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Insecticidal Control of Fall Armyworm on Sweet Corn With Bt and an Insect Growth Regulator, 2000
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P. A. Stansly and J. M. Conner
University of Florida/IFAS
Southwest Florida Res. and Ed. Center
2686 State Road 29 North
Immokalee, Florida 34142-9515
Phone: (239) 658-3427
Fax: (239) 658-3470
Email: pas@ifas.ufl.edu
CORN (Sweet): Zea mays (L.) ‘Primetime plus’
Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith)
Selective insecticides such as endotoxins of Bacillus thruingiensis and insect growth regulators offer the opportunity to better integrate chemical and biological management tactics. However, pesticidal efficacy must still be demonstrated for key pests such as fall armyworm on sweet corn. For this trial, 6 raised beds 32 inches wide and 240 ft long on 6 ft centers were prepared by fumigating with 67/33% methyl bromide/chloropicrin at 300 lbs/acre, and fertilizing with a bottom mix of 700 lbs/acre 5-16-8. A single driptape irrigation line with emitters spaced every 12 inches was laid on the surface of each bed and covered with white faced polyethylene mulch. Beds were divided into 2, 3 row sets separated by a 15 feet of fallow land with a ditch in the
middle. The center row of each 3 row set was planted 12 Sep and left untreated to provide pest inoculum. The remaining 4 rows were divided into 5 single row plots in a RCB design with 4 replications and planted by direct seeding 18 Oct at 10 inch spacing. Additional fertilizer in liquid form with an analysis of 8-0-8 was injected through the irrigation system to provide a total of 150 lbs nitrogen/acre for the growing season. Four weekly spray applications were initiated 1 Nov using a high clearance sprayer equipped with 2 overhead nozzles fitted with ceramic Albuz ATR ® "yellow" hollow cone nozzles/row with delivery pressure of 200 psi and rate of 22 GPA. A pre-treatment sample on 1 Nov of 20 plants per plot indicated 25% were damaged by FAW. 20 randomly selected plants/plot
were evaluated weekly for 5 weeks after the initiation of the treatments for the presence of fall armyworm larvae in the whorl. Ears were harvested 28 Dec from 25 plants in the center of each plot. Ears were evaluated for marketability noting total weight of ears in each category.
Pest pressure decreased continuously through the trial period until the last evaluation on 5 Dec when no larva were found. After tasseling there were no additional sprays applied and all the ears harvested were marketable. Some pressure was observed during first 3 evaluations on plants sprayed with the Bt TTC-1507 although significantly fewer than on untreated plants. No larvae were observed after the first evaluation with either rate of Intrepid. There were no significant differences in yield.
|
Treatment/
Formulation
|
Product/
Acre |
Mean larva from 20 plants |
Marketable Ears from 25 plants |
|
7 Nov |
14 Nov |
21 Nov |
27 Nov |
No. |
Wt (lb) |
|
TTC-1507 |
3 pt |
0.75b |
0.50b |
0.25b |
0.00b |
44.3 |
22.2 |
|
Intrepid |
4 oz |
0.50b |
0.00b |
0.00b |
0.00b |
45.8 |
22.7 |
|
Intrepid |
8 oz |
0.25b |
0.00b |
0.00b |
0.00b |
51.0 |
24.9 |
|
Lannate |
1 pt |
0.00b |
0.00b |
0.50b |
0.00b |
49.3 |
24.0 |
|
Untreated |
|
2.75a |
2.00a |
1.50a |
1.00a |
45.5 |
22.3 |
Means in columns followed by the same letter are not significantly different (LSD, P < 0.05). |
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