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

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A trial was established at the University of Illinois, Champaign, to compare the effectiveness of different Bt-corn hybrids with non-Bt corn hybrids and two standard chemical treatments for control of European corn borer (ECB). The non-Bt hybrids had 65 to 75% of the plants with ECB tunneling. The Bt hybrids had significantly fewer plants with cavities and fewer centimeters of tunneling per plant than non-Bt hybrids. Some statistical differences in percentages of plants damaged and ear and shank damage were apparent among Bt hybrids.

Plot Information and Methods

Locations	University of Illinois Cruse Farm, Champaign, Illinois.
Plot Size	Each plot consisted of four rows by 25 feet long with 40 plants per row after thinning. There were 10-foot-wide alleys between each of the six replications.
Experimental Design	A randomized complete block design with six replications. Two chemically treated plots and three untreated non-Bt plots were included in each replication.
Planting Date and Agronomic Factors	See Table 12.1.
Weather Information	See Appendix A, Table A.2, Table A.3, Table A.4, Table A.5 and Table A.6.
Manual Corn Borer Infestation	Manual infestations of European corn borer (ECB) were made to 20 consecutive plants in each of the middle two rows of each four-row plot. Manual infestations to simulate the first-generation were made on July 9 and10 when corn plants were in the V6 leaf stage (Ritchie et al. 1993). Two ECB egg masses (black-head stage) were dropped into the whorls of each corn plant on each of the two days. Manual infestations to simulate the second-generation were made to the same 40 plants at corn anthesis (V18 - VT corn stage, Ritchie et al. 1993) on August 13. Two ECB egg masses were placed in the first leaf axil above and below the ear node. On August 14, these same plants received two more ECB egg masses in the primary ear node leaf axil.
Method of Insecticide Application	Insecticides were applied to the appropriate plots with a modified John Deere 6000 high-clearance vehicle (HCV). Liquid insecticides were applied on July 15 and again on August 18, with two 8003 TeeJet flat fan nozzles (one per row), in a band over the row, with a compressed-air system calibrated to deliver 9.8 gpa at 20 psi and a speed of 2.5 mph. On July 15, the height of the nozzles above the whorls was 8 to 10 inches; on August 18, the height of the nozzles above the tassels was 10 to 12 inches.
Post-Infestation Evaluations of Injury Caused by First-and Second-Generation ECB	On September 17 and 18, five corn plants from each of the middle two rows were split with a corn knife for evaluation. The numbers of cavities per plants and the total length of cavities per plant were recorded. The numbers of live larvae per plant, ear, and shank also were recorded. Damage to the ear and shank were recorded separately. The mean percentages of plants with cavities, the mean lengths of stalk tunneling (cm) per plant, and the mean numbers of cavities per plant were determined for each plot. ECB damage to the ear and shank were analyzed separately from the stalk damage data.
Harvest	Hand-harvested yields were determined from the shelled grain weights taken from the ears of all 40 manually infested plants (including the ten dissected plants) and corrected to 15.5% moisture. The number of poorly developed ears and the percentage moisture were recorded for all plots at harvest. An ear was considered to be poorly developed if the ear length was shorter than 12 cm (4.5 in) long or there were only a few kernels on the ear. Yields were not statically analyzed.
Statistical Analysis	Data were analyzed with the Pesticide Research Manager, version 5.0.22, from Gylling Data Management, Inc. (GDM). Means were separated by Duncan's New Multiple Range Test (MRT) (P=0.05).
Results and Discussion	Agronomic factors, treatment dates, and evaluation dates for the Bt-corn trial are shown in Table 12.1. The hybrids planted in the trial are presented in Table 12.2, along with the days to relative maturity for each hybrid and the crystalline protein form of the Bt-corn hybrids. All plots were examined periodically throughout the growing season for signs of infestation and/or damage caused by insects other than ECB, but nothing was found in sufficient quantity to analyze. Therefore, none of the information is presented. All Bt hybrids had significantly fewer cavities per plant and percentages of plants with cavities than the non-Bt hybrids not treated with insecticides and the non-Bt hybrids treated with Baythroid or Pounce (Table 12.3). Both Baythroid and Pounce failed to prevent damage by ECB in this trial. The percentage of non-Bt plants with cavities indicated that the ECB infestation in the trial was quite severe; 65 to 75% of the non-Bt plants not treated with insecticides had cavities caused by ECB. All but one Bt hybrid (Pioneer 34R07) had shorter cavity lengths per plant than the non-Bt hybrids. However, the mean cavity length in Pioneer 34R07 (1.33 cm) was not significantly shorter than in the other Bt hybrids. For the most part, fewer live ECB larvae were found in the Bt hybrids than in the non-Bt hybrids (Table 12.4). The mean number of larvae per plant in AgrEvo's 8481 non-Bt hybrid (0.83 larva per plant) was significantly larger than in all other hybrids. The mean numbers of larvae per ear shank were so low that significant differences among plots were not as apparent (Table 12.4). Only Pioneer 3489 (0.15 larva per shank) and AgrEvo's 8481 (0.28 larva per shank) had significantly more larvae per shank than most of the Bt hybrids. Mean numbers of live larvae per ear were not significantly different among any of the 10 treatments (Table 12.4). All Bt hybrids had some ear damage (Table 12.5), and differences between Bt hybrids and non-Bt hybrids not treated with insecticides were not significant. However, the percentage of ears with side damage in the Warrior-treated plots (18.33%) was significantly greater than in the plots with Garst's 8342 Bt hybrid (0%). After treatment of the plots with Baythroid and Warrior on August 18, numbers of ECB adults captured in light traps remained high for at least a couple of weeks (Appendix C, Table C.1 and C.2). Consequently, ECB larvae may have attacked the ears after Warrior had degraded below toxic levels. Shank damage in one Bt hybrid (20%, Pioneer 34R07) was not significantly less than the amount of shank damage in the non-Bt hybrids (Table 12.5). However, no shanks of the other Bt hybrids were damaged by ECB. Few stalks were broken above or below the ears, and no ears were found on the ground at the time of harvest. Also, no stalk rot was observed at harvest time. The percentage moisture at harvest, percentages of ears that were poorly developed, and yields are presented in Table 12.6. There were no significant differences in percentage moisture among plots at harvest time. Also, no distinct pattern of poorly developed ears was apparent among plots. Yields ranged from 130.5 bushels per acre (Pioneer 3489) to 171 bushels per acre (Pioneer 34R07). However, because yields were not assessed for some of the plots, the yield data were not analyzed statistically. As in past years in our trials, Bt-corn hybrids were quite effective in reducing the amount of injury caused by ECB. However, differences among hybrids with respect to these assessments did not always translate to differences in yield.
References Cited	Ritche, S.W., J.J. Hanaway, and G.O. Benson. 1993. How a corn plant develops. Special Report No. 48, Iowa State University of Science and Technology, Cooperative Extension Service, Ames.

