Insect Management & Insecticide Evaluations, Illinois 1998
Field, Forage, & Vegetable Crops

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Trials to determine the efficacy of registered and experimental soil insecticides for control of corn rootworm larvae were conducted at DeKalb, Monmouth, and Urbana in 1998. In untreated control plots at these locations, the average root ratings were 2.22, 2.85, and 2.10, respectively. Negligible differences in root ratings were observed among treatments at all three locations. Yields and plant heights were significantly greater for all treatments compared with the control at the Urbana location. The average yield in the control was numerically less than all other treatments at the DeKalb location.

Plot Information and Methods

Locations	Corn rootworm insecticide trials were established at the following locations: Northern Illinois Agronomy Research Center, DeKalb, Illinois Northwestern Illinois Agricultural Research and Demonstration Center, Monmouth, Illinois University of Illinois, Crop Sciences Research & Education Center, Field 200 SW, Urbana, Illinois
Plot Size	Each treatment was applied to two rows 100 feet long at Monmouth, and two rows 50 feet long at Urbana and DeKalb with 20 feet wide alleys between all replications.
Experimental Design	A randomized complete block with four replications was utilized as the experimental design at Monmouth and DeKalb. Six replications were used at Urbana. Included within each replication at all three locations were two untreated control plots. Data collected from the untreated control plots were averaged for the ANOVA.
Planting Date and Agronomic Factors	See Table 5.1.
Pre-Treatment Population	All locations were planted (1997) as trap crops (late planted corn and pumpkins) in an effort to enhance rootworm oviposition and increase larval densities in 1998.
Method of Application for Granules at Planting Time	Granular insecticides applied at planting were metered through computer controlled SmartBox (SBX) granular applicators or Noble® units mounted on each row of an ALMACO® four-row precision planter and applied in-furrow or in a 7-inch band ahead of the firming wheels on the planter. Spring tines mounted behind each planter unit were used to incorporate the insecticide. All rates are specified as lb (AI)/acre based on 30-inch row spacing.
Method of Application for Liquids at Planting Time	At Monmouth and DeKalb, liquid applications of Regent 80WG and Regent 4SC were delivered in-furrow at planting through microtubes calibrated to deliver 1.6 gpa at 20 psi at a speed of 3.0 mph. Lorsban 4E was applied at all three locations in a band at-planting with a single 80067 nozzle calibrated to deliver 3.3 gpa at 18 psi at 3.0 mph. Nufos 4E was applied at Urbana in the same manner.
Stand Counts	Stand count data (Table 5.2) were determined by recording the number of plants per 0.001 acre (17.4 linear feet of row).
Phytotoxicity	There were no indications of phytotoxicity at any of the three locations.
Other Observations	No major problems were observed with any of the treatments regarding handling or calibration. However, Pilot 15G had a tendency to clump when left in the Noble® units for more than 24 hours.
Post-Treatment Evaluation of Rootworm Injury	Five plants per treatment per replication were dug, washed, and evaluated for rootworm injury. The root-rating system used was the Iowa State University root-rating scale described by Hills and Peters (1971): No visible damage or only a few minor feeding scars Some roots with feeding scars but none eaten off to within 1.5 inches of the plant Several roots eaten off to within 1.5 inches of the plant but never the equivalent of an entire node of roots destroyed One node of roots destroyed or the equivalent Two nodes of roots destroyed or the equivalent Three or more nodes of roots destroyed The consistency ratings were based upon the percentage of the total number of roots examined for each treatment that had root ratings less than 4.0.
Plant Heights	Urbana: The total plant height taken from the plant base to the extended tassel was measured in inches on August 6 (Table 5.5).
Yield	Urbana: Hand-harvested yields were determined for the Urbana location from shelled grain weights taken from 0.001 acre in each of two rows for a total of 0.002 acres in each treatment by replicate combination and corrected to 15.5% moisture. DeKalb: Machine harvested yields (corrected to 15% moisture) were taken on October 28 utilizing both rows of the two-row plots (Table 5.6).
Weather Information	See Appendix A: Table A.2, Table A.3, Table A.4 and Table A.5 for Urbana Table A.7, Table A.8, Table A.9 and Table A.10 for DeKalb Table A.11, Table A.12 and Table A.13 for Monmouth
Soil Information	See Appendix B
Statistical Analysis	Data were analyzed with the Pesticide Research Manager version 5.0.22, from Gylling Data Management, Inc.(GDM).
Results and Discussion	The 1998 growing season proved to be another atypical year for all experimental locations in Illinois. The cool wet spring conditions held soil temperatures well below normal for all three locations and had an adverse effect on corn rootworm larval survival. Larvae were observed feeding in the control plots and injured plants were beginning to show signs of stress. From planting to root evaluations, 14.87, 5.99 and 7.19 inches of rain fell at the Urbana, Monmouth and DeKalb locations respectively. We believe the saturated soil conditions had a very detrimental effect on larval survival. Although early-season root injury was apparent in the control plots, standard root rating scores made in July did not reflect this fact. DeKalb The mean root rating in the control was 2.22 (Table 5.3). Only Force 3G banded at 0.13 lb(AI)/acre and Lorsban 15G banded at 1.3 lb(AI)/acre differed significantly from the control. There were no significant differences among any of the insecticide treatments. All insecticide treatments had consistency ratings of 100% as compared with 93% for the control (Table 5.4). Monmouth The mean root rating in the control plots was 2.85 (Table 5.3). All treatments except for Lorsban 4E banded at 1.3 lb(AI)/acre and Thimet 20G banded at 1.3 lb(AI)/acre had significantly less root injury than the control. Also, consistency ratings were 100% for all insecticides except for these two treatments (Table 5.4). Urbana The mean root rating in the control was 2.10 (Table 5.3). No significant differences in root injury were observed among the treatments. Consistency ratings for all treatments including the control were greater than 90% (Table 5.4). Because of the very noticeable differences in plant heights between the control and the insecticide treatments, total plant lengths were measured on August 6 (Table 5.5). Plant heights and yield were significantly greater for all insecticide treatments compared with the control (Table 5.5).
References Cited	Hills, T.M., and D.C. Peters. 1971. A method of evaluating post-plant insecticide treatments for control of western corn rootworm larvae. J. Econ Entomol. 64: 764-765.

