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Corn Insect Management


Managing Corn Insects

A number of insects may attack corn, and some carry diseases. For example, aphids carry maize dwarf mosaic, and leafhoppers carry corn stunt. In some years heavy infestations of insects may drastically reduce yields. In other years insect populations never reach damaging levels. In order to prevent losses due to insect damage, you must know about the pest, its biology, and recommended control methods. The following information contains brief descriptions of insect pests often found in Mississippi corn fields. This information is presented to help you identify insect pests, the resulting damage, current economic thresholds, and control practices.

To minimize the impact of pests and pest control costs,

  1. Scout fields Make careful counts of insect pest populations.
  2. Use all available, practical noninsecticidal IPM
  3. Apply insecticides promptly when
  4. Use the most cost-efficient insecticide recommended for the target Apply insecticide during the most susceptible stage of development.
  5. Follow recommended guidelines for practicing insecticide-resistance

Before deciding to treat and before choosing the insecticide, consider such factors as the potential to intensify secondary pest problems and insecticide resistance.


Information in this guide is provided for educational and planning purposes only. When using agricultural chemicals, you (the user) are responsible for making sure the intended use complies with current regulations and conforms to the product label. Before applying any insecticide, be sure to get current usage information. Read and follow the product label.


Before using a pesticide, read the label carefully. Follow the directions. Pay attention to all precautions on the pesticide container label. Observe all regulations on worker protection and pesticide record-keeping. Store pesticides in plainly labeled containers safely away from livestock, pets, and children. Store pesticides in an area where they will not contaminate food or feed.

Integrated Pest Management

The best approach for pest control is to combine all available management practices to reduce damage. Proper selection of corn varieties and planting dates, regular scouting for pest infestations, wise use of insecticides, timely harvest, and sanitation of crop residue will reduce the likelihood of insect damage.


Regularly scouting corn fields is the best way to find damaging insect populations. Sample at least ten consecutive plants at each of four to five representative sites within a field. Treatment thresholds for many corn pests are much higher than in other crops, such as cotton. Therefore, you can generally check a fairly small number of plants to determine the presence of a particular pest species. If pests are present, step up scouting efforts to determine infestation levels more precisely. Corn is most open to insect injury in the seedling stage. From emergence until plants are approximately 10 inches tall, scout fields every 4 to 5 days. When plants are taller than 10 inches, sample for insect pests every week until crops mature.

Plants less than 6 inches tall: Record the number of plants examined and the number with five or more chinch bugs. Observe plants for signs of feeding or wilting from cutworms or other soil insects. Cutworms often cleanly cut plants off near the soil surface. If cut plants are found, determine whether anticipated stand loss will reduce the plant population below acceptable levels.

Emergence until tassel development: Look for signs of leaf feeding by caterpillars, flea beetles, or other pests on leaves within the whorl. As leaves emerge and unfurl from within the whorl, feeding damage usually appears as small, often regularly spaced holes or long scars on the leaves. Cut plants below the whorl. Check the leaves for worms. Record the species and the average number of worms present per plant.

After tassel development to maturity: Concentrate plant examinations from the tassel to the ear zone of the plant. In late- planted corn, look for second- and third-generation corn borers. Eggs are deposited on the upper and lower leaf surfaces. Look for evidence of recent feeding by small larvae on the leaf surface, at the base of the leaf, or behind the leaf sheath. When there is evidence of a corn borer infestation, randomly select plants from representative areas of the field and examine the stalks and ears. Larvae tunneling in the stalk cannot be controlled with insecticides. Corn earworms, fall armyworms, and corn borers may all be found in the ear, so species identification is important.


Suggested Planting Dates for Corn

South Mississippi: February 25 – March 15 South-Central:         March 5 – April 10
North-Central: March 15 – April 20 North Mississippi: March 20 – April 25


Making insect management decisions based on established treatment thresholds rather than applying treatments based on schedules or presence of pests is a proven method of reducing insect management costs. Effective use of thresholds requires frequent, intensive scouting to get accurate estimates of populations of various pest species that may be present in a field.

