Corn Rootworm
Pest Facts
Larval Symptoms
• Latin names:
• 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
• Western Corn Rootworm (WCR) – Diabrotica virgifera
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 US 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
Distribution of Life Cycle Variations
• 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
Pioneer Agronomy Sciences
“Goose-necking”
No feeding
Feeding scars
Example
of root
pruning
due to
corn
rootworm
®, TM, SM Trademarks and service marks of Pioneer Hi-Bred. © 2010, PHII
Corn Rootworm Comparisons
Management
Western Corn
Rootworm (WCR)
• Yellow with black
(more or less
distinct) stripes
• Males darker and
NCR
smaller
Northern Corn Rootworm (NCR)
• Green or yellow
• Females larger
Mexican Corn Rootworm
• Found from Mexico north to
Kansas
• Yellow wing covers
Southern Corn Rootworm
• Also called Spotted
Cucumber Beetle
• Overwinters in Southern
US as adult only
Striped Cucumber Beetle
• May be found on cucurbits
intermingled with corn
rootworm species
• Yellow with black distinct
stripes
• 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 using Pioneer Products
• Suppression of larval development by planting
genetically modified hybrids, such as Pioneer®
brand hybrids with the HXX trait
Corn
Rootworm
Annual Cycle
in Maize
WCR
Unprotected
Herculex XTRA
JUNE
MAY
Overwintering
is as an egg in
the soil
Eggs hatch in
May and larvae
feed on corn
roots
…may cause lodging,
then pupate
Emerged adults
feed on silks,
disperse, mate
and lay eggs
AUG/SEPT
JULY/AUG
Pioneer Agronomy Sciences
®, TM, SM Trademarks and service marks of Pioneer Hi-Bred. © 2010, PHII
® Herculex XTRA is a registered trademark of Dow AgroSciences LLC.