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Terry A DeVries, Robert J Wright, Evaluation of Traited Corn Rootworm and Refuge Corn Hybrids in Combination With Soil Insecticides at Planting for Larval Corn Rootworn Control, 2017, Arthropod Management Tests, Volume 43, Issue 1, 2018, tsy039, https://doi.org/10.1093/amt/tsy039
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Several corn rootworm-traited and refuge corn hybrids in combination with at-planting soil insecticides were evaluated for effectiveness of larval WCR control near Clay Center, NE during 2017. Trial site was late-planted corn and pumpkin (insecticide-free) during 2016. Experimental design was an RCB with four replicates. Plot size was 4 rows × 68–72 ft length with 30-inch row spacing. Soil type was a Crete silt loam. ‘DeKalb DKC60-69RIB’ (contains GENVT2PRIB [Genuity VT Double Pro, refuge] insect and herbicide traits), ‘DeKalb DKC60-67RIB’ (contains GENSSRIB [Genuity SmartStax] insect and herbicide traits), ‘Pioneer P0987’ (contains AMX [Optimum AcreMax Xtra] insect and herbicide traits), and ‘Pioneer P0801’ (contains AMXT [Optimum AcreMax Xtreme] insect and herbicide traits) corn hybrids were planted on 12 May with a 4-row Kinze planter with finger pickup seed units. GENVT2PRIB-, AMX-, and AMXT-traited corn hybrids received a seed-applied insecticide treatment of Poncho 250 (clothianidin at 0.25 mg AI/kernel). The GENSSRIB-traited corn hybrid received a seed-applied insecticide treatment of Poncho 500 (clothianidin at 0.5 mg AI/kernel). A northeast wind at 6–7 mph occurred at planting. Aztec HC insecticide granules were applied IF at planting via SmartBox application system. Index 2.8CS liquid formulations were applied IF at planting in a 5-gpa water solution. Initial WCR egg hatch was first documented on 31 May. Plant populations were evaluated on 1 Jun. The total number of plants in the center two rows of each plot was recorded and converted to plants per acre (PPA). Extended leaf height (ELH) of 20 randomly selected plants in the center two rows of each plot was recorded in inches on 22 Jun. Initial adult WCR emergence was witnessed on 28 Jun. The total number of root-lodged plants in the center two rows of each plot due to larval WCR feeding was recorded on 5 Jul and converted to percentage root lodging. Larval feeding damage was evaluated on 13 Jul. Five randomly selected plants were dug from each plot (three from row 1 and two from row 4), washed, and rated using the Iowa State 0–3 scale (0 = no feeding, 1 = one node of roots pruned to within 1.5 inches of the stalk, 2 = two nodes of roots pruned to within 1.5 inches of the stalk, 3 = three or more nodes of roots pruned to within 1.5 inches of the stalk). Percent consistency performance levels were calculated by determining the percentage of rated roots in each plot with an Iowa 0–3 scale root injury rating less than or equal to 0.25. The center two rows of each plot were machine harvested on 20 Oct. Percent moisture and lbs of grain were recorded and corrected to 56 lbs/bu at 15.5% moisture to evaluate yield levels. Data were analyzed by PROC MIXED with mean separation using differences of least square means (P = 0.05) (Table 1).
