Wednesday, May 09, 2012

Iowa: Start Scouting for Stalk Borer in Corn

AgFax.Com - Your Online Ag News Source


Iowa has been steadily accumulating degree days ahead of schedule in 2012. Over the weekend, some parts of southern Iowa hit an important degree day benchmark for common stalk borer.

About 10 percent of stalk borer larvae can begin moving to corn after accumulating 1,300 to 1,400 degree days. Part of southwestern and southeastern Iowa have reached that threshold and we recommend starting to scout this week in corn (Fig. 1). Central and northern Iowa should start scouting May 12 to May 18, if warm temperatures continue. This is about three weeks earlier than last year.


Figure 1. Growing degree days accumulated (base 41°F) for stalk borer larval movement in Iowa for 2012. Begin scouting around 1,300 to 1,400 degree days. Map courtesy of Iowa Environmental Mesonet, ISU Department of Agronomy.

 

Stalk borer eggs are laid on grasses and weeds in the fall, and young larvae will feed in the spring until they outgrow the plant. Corn can become infested when stalk borer larvae move to find bigger host plants, typically adjacent to grassy edges of emerging corn. The most susceptible stages of infestation are at V1-V5, or about 2 to 24 inches in plant height. Larvae can damage corn by defoliating leaves and burrowing into stalks. Stalk borers do not typically cause economic damage when feeding on the leaves, but can clip newly emerging plants and cause death (Fig. 2). More often, larvae kill corn plants by entering the stalk and destroying the growing point (i.e., flagging or dead heart). A dead heart plant will have outer leaves that appear healthy, but the newest whorl leaves die and can cause barren plants.


Figure 2. Stalk borer can shred corn leaves and destroy the growing point.

Stalk borer infestations are more likely in corn surrounded by giant ragweed. Female moths prefer to lay eggs in weedy areas in August and September, so minimizing weeds in and around corn during that time will discourage egg-laying. Using herbicides to kill spring weeds can force stalk borer larvae to infest young corn plants. Long term management requires controlling grassy edges around corn so that mated females will not lay eggs in that area during the fall.




Fields with persistent stalk borer infestations should be monitored every year. Applying insecticides to infested corn is not effective because the larvae are protected once tunneled into the stalk. Instead, target foliar applications to larvae as they migrate from grasses to corn. Look for larvae inside the whorls to determine the number of plants infested. The larvae are not highly mobile and typically only move into the first four to six rows of corn. Look for new leaves with irregular feeding holes or for small larvae resting inside the corn whorls. Larvae will excrete a considerable amount of frass pellets in the whorl or at the entry hole in the stalk. Young corn is particularly vulnerable to severe damage, but plants are unlikely to be killed once reaching V7 (seven true leaves).

Control

To prevent stand loss, scout and determine the percent of infested plants. The use of an economic threshold (Table 1), first developed by ISU entomologist Larry Pedigo, will help determine justifiable insecticide treatments based on market value and plant stage. Young plants have a lower threshold because they are more easily killed by stalk borer larvae.


Table 1. Economic thresholds for stalk borer in corn, based on plant stage, expected yield and market value.

If an insecticide is warranted, some products can be tank-mixed with a fast burndown herbicide, or applied seven days after a slow burndown herbicide. Border treatments should be considered if infestations are localized. Insecticides must be well-timed so that products are reaching exposed larvae before they burrow into the stalk. Make sure to read the label and follow directions, especially if tank-mixing with a herbicide, for optimal stalk borer control.

Life cycle

There is just one generation per year in Iowa, and the egg is the overwintering stage. Like all insects, stalk borers develop based on temperature. Egg hatch typically occurs around April 19 to June 5, or 50 percent egg hatch happens at 494 growing degree days. The number of larval molts is variable depending on food quality, and ranges from seven to nine instars. Fully developed larvae drop to the soil to pupate. Approximately 50 percent of pupation happens at 2,746 growing degree days, with 50 percent adult emergence at 3,537 growing degree days. Peak adult flight occurs during the first two weeks of September.

Description

Stalk borer larvae have three pairs of true legs and four pairs of fleshy prolegs. The body is creamy white and dark purple with brown stripes. Often there is a creamy white stripe running down the back. A distinctive feature is an orange head with two dark lateral stripes (Fig. 3). The adults are dark gray and brown colored moths, with jagged white lines and two to three clusters of white spots.


Figure 3. Stalk borer larva. Photo credit Marlin E. Rice.

For more information on stalk borer biology and management, read a recent Journal of Integrated Pest Management article by Rice and Davis (2010), called “Stalk borer ecology and IPM in corn.”


Tags: , ,


Leave a Reply

Name and Email Address are required fields. Your email will not be published or shared with third parties.

Sunbelt Ag News

    DTN Livestock Close: Lean Hog Futures Make Decent Gains9-30

    Farm Bill Decision Deadlines and the Farm Bill Toolbox9-30

    Doane Cotton Close: Analyst Predicts 40 Cent Futures9-30

    AFB Grain-Soybean Close: Prices Lower Despite Bullish Soy Stocks9-30

    AFB Cotton Close: Futures in the Red9-30

    AFB Rice Close: Futures Fractionally Mixed9-30

    DTN Cotton Close: Slips to New Lows9-30

    AgFax Cotton Review: Global Supply Hurts Prices; Cotton Transition Assistance Program Deadline Looms9-30

