPRING FIELD DAY & SPECIAL SESSION FOR CCAs
SE IA RESEARCH FARM – CRAWFORDSVILLE
Certified Crop Advisors can obtain 5 hours of credit (including 3.5 hours in soil and water management) by attending a residue management training workshop in the morning followed by the afternoon tour at the ISU SE Iowa Research & Demonstration Farm near Crawfordsville on June 24. There is a $50 fee ($70 after June 22) for CCAs attending for credit. Non CCAs can attend the morning residue management training workshop for $10 (which includes lunch). There is no charge for the afternoon field day except a $5 fee for those wanting lunch at noon. Fees (check or cash) can be paid at the door, but if you plan to attend the morning session or want to reserve a lunch at noon, please send Jim Fawcett (firstname.lastname@example.org) a note by June 22.
8:30 a.m. – Noon Residue Management Training Workshop (targeted at Certified Crop Advisors)
Ø Residue/Soil Carbon/Nutrient Cycling
Mahdi Al-Kaisi, ISU Extension Agronomist – Soils
Ø Cover Crops, Erosion, and N-leaching
Tom Kaspar, Plant Physiologist, National Soil Tilth Lab
Ø What is the Value of Soil & Crop Residue?
Andy Herringshaw, Graduate Research Assistant, Sustainable Ag - Economics
Noon Lunch ($5 for those not attending the morning session. Reservations required by June 22.)
1:00 p.m. – 3:00 p.m. Spring Field Day Tour (for everyone)
Ø Crop Season Review & Current Crop Concerns
Kevin Van Dee, Farm Superintendent, & Jim Fawcett, ISU Extension Field Agronomist
Ø Monitoring Yield Data for the ACRE Program
Jim Jensen, ISU Extension Farm Management Specialist
Ø Cover Crops for Soil Conservation & Better Soils
Tom Kaspar, Plant Physiologist, National Soil Tilth Lab
Ø Corn & Soybean Fungicide Research Results
Alison Robertson, ISU Extension Plant Pathologist
Ø Organic Crop Opportunities
Kathleen Delate, ISU Extension Organic Specialist
Advances in Precision Ag Field Day
ISU SE Iowa Research & Demonstration Farm – Crawfordsville
See the latest in precision agriculture technology, including RTK guidance systems, auto-steer, automatic shut-off planters, and sprayers. As details emerge, they will be posted at http://www.extension.iastate.edu/Pages/eccrops/meetserc.html.
If you have any questions, please feel free to contact the Iowa State University Extension Office.
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