Control of Lepidopterous Larvae on Cabbage, 1986

“Greenback” cabbage was direct seeded in single row beds with 40 in center spacing. Plots were 2 rows wide and 20 ft long with one unplanted row between plots. Experimental design was a randomized complete block with 5 replicates. All chemical applications were applied using a tractor mounted sprayer that delivered 12.4 gal/acre at 40 psi and 4 mph. Control plots were not sprayed. Weekly counts were made of all larvae present (cabbage looper, diamondback moth and beet armyworm) on 5 plants per plot. When the mean number of larvae per plant of all species exceeded 0.3 larvae/plant in methomyl treated plots, all plots were sprayed the following day. A total of 6 applications were made between 22 Apr and 27 May. Percent marketable cabbage heads (excluding wrapper leaves) was determined on 2 Jun. Heads were considered marketable if no visible evidence of feeding damage was observed. Beet armyworm egg masses oviposited on wax paper by moths in a laboratory culture were attached to the underside of wrapper leaves on one plant per plot. Egg masses were placed on 9, 28 Apr and 15 May at a rate of approximately 250 eggs/plant per date. Beet armyworm larvae were counted weekly on these plants. Total larval counts were analysed using AOV and Duncan's mean separation test while beet armyworm count analyses were made using a Ranks procedure (SAS Institute, 1984). Marketable head data was analysed using an arcsin transformation of percentage marketable data and reported as % marketable heads.