TABLE OF CONTENTS
Weather
Corn GDD
Soil Crusting and Poor Emergence
Rotary Hoe
Replant Decision
Insect Update
Black Cutworm
Bean Leaf Beetle
Common Stalk Borer
Corn Flea Beetle
Millipedes
Potato Leafhopper
Disease Update
Anthracnose in Trees
Alfalfa
PEAQ Update for May 25
Sulfur Deficiency Problems
Miscellaneous
Ag Decision Maker
New Marketing Tool to Assist Ag Producers in Mapping Marketing Areas
Events
June 15-17: Master Gardeners Conference, Cedar Rapids.
June 16: Ag Professional Tour, ISU Northeast Research Farm, Nashua.
June 21-22: Farm Progress Hay Expo, Strawberry Point.
June 22: ISU Southeast Research and Demonstration Farm Crops Field Day, Crawfordsville.
June 28: ISU Northeast Research and Demonstration Farm Crops Field Day, Nashua.
June 29: ISU Northern Research and Demonstration Farm Crops Field Day, Kanawha.
WEATHER
Corn Growing Degree Days (May 1 to May 24)
Normal (Fayette) = 231
Calmar/Nashua = 205
Cedar Rapids = 213
I received an interesting note from Ken Pecinovski, Superintendent of the ISU Northeast Research Farm, Nashua…current May monthly total rainfall = 0.85 inches which is the lowest in 50 years of records at Nashua. Only the 1988 drought year (1.13" in May) and 1958 (1.47" in May) come close.
SOIL CRUSTING & POOR ENERGENCE
Rotary Hoe
For the last 10 days, there has been rotary hoe activity in scattered corn and soybean fields from NW Iowa to NE Iowa and down along the east central counties bordering the Mississippi River. In northeast Iowa the main culprit is our silt loam soils (mostly the Fayette silt loam soils). The fine silt particles become dislodged in a rain, and when the water drains into the soil these fine particles are the last to settle down and essentially fill in all of the holes and seal up the soil surface. If this is followed by a sunny day, the soil can crust quite easily. It is easy to rotary hoe corn, but be aware of soybeans development stage before running a hoe. If the “hypocotyl hook” is close to the soil surface, and you break it with the hoe, the plant is killed.
Replant Decision
The following table can help in making replant decisions:
Influence of planting date and plant population on % corn grain yields.
Numerous gaps of up to 4-6 feet can reduce yields by an additional 5-6%.
Assuming a cost of $10 per acre to destroy the existing stand, $10 per acre to replant, and $30 per acre for seed, the cost of a replant is about $50 per acre. At $2 per bushel, that is 25 bushels of corn. If the average yield is 180 bushels, then 25 bushels equals 14% of the yield. Using the above chart, a re-plant in the May 26 – June 1 range has a yield of 90% of an earlier planting, so there is 10% yield loss due to lateness of planting. Adding the loss from late planting to the loss due to the cost of replanting (10% + 14%), the total loss is 24%. Looking at the above chart, you will note that a uniform stand of 16,000 has a loss of 26%, which is essentially a break-even with performing a replant. If some of these replant costs are negated or the price of corn is higher, than a uniform stand of 18 to 20,000 may still suggest a replant. For more information, see Pm-1885 "Corn Planting Guide" http://www.extension.iastate.edu/Publications/PM1885.pdf and NCR 344 "Uneven Emergence in Corn" http://www.extension.iastate.edu/Publications/PM1885.pdf.
If the field would be used for corn silage, than we are more concerned about total forage yield rather than grain yield, and a 20,000 stand would very likely still benefit from a replant.
INSECT UPDATE
Black Cutworm
Southern Iowa continues to report scattered situations at treatable levels. No significant activity noted in northern Iowa. Continue scouting through V-5 stage. This is an infrequent and spotty pest. The economic threshold is when cutworms average less than 3/4 inch in length and 2-3% of the plants are wilted or cut, or if cutworms are longer than 1 inch, treatment should be applied if 5% of the plants are cut. For more information, go to the May 1 issue of the ICM Newsletter:
http://www.ipm.iastate.edu/ipm/icm/2006/5-1/cutworms.html
Bean Leaf Beetles
Jim Fawcett, ISU Crops Specialist in Iowa City reports many BLBs early planted soybean fields in southeast Iowa. ISU Ames reported 2 weeks ago that scouting alfalfa fields in central Iowa indicated a large survival of overwintering BLBs. A few points to emphasize:
1) Scout soybeans as they emerge. If Gaucho or Cruiser seed treatments were used, they should be protected.
