2007 PMR REPORT #ECORSMI2 SECTION E: CEREAL, FORAGE CROPS, and OILSEEDS - Insects

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1 2007 PMR REPORT #ECORSMI2 SECTION E: CEREAL, FORAGE CROPS, and OILSEEDS - Insects CROP: PEST: Corn, Zea mays (L.), Maizex cvs. MZ55 and MZ-0RR Western corn rootworm, Diabrotica virgifera virgifera (LeConte) NAME AND AGENCY: SMITH J L and PHIBBS T R 2. University of Guelph, Ridgetown Campus, 20 Main St. E. Ridgetown, Ontario, N0P 2C0 Tel: ; Fax: ; jsmith@ridgetownc.uoguelph.ca 2 Tel: ; Fax: ; tphibbs@ridgetownc.uoguelph.ca TITLE: EVALUATION OF CORN SEED TREATMENTS FOR CONTROL OF WESTERN CORN ROOTWORM MATERIALS: MAXIM XL (fludioxonil + metalaxyl-m, g ai/l); DYNASTY 00 FS (azoxystrobin 00 g ai/l), CRUISER 5 FS (thiamethoxam, 5 g ai/l); PONCHO 600 FS (clothianidin, 600 g ai/l); FORCE.0 G (tefluthrin, % v/v). METHODS: Seed was treated on 7 May, 2007 in 500 g lots in individual plastic bags by applying a slurry of the material via syringe to each bag (all treatments diluted to a total volume of 4.75 ml/kg using water). The bag was inflated, and the seed was mixed for min to ensure thorough seed coverage. Seed weights were 275 and 265 g/000 seeds for MZ55 and MZ-0RR, respectively. At Ridgetown, ON, corn was planted on 5 May as third year corn. MZ-0RR was planted on 2 May at Wyoming, ON as second year corn. Trials at both locations were planted on clay loam soil in a RCBD with four replications. Plots were planted using a two-row cone-seeder at a rate of 8 seeds/m. Plots were 4 rows, 0.76 m wide and 0 and 6 m long at Ridgetown and Wyoming, respectively. FORCE G was applied in-furrow at planting using a Noble plot scale applicator. The trial at Wyoming was inoculated with corn rootworm eggs prior to planting using a two-row cultivator modified to apply a 4 cm band of eggs, 5 cm deep and 9 cm on each side of the corn row. Eggs were suspended uniformly in a 0.5% agar solution at a concentration of 20 eggs/ml and delivered through tubes from a holding tank at a rate of 2000 eggs/m by a ground driven metering pump (Demco model MP-466). Plots were fertilized and maintained according to provincial recommendations. Plant populations were recorded by counting all plants in the interior two rows of each plot. Vigour of the entire plot was assessed using a scale of 0-00% (00 = furthest developed plants and 0 = dead plants). Plant height and fresh weight assessments were conducted on ten plants from the outer rows of each plot. Six plants per plot were carefully dug from the outside two rows to maintain the entire root mass and were thoroughly washed to assess corn rootworm feeding injury using the Iowa State Node- Injury scale where 0.00 = no damage and.00 = or more nodes pruned to within.8 cm (Oleson, J.D. et al. 2005). The interior two rows of each plot were harvested to obtain yield and test weight measurements and all yields were corrected to 5.5% moisture. Data were analysed by analysis of variance in SAS v. 9. (SAS Institute, Cary, NC) using PROC MIXED and means were separated using Fisher s least significant difference test at P Tukey s HSD test was used for multiple treatment comparisons. OBSERVATIONS: At the Wyoming location, inoculation of western corn rootworm eggs was successful and adult populations were very high (approx beetles/plant) in July and August, causing severe silk clipping and reduced pollination. Following planting at Wyoming, wet conditions caused the soil to crust

