J.V. Edelson and C. Mackey

Oklahoma State University

Lane, OK 74555

Corn Earworm (CEW); Helicoverpa zea (Boddie)

Two isogenic lines of sweet corn, one containing a B.t. event and the other without, were planted to a field at the Wes Watkins AREC, Lane, OK on 2 May. Rows were set at 36 inch intervals and seed planted at six inch intervals with a Monosem precision planter. The experimental design was a randomized complete block with 2 treatments and 5 replicate blocks. Plots were two rows wide by 200 ft long. Plots were separated by 12 ft alleys. Twenty-five ears of corn were removed from each plot at the kernel ‘milk’ stage and evaluated for CEW presence and damage. Number of CEW per ear, presence of tip feeding on the ear and rating of the extent of damage on each ear were recorded. Data were summarized and analyzed using ANOVA and a LSD test to make comparisons between treatments.

The Rogers CSS 0966 with the CryIA(b) delta endotoxin event had significantly fewer damaged ears of corn with signficantly fewer CEW present in the ears. The isogenic Rogers line without the B.t. event had an average of 0.9 CEW per ear and thus would have been non-marketable without the use of insecticide applications to control the CEW. Planting CSS 0966 resulted in significant control of CEW in comparison to production of the Rogers Prime Plus without the B.t. gene and resulted in a marketable crop without application of insecticides.

% Ears with % of ear

Cultivar CEW / ear damaged tips damaged

Rogers Prime

Plus 0.93 a 99 a 30 a

Rogers CSS 0966 0.17 b 22 b 2 b

Means in a column followed by different lower case letters are significantly different (LSD, P=0.1).

SWEET CORN: Zea mays L., ‘Rogers Prime Plus’ and ‘Rogers CSS0966’

CONTROLLING CORN EARWORM WITH B.t. TRANSGENIC SWEET CORN, OKLAHOMA, 2002

J.V. Edelson and C. Mackey

Oklahoma State University

Lane, OK 74555

E-mail: jedelson-okstate @lane-ag.org

Phone: 580-889-7343

Corn Earworm (CEW): Helicoverpa zea (Boddie)

Two isogenic lines of sweet corn, one containing a B.t. event and the other without, were planted to a field at the Wes Watkins AREC, Lane, OK on 15 May. Rows were set at 36 inch intervals and seed planted at six inch intervals with a Monosem precision planter. The experimental design was a RCB with 2 treatments and 4 replicate blocks. Plots were two rows wide by 200 ft long. Twenty-five ears of corn were removed from each plot at the kernel ‘milk’ stage and evaluated for CEW presence and damage. Number of CEW per ear, presence of tip feeding on the ear and rating of the extent of damage on each ear were recorded. Data were summarized and analyzed using ANOVA and a LSD test to make comparisons between treatments.

CEW larvae were abundant. The Rogers CSS 0966 with the CryIA(b) delta endotoxin event had significantly fewer damaged ears of corn with signficantly fewer CEW present in the ears. The isogenic Rogers line without the B.t. event (Prime Plus) had an average of 0.8 CEW per ear and the CSS 0966 had significantly fewer. The B.t. event corn had fewer damaged ears and the percentage of the individual ear damaged was considerably less. Planting CSS 0966 resulted in significant reductions in CEW, number of ears with tip damage and total amount of each ear damaged in comparison to production of the Rogers Prime Plus without the B.t. gene.

Table 1.

% Ears with % of ear

Cutivar CEW / ear damaged tips damaged

Rogers Prime Plus 0.8 a 95 a 31 a

Rogers CSS 0966 0.6 b 68 b 5 b

Means in a column followed by different lower case letters are significantly different (LSD, P=0.1).

SWEET CORN: Zea mays L., ‘Rogers Prime Plus’, ‘Florida Sta-Sweet’

CONTROLLING CORN EARWORM ON SWEET CORN, 2003

Corn Earworm (CEW): Helicoverpa zea (Boddie)

Two lines of sweet corn, one containing a B.t. event and the other without, were planted to a field at the Wes Watkins AREC, Lane, OK on 15 May. Rows were set at 36 inch intervals and seed planted at six inch intervals with a Monosem precision planter. The experimental design was a RCB with 5 treatments and 4 replicate blocks. Plots were four rows wide by 40 ft long. Insecticide treatment plots were sprayed on 27 and 30 Jun, 3, 8, 11 and 15 Jul using a tractor mounted hydraulic sprayer. The Bt event cultivar was not treated with insecticides. The sprayer had a 12 ft wide boom with 8 nozzles mounted to spray over the top of the plants. The sprayer output was 20 gpa at 45 psi. Ears were harvested 17 Jul by picking 25 mature ears from each plot. The ears were then individually rated for damage. If the ear had any damage it was assigned a (1) if there was no damage it was assigned a (0). The ears with damage were then rated on a percent damaged scale of either 0%, 1-25%, 26-50%, 51-75% or 76-100% damage. Data were summarized and analyzed using ANOVA and a LSD test to make comparisons among treatments.

CEW larvae were abundant. Neemix and Dipel treated corn and Bt transgenic corn had significantly fewer larvae per ear than the other treatments. Applications of Capture and Dipel resulted in fewer damaged ears than did the other treatments. Treatments with Capture and Dipel and the Bt event corn resulted in less damage per ear than the use of Neemix or Pyrenone. The CEW larvae were so abundant that none of the treatments provided levels of control and reductions in damage required for use of the corn in a processing market.

Table 1.

Larvae/ % ears % of ear

Treatment and rate/acre ear damaged damaged

Capture 2EC 0.1 lb (AI) 1.1 ab 92 b 17 c

Neemix 4.5 10 fl oz 1.0 b 99 a 29 b

Pyrenone 0.05 lb (AI) 1.3 a 99 a 39 a

Dipel DF 2 lbs 0.9 b 82 c 22 c

Prime plus Bt -- 0.9 b 95 ab 22 c

Numbers in a column are significantly different if not followed by the same letter, LSD, P=0.1.