2) Those few farmers in northeast Iowa that planted some soybeans early should pay particular attention to those emerging fields. Beetles from surrounding areas (alfalfa fields) with no soybeans emerged could initially concentrate on these few fields. In this case, it is possible for BLB to feed on emerging soybean hypocotyls and significantly reduce stand.
3) Once soybeans have emerged, ISU has researched threshold levels to base your management decisions. Go to the May 15, 2006 issue of the ICM Newsletter:
http://www.ipm.iastate.edu/ipm/icm/
4) The thresholds mentioned in 3) are to protect yield. If you are growing food grade soybeans and need to protect your soybeans from the potential transmission of the Bean Pod Mottle Virus, insecticide may be justified with considerably lower levels of beetles
Common Stalk Borer
Five control options were discussed in the April 3 Crop Notes.
Option 3 relates to in-field situations. Apply insecticide with "in-field" POST herbicide program if perennial grasses and ragweed (populations from last year) are extensive. If stalk borer larva are in these weeds (quackgrass, wirestem, and giant ragweed) when the weeds are killed with post-emergence herbicide, the larva are forced to move out of the weed and into something else (i.e. corn or soybeans). Scouting ahead of the POST application could indicate the presence of the stalk borer in these weeds, such that an insecticide could be tank mixed with the POST herbicide application to control the insects.
Option 4 is timed to catch the insects during migration from grassy boarders into the first few rows of adjacent corn. This occurs at 1,400 to 1,700 DD. We recommend scouting the field border areas at 1,300 DD for grasses with dead seed heads, which would be a sign that the stalk borers are or were present in the grass. Current DD (Jan. 1 – May 24, base 41 degrees) for Nashua/Calmar = 829, and for Cedar Rapids = 956. Anticipated date to reach 1,300 DD for:
Nashua/Calmar = June 12
Cedar Rapids = June 7
For insect identification and management tips go to:
http://www.ipm.iastate.edu/ipm/icm/2004/6-14-2004/stalkborer.html
Corn Flea Beetle
There have been just a few of reports of significant Flea Beetle activity in southern Iowa. Scout to V-5 stage. Management information is in the April 17, 2006 issue of the ICM Newsletter:
http://www.ipm.iastate.edu/ipm/icm/2006/4-17/stewarts.html
Millipedes
Illinois is reporting widespread concerns with millipede damage to germinating or seedling corn and soybeans. This is unusual. Millipedes usually just feed on decaying organic matter. Apparently some seeds in close proximity to decaying organic matter are also being damaged by the Millipedes in Corn & Soybeans. For details on this pest, I attached a very nice bulletin written by FS Growmark Inc.
Potato Leafhopper
This pest migrates north every year and reaches Iowa in May through June. As 1st crop harvests are complete, it is time to routinely scout weekly for this pest, and treat if populations exceed threshold. Threshold information as at:
http://www.ipm.iastate.edu/ipm/icm/1999/6-21-1999/potlhmang.html
DISEASE UPDATE
Anthracnose in Trees
Once again, a cold May has help create conditions for significant anthracnose leaf disease problems in many species. The Horticulture Newsletter referenced below has an article on trees. I mention this just because sometimes we get some very timely herbicide drift complaints associated with leaf defoliation of trees, and we need to be aware of possible causes of these problems.
http://www.ipm.iastate.edu/ipm/hortnews/
ALFALFA
PEAQ Update for May 25
Timing 1st Alfalfa Harvest with PEAQ: PEAQ results estimate "in-field" alfalfa forage quality based on stage of maturity and plant height. Under typical harvest conditions, the forage quality will drop 15 to 20 RFV points. So to harvest "dairy quality" alfalfa at 150 RFV, harvest should actually occur at a 165 to 170 RFV PEAQ reading. Between PEAQ readings a typical drop in "bud stage" alfalfa quality is 3 to 5 RFV points per day. This is more variable with vegetative stage or flowering stage alfalfa. RFV of alfalfa-grass fields will drop faster than this.
The Fact Sheet that explains PEAQ was included in the May 8, 2006 Crop Notes.
Here is a report of PEAQ readings on May 25 from various locations across NE Iowa.
Winneshiek Co.: 24-inch ht., bud stage = 181 RFV
Allamakee Co.: 28-inch ht., bud stage = 164 RFV
Howard Co.: 25-inch ht., bud stage = 176 RFV
Chickasaw Co.: NA
Floyd Co.: 28-inch ht., bud stage = 165 RFV
Clayton Co.: NA
Butler Co. site 1: 26-inch ht., bud stage = 173 RFV
Butler Co. site 2: NA, Harvested.
