Overview
According to USDA reports, commercial sweet corn production in 2007 surpassed $860 million in value, with over 631,000 acres under production. Of all processed (e.g., canned, frozen) vegetables,
processed sweet corn accounted for the second largest and second most valuable crop in 2007. While sweet corn is grown in all 50 states, the production of sweet corn for processing is heavily concentrated in the upper Midwest and the Pacific Northwest. Since 2004, the value of Minnesota’s sweet corn crop for canning and freezing has surpassed the value of Washington’s and Wisconsin’s sweet corn crop. Coastal states dominate the commercial fresh sweet corn market. During 2007, Florida remained the leading producer of fresh sweet corn; California, New York, and Georgia produced significant amounts of sweet corn as well [1].
U.S. Sweet Corn Production Acres Planted 2003 – 2008 Acres Planted 2003 Acres Planted 2004 Acres Planted 2005 Acres Planted 2006 Acres Planted 2007 Acres Planted 2008 Average Acres Planted 2003 – 2008 Fresh 261,100 247,900 246,500 240,300 248,400 246,600 248,467 Processing-All 438,400 412,700 421,500 394,400 381,100 370,750 403,142 Source: USDA NASS
Target Pests
According to the University of Florida, IFAS Extension, “foliar, ear and root feeding insects can routinely cause economic losses to sweet corn if left untreated. The most important pests of sweet corn in Florida are the fall armyworm, corn earworm, lesser cornstalk borer, cutworms, corn silk fly, cucumber beetles, aphids and wireworms” [2].
Chlorpyrifos Use
In 2008, Doane reported 98,254 acres of sweet corn were treated with just over 87,000 lb of chlorpyrifos.
Lbs a.i. Chlorpyrifos Use 2003 – 2008 Lb a.i. 2003 Lb a.i. 2004 Lb a.i. 2005 Lb a.i. 2006 Lb a.i. 2007 Lb a.i. 2008 Average Lb a.i. 2003 – 2008 99,735 123,530 109,926 139,374 131,841 87,056 115,244 Source: dmrkynetec, inc. 2009
The largest use of chlorpyrifos on sweet corn was in the south, where nearly 63,000 acres were treated with chlorpyrifos.
2008 Chlorpyrifos Use by Region Acres Treated Region Acres Treated 2008 Atlantic 7,044 Midwest 13,398 South 62,657 West 15,155 Grand Total 98,254
Source: dmrkynetec, inc. 2009
Because of its broad spectrum control, chlorpyrifos is used in Florida on the following insects that attack sweet corn: aphids, beet armyworm, chinch bugs, corn earworm, corn rootworm (adult), cutworms, fall
armyworm, and grasshoppers. In granular form at planting, chlorpyrifos is also used for corn rootworm larvae, cutworms, lesser corn stalk borer, seed corn maggot, and wireworms [2]. According to Doane, in 2008 34,000 acres of sweet corn were treated in the South to control corn earworm.
In the Midwest, corn rootworm was the insect pest most often targeted with chlorpyrifos, with 13,289 acres treated, followed by cutworm, corn earworm, and flea beetle. In Western region states, 6,411 acres of sweet corn were treated with chlorpyrifos to control armyworm and 5,735 acres were treated to control symphylan. Corn earworm is another primary target pest in Western sweet corn. In the Atlantic region, chlorpyrifos use is primarily as Lorsban 15G at-plant for corn rootworm control.
The CDPR reported that in 2007, 11,863 lb a.i. of chlorpyrifos were used in 305 treatments on 12,857 acres of corn grown in California for human consumption [3].
Control of many of the insect pests in sweet corn, such as the corn earworm, requires multiple
sequential applications. Therefore, there is a great need for alternative efficacious products that can be rotated to delay resistance. Chlorpyrifos is a valuable component in an insect resistance management program due to its different mode of action to pyrethroids and carbamate insecticides, two insecticide classes where there is known insect resistance and that are used to control target pests in sweet corn. Externally applied Bts (Bacillus thuringiensis, a biopesticide bacteria specially formulated for insect control) are another mode of action, but are considered less effective than chlorpyrifos.
