Arthropod Management Tests 2013, Vol. 38
doi: 10.4182/amt.2013.F24
(F24)
CORN (FIELD): Zea mays L.
CONTROL OF CORN ROOTWORM LARVAE WITH BT HYBRIDS, SEED-BLENDS, AND SOIL-APPLIED
INSECTICIDES, 2012
Nicholas A. Tinsley
Department of Crop Sciences
University of Illinois at Urbana-Champaign
1102 S. Goodwin Ave.
Urbana, IL 61801
Phone: 217-265-4113
Fax: 217-333-5299
E-mail: [email protected]
Ronald E. Estes
E-mail: [email protected]
Michael E. Gray
E-mail: [email protected]
Corn rootworm (CRW): Diabrotica spp.
Western corn rootworm (WCR): Diabrotica virgifera virgifera LeConte
Northern corn rootworm (NCR): Diabrotica barberi Smith & Lawrence
We established one trial near DeKalb, IL, to evaluate the ability of Bt hybrids, seed-blends, and soil-applied insecticides to
control CRW larvae. The experimental design was a RCB with four replications. The plot size for each treatment was 10 ft
(four rows) x 20 ft. The trial was planted on 23 Apr. We used a four-row, vacuum style planter constructed by Seed
Research Equipment Solutions (South Hutchinson, KS). The previous crop for the trial location was a trap-crop (lateplanted corn and pumpkins). Standard tillage practices were used. Seeds were planted at a population of 36,000 seeds/acre
in 30-inch rows and a depth of 1.75 inches. Granular insecticides were applied through modified Noble metering units
mounted to each row and plastic tubes directed the insecticide granules into the seed furrow. Force CS was applied in a
band over the seed furrow at a spray volume of 5 gpa using a CO2 system. Hybrids evaluated included Mycogen 2K594
(SmartStax, Cry34/35Ab1 + Cry3Bb1), Mycogen 2K592 (Herculex XTRA, Cry34/35Ab1), and Mycogen 2K591 (untreated
check [UTC]) (Dow AgroSciences LLC, Indianapolis, IN). Additionally, two seed-blend treatments were evaluated: (1) a
seed-blend containing 90% Herculex XTRA seed with 10% UTC seed and (2) a seed-blend containing 95% SmartStax seed
with 5% UTC seed. For seed-blend treatments, two root clusters were extracted from the first row of each plot on 16 Jul.
Each root cluster contained one non-Bt refuge root system and two Bt root systems. For non-seed-blend treatments, six
randomly selected root systems were extracted from the first row of each plot. Root systems were washed and rated for
CRW larval injury using the 0–3 node-injury scale. For seed-blend treatments, a weighted formula was used to calculate
overall mean node-injury ratings. Yields were estimated by harvesting the center two rows of each plot on 16 Oct. Weights
were converted to bu/acre at 15.5% moisture. Plant populations were thinned at the V6 growth stage to 33,000 plants/acre.
Data were analyzed using SAS 9.2 (SAS Institute, Inc., Cary, NC). The LSMEANS option of PROC MIXED was
performed to provide mean separations.
The mean node-injury rating for the UTC was 2.28, indicating that CRW larval feeding was severe. Adding Force CS to the
UTC enhanced root protection; however, the mean node-injury rating for this treatment remained relatively high (0.75).
Mean node-injury ratings for the remainder of the treatments were low (< 0.25), with the exception of the 90% Herculex
XTRA + 10% UTC seed-blend (0.43). Adding Force CS to the UTC resulted in a significantly greater mean yield. The
mean yields for Herculex XTRA, 90% Herculex XTRA + 10% UTC, and 95% SmartStax + 5% UTC were statistically
similar. Adding an insecticide (Aztec 2.1G, Force CS, or Lorsban 15G) to these treatments did not result in significantly
improved mean yields. This research was supported by industry gifts of products and research funding.
1
Arthropod Management Tests 2013, Vol. 38
doi: 10.4182/amt.2013.F24
d
Rate
Application
method
Nodeb,c
injury rating
Yield
(bu/acre)
---
---
0.43c
153abc
---
---
0.12de
157abc
6.7
NU furrow
0.02e
159ab
0.46
Band
g
0.10de
142c
0.46
Band
g
0.04de
159ab
0.46
Band
g
0.05de
165ab
0.46
Band
g
0.75b
59d
0.46
Band
g
0.03e
167a
0.10de
0.18d
0.07de
2.28a
154abc
150bc
160ab
22e
a
Treatment/formulation
e
90% Herculex XTRA (Mycogen 2K592 )
e
+ 10% UTC (Mycogen 2K591 )
e
95% SmartStax (Mycogen 2K594 )
e
+ 5% UTC (Mycogen 2K591 )
Aztec 2.1G
e
+ Herculex XTRA (Mycogen 2K592 )
Force CS
e
+ 90% Herculex XTRA (Mycogen 2K592 )
e
+ 10% UTC (Mycogen 2K591 )
Force CS
e
+ 95% SmartStax (Mycogen 2K594 )
e
+ 5% UTC (Mycogen 2K591 )
Force CS
e
+ Herculex XTRA (Mycogen 2K592 )
Force CS
e
+ UTC (Mycogen 2K591 )
Force CS
e
+ SmartStax (Mycogen 2K594 )
Lorsban 15G
e
+ Herculex XTRA (Mycogen 2K592 )
e
Herculex XTRA (Mycogen 2K592 )
e
SmartStax (Mycogen 2K594 )
e
UTC (Mycogen 2K591 )
8
-------
f
f
NU furrow
-------
Means within a column followed by the same letter do not differ significantly (SAS 9.2, PROC MIXED).
a
Rates are reported in oz of product per 1,000 ft of row.
b
Mean node-injury ratings are based on the 0–3 node-injury scale (P < 0.05).
c
Data were analyzed using a square-root transformation; actual means are shown.
d
Corn was harvested from the center two rows of each plot and converted to bu/acre at
15.5% moisture (P < 0.10).
e
Seed was treated with thiamethoxam, 0.25 mg active ingredient per seed.
f
Applied in-furrow using modified Noble metering units.
g
Applied in a band over the seed furrow.
2