Treatment threshold is the pest population level at which treatment must be applied to avoid economic loss that would be greater than the cost of the treatment. Thresholds can vary, depending on species of pest present, stage of crop development, yield potential of the crop, cost of the treatment, market price, populations of other pests present, number of beneficial insects, potential for flaring secondary pests, ability to control secondary pests, and other factors. The thresholds recommended in this guide vary ac- cording to pest species and stage of crop development, but fixed thresholds cannot fully consider the many other factors that can influence a treatment decision.

Additional Information

In addition to this publication, you can get several other Extension publications on corn insect biology and management from your county Extension agent.

Information Sheet 864 – Corn Fertilization

Information Sheet 1548 – Corn Plant Population

Information Sheet 1563 – Minimizing Aflatoxin in Corn

Information Sheet 866 – Corn Planting Dates Information Sheet 1547 – Corn Hybrid Selection

Insecticide Resistance and Resistance Management

CAUTION: Recommendations of specific insecticides are based on information on the manufacturer’s label and performance in a limited number of tests. Levels of insecticide resistance, environmental conditions, and methods of application by growers may vary widely. For this reason, insecticide performance will not always match the safety and pest control standards indicated by experimental data.

Insecticides are listed alphabetically, not in order of their effectiveness. Effectiveness of a particular insecticide can vary greatly from field to field, depending on previous insecticide use, pest species, levels of resistance, and many other factors. A group of in- secticides recommended for control of a specific pest will vary in cost, effectiveness against the primary target pest, and secondary pests controlled. When selecting insecticides, growers must consider each of these factors plus the need to rotate among different insecticide classes to limit insecticide resistance problems.

Classes of insecticides: Effective resistance management requires rotation among the various classes of available insecticide chemistry. Often when one insecticide in a class fails because of insecticide resistance, other insecticides in the same class will also be ineffective. Selection of an insecticide from a different class will improve the chances of obtaining control. Growers need to be very aware of the type of insecticide chemistry being used. Classes of insecticides recommended in this guide are identified by the following abbreviations:

Avermectins – (AV) Chloro-nicotinyl – (CN) Organophosphate – (OP) Pyridine Carboxamide – (PC)
Biologicals – (B) Insect Growth Regulators – (IGR) Oxadiazine – (OX) Spinosyns – (SPN)
Carbamate – (C) Organochlorine – (OC) Pyrethroid – (P) Tetronic Acid – (TA)
Diamindes – (D) METI-Acaricides – (M)

Bt Corn

Relative efficacy of selected Bt Corn Products
Traits/BrandsPrimary target PestsCorn borersCutwormsCorn earwormsFall armywormsWestern corn rootworms
YieldGard Corn Borer, Agrisure CB/LLCorn borersExcellentPoorFairFair-GoodNone
Herculex ICorn borersExcellentGoodPoorGoodNone
YieldGard VT TripleCorn borers, corn rootwormsExcellentPoorFairFair-GoodExcellent
Herculex XTRACorn borers, corn rootwormsExcellentGoodPoorGoodExcellent
Genuity VT ProCorn borers, other caterpillar pestsExcellentPoorVery GoodExcellentNone
Genuity VT Triple ProCorn borers, corn rootworms, other caterpillar pestsExcellentPoorVery GoodExcellentExcellent
Genuity SmartStaxCorn borers, corn rootworms,other caterpillar pestsExcellentGoodVery GoodExcellentExcellent
Agrisure VipteraCorn borers, other caterpillar pestsExcellentGoodExcellentExcellentNone unless stacked with rootworm resistance

Bt is a bacterium that occurs naturally in the soil. Bt, or Bacillus thruingensis, produces crystal-like proteins (cry proteins) that can kill certain insects once ingested. Bt corn hybrids express cry proteins. Therefore, Bt corn hybrids are protected from certain in- sects, depending on what cry protein(s) the plant expresses.

The Bt corn hybrids planted in the Midsouth resist southwestern corn borers, European corn borers, and sugarcane borers. Be- fore 2009, the commercial Bt corn hybrids expressed one protein to protect against lepidopterian pests. In 2009 Bt corn hybrids became available that expressed two proteins to protect against lepidopterian pests, corn earworms, and fall armyworms. In 2010, Bt corn hybrids became available that express multiple proteins to control these pests.

