INSECTICIDAL CONTROL OF FALL ARMYWORM ON SWEET CORN, 2009

FAW is the key pest of sweet corn in southern Florida with the larvae feeding in whorls, tassels, silks, and ears. Broad-spectrum insecticides are often sprayed daily after tasselling but more selective chemistries could provide advantages of better control with less collateral impact on non-target organisms. The present trial was initiated at the Southwest Florida Research and Education Center in Immokalee FL by preparing 4 raised beds 32 inches wide and 220 ft long on 12 ft centers covered with whiteface polyethylene mulch under which was placed a single drip tape irrigation line with 4 inch emitter spacing. Fertilizer (12-3-12) was mixed into the beds at 50 lbs N per acre and an 8-0-8 liquid fertilizer was applied through the drip tape five times a week during the growing season for a total of 200 lbs N over the crop cycle. Corn was direct seeded 11 Sep at 10-inch spacing. Four treatments were assigned in an RCB design. Plots in reps 1, 2 and 3 contained 24 plants with 3 plants as buffer between treatments and in rep 4, 23 plants with 2 plants between plots due to some uneven germination. Applications were made with a high clearance sprayer travelling at 2.3 mph equipped with ceramic Albuz ® “yellow” hollow cone tips each delivering 10 gpa at 180 psi. On 5 Oct, one nozzle was placed overheard and one nozzle was located on each of the two drops (3 nozzles for a total volume of 30 gpa). All other applications were done with two nozzles on each of the two drops (4 nozzles for a total volume of 40 gpa) (Table 1). The 23 Oct drip application of Coragen was made by initially filling the drip tube with water and then injecting the suspension of Coragen using a 12 volt pump operating at 0.23 gpm providing an equivalent of 90 mls per plant. Lines were then flushed with an equal volume of water to ensure all insecticide was evenly distributed. Larval counts were made on 7 and 14 Oct by inspecting 10 plants per plot and noting the number of larvae in the top of the whorl. Larvae were counted in the tassel on 23 and 27 Oct and in silks on 30 Oct and 4 Nov. On 12 and 19 Nov the dominant ear on each of 20 plants per plot was evaluated by removing the husks and grading to 3 categories: no damage, minor tip damage and significant ear damage. Data were subjected to ANOVA and means separated using LSD (P = 0.05) are presented.