| Treatment/formulation . | Rate-amt form/1000 row ft . | Placement . | Yielda (bu/acre) . | Root injury ratinga . | % Consistency Iowa 0–3 scale ≤ 0.25a,b . | % Root lodginga . | ELHa (inches) . | PPAc . |
|---|---|---|---|---|---|---|---|---|
| GENSSRIB + Index 2.8CSd | 0.72 fl oz | IF | 263.9 a | 0.08 a | 100 a | 0.3 a | 37.7 a | 34,704 |
| AMXT | – | – | 263.4 ab | 0.10 a | 100 a | 0.0 a | 38.1 a | 35,170 |
| GENSSRIB | – | – | 261.9 ab | 0.08 a | 100 a | 0.0 a | 38.2 a | 34,633 |
| GENSSRIB + Aztec HCe | 1.5 oz | IF | 257.0 abc | 0.08 a | 100 a | 0.2 a | 38.3 a | 34,055 |
| AMXT +Aztec HCe | 1.5 oz | IF | 255.4 abc | 0.17 a | 95 a | 0.0 a | 38.4 a | 33,784 |
| AMXT + Index 2.8CSd | 0.72 fl oz | IF | 252.2 abc | 0.10 a | 100 a | 0.1 a | 38.1 a | 34,683 |
| GENVT2PRIB + Aztec HCe | 1.5 oz | IF | 252.2 abc | 0.13 a | 95 a | 0.0 a | 35.2 b | 35,032 |
| GENVT2PRIB + Index 2.8CSd | 0.72 fl oz | IF | 250.7 abc | 0.89 b | 25 b | 0.6 a | 34.4 b | 34,939 |
| AMX + Index 2.8CSd | 0.72 fl oz | IF | 244.8 abc | 0.11 a | 95 a | 0.0 a | 35.3 b | 33,811 |
| AMX + Aztec HCe | 1.5 oz | IF | 243.1 bc | 0.25 a | 90 a | 0.0 a | 35.7 b | 34,297 |
| AMX | – | – | 240.2 cd | 0.16 a | 95 a | 0.0 a | 35.5 b | 35,058 |
| GENVT2PRIB (refuge) | – | – | 221.1 d | 1.07 b | 35 b | 3.1 b | 32.3 c | 34,820 |
| P | 0.0104 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | 0.3497 |
| Treatment/formulation . | Rate-amt form/1000 row ft . | Placement . | Yielda (bu/acre) . | Root injury ratinga . | % Consistency Iowa 0–3 scale ≤ 0.25a,b . | % Root lodginga . | ELHa (inches) . | PPAc . |
|---|---|---|---|---|---|---|---|---|
| GENSSRIB + Index 2.8CSd | 0.72 fl oz | IF | 263.9 a | 0.08 a | 100 a | 0.3 a | 37.7 a | 34,704 |
| AMXT | – | – | 263.4 ab | 0.10 a | 100 a | 0.0 a | 38.1 a | 35,170 |
| GENSSRIB | – | – | 261.9 ab | 0.08 a | 100 a | 0.0 a | 38.2 a | 34,633 |
| GENSSRIB + Aztec HCe | 1.5 oz | IF | 257.0 abc | 0.08 a | 100 a | 0.2 a | 38.3 a | 34,055 |
| AMXT +Aztec HCe | 1.5 oz | IF | 255.4 abc | 0.17 a | 95 a | 0.0 a | 38.4 a | 33,784 |
| AMXT + Index 2.8CSd | 0.72 fl oz | IF | 252.2 abc | 0.10 a | 100 a | 0.1 a | 38.1 a | 34,683 |
| GENVT2PRIB + Aztec HCe | 1.5 oz | IF | 252.2 abc | 0.13 a | 95 a | 0.0 a | 35.2 b | 35,032 |
| GENVT2PRIB + Index 2.8CSd | 0.72 fl oz | IF | 250.7 abc | 0.89 b | 25 b | 0.6 a | 34.4 b | 34,939 |
| AMX + Index 2.8CSd | 0.72 fl oz | IF | 244.8 abc | 0.11 a | 95 a | 0.0 a | 35.3 b | 33,811 |
| AMX + Aztec HCe | 1.5 oz | IF | 243.1 bc | 0.25 a | 90 a | 0.0 a | 35.7 b | 34,297 |
| AMX | – | – | 240.2 cd | 0.16 a | 95 a | 0.0 a | 35.5 b | 35,058 |
| GENVT2PRIB (refuge) | – | – | 221.1 d | 1.07 b | 35 b | 3.1 b | 32.3 c | 34,820 |
| P | 0.0104 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | 0.3497 |
aMeans in column followed by the same lowercase letter are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
bAverages are converted by the angular transformation of percentages to degrees, before MIXED, original percentages are reported.
cMeans in column are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
dLiquid insecticide applied in 5-gpa water solution at planting.
eGranular insecticide applied via SmartBox application system at planting.
