More In-Depth Information

Corn Earworm

Helicoverpa zea

  •  

Hosts

Corn Earworm damage on hemp Corn earworm damage.

green corn earworm larva
Corn earworm larva with green coloration.

Tomato fruitworm exit hole on corn.
Corn earworm larva with brown coloration.

corn earworm adult moth.
Corn earworm adult moth.

trap with lure inside in field
Corn earworm trap with pheramone lure.

  • Field-grown hemp
  • Artichoke
  • Asparagus
  • Corn
  • Solonaceae crops (tomato, pepper, potatoes,etc.)
  • Curcurbits
  • Peas
  • Beans
  • Various weeds

Description

Caterpillars are brownheaded, with green, brown, or black bodies that have alternating dark and light stripes running lengthwise. Adult moths are tan-brown and the front wings are marked with a distinct dark spot in the center and darker bands near the outer margins. 

Life Cycle

Egg | Larva | Pupa | Adult

  • 2-4 generations per year in Utah may be possible depending on latitude and elevation.
  • Pupae overwinter in soil in central and southern Utah, but they do not survive in northern Utah.
  • Adults emerge in spring and migrate to northern locations.
  • Adults mate and lay eggs singly on multiple host plants.
  • Larvae feed on leaves and flower buds.
  • When mature, larvae fall from the plant and pupate in the soil.

Damaing Lifestage(s): Larva

Damage Symptoms

Larvae tunnel into and destroy developing buds and seeds, which can negatively affect CBD production. Hemp grown for fiber will be less affected.

Time for Concern

During flower bud formation and through harvest.

When and Where to Scout

  • Monitor adult moths with a Heliothis trap and corn earworm pheromone lure starting in July, and check traps every three to five days.
  • Each week, inspect plants during flowering stage for larvae or brown frass (excrement) on flower buds.

Threat Level

High for field-grown CBD. 

Occurrence in Utah

Damage has been found on flower buds in scattered locations in Utah, but it is not as widespread as in neighboring states.

Management

  • There is no trap threshold for treatment in hemp, so periods of abundant trap catch based on your own historic records will be the critical time for crop protection.
  • Approved insecticides are available. One option is Bacillus thuringiensis (Bt), which should only be used when caterpillars are less than one-half inch in size. Target developing buds with insecticides.
  • Crops will have to be protected throughout the adult flight periods, so continued monitoring and reapplications must occur. 

When to Consider Treatment

During flowering stage, if large numbers are trapped or larvae are found.

Look-alikes

Other caterpillars in the Noctuidae family (cutworms; armyworms)

Caterpillar Insecticides

Utah-Registered Product Active Ingredient(s) Notes
Agree WG Bacillus thuringiensis ssp. aizawa  
Aza-Direct Biological Insecticide azadirachtin  
AzaGuard  azadirachtin  
AzaSol azadirachtin  
Azatin O Biological Insecticide azadirachtin  
Azatrol EC Insecticide azadirachtin  
Azera Insecticide azadirachtin  
BT Now Bacillus thuringiensis ssp. kurstaki Greenhouse use only.
Bug Buster-O Extinguish Ant Bait pyrethrins Greenhouse use only.
Deadzone diatomaceous earth  
Deliver Biological Insecticide Bacillus thuringiensis ssp. kurstaki  
DiPel DF Biological Insecticide Bacillus thuringiensis ssp. kurstaki  
DiPel DF Biological Insecticide Dry
Flowable		 Bacillus thuringiensis ssp. kurstaki  
DiPel PRO DF Biological Insecticide Bacillus thuringiensis ssp. kurstaki  
Evergreen Crop Protection EC 60-6 pyrethrins  
Ferti-Lome Dipel Dust Biological Insecticide (RTU) Bacillus thuringiensis ssp. kurstaki  
Ferti-lome Fruit Tree Spray pyrethrins  
Gemstar LC Polyhedral occulsion
bodies (Obs) of nuclear
polyhedrosis virus of
Helicoverpa zea (corn
earworm)		  
Grandevo CG;WDG Chromobacterium sub strain PRAA4-1 cells  
Javelin WG Biological Insecticide Bacillus thuringiensis ssp. kurstaki  
Leprotec Bacillus thuringiensis ssp. kurstaki  
Molt-X azadirachtin  
Neemix 4.5 Insect Growth Regulator azadirachtin  
Prizefighter ammonium nonanoate  
Pycana  pyrethrins Greenhouse use only.
Pyganic Crop Protection EC 1.4 II; 5.0 II pyrethrins  
SPEAR-LEP gs-omega/kappahxtx-hv1a Supression only; combine with a Bt product for greater efficacy.
Tersus Insecticide pyrethrins  
Thuricide N/G Bacillus thuringiensis ssp. kurstaki  
Valent Professional Products DiPel Pro DF Biological Insecticide Dry
Flowable		 Bacillus thuringiensis ssp. kurstaki  
Venerate CG Burkholderia sp. strain A396  
XenTari Biological Insecticide Dry Flowable Bacillus thuringiensis ssp. aizawai  

Photo Credits

Damage/Brown larva - Whitney Cranshaw, Colorado State University, Bugwood.org
Adult - Purdue University Extension Entomology
Trap/green larva - USU Extension IPM Program

Precautionary Statement: Utah State University and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks, and not all are registered for edible crops. “Restricted use” pesticides may only be applied by a licensed applicator. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed in this publication.