Dubuque Co.: NA, Harvested.
Sulfur Deficiency Problems
We continue to notice large “pale” areas in alfalfa fields, mostly associated with the lower organic matter levels of Fayette silt loam soils and sandy soils. The problems on the Fayette silt loam soils are not very uniform, but are most commonly found on the hillsides. Sulfur Deficiency in Alfalfa.
We just completed 1st crop harvest of two research sites associated with this “pale” patchy problem. On average, the yields in these “pale” areas were doubled with the addition of sulfur fertilizer.
MISCELLANEOUS
Ag Decision Maker
The Ag Decision Maker website (http://www.extension.iastate.edu/agdm) is designed for farmers, lenders, farm managers and other professionals involved in agriculture and/or the representation of agricultural clients. It offers a wide range of business information on legal and tax issues, marketing, leasing, land values, costs and returns and new business development among other topics.
New Marketing Tool to Assist Ag Producers in Mapping Marketing Areas
Iowa Market Maker is an interactive Web site designed to connect food producers, distributors, buyers and sellers. This unique Web tool integrates Census Data, North American Industry Classification System (NAICS) Codes and Global Satellite Imagery (GSI). By overlaying this data and technology, buyers and sellers have the ability to “target” market their sales and purchases. Market Maker is a project originated by the University of Illinois Extension Initiative for the Development of Entrepreneurs in Agriculture (IDEA) program. Funding for the Iowa project was provided by the Leopold Center for Sustainable Agriculture’s Marketing and Food Systems Initiative, Altria, the Agricultural Marketing Resource Center (AgMRC) and Iowa State University Extension Value Added Agriculture Program. The Iowa Market Maker Web site is:
www.marketmakeriowa.com
EVENTS
June 15-17: Master Gardeners Conference, Cedar Rapids.
http://www.mastergardener.iastate.edu/info/06uppermidwestmgconf.html
June 16: Ag Professional Tour, 9:30 a.m. to Noon, ISU Northeast Research Farm, Nashua.
The program will include observations and experiences related to current crop growth and development, soil fertility, and pest management problems as they develop across the area; a review of the various research projects underway on the research farm and with on-farm cooperators; and a discussion of the new technologies/ products that are or soon will be available to our clients. Brian Lang and George Cummins, Extension Crop Specialists, and Ken Pecinovsky, Farm Superintendent, will lead the discussions. The tour is organized by the Northeast Iowa Ag Experimental Association which owns the farm. 2.5 CCA credits can be earned. A $10 registration fee will be charged at the door ($25 for CCA credits). Pre-registration is not required.
June 21-22: Farm Progress Hay Expo, Strawberry Point.
http://www.hayexpo.com/ME2/Audiences/Default.asp
June 22: ISU Southeast Research and Demonstration Farm Crops Field Day, Crawfordsville.
9:00 a.m. Special Session for CCAs. Earn 5 hours of CCA credit (including 1.5 hours in soil & water) by attending this special morning session and the afternoon field day. $50 Fee (if pre-registered by June 20). Send an e-mail note to < fawcett@iastate.edu > if you plan to attend. The morning session includes: “Goof Plots – Identifying Herbicide Injury Symptoms” (Jim Fawcett, ISU Extension Crop Specialist); “Tillage Impacts on the Soil Environment, Soil Compaction, and Root Development” (Rick Cruse, ISU Professor of Agronomy – Soil Management); “Know Your Spots – Identifying Foliar Soybean Diseases” (Alison Robertson, ISU Extension Plant Pathologist); “Does the N Calculator Work in High Yield Environments?” (John Sawyer, ISU Extension Agronomist – Soil Fertility).
Noon: ISU Dean of Agriculture Wendy Wintersteen will be featured at noon with a presentation on “Future Direction of Ag Research”
1:00: Tour begins… includes: Crop Season Review; Early Planting Options Using Polymer Coatings; Asian Soybean Rust Outlook & Fungicide Trial Results; Corn Population & Planting Date Trial Results; Diagnostic Tools for Nitrogen Management.
Lunch Reservation Deadline June 20: Please call the Johnson County Extension Office (319-337-2145) or e-mail Jim Fawcett purchase lunch.
June 28: ISU Northeast Research and Demonstration Farm Crops Field Day, 1:30 p.m., Nashua.
Details included in the next Crop Notes.
June 29: ISU Northern Research and Demonstration Farm Crops Field Day, 9:30 a.m., Kanawha.
Details included in the next Crop Notes.