Bt corn hybrids protected against western and northern corn rootworms are of little value in Mississippi. They were developed for use in the Corn Belt and have little or no efficacy on southern corn rootworms.

Refuge requirements for the Bt corn hybrids in cotton-growing regions depend on the number of proteins expressed in the plant. Bt corn hybrids expressing one protein can be planted to only 50 percent of a grower’s acreage. Bt corn hybrids expressing two or more proteins can be planted to 80 percent of a grower’s acreage. For specific information regarding refuge location and refuge configurations, see your local Extension agent or seed dealer.


Traits and Refuge Requirements for Commercial Hybrids Containing Bt technology

Traits and Refuge Requirements for Commerical Hybrids Containing Bt Technology
TrademarkAbbreviationProteins/TraitsRefuge Requirements Target Insect Pest(s)
Genuity SmartStaxVT3P/HXXCry3Bb1 + RR2 + Cry1A.105 + Cry2Ab2 + Cry34Ab1 + Cry35Ab1 + Cry1F + LL20% 1corn rootworm, corn borer spp., corn earworm, fall armyworm
Genuity VT Triple ProVT3PCry3Bb1 + RR2 + Cry1A.105 + Cry2Ab220% 1corn rootworm, corn borer spp., corn earworm, fall armyworm
Genuity VT Double ProVTPRR2Cry1A.105 + Cry2Ab2 + RR220% 2corn rootworm, corn earworm, fall armyworm
Roundup Ready Corn 2RR2RR20---
Herculex RootwormCRW (HXRW)Cry34Ab1 + Cry35Ab1 + LL +RR220% 1corn rootworm
Herculex IBt (HX1)Cry1F + LL + RR250% 2corn borer spp., fall armyworm
Herculex XtraCRW (HXRW) + Bt (HX1)Cry34Ab1 + Cry35Ab1 + Cry1F + LL + RR250% 1corn rootworm, corn earworm, fall armyworm
Agrisure CB/LL/GTCB/LL/GT Cry1Ab+glufosinate tolerance+glyphosate tolerance50% 2corn borer spp.
Agrisure CB/LL/RWCB/LL/RWCry1Ab + modified Cry3A + glufosinate tolerance
50% 1corn rootworm, corn borer spp.
Agrisure 3000GTCB/LL/RR/RW/GTCry1Ab + modified Cry3A + glufosinate tolerance + glyphosate tolerance50% 1corn rootworm, corn borer spp.
Agrisure GTGTglyphosate tolerance 0---
Agrisure Viptera 3110CB/LL/Viptera/GTCry1Ab + Vip3A + glufosinate tolerance + glyphosate tolerance
20% 2corn rootworm, corn earworm, fall armyworm
Agrisure Viptera 3111CB/LL/RW/Viptera/GTCry1Ab + modified Cry3A + Vip3A + glufosinate tolerance + glyphosate tolerance20% 1corn rootworm, corn borer spp., corn earworm, fall armyworm
Optimum IntrasectYGCB/HX1/LL/RR2Cry1Ab+Cry1F + LL + RR220% 2corn borer spp., fall armyworm
Optimum LeptraHX1/YGCB/Viptera/LL/RR2Cry1F + Cry1Ab + Vip3A + glyfosinate tolerance + glyphosate tolerance20% 2 corn borer spp., corn earworm, fall armyworm
Optimum TRIsectRW/HX1/LL/RR2Modified Cry3A + Cry1F + LL + RR2
50% 1corn rootworm, corn borer spp., fall armyworm
Agrisure 3122RW/CB/LL/HX1/HXRW/GTModified Cry3A + Cry1Ab + Cry1F + Cry34Ab1 + Cry35Ab1+ LL + RR220% 1corn rootworm, corn borer spp., fall armyworm
Agrisure Viptera 3220CB/LL/GT/Viptera/HX1Cry1Ab + Vip3A +glufosinate tolarance + glyphosate tolerance + Cry1F20% 2 corn borer spp., corn earworm, fall armyworm