Table 12.1: Agronomic factors, treatment dates, and evaluation dates for Bt-corn trial, Champaign, Illinois, 1998

Variables	Champaign
Planting date	May 27
Hybrid	see table 12.2
Plant population	28,600 seeds per acre
Row spacing	30 inches
Soil condition (top 2-3 inches)	moist
Soil temperature (4-inch level)	80° F
Air temperature	85° F
Wind	0-3 mph
Soil insecticides	none
Herbicides	Guardsman
Fertilizer	N 180 lbs/acre
Fall tillage	chisel and ripper
Spring tillage	field finisher
Infestation dates ECB 1 Corn development stage ECB 2 Corn development stage	July 9-10 V-6 August 13-14 VT (emerging tassel)
Treatment dates ECB 1| Wind Temperature ECB 2 Wind Temperature	July 15 0-3 mph 69° F August 18 0-2 mph 75° F
Evaluation dates Stalk splitting Yield	September 17 October 19

Table 12.2 Hybrids planted in the Bt-corn trial, Champaign, Illinois, 19981

Company	Hybrid	Days to relative maturity	Crystalline protein form
Garst	Starlink 8366 Bt	113	Cry9C
Garst	8366 non-Bt	113	---
Garst	8481Bt	112	Cry9C
Garst	8481 non-Bt	112	---
Garst	8342 Bt YieldGuard	114	CryIA(b)
Pioneer	34R07 Bt	107	CryIA(b)
Pioneer	33A14 Bt	113	CryIA(b)
Pioneer	3489 non-Bt	108	---

Table 12.3 Mean number of cavities per plant, mean cavity lengths (cm) per plant, and mean percentages of plants with cavities in Bt-corn trial, Champaign, Illinois, 19981

Variety	Mean number of cavities per plant2	Mean cavity length (cm) per plant2	Mean % plants with cavities2,3
8481 Bt	0.00 b	0.00 c	0.00 b
8342 Bt	0.00 b	0.00 c	0.00 b
8366 Bt	0.02 b	0.07 c	1.67 b
33A14 Bt	0.03 b	0.05 c	3.33 b
34R07 Bt	0.30 b	1.33 bc	13.33 b
3489 + Baythroid 2EC4	1.15 a	3.65 ab	71.67 a
3489 + Warrior T 1CS4	1.22 a	4.68 a	71.67 a
3489 non-Bt control	1.27 a	3.70 ab	66.67 a
8366 non-Bt	1.32 a	5.38 a	65.00 a
8481 non-Bt	1.83 a	5.93 a	75.00 a
1 Manual infestation of two European corn borer egg masses per plant (40 plants per plot) was conducted on July 9-10 to simulate first generation and on August 13-14 to simulate second generation. Plots were evaluated and harvested on September 17; yield was determined on October 19. 2 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 3 Arcsine square root transformations (data not shown) were performed before analysis. 4 Baythroid 2EC (0.031 lb (AI)/acre) and Warrior T 1CS (0.025 lb (AI)/acre) were banded over the row on July 15 for control of first generation ECB, and on August 18 for control second generation ECB.