| Treatment/formulation . | Rate-amt form/1000 row ft . | Placement . | Yielda (bu/acre) . | Root injury ratinga . | % Consistency Iowa 0–3 scale ≤ 0.25a,b . | % Root lodginga . | ELHa (inches) . | PPAc . |
|---|---|---|---|---|---|---|---|---|
| GENSSRIB + Index 2.8CSd | 0.72 fl oz | IF | 263.9 a | 0.08 a | 100 a | 0.3 a | 37.7 a | 34,704 |
| AMXT | – | – | 263.4 ab | 0.10 a | 100 a | 0.0 a | 38.1 a | 35,170 |
| GENSSRIB | – | – | 261.9 ab | 0.08 a | 100 a | 0.0 a | 38.2 a | 34,633 |
| GENSSRIB + Aztec HCe | 1.5 oz | IF | 257.0 abc | 0.08 a | 100 a | 0.2 a | 38.3 a | 34,055 |
| AMXT +Aztec HCe | 1.5 oz | IF | 255.4 abc | 0.17 a | 95 a | 0.0 a | 38.4 a | 33,784 |
| AMXT + Index 2.8CSd | 0.72 fl oz | IF | 252.2 abc | 0.10 a | 100 a | 0.1 a | 38.1 a | 34,683 |
| GENVT2PRIB + Aztec HCe | 1.5 oz | IF | 252.2 abc | 0.13 a | 95 a | 0.0 a | 35.2 b | 35,032 |
| GENVT2PRIB + Index 2.8CSd | 0.72 fl oz | IF | 250.7 abc | 0.89 b | 25 b | 0.6 a | 34.4 b | 34,939 |
| AMX + Index 2.8CSd | 0.72 fl oz | IF | 244.8 abc | 0.11 a | 95 a | 0.0 a | 35.3 b | 33,811 |
| AMX + Aztec HCe | 1.5 oz | IF | 243.1 bc | 0.25 a | 90 a | 0.0 a | 35.7 b | 34,297 |
| AMX | – | – | 240.2 cd | 0.16 a | 95 a | 0.0 a | 35.5 b | 35,058 |
| GENVT2PRIB (refuge) | – | – | 221.1 d | 1.07 b | 35 b | 3.1 b | 32.3 c | 34,820 |
| P | 0.0104 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | 0.3497 |
| Treatment/formulation . | Rate-amt form/1000 row ft . | Placement . | Yielda (bu/acre) . | Root injury ratinga . | % Consistency Iowa 0–3 scale ≤ 0.25a,b . | % Root lodginga . | ELHa (inches) . | PPAc . |
|---|---|---|---|---|---|---|---|---|
| GENSSRIB + Index 2.8CSd | 0.72 fl oz | IF | 263.9 a | 0.08 a | 100 a | 0.3 a | 37.7 a | 34,704 |
| AMXT | – | – | 263.4 ab | 0.10 a | 100 a | 0.0 a | 38.1 a | 35,170 |
| GENSSRIB | – | – | 261.9 ab | 0.08 a | 100 a | 0.0 a | 38.2 a | 34,633 |
| GENSSRIB + Aztec HCe | 1.5 oz | IF | 257.0 abc | 0.08 a | 100 a | 0.2 a | 38.3 a | 34,055 |
| AMXT +Aztec HCe | 1.5 oz | IF | 255.4 abc | 0.17 a | 95 a | 0.0 a | 38.4 a | 33,784 |
| AMXT + Index 2.8CSd | 0.72 fl oz | IF | 252.2 abc | 0.10 a | 100 a | 0.1 a | 38.1 a | 34,683 |
| GENVT2PRIB + Aztec HCe | 1.5 oz | IF | 252.2 abc | 0.13 a | 95 a | 0.0 a | 35.2 b | 35,032 |
| GENVT2PRIB + Index 2.8CSd | 0.72 fl oz | IF | 250.7 abc | 0.89 b | 25 b | 0.6 a | 34.4 b | 34,939 |
| AMX + Index 2.8CSd | 0.72 fl oz | IF | 244.8 abc | 0.11 a | 95 a | 0.0 a | 35.3 b | 33,811 |
| AMX + Aztec HCe | 1.5 oz | IF | 243.1 bc | 0.25 a | 90 a | 0.0 a | 35.7 b | 34,297 |
| AMX | – | – | 240.2 cd | 0.16 a | 95 a | 0.0 a | 35.5 b | 35,058 |
| GENVT2PRIB (refuge) | – | – | 221.1 d | 1.07 b | 35 b | 3.1 b | 32.3 c | 34,820 |
| P | 0.0104 | <0.0001 | <0.0001 | <0.0001 | <0.0001 | 0.3497 |
aMeans in column followed by the same lowercase letter are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
bAverages are converted by the angular transformation of percentages to degrees, before MIXED, original percentages are reported.
cMeans in column are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
dLiquid insecticide applied in 5-gpa water solution at planting.
eGranular insecticide applied via SmartBox application system at planting.
From planting (12 May) to larval feeding damage evaluation (13 Jul), rainfall totaled 7.00 inches and overhead irrigation, 2.56 inches. Mean root injury ratings (Iowa 0–3 scale) for the untreated GENVT2PRIB refuge corn hybrid averaged 1.07. With the exception of the GENVT2PRIB trait in combination with Index 2.8CS IF at planting, remaining trait packages and planting-time soil insecticide combinations significantly reduced root injury and enhanced % consistency performance levels (Iowa 0–3 scale ≤ 0.25) compared with the untreated GENVT2PRIB refuge. Application of a soil insecticide to the GENVT2PRIB trait package at planting significantly enhanced final grain yields compared with the untreated GENVT2PRIB refuge. Furthermore, application of a planting time soil insecticide to a single or dual rootworm-traited corn hybrid did not statistically improve final grain yields.
This research was supported by industry gifts of pesticide and research funding.