Chlorpyrifos Formulations, Rates, and Applications
Current chlorpyrifos formulations listed for controlling insect pests in sweet corn include Lorsban Advanced, Lorsban-4E (and other 4 lb per gallon EC formulations of chlorpyrifos), Lorsban 50W, Lorsban 15G (and other chlorpyrifos granular formulations), and Cobalt.
Location: Pacific Northwest
• Pests: corn earworm
• Application Type: ground, chemigation, aerial • Application Method: broadcast
• Rate: 0.25 – 1.0 lb a.i./A • Number of Applications: 1-3
• Timing of Application: during the Summer • Alternatives: lambda cyhalothrin; methomyl
Location: FL
• Pests: fall armyworm, corn earworm, silk fly • Application Type: ground and aerial
• Application Method: low pressure sprayers • Rate: 0.5 – 1.0 lb a.i./A
• Number of Applications: 3 (max) • Timing of Application: October-June • Alternatives: lambda-cyhalothrin; methomyl
Location: Midwest and Northeast
• Pest: armyworm, cutworms
• Application Type: ground, air, chemigation • Application Method: broadcast
• Rate: 0.5 – 1.0 lb a.i./A • Number of Applications: 1
Location: Midwest and Northwest
• Pest: armyworm, cutworms, aphids, rootworm adults, European corn borer, flea beetle adults, southern corn leaf beetle, webworms, western bean cutworm
• Application Type: ground, air, chemigation • Application Method: broadcast
• Rate: 0.5 – 1.0 lb a.i./A • Number of Applications: 1
• Timing of Application: post to corn emergence
Location: Midwest and Northeast
• Pest: corn earworm
• Application Type: ground, air, chemigation • Application Method: broadcast
• Rate: 0.75 – 1.0 lb a.i./A • Number of Applications: 1
• Timing of Application: post to corn emergence
Location: Midwest and Northwest
• Pest: rootworms, cutworms, wireworm, lesser seed corn borer, billbugs • Application Type: ground
• Application Method: at plant • Rate: 1.30 lb a.i./A (granular) • Number of Applications: 1 • Timing of Application: at planting
Location: Midwest
• Pest: European corn borer • Application Type: aerial, ground
• Application Method: broadcast or directed • Rate: 0.75 – 1.0 lb a.i./A (granular) • Number of Applications: 1
• Timing of Application: in relation to corn growth from V9 to R1
Grower Perspective
In late 2007, the EPA asked for public comments on issues related to the agricultural use of chlorpyrifos. Following is an excerpt explaining why chlorpyrifos is essential for protecting crops. Submissions to the docket are public information and have been posted by the EPA at www.regulations.gov, docket
number EPA-HQ-OPP-2007-1005.
“Chlorpyrifos is widely used in Oregon as a seed treatment to control pests that feed on snap bean and sweet corn and young seedlings…Producers also use it on sweet corn at planting, to help control corn rootworm larvae, cutworms and symphylans. Growers have not found alternative products that offer the control of chlorpyrifos. Elimination of chlorpyrifos would have significant negative impacts on Oregon growers’ ability to competitively produce processed vegetable crops and consequently would severely hamper the entire processed vegetable industry in the state.” – Oregon Processed Vegetable Commission
Other Perspective
In preparing this report, growers and crop consultants were recently asked to share their thoughts on the benefits and use of chlorpyrifos for pest control.
“We need Lorsban in our pest management rotation, as it is one of only a few organophosphates left that control silk flies in sweet corn. Right now, silk flies are a major pest and require frequent sprays. Growers use chlorpyrifos at tassel push and green silk. Lorsban is also used on lesser corn stalk borer and wireworms.” – Loren Horseman, Glades Crop Care (April 2009)
References
1. Agricultural Marketing Resource Center. Sweet Corn.
http://www.agmrc.org/commodities__products/grains__oilseeds/corn/sweet_corn.cfm. Accessed April 1, 2009.
2. Nuessly, G.S. and Webb, S.E. University of Florida, IFAS Extension. Insect Management for Sweet
Corn. Revised September 2007. http://edis.ifas.ufl.edu/IG158. Accessed April 10, 2009. 3. California Department of Pesticide Regulation. Summary of Pesticide Use Report Data 2007,
Indexed by Chemical. 2007. http://www.cdpr.ca.gov/docs/pur/pur07rep/chmrpt07.pdf. Accessed April 5, 2009.