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Terry A DeVries, Robert J Wright, Evaluation of Liquid and Granular Insecticide Formulations at Planting for Larval Corn Rootworm Control, 2017A, Arthropod Management Tests, Volume 43, Issue 1, 2018, tsy036, https://doi.org/10.1093/amt/tsy036
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The western corn rootworm is the most important insect pest of continuous corn in the western U.S. Corn Belt. Increasing incidence of resistance to Bt rootworm corn hybrids has led to increased interest in using planting time insecticides for corn rootworm control. Liquid and granular insecticide formulations applied at planting 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 × 67–78 ft length with 30-inch row spacing. Soil type was a Crete silt loam. ‘DeKalb DKC60-69RIB’ (contains GENVT2PRIB [Genuity VT Double Pro] insect and herbicide traits) corn hybrid was planted on 19 Apr with a 2-row JD 7100 Maximerge planter with finger pickup seed units. The corn hybrid received a seed-applied insecticide treatment of Poncho 250 (clothianidin at 0.25 mg AI/kernel). A southwest wind at 10–15 mph occurred at planting. Liquid insecticide formulations were applied IF in a 5-gpa water solution via compressed air system. Granular insecticide formulations were applied IF via SmartBox application system. 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 19 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 30 Jun and converted to percentage root lodging. Larval feeding damage was evaluated on 10 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 = 3 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 ratingb . | % Consistency Iowa 0–3 scale ≤0.25b,c . | % Root lodgingb . | ELHa (inches) . | PPAa . |
|---|---|---|---|---|---|---|---|---|
| Index 2.8CSd | 0.72 fl oz | IF | 266.3 | 1.16 bc | 30 a | 2.5 a | 39.1 | 34,699 |
| Capture LFRd | 0.98 fl oz | IF | 258.3 | 1.28 c | 25 ab | 10.9 a | 38.1 | 34,672 |
| Force 10Ge | 1.30 oz | IF | 257.7 | 0.68 ab | 30 a | 0.8 a | 37.0 | 34,696 |
| Force CSd | 0.50 fl oz | IF | 253.5 | 0.74 ab | 20 ab | 0.6 a | 39.6 | 33,916 |
| Aztec HCe | 1.50 oz | IF | 253.1 | 0.57 a | 50 a | 4.6 a | 39.9 | 34,888 |
| SmartChoice HCe | 1.70 oz | IF | 252.7 | 1.47 c | 5 b | 16.1 a | 33.4 | 34,937 |
| Untreated check | – | – | 247.7 | 2.00 d | 5 b | 53.1 b | 37.1 | 34,621 |
| P | 0.1106 | 0.0001 | 0.0410 | <0.0001 | 0.0911 | 0.8258 |
| Treatment/formulation . | Rate-amt form/1000 row ft . | Placement . | Yielda (bu/acre) . | Root injury ratingb . | % Consistency Iowa 0–3 scale ≤0.25b,c . | % Root lodgingb . | ELHa (inches) . | PPAa . |
|---|---|---|---|---|---|---|---|---|
| Index 2.8CSd | 0.72 fl oz | IF | 266.3 | 1.16 bc | 30 a | 2.5 a | 39.1 | 34,699 |
| Capture LFRd | 0.98 fl oz | IF | 258.3 | 1.28 c | 25 ab | 10.9 a | 38.1 | 34,672 |
| Force 10Ge | 1.30 oz | IF | 257.7 | 0.68 ab | 30 a | 0.8 a | 37.0 | 34,696 |
| Force CSd | 0.50 fl oz | IF | 253.5 | 0.74 ab | 20 ab | 0.6 a | 39.6 | 33,916 |
| Aztec HCe | 1.50 oz | IF | 253.1 | 0.57 a | 50 a | 4.6 a | 39.9 | 34,888 |
| SmartChoice HCe | 1.70 oz | IF | 252.7 | 1.47 c | 5 b | 16.1 a | 33.4 | 34,937 |
| Untreated check | – | – | 247.7 | 2.00 d | 5 b | 53.1 b | 37.1 | 34,621 |
| P | 0.1106 | 0.0001 | 0.0410 | <0.0001 | 0.0911 | 0.8258 |
aMeans in column are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
bMeans in column followed by the same lowercase letter are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
cAverages were converted by the angular transformation of percentages to degrees, before MIXED, original percentages are reported.