Table 5.1: Agronomic factors and evaluation dates at three locations to test corn rootworm soil insecticides, Illinois, 1998

Variables	DeKalb	Monmouth	Urbana
Planting date	May 14	May 13	May 19
Hybrid	Pioneer hybrid 3489	Pioneer hybrid 3489	Pioneer hybrid 3489
Plant population	28,500 seeds per acre	28,500 seeds per acre	28,500 seeds per acre
Row spacing	30 inches	30 inches	30 inches
Soil condition (top 2-3 inches)	moist	moist	dry
Soil temperature (4-inch level)	76° F	76° F	90° F
Air temperature	80° F	84° F	92° F
Wind	20-30 mph	0-5 mph	3-6 mph
Previous crop	trap crop - corn + pumpkins (97)	trap crop - corn + pumpkins (97)	trap crop - corn + pumpkins (97)
Soil insecticides	none (97)	none (97)	none (97)
Herbicides	Harness extra, Clarity	Lasso MT, Aatrex, Tandem	Guardsman
Fertilizer	N 190 lb/acre urea	N 160 lb/acre anhydrous	N 180 lb/acre 28%
Fall tillage	chisel	ripper	ripper (once) chisel (once)
Spring tillage	mulch finisher (twice)	field cultivator	field finisher (once)
Cultivation date	June 5	June 1	June 23
Evaluation dates Stand counts Root ratings Plant height Yield	June 24 July 13 --- October 28	June 24 July 22 --- ---	June 25 July 20 August 6 October 20

