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Corn Rootworm

In-Depth Downloads

Larval Symptoms

  • Progressive feeding on the roots causes difficulty for the plant to take up moisture and nutrients
  • A reduced root system can also predispose the corn plant to fall over in wet or windy conditions
  • Often this lodging occurs prior to tasseling, and the plant attempts to grow upright, causing a tangled condition known as "goose-necking"
  • Injured roots are also easy entry points for fungi and bacteria that may increase severity of root and stalk rots and premature death

goose-necking corn plants

Feeding scars

Root pruning
Example of root pruning due to corn rootworm (photo above)

Corn Rootworm Comparisons

Western Corn Rootworm and Northern Corn Rootworm
Western Corn Rootworm (WCR)
  • Yellow with black (more or less distinct) stripes
  • Males darker and smaller
Northern Corn Rootworm (NCR)
  • Green or yellow
  • Females larger

Mexican Corn Rootworm
Mexican Corn Rootworm
  • Found from Mexico north to Kansas
  • Yellow wing covers

Southern Corn Rootworm
Southern Corn Rootworm
  • Also called spotted cucumber beetle
  • Overwinters in southern U.S. as adult only

Striped Cucumber Beetle
Striped Cucumber Beetle
  • May be found on cucurbits intermingled with corn rootworm species
  • Yellow with black distinct stripes

Facts

  • Latin names:
    • western corn rootworm (WCR) - Diabrotica virgifera
    • northern corn rootworm (NCR) - Diabrotica barberi
    • southern corn rootworm (SCR) - Diabrotica undecimpunctata howardi
    • Mexican corn rootworm (MCR) - Diabrotica virgifera zeae
  • WCR and NCR are found throughout the western and northern Corn Belt - MCR is locally important in the West only, and SCR can be found throughout the U.S. but rarely causes economic damage
  • Most damaging corn pest, considered to cause more than $1 billion annual loss in North America
  • More prevalent in fields following corn
  • Besides corn, there is some larval survival on a few grasses such as foxtails and especially Miscanthus

Life Cycle

Corn Rootworm Annual Cycle in Maize

  • Most corn rootworms are attracted to corn to lay their eggs and therefore easily managed with a crop rotation that alternates corn with other crops
  • However, two variations of this life cycle exist:
    • Soybean variant of western corn rootworm has evolved to lay eggs in fields other than corn, so larvae are present even when a field was not in corn the preceding year

  • Diapausing variant of the northern corn rootworm has evolved to lay dormant (diapause) in the soil as an egg for additional years before hatching so that larvae may also appear when corn is planted after a break in the rotation

Management

  • Favorable conditions for increase are moist soils at egg laying and mild winters
  • Several natural enemies exist, including nematodes, parasites, predators and diseases, but the population rebuilds rapidly

IPM Practices

  • Management selections may be aided by a careful scouting program that monitors adult presence and potential egg laying, allowing rough prediction of a future problem and the need for applying specific control measures
    • Avoidance using crop rotation
    • Control of larvae
      • Use of insecticide at planting to control newly hatching larvae
      • Use of seed treated with an insecticide
    • Control egg laying by spraying emergent adults

Best Practices with Pioneer Products

  • Suppression of larval development by planting genetically modified hybrids such as Pioneer® brand hybrids with the HXX trait.

A18E0FE0-5B58-3888-E60A-694200EFFC67

Herculex® XTRA Herculex® I Herculex® RW
HXX – Herculex® XTRA contains both the Herculex I and Herculex RW genes.
Herculex® XTRA Insect Protection technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex® and the HX logo are registered trademarks of Dow AgroSciences LLC.
 
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