2 (26 May to 8 June: 8 mm total precipitation) resulting in difficult plant emergence, and for the remainder of the growing season, drought conditions were experienced with very little rainfall; 6.8 mm total rainfall from 2 May to 0 October. At Ridgetown, western corn rootworm adult populations were also high in July and August (approx beetles/plant). RESULTS: At both trial locations, no differences were detected among treatments in plant population (Tables, 2). Vigour was unaffected by treatments at Ridgetown (Table ). At Wyoming, vigour at the V stage was highest in Force.0 G treated plots and lowest in plots treated with Cruiser 5 FS at a rate of mg ai/seed, but differences were not observed on subsequent sampling dates (Table 2). Height and fresh weight of plants was not different among treatments at the V8 stage at Ridgetown (Table ). At the R stage, plots treated with Cruiser (0.625 g ai/00 were significantly taller than those treated with Poncho 600 FS (.25 mg ai/seed); fresh weight is not reported due to missing data points (Table ). No differences were measured in plant height and fresh weight at the Wyoming location (Table 4). Feeding injury by corn rootworm was significantly decreased by all insecticide treatments at Ridgetown (Table ). The least amount of injury was rated consistently on plants treated with the high rate of Cruiser (2.5 mg ai/seed) followed by Poncho (Table ). Similar levels of damage were observed on Force and Cruiser (.25 mg ai/seed) treated plants, but protection by Force was more consistent (Table ). At Wyoming, rootworm feeding injury ratings averaged higher than at Ridgetown and treatment performance was not as consistent (Table 4). Plots treated with Cruiser (2.5 mg ai/seed) had the least amount of injury followed closely by Poncho (Table 4). Again, Cruiser (.25 mg ai/seed) and Forcetreated plots had similar levels of feeding damage (Table 4). No differences in test weight were detected among any treatment (Table 5). No statistical differences existed among treatments in yield at either location (Table 5). At the Wyoming location, the high rate seed treatments of Cruiser (2.5 mg ai/seed) and Poncho produced numerically higher yields, followed by Force, but all plots yielded poorly (Table 5). CONCLUSIONS: No consistent significant differences were measured in plant population and vigour among treatments. All insecticide treatments provided some root protection from injury by western corn rootworm under high population pressure. The high rate of Cruiser 5 FS (2.5 mg ai/seed) provided the greatest protection from root injury. Force.0 G and Cruiser (.25 mg ai/seed) had similar levels of root injury. Low rates of Cruiser (0.25 and 0.625) did not provide root protection. Only Cruiser (2.5 mg ai/seed) had a root injury rating less than 0.25 at Blenheim, ON; this is the level considered to provide very good root protection (Rice et al., 2007) REFERENCES: Rice, M.E., J.D. Oleson, and J. J. Tollefson Evaluation of corn rootworm hybrids. Integrated Crop Management. Iowa State University. December 0, 2007: Oleson, J.D., Y.L. Park, T.M. Nowatzki, and J.J. Tollefson Node-injury scale to evaluate root injury by corn rootworms (Coleoptera: Chrysomelidae). J. Econ. Entomol. 98(): -8. ACKNOWLEDGEMENTS: Thanks to Weather Innovations Network (WIN) for providing precipitation data for the Wyoming location. Table. Mean plant population and vigour of corn with seed and in-furrow applied insecticides

3 for corn rootworm control in a continuous corn rotation at Ridgetown, Ontario in (g ai/00 Mean Plant Population (# plants/m 2 ) Mean Plant Vigour (0-00%) 29 May (VE) June 29 May (VE) June Untreated Check a a 4.4 a 85.0 a 92.5 a 78.8 a.0.7 a 4.2 a 4. a 79.5 a 85.0 a 80.0 a.0.7 a 4.0 a 4.0 a 87.5 a 88.8 a 8.8 a.0.7 a 4. a 4.2 a 88.8 a 90.0 a 78.8 a a.8 a 4.0 a 82.5 a 8.8 a 7. a.0.8 a 4.0 a.9 a 87.5 a 87.5 a 75.0 a a 4.4 a 4.4 a 82.5 a 96. a 8.8 a a 4.2 a 4. a 88.8 a 92.5 a 88.8 a SEM g per 00 m length of row applied in-furrow at planting. 0 = plants dead in plot and 00 = furthest developed plants in the trial.. 4 Means followed by the same letter do not significantly differ (P 0.05, LSD) as determined by ANOVA and Fisher s Protected LSD.