Table 12.4 Mean numbers of live larvae per plant, ear shank, and ear in Bt-corn trial, Champaign, Illinois, 19981

Variety	Mean number of larvae per plant2	Mean number of larvae per ear shank2	Mean number of larvae per ear3
8481 Bt	0.00 d	0.00 c	0.00
8342 Bt	0.00 d	0.00 c	0.02
8366 Bt	0.00 d	0.00 c	0.00
33A14 Bt	0.00 d	0.00 c	0.02
34R07 Bt	0.12 cd	0.05 bc	0.02
3489 + Baythroid 2EC4	0.30 bc	0.05 bc	0.00
3489 + Warrior T 1CS4	0.42 b	0.10 bc	0.07
3489 non-Bt control	0.55 b	0.15 b	0.05
8366 non-Bt	0.45 b	0.10 bc	0.00
8481 non-Bt	0.83 a	0.28 a	0.07
1 Manual infestation of two European corn borer egg masses per plant (40 plants per plot) was conducted on July 9-10 to simulate first generation and on August 13-14 to simulate second generation. Plots were evaluated and harvested on September 17; yield was determined on October 19. 2 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 3 Means were not significantly different (P=0.05; Duncan's New MRT). 4 Baythroid 2EC (0.031 lb (AI)/acre) and Warrior T 1CS (0.025 lb (AI)/acre) were banded over the row on July 15 for control of first generation ECB, and on August 18 for control of second generation ECB.

Table 12.5 Mean percentages of ears with tip, side, and shank damage in Bt-corn trial, Champaign, Illinois, 19981

Variety	Mean % of ears with tip damage 2,3	Mean % of ears with side damage 2,4	Mean % of ears with shank damage2,4
8481 Bt	1.67	5.00 ab	0.00 c
8342 Bt	6.00	0.00 b	0.00 c
8366 Bt	1.67	1.67 ab	0.00 c
33A14 Bt	1.67	5.00 ab	0.00 c
34R07 Bt	11.67	5.00 ab	20.00 abc
3489 + Baythroid 2EC5	3.33	1.67 ab	16.67 bc
3489 + Warrior T 1CS5	13.33	18.33 a	30.00 ab
3489 non-Bt control	13.33	13.33 ab	23.33 abc
8366 non-Bt	3.33	8.33 ab	15.00 bc
8481 non-Bt	10.00	15.00 ab	43.33 a
1 Manual infestation of two European corn borer egg masses per plant (40 plants per plot) was conducted on July 9-10 to simulate first generation and on August 13-14 to simulate second generation. Plots were evaluated and harvested on September 17; yield was determined on October 19. 2 Arcsine square root transformations (data not shown) were performed before analysis. 3 Means were not significantly different (P=0.05; Duncan's New MRT). 4 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 5 Baythroid 2EC (0.031 lb (AI)/acre) and Warrior T 1CS (0.025 lb (AI)/acre) were banded over the row on July 15 for control of first generation ECB, and on August 18 for control of second generation ECB.

Table 12.6 Percentage moisture, percentage of poorly developed ears, and yields in Bt-corn trial, Champaign, Illinois, 19981

Variety	% Moisture	% of ears poorly developed2,3	Yield bu/acre3,4
8481 Bt	19.74	10.95 ab	not assessed
8342 Bt	20.52	7.24 b	not assessed
8366 Bt	19.73	11.46 ab	not assessed
33A14 Bt	21.45	18.43 a	158.5
34R07 Bt	19.50	12.24 ab	171.0
3489 + Baythroid 2EC5	18.47	6.30 b	168.1
3489 + Warrior T 1CS5	20.46	17.75 a	153.6
3489 non-Bt control	19.24	11.28 ab	130.5
8366 non-Bt	20.10	10.79 ab	not assessed
8481 non-Bt	19.87	12.76 ab	not assessed
1 Manual infestation of two European corn borer egg masses per plant (40 plants per plot) was conducted on July 9-10 to simulate first generation and on August 13-14 to simulate second generation. Plots were evaluated and harvested on September 17; yield was determined on October 19. 2 An ear was considered to be poorly developed if the ear length was less than 12cm or there were only a few kernels on the ear, based on 40 plants per plot. Arcsine square root transformations (data not shown) were performed before analysis. 3 Means in a column followed by the same letter are not significantly different (P=0.05; Duncan's New MRT). 4 Hand-harvested yields were determined from the shelled grain weights (converted to 15.5% moisture) taken from 20 consecutive plants in each of the two middle rows of each four-row plot. 5 Baythroid 2EC (0.031 lb (AI)/acre) and Warrior T 1CS (0.025 lb (AI)/acre) were banded over the row on July 15 for control of first generation ECB, and on August 18 for control of second generation ECB.

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