Three approaches to cucumber beetle [striped, Acalymma vittata (Fabricius)]; spotted, Diabrotica undecimpunctata howardi Barber] management on cucurbits were tested on 11 farms in Virginia. Visual counts of striped cucumber beetles/five squash plants were similar in 1996 (2.6 ± 3.1, max 16) and 1997 (3.1 ± 3.8, max 18), but counts on adjacent yellow sticky traps were higher in 1996 (11.5 ± 14.5, max 66) than in 1997 (4.9 ± 4.1, max 16). Correlation between visual and card counts was stronger in 1996 (r = 0.66) than 1997 (r = 0.38). Regression indicated that a threshold of five beetles/five plants was equivalent to 16 beetles/trap in 1996, but only six beetles/trap in 1997. On two peak count dates in Aug. 1996, trap crop squash cultivar NK530 had 10 beetles/sticky card, significantly higher than the three to seven beetles/sticky card on `Seneca' and `Scallop'. Similar trends were seen in visual counts in these plots. In 1997, `NK530' also showed preferential beetle attraction over pumpkin cultivar Howden. On early squash in 1997, cucumber beetle counts on two June peak dates were higher on black plastic (40 and 23 beetles/trap) than on solid aluminum (eight and five beetles/trap) or black with aluminum strips (15 and 10 beetles/trap). Black plastic required 1.8 insecticidal applications compared to none for solid aluminum. There were no significant differences in cumulative yield, although yield at first picking was 38% less on aluminum. Premiums for lower pesticide use (25%) compare favorably with the $102/acre added expense for aluminum plastic.
Spotted cucumber beetle Diabrotica undecimpunctata howardi Barber (Insecta: Coleoptera: Chrysomelidae)