Table 5.2 Mean stand counts for corn rootworm soil insecticides at three locations, Illinois, 1998

Treatment	Rate1	Placement2	DeKalb stand count3,4	Monmouth stand count3,5	Urbana stand count3,5
Aztec 2.1G	0.15	band	21.67 b	23.25	26.75
Aztec 2.1G	0.15	furrow	23.67 ab	26.25	25.25
Aztec 4.7G-C	0.15	band-SBX	---	---	26.25
Aztec 4.7G-B	0.15	band-SBX	---	---	26.00
Counter 20CR	1.3	band	25.33 ab	24.00	26.25
Counter 20CR	1.3	furrow	26.33 a	26.00	26.25
Force 3G	0.13	band	25.33 ab	24.50	25.75
Fortress 5G	0.16	furrow-SBX	24.33 ab	25.50	25.50
Lorsban 15G	1.3	band	23.33 ab	25.00	26.50
Lorsban 4E	1.3	band	23.67 ab	26.25	25.00
Pilot 15G	1.3	band	23.00 ab	26.00	25.75
Regent 4SC	0.13	microtube-furrow	22.67 ab	23.50	---
Regent 80WG	0.13	microtube-furrow	23.67 ab	25.00	---
Thimet 20G	1.3	band	27.00 a	26.75	26.00
Control			25.50 ab	27.50	25.50
1 All rates are specified as lb (AI)/acre, based on 30-inch row spacing. 2 All treatments were applied at planting, May 14 for DeKalb, May 13 for Monmouth and May 19 for Urbana. 3 Stand counts are based on the number of plants per 0.001 acres (17.4 linear feet of row). Counts were made on June 24 for DeKalb and Monmouth and on June 25 for Urbana. 4 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 5 Means were not significantly different (P=0.05).

Table 5.3 Mean root ratings for corn rootworm soil insecticides at three locations, Illinois, 1998

Treatment	Rate1	Placement2	DeKalb root ratings3	Monmouth root ratings3	Urbana root ratings4
Aztec 2.1G	0.15	band	2.00 ab	2.00 c	2.00
Aztec 2.1G	0.15	furrow	2.00 ab	2.00 c	2.09
Aztec 4.7G-C	0.15	band-SBX	---	---	1.93
Aztec 4.7G-B	0.15	band-SBX	---	---	1.70
Counter 20CR	1.3	band	2.05 ab	1.95 c	1.93
Counter 20CR	1.3	furrow	2.15 ab	1.95 c	2.00
Force 3G	0.13	band	1.90 b	1.95 c	1.73
Fortress 5G	0.16	furrow-SBX	2.00 ab	2.10 bc	1.93
Lorsban 15G	1.3	band	1.88 b	2.10 bc	1.87
Lorsban 4E	1.3	band	2.15 ab	2.70 ab	2.00
Nufos 4E	1.3	band	---	---	1.73
Pilot 15G	1.3	band	2.05 ab	2.20 bc	1.97
Regent 4SC	0.13	microtube-furrow	2.08 ab	2.05 bc	---
Regent 80WG	0.13	microtube-furrow	2.05 ab	2.08 bc	---
Thimet 20G	1.3	band	2.10 ab	2.55 abc	1.64
Control			2.22 a	2.85 a	2.10
1 All rates are specified as lb (AI)/acre, based on 30-inch row spacing. 2 All treatments were applied at planting, May 14 for DeKalb, May 13 for Monmouth, and May 19 for Urbana. 3 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 4 Means were not significantly different (P=0.05).