    DTN Grain Close: Markets Move Lower Following USDA Report9-30

    USDA: Weekly National Peanut Prices9-30

    DTN Livestock Midday: Live Cattle Futures Slip Lower9-30

    USDA Grain Stocks: Corn Up 50%, Wheat 2; Soybeans Drop 359-30

    DTN Grain Midday: Wheat Futures 7 to 10 Lower9-30

    USDA Wheat: Production Drops 5 Percent from 20139-30

    DTN Cotton Open: Trades on Slight Loss Near Low9-30

    DTN Livestock Open: Cattle Futures Staged to Begin Higher9-30

    DTN Grain Open: Futures Start Out Lower9-30

    Keith Good: ‘Misinformation’ Muddles Clean Water Act, EPA Chief Says9-30

    Grain Storage, Transportation Worries Mount — DTN9-29

    Soybeans: Protein, Oil Values Rate More Market Attention — DTN9-29

    Soybean Harvest Rises by 7 Points, Corn 5 — DTN9-29

    Growing Demand for Pork Likely to be Met — and Quickly9-29

    Peanut Stocks and Processing: Utilization Up 4%, Stocks at 1.4B Pounds9-29

    Peanuts: New Revenue Policy Implemented by USDA9-29

    Flint on Crops: What is a Good Variety Worth?9-29

    Southern Grain Crops In 2014 – Top 10 Trends, Issues, Setbacks – AgFax9-28

    Farm to Table: Something Old is New Again. – AgFax9-26

    Rice: Mexico To Restore Import Tariffs on Asian Rice9-26

    Rice Crop: Delta Area Harvests Picking Up Steam9-26

    Rice Market: Strong Friday Push Makes for a Positive Week9-26

    Rose on Cotton: Bearish News – We got plenty.9-26

    Cleveland on Cotton: Chinese Moves Send Market into Free Fall9-26

    Sizing Up Sudden Death Syndrome: Management Decisions to Fight Back – DTN9-26

    Nebraska: New Study Addresses Climate Change Challenges – DTN9-26

    GMO Wheat Appears in Montana as USDA Wraps Up Oregon Investigation – DTN9-26

    Welch on Wheat: Harvest Behind Normal, Conditions Decline9-26

    Louisiana: Ag Officials Ask for New Rules for Drones9-26

    Welch on Grain: Corn Condition Improves Slightly9-26

    USDA: Peanut Price Highlights9-26

    Shurley on Cotton: Carefully Consider Selling Options9-26

    AgFax Wildlife Review: S.C. National Park Confronts Wild Hog Problem9-26

    Crop Insurance Details Clearing Up — DTN9-26

    Crop Insurance: ARC-PLC Regulation and Decision Tools9-25

    Taxes: Definition of Insanity, Cheat the IRS on Land Sales – DTN9-25

    Kansas: Revised Edition of Midwest Cover Crops Field Guide Now Available9-25

    U.S. Energy: Weak Demand, Plentiful Supply Drive Drop in Oil Prices9-25

    Gasoline Prices: Average Down 6 Cents9-25

    Propane Stocks: Rise by 1.7M Barrels9-25

    Diesel Prices: Lowest in Over 2 Years9-25

    U.S. Grain Transportation: Inspections Highest Since May9-25

    Growing Cycles Differ Greatly from Iowa to Florida — DTN9-25

    Iowa-Based Company to Build Ethanol Plant in Brazil — DTN9-25

    Big Data Drives Smarter Decisions on Farm — DTN9-25

    Corn Belt Growers Eager to Get Harvest Rolling — DTN9-25

    Sunbelt Ag Events

     

    About Us

    AgFax.Com covers agricultural trends and production topics, with an emphasis on news about cotton, rice, peanuts, corn, soybeans, wheat and tree crops, including almonds, pecans, walnuts and pistachios.

      

    This site also serves as the on-line presence of electronic crop and pest reports published by AgFax Media LLC (formerly Looking South Communications).

        

    Click here to subscribe to our free reports.

      

    We provide early warnings and confirmations about pests, diseases and other factors that influence yield. Our goal is to quickly provide farmers and crop advisors with information needed to make better and more profitable decisions.

         

    Our free weekly crop and pest advisories include:

    • AgFax Midsouth Cotton, covering cotton production and news in Alabama, Arkansas, Louisiana, Mississippi, Tennessee and Missouri.

    • AgFax Southeast Cotton, covering cotton production and news in Alabama, Florida, Georgia, North Carolina, South Carolina and Virginia.

    • AgFax Southwest Cotton (new for 2013!), covering cotton production and news in Texas, Oklahoma, Kansas and New Mexico.

    • AgFax West (formerly MiteFax: SJV Cotton), covering California cotton, alfalfa, tomatoes and other non-permanent crops in California's Central Valley.

    • AgFax Rice covering rice production and news in Arkansas, Louisiana, Mississippi, Missouri and Texas.

    • AgFax Peanuts, covering peanut production in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas and Virginia.

    • AgFax Southern Grain: covering soybeans, corn, milo and small grains in Southern states.

    • AgFax Almonds, covering almonds, pistachios, walnuts and other tree crops in California's Central Valley.

    • AgCom 101, providing guidance to ag professionals involved in social media.

    Our newsletters are sponsored by the following companies: FMC Corporation Chemtura Dow AgroSciences.

          

    Mission statement:

    Make it as easy as possible for our community of readers to find and/or receive needed information.

              

    Contact Information:

    AgFax Media. LLC

    142 Westlake Drive Brandon, MS 39047

    601-992-9488 Office 601-992-3503 Fax

    Owen Taylor Debra L. Ferguson Laurie Courtney

          

    Circulation Questions?

    Contact Laurie Courtney