| Abstrakt: |
Seasonal changes in within-vineyard distribution and abundance of Erythroneura comes (Say) adults and nymphs were investigated from 1989 to 1992. Trap catches of adults were highest in May and were concentrated in wooded areas next to vineyards. In 1989 and 1990 surveys, nymphal densities did not decline as distance from the vineyard edge increased. In 1991, however, nymphal densities were significantly higher at vineyard edges than in vineyard interiors in July, suggesting that oviposition initially was aggregated at vineyard edges. Subsequently, nymphal densities at vineyard edges and interiors were similar. Cumulative degree days (DD) for mean observation of first nymphs, first-generation, and second-generation peak populations, sampled at 14 vineyards in 1989, 1990, and 1991, were 390 ± 71, 648 ± 86, and 1,190 ± 154 DD (mean ± SD; base 10°C), respectively. Nymphal densities exceeded a provisional threshold of five per leaf in only 2, 25, 13, and 8% of vineyards untreated with insecticides in 1989, 1990, 1991, and 1992, respectively. These results show that leafhoppers do not cause economic injury in most New York vineyards in most years. Reduced insecticide strategies recently implemented for grape berry moth control will not greatly increase the need for insecticide applications directed at leafhoppers in New York. |