Table 5.4 Mean consistency ratings for corn rootworm soil insecticides at three locations, Illinois, 1998

Treatment	Rate1	Placement2	DeKalb consistency ratings3	Monmouth consistency ratings3	Urbana consistency ratings3
Aztec 2.1G	0.15	band	100	100	93
Aztec 2.1G	0.15	furrow	100	100	90
Aztec 4.7G-C	0.15	band-SBX	---	---	100
Aztec 4.7G-B	0.15	band-SBX	---	---	100
Counter 20CR	1.3	band	100	100	100
Counter 20CR	1.3	furrow	100	100	97
Force 3G	0.13	band	100	100	100
Fortress 5G	0.16	furrow-SBX	100	100	100
Lorsban 15G	1.3	band	100	100	100
Lorsban 4E	1.3	band	100	75	100
Nufos 4E	1.3	band	---	---	100
Pilot 15G	1.3	band	100	100	100
Regent 4SC	0.13	microtube-furrow	100	100	---
Regent 80WG	0.13	microtube-furrow	100	100	---
Thimet 20G	1.3	band	100	85	100
Control			93	80	97
1 All rates are specified as lb (AI)/acre, based on 30-inch row spacing. 2 All treatments were applied at planting, May 14 for DeKalb, May 13 for Monmouth, and May 19 for Urbana. 3 Consistency rating is the percentage of the total number of roots examined with a root rating less than 4.0.

Table 5.5 Mean plant heights and yields for corn rootworm soil insecticides, Urbana, Illinois, 1998

Treatment	Rate1	Placement2	Plant heights3,4	Yield bu/acre3,5
Aztec 2.1G	0.15	band	94.50 bc	142.3 cd
Aztec 2.1G	0.15	furrow	93.53 bc	129.6 bc
Aztec 4.7G-C	0.15	band-SBX	91.27 bc	147.4 cd
Aztec 4.7G-B	0.15	band-SBX	93.04 bc	156.5 d
Counter 20CR	1.3	band	90.77 b	148.3 cd
Counter 20CR	1.3	furrow	92.53 bc	151.9 cd
Force 3G	0.13	band	93.87 bc	147.1 cd
Fortress 5G	0.16	furrow-SBX	92.63 bc	143.8 cd
Lorsban 15G	1.3	band	93.90 bc	150.3 cd
Lorsban 4E	1.3	band	90.12 b	118.0 b
Nufos 4E	1.3	band	93.13 bc	152.4 cd
Pilot 15G	1.3	band	94.18 bc	142.1 cd
Thimet 20G	1.3	band	96.52 c	165.4 d
Control			83.87 a	84.0 a
1 All rates are specified as lb (AI)/acre, based on 30-inch row spacing. 2 All treatments were applied at planting, May 19 for Urbana. 3 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 4 The plant height (inches) was taken from the soil surface to the base of the tassel node on August 6. 5 Hand-harvest yields were determined from shelled grain weights (converted to 15.5% moisture) taken from 0.002 acre in each two-row plot.

Table 5.6 Mean plant yields for corn rootworm soil insecticide evaluations, DeKalb, Illinois, 1998

Treatment	Rate1	Placement2	Yield bu/acre3,4
Aztec 2.1G	0.15	band	157.89 cde
Aztec 2.1G	0.15	furrow	155.90 cde
Counter 20CR	1.3	band	181.21 ab
Counter 20CR	1.3	furrow	178.39 abc
Force 3G	0.13	band	195.86 a
Fortress 5G	0.16	furrow-SBX	189.30 a
Lorsban 15G	1.3	band	160.84 b-e
Lorsban 4E	1.3	band	155.67 cde
Nufos 4E	1.3	band	147.04 de
Pilot 15G	1.3	band	165.89 bcd
Regent 4SC	0.13	microtube-furrow	164.69 b-e
Regent 80WG	0.13	microtube-furrow	161.36 b-e
Thimet 20G	1.3	band	160.49 b-e
Control			142.42 e
1 All rates are specified as lb (AI)/acre, based on 30-inch row spacing. 2 All treatments were applied at planting, May 14 for DeKalb. 3 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 4 DeKalb yields were determined by machine harvesting both treated rows 50 feet long (converted to 15.5% moisture).

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