4 Table 2. Mean plant population and vigour of corn with seed and in-furrow applied insecticides for corn rootworm control in second year corn at Wyoming, Ontario in (g ai/00 Mean Plant Population (# plants/m 2 ) Mean Plant Vigour (0-00%) (V) June (V2) 9 June (V) June (V2) 9 June Untreated Check a a 4.6 a 87.5 ab 77.5 a 8.8 a.0 4. a 4.7 a 4.7 a 80.0 ab 77.5 a 78.8 a.0 4. a 4.7 a 4.8 a 80.0 ab 80.0 a 78.8 a.0.9 a 4.6 a 4.7 a 72.5 b 70.0 a 78.8 a a 4.8 a 4.9 a 82.5 ab 78.8 a 8. a.0 4. a 4.5 a 4.7 a 82.5 ab 75.0 a 80.0 a a 4.8 a 5.0 a 82.5 ab 70.0 a 8.8 a a 4.9 a 5.0 a 90.0 a 80.0 a 85.0 a SEM g per 00 m length of row applied in-furrow at planting. 0 = plants dead in plot and 00 = furthest developed plants in the trial. 4 Means followed by the same letter do not significantly differ (P 0.05, LSD) as determined by ANOVA and Tukey s LSD test.

5 Table. Mean plant height, fresh weight, corn rootworm injury, and product performance consistency of seed and in-furrow applied insecticides for corn rootworm control in a continuous corn rotation at Ridgetown, Ontario in (g ai/00 Mean Plant Height (cm) Mean Fresh Weight (kg) 2 (V8) Mean Node- Injury Product Consistency July 20 July (R) (V8) (R) Untreated Check a 5 4 ab 0.77 a.42 c 2.5 ab 8.4 a 49. ab 0.88 a.6 bc 0.0 b a 57.5 ab 0.95 a 0.56 ab. ab a 60.9 a.00 a 0.68 ab 25.0 ab a 55. ab 0.85 a 0.2 a 46.0 ab.0 8. a 52.2 ab 0.82 a 0.2 a 66.8 a a 8. b 0.78 a 0.0 a 62.5 a a 50.8 ab 0.80 a 0.4 a 62.5 a SEM g per 00 m length of row applied in-furrow at planting. Iowa State Node-Injury Scale ( ). 4 Percentage of times node-injury rating was Means followed by the same letter do not significantly differ (P 0.05, LSD) as determined by ANOVA and Tukey s HSD test.

6 Table 4. Mean plant height, fresh weight, corn rootworm injury, and product performance consistency of seed and in-furrow applied insecticides for corn rootworm control in second year corn at Wyoming, Ontario in (g ai/00 Mean Plant Height (cm) Mean Fresh Weight (kg) Mean Node- Injury Product Consistency 4 6 July August 6 July August (R) (R) August (R) Untreated Check a a 0.65 a.47 a.49 a 0.0 b a 2.8 a 0.58 a.56 a.70 a 0.0 b a a 0.55 a.4 a.29 ab 2.5 ab a 5.4 a 0.7 a.49 a 0.84 ab 8.5 ab a 24. a 0.85 a.88 a 0.78 ab 2.5 ab a 27.2 a 0.88 a.85 a 0.45 b. ab a 7. a 0.7 a.55 a 0.45 b 46.0 a a 9.4 a 0.68 a.6 a 0.80 ab 8. ab SEM g per 00 m length of row applied in-furrow at planting. Iowa State Node-Injury Scale ( ). 4 Percentage of times node-injury rating was Means followed by the same letter do not significantly differ (P 0.05, LSD) as determined by ANOVA and Tukey s HSD test.

7 Table 5. Mean test weight and yield of corn with seed and in-furrow applied insecticides for corn rootworm control in continuous corn at Ridgetown and Wyoming, Ontario in (g ai/00 kg seed) Mean Test Weight (kg/hl) Ridgetown 9 October Mean Yield (T/ha) Mean Test Weight (kg/hl) Wyoming October Mean Yield (T/ha) Untreated Check a 6. a 0.5 a.74 a a 6.27 a 0.6 a.40 a a 7.8 a 0.6 a.90 a a 8.2 a 0.6 a 2.05 a a 6.44 a 0.6 a 2.2 a a 7.90 a 0.6 a.66 a a 5.9 a 0.5 a 2.99 a a 7.2 a 0.5 a.70 a SEM g per 00 m length of row applied in-furrow at planting. Means followed by the same letter do not significantly differ (P 0.05, LSD) as determined by ANOVA and Fisher s Protected LSD.