Hal Willson
Extension Entomologist
The Ohio State University

During the past three years, trials including multiple hybrids of Bt-corn and comparable isolines have been conducted at the Western and Northwestern Branch Stations to evaluate yield benefits that may be attributed to the use of corn that has been genetically modified to prevent losses due to annual infestations of European corn borer (ECB). Results of trials conducted during the 1999 growing season are presented in Table 1.

Table 1 - Comparison of Bt-Corn Hybrids and Non-Bt Isolines at the Western and Northwestern Branch Stations, 1999.

Treatment	Properties	Stand per	ECB Obs. / Plant		Yield
		100 Row Ft	Cavities	Larvae	Bu./ Ac.
Western Branch Station, Clark County
Asgrow 730	Non-Bt Isoline	98.50 b	0.20	0.20	145.9
Asgrow 730 Bt	Yieldgard	93.75 b	0.00	0.00	137.6
DeKalb 647	Non-Bt Isoline	105.75 ab	0.70	0.55	156.2
DeKalb 647 Bt	Yieldgard	98.25 b	0.00	0.00	137.6
Garst 8481	Non-Bt Isoline	93.75 b	0.75	0.55	133.4
Garst 8481 Bt	Starlink	116.75 a	0.00	0.00	144.8
Northwestern Branch Station, Wood County
Asgrow RX601	Non-Bt Isoline	130.9 a	1.10	0.75	166.0
Asgrow RX601YG	Yieldgard	131.3 a	0.00	0.00	163.7
DeKalb 595	Non-Bt Isoline	128.4 ab	0.90	0.60	171.7
DeKalb 595 Bty	Yieldgard	124.1 b	0.00	0.06	161.3
Garst 8481	Non-Bt Isoline	128.8 a	1.25	0.95	168.7
Garst 8481 Bt	Starlink	128.3 ab	0.00	0.00	163.6
Means in a column followed by the same letter are not significantly different @ P = 0.05.

• Bt-corn hybrid suppressed ECB injury to minimal levels. However, ECB infestations observed in non-Bt corn isolines at both the Western and Northwestern Branch Station trials were marginal in regard to causing economic losses.

• At the Western Branch, stand loss due to cutworm infestation was prevented by the Garst 8481 Bt hybrid, which includes the Starlink trait. This is the first case of significant prevention of a natural infestation of black cutworm injury documented in a Ohio replicated field trial (and possibly within the mid-west region).

• Differences in yield observed between Bt-corn hybrids and non-Bt corn isolines evaluated were not significant.

A summary of results observed in three years of field evaluations of Bt-corn hybrids and equivalent non-Bt isolines conducted at both the Western and Northwestern Branch stations is presented in Table 2.

Table 2 - Evaluation of Stand, Corn Borer Infestation and Yield of Bt-Corn Hybrids and Non-Bt Isolines At Two OARDC Research Stations from 1997 to 1999.

Year of	No. Hybrids	Stand per	ECB Obs. per Plant		Yield
Trial	Evaluated	100 Row Ft.	Cavities	Larvae	Bu. per Ac.
Western Branch Station, Clark County
1997	4 Bt-Corn	137.7	0.15	0.01	156.5
	4 Isolines	135.6	0.91	0.26	152.2
1998	3 Bt-Corn	136.1	0.02	0.00	131.5
	3 Isolines	130.0	0.15	0.11	130.2
1999	3 Bt-Corn	102.9	0.00	0.00	140.0
	3 Isolines	99.3	0.55	0.43	145.2
3 Yr. Avg.	Bt-Corn	125.6	0.06	0.00	142.7
	Isolines	121.6	0.54	0.27	144.5
Northwestern Branch Station, Wood County
1997	4 Bt-Corn	116.4	0.20	0.08	176.1
	4 Isolines	114.7	1.66	0.45	175.5
1998	3 Bt-Corn	123.5	0.00	0.00	174.9
	3 Isolines	114.5	0.07	0.12	163.8
1999	3 Bt-Corn	127.9	0.00	0.02	162.9
	3 Isolines	129.4	1.08	0.77	168.8
3 Yr. Avg.	Bt-Corn	122.6	0.07	0.03	171.3
	Isolines	119.5	0.94	0.45	169.4

• The bottom line of the results presented in the preceding table is that the corn yields of Bt-Corn hybrids and their non-Bt isolines evaluated at two locations in Ohio over a three year time period are equal.

• Exceptions may exist, but the results demonstrate that corn borer impact over time on Ohio corn is not significant and that the benefit derived from an investment in Bt-Corn may not be warranted under Ohio growing conditions.

Acknowledgements:

Extension personnel responsible for providing significant assistance on projects reported include: B. Eisley, Research Associate, Dept. of Entomology; J. Jasinski, IPM Extension Associate, Southwest District; C. Young, Extension Associate, Northwest District; and A. Ba, Research Associate, Dept. of Entomology.

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