dLiquid insecticide applied in a 5-gpa water solution at planting.
eGranular insecticide applied with SmartBox application system at planting.
| Treatment/formulation . | Rate-amt form/1000 row ft . | Placement . | Yielda (bu/acre) . | Root injury ratingb . | % Consistency Iowa 0–3 scale ≤0.25b,c . | % Root lodgingb . | ELHa (inches) . | PPAa . |
|---|---|---|---|---|---|---|---|---|
| Index 2.8CSd | 0.72 fl oz | IF | 266.3 | 1.16 bc | 30 a | 2.5 a | 39.1 | 34,699 |
| Capture LFRd | 0.98 fl oz | IF | 258.3 | 1.28 c | 25 ab | 10.9 a | 38.1 | 34,672 |
| Force 10Ge | 1.30 oz | IF | 257.7 | 0.68 ab | 30 a | 0.8 a | 37.0 | 34,696 |
| Force CSd | 0.50 fl oz | IF | 253.5 | 0.74 ab | 20 ab | 0.6 a | 39.6 | 33,916 |
| Aztec HCe | 1.50 oz | IF | 253.1 | 0.57 a | 50 a | 4.6 a | 39.9 | 34,888 |
| SmartChoice HCe | 1.70 oz | IF | 252.7 | 1.47 c | 5 b | 16.1 a | 33.4 | 34,937 |
| Untreated check | – | – | 247.7 | 2.00 d | 5 b | 53.1 b | 37.1 | 34,621 |
| P | 0.1106 | 0.0001 | 0.0410 | <0.0001 | 0.0911 | 0.8258 |
| Treatment/formulation . | Rate-amt form/1000 row ft . | Placement . | Yielda (bu/acre) . | Root injury ratingb . | % Consistency Iowa 0–3 scale ≤0.25b,c . | % Root lodgingb . | ELHa (inches) . | PPAa . |
|---|---|---|---|---|---|---|---|---|
| Index 2.8CSd | 0.72 fl oz | IF | 266.3 | 1.16 bc | 30 a | 2.5 a | 39.1 | 34,699 |
| Capture LFRd | 0.98 fl oz | IF | 258.3 | 1.28 c | 25 ab | 10.9 a | 38.1 | 34,672 |
| Force 10Ge | 1.30 oz | IF | 257.7 | 0.68 ab | 30 a | 0.8 a | 37.0 | 34,696 |
| Force CSd | 0.50 fl oz | IF | 253.5 | 0.74 ab | 20 ab | 0.6 a | 39.6 | 33,916 |
| Aztec HCe | 1.50 oz | IF | 253.1 | 0.57 a | 50 a | 4.6 a | 39.9 | 34,888 |
| SmartChoice HCe | 1.70 oz | IF | 252.7 | 1.47 c | 5 b | 16.1 a | 33.4 | 34,937 |
| Untreated check | – | – | 247.7 | 2.00 d | 5 b | 53.1 b | 37.1 | 34,621 |
| P | 0.1106 | 0.0001 | 0.0410 | <0.0001 | 0.0911 | 0.8258 |
aMeans in column are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
bMeans in column followed by the same lowercase letter are not statistically different using the differences of least square means (MIXED; p|t| > 0.05).
cAverages were converted by the angular transformation of percentages to degrees, before MIXED, original percentages are reported.
dLiquid insecticide applied in a 5-gpa water solution at planting.
eGranular insecticide applied with SmartBox application system at planting.
From planting (19 Apr) to larval feeding damage evaluation (10 Jul), rainfall totaled 9.42 inches and overhead irrigation, 2.56 inches. Mean root injury ratings (Iowa 0–3 scale) for the untreated check averaged 2.00. All insecticide formulations significantly reduced larval WCR root injury ratings and early season root lodging percentages compared with the untreated check. Furthermore, Aztec HC, Force 10G, and Force CS provided significantly more reduction in larval CRW injury versus Capture LFR and SmartChoice HC formulations based on average root injury ratings (Iowa 0–3 scale). However, differences in harvested grain-yield levels were not significant.
This research was supported by industry gifts of pesticide and research funding.