Refuge Deployment options

When both rootworm and caterpillar traits are present in a hybrid, growers are required to follow refuge requirements and de- ployment strategies that satisfy the criteria for both. For example, if a field is planted to a hybrid that has a single caterpillar trait (requires 50% refuge up to ½ mile away) and a single rootworm trait (requires 20% refuge within field or adjacent to the field) the total refuge for that field has to be 50%. There are several ways that this can be accomplished. The entire 50% refuge can be planted within the field or adjacent to the field. Another possibility is that 20% of the refuge may be planted within the field or ad- jacent to the field and the remaining 30% within ½ mile of the field. Examples of refuge deployment options are illustrated here.

Blended refuge corn products (refuge, i.e., non-Bt seed mixed with Bt) may be encountered. This refuge strategy was developed for the Midwest. If these products are planted, a separate structured refuge (as in the examples below) is still required.


Within field deployment configurations. All must be at least four rows wide.


Within adjacent


Adjacent to field deployment configurations. All must be at least four rows wide.


1/2 mile option


Non-adjacent deployment configuration. Must be at least four rows wide.


Relative efficacy of Corn seed treatments for Control of seedling Insect Pests

Relative efficacy of the seed treatment
Common name , Trade NamesRateCorn Billbug White GrubWirewormSeed-corn maggot CutwormsSugarcane beetleSouthern Green stinkbugBrown stinkbug Chinch BugSouthern Western Lesser, Corn Corn Cornstalk, Rootworm2 Rootworm Borer
clothianidin Poncho 250 or Acceleron30.25 mg a.i./ kernelNLFGGP-FFFNLGENLG, NL
Poncho 500 or Acceleron with Poncho VOTiVO40.50 mg a.i./ kernelFGGEP-FGGNLG-EEP,NLG, NL
Poncho 1250 or Acceleron31.25 mg a.i./ kernelGEEEF-GGGG, NLEEGE, NL
thiamethoxam Cruiser Extreme 25030.25 mg a.i./ kernelNLFGEPPPNLFG-E, NLNLG, NL
Cruiser Extreme 500 3 or Avicta Complete Corn40.5 mg a.i./ kernelNLGGEPPFNLFENLG, NL
Cruiser Extreme 125031.25 mg a.i./ kernelGEEEFPGNLGEPE, NL
imidacloprid Gaucho 600, Imida E-AG 5 FST, Senator, Imidacloprid 5, Attendant 6000.60mg a.i./ kernel5NLGGEP, NLP,NLP,NLNLFG, NLNLNL
Latitude 33.5 oz./cwtNLF, NLGGNLNLNLNLF, NLG, NLNLNL
Concur 31.5 oz./ 42 lb. seedNLFGGNLNLNLNLF, NLG, NLNLNL
permethrin Kernel Guard Supreme3 or Kickstart VP3 1.5 oz./ 42 lb. seedNLF,NLP?fNLNLNLNLNLNLNLNL

1E = highly effective, G = effective, F = inconsistent results, P = not effective, based on trials in the Southeastern U.S.; L = insect is on the label for this product; NL = insect is not on the label for this prod- uct. In this case, it is best to assume that the product is ineffective against that particular pest, unless there is specific knowledge to the contrary about product efficacy in the Southeast.

2In the Southeast, several species of cutworms overwinter as medium- to large-sized larvae. They may be capable of cutting considerable numbers of seedlings before they eat a lethal dose of the insecticide. Black cutworm, the cutworm that appears on the label of most of these products, has a different life cycle in which eggs are laid in the spring, so that black cutworm larvae will be small if they have hatched out by the time the corn is planted. Southern corn rootworm larvae are a seedling pest, not a midseason pest like western corn rootworm larvae.

3Product name as marketed includes fungicides.

4Product name as marketed includes fungicides and a nematicide. Avicta Complete Corn contains the nematicide abamectin, Acceleron with VOTiVO contains the nematicide Bacillus firmus I-1582.

5Other rates for this active ingredient are available. See label.

This table is published in the Alabama Cooperative Extension System Corn IPM Guide, which is part of the Alabama Pest Management Handbook Vol. 1, It is revised annually.