The Georgia Agricultural Experiment Stations
College of Agricultural and Environmental Sciences
The University of Georgia
Research Report Number 707
October 2006
Insect Screening Results
Assessment of Corn Hybrids for Insect Resistance
Xinzhi Ni, Matthew Krakowsky, Gunawanti Gunawan, David Buntin, and Steve Brown
During the growing season of 2006, the relatively dry environmental conditions in Tifton,
Georgia were favorable for the rapid buildup of corn earworms, providing the potential for
considerable damage to the corn crop. Six ear-feeding insects recorded in the order of
infestation severity were: the corn earworm and the fall armyworm, the pink scavenger
caterpillar, the maize weevil, the sap beetles, and the southern green and brown stink bugs.
In contrast to 2005, stink bug damage was very low (only 0-1.5% of discolored kernels) in
2006. The most important insect was the corn earworm, which caused the greatest kernel loss
among all ear-feeding insects examined. The corn earworm and fall armyworm feeding
penetration in corn ears on the 58 hybrids was between 2.6 and 6.7 cm. Because the earfeeding damage caused by the corn earworm and the fall armyworm was hard to separate, the
penetration measurement included the feeding damage by both species. Some of the
transgenic Bt hybrids showed poor insect resistance ratings (with deep ear penetration), which
could be caused by the fact that these hybrids might only be resistant to either species but not
to both species. The maize weevil damage was between 0 and 0.5%, while pink scavenger
damage was between 0.1 and 3% of the total number of kernels. Insect resistance was rated
by amount of total insect damage using five categories; they were very good (VG), good (G), fair
(F), poor (P), and very poor (VP) as shown in the table. While VG represents the least amount
of insect damage, VP represents the most amount of insect damage. Losses to the pink
scavenger caterpillar and the maize weevil were based on damage by multiple generations of
these insects as the crop dries in the field. Timely harvest can substantially reduce losses
caused by these two insects. Rankings of the 58 hybrids for their resistance to the five main
ear-feeding insects (i.e., the corn earworm and the fall armyworm, the pink scavenger caterpillar,
the maize weevil and the stink bugs) are given in the following table. The lettered ratings in the
tables refer only to relative resistance to insects and are not indicative of yield. Please refer to
the yield data in other tests for specific information.
During the damage evaluation process, husk tightness ratings were assigned using a scale
of 1 to 5, in which 1 = very loose and 5 = very tight. Because average rating for husk tightness
is between 3.6 and 4.5, only loose (L), medium (M), and tight (T) ratings are given in the table.
Hybrids resistant to insects are highly recommended for planting and are presently the most
economical means, especially in late plantings, for the reduction of ear-feeding insect damage.
Consult your local county agent and/or extension entomologists for additional control
recommendations for a specific insect pest in your region.
All entries were planted on April 7, 2006 and harvested on September 1, 2005. Plots were
thinned to 20,000 plants per acre. Data for this section were compiled by J. C. Mullis, M.
McDaniel, and H. Hilton working at the University of Georgia, Tifton, Georgia.
The Georgia Agricultural Experiment Stations
College of Agricultural and Environmental Sciences
The Univeristy of Georgia
Research Report Number 707
October 2006
Tifton, Georgia:
Evaluations of Corn Hybrids for Resistance to Insects
and Related Traits, 2006
Overall Resistance
to Insect Injury 2
2 or more
years
2006
Hybrid
Name
Days to
Antheses
Husk
Tightness1
Pioneer
DeKalb
Terral
AgraTech
Pioneer
31G68
DKC69-71(RR2/YGCB)
TVX25BR604
860RR
31P41
62
62
61
61
60
M
M
M
M
M
VG
VG
VG
VG
VG
G
-
Garst
DynaGro
Pioneer
Pioneer
AgraTech
8295YG1/RR
58K40
33M53
31N26
695RR
59
61
60
62
59
M
M
M
M
M
VG
G
G
G
G
F
F
-
Hytest
Terral
NK
Greenwood
SS
7790 RR2/Bt
TV25BR23
1851W*
775
842RR2YG
62
61
62
62
61
L
T
M
L
M
G
G
F
F
F
F
G
G
F
Pioneer
Vigoro
Croplan
DeKalb
Terral
33V15
V58Y41
895Bt
DKC69-72(RR2)
TV26BR41
60
62
60
62
59
M
M
M
M
M
F
F
F
F
F
F
F
G
G
F
Croplan
Hytest
Hytest
Hytest
Vigro
799Bt
7729HX/LL
7799Bt
7930Bt
V62R66
59
60
61
60
61
M
T
M
M
M
F
F
F
F
F
G
F
G
F
Croplan
Croplan
Croplan
Hytest
Terral
751RR2/Bt
731HX/LL
DS822RR2/BT
7891RR2/BT
TVX25BR603
62
61
62
62
59
M
M
M
M
M
F
F
F
F
F
F
G
-
Terral
Garst
Garst
Garst
Pioneer
TVX26BR601
8248RR
8247YG1
8353CB/LL
31D58
60
59
59
60
61
M
M
M
M
M
F
F
F
F
F
-
SS
DeKalb
DeKalb
DeKalb
DeKalb
SS783RR2YGCB
DKC64-81(YGCB)
DKC66-23(RR2/YGCB)
DKC67-23(RR2/YGCB)
DKC69-68(RR2/YGRW)
61
59
59
61
62
M
M
M
M
T
F
F
F
F
F
-
Company or
Brand Name
Tifton, Georgia:
Evaluations of Corn Hybrids for Resistance to Insects
and Related Traits, 2006 (Continued)
Overall Resistance
to Insect Injury 2
2 or more
years
2006
Company or
Brand Name
Hybrid
Name
Days to
Antheses
Husk
Tightness1
AgraTech
AgraTech
Greenwood
Croplan
Golden Acres
695CRWRR
845RR
762
799RR2
2831RRB
60
61
61
61
59
M
M
L
M
M
F
F
F
F
F
-
Golden Acres
AgraTech
SS
DynaGro
AgraTech
2841RRB
760RR
804RR
58K02
797RR
61
62
62
61
61
M
M
M
M
M
F
P
P
P
P
-
Greenwood
DeKalb
DeKalb
Croplan
Pioneer
780
DKC61-45(RR2/YGCB)
DKC61-72(RR2)
851RR2/BT
34B24
61
58
58
61
59
M
M
M
T
M
P
P
VP
VP
VP
F
P
P
F
SS
DeKalb
DeKalb
SS775RR2
DKC67-60(RR2)
DKC63-81(RR2/YGCB)
59
62
60
M
L
M
VP
VP
VP
F
-
* White kernel hybrid.
1. L = loose husks, M = medium-tight husks, and T = tight husks.
2. Overall insect resistance to ear-feeding insects (i.e., the corn earworm, the fall armyworm, the pink
scavenger caterpillar, the maize weevil, and the stink bugs). Insect resistance measured by the percentage
of kernels infested with the ear-feeding insects from five ears, where VG = very good, G = good, F= fair, and
VP = very poor.