Effects of mowing frequency on ground cover composition and on numbers of predators, parasitoids, and select phytophagous arthropods in the ground cover of three reduced-insecticide pear orchards were determined. Concurrent samples taken in the tree canopy (with beating trays) and in the herbicide strips on the orchard floor (with pitfall traps) tested whether counts of natural enemies in these two habitats were also affected by mowing regime. A reduction in frequency of mowing from two to three times per month (= control) to once per month or once per growing season led to increased cover of grasses, broadleaf plants, and broadleaf plants in flower. Sweep net samples of natural enemies in the ground cover were dominated numerically by spiders (Araneae), parasitic Hymenoptera, and predatory Heteroptera, with lesser numbers of other taxa (Syrphidae, Neuroptera, Coccinellidae). Predators and parasitoids showed substantial increases in numbers associated with decreased mowing frequency. Sweep net counts of aphids, Lygus spp. (Heteroptera: Miridae), and leafhoppers/planthoppers, all potential prey of predators, also increased significantly with decreased mowing frequency. In the pitfall samples, only the European earwig ( Forficula auricularia L.) (Dermaptera: Forficulidae) exhibited a change in counts associated with mowing treatment; numbers of earwigs in pitfall traps declined as mowing frequency decreased. For the beat tray samples, mean tray counts for most natural enemy taxa were higher in the less frequently mowed plots, but significantly (P < 0.05) so only for two taxa: spiders and a predatory mirid, Deraeocoris brevis (Uhler) (Heteroptera: Miridae). It remains to be determined whether biological control of pests in the tree canopy can be enhanced by manipulating mowing frequency. Questions raised by this study include whether there is extensive movement by natural enemies between the ground cover and tree canopy, and whether plot size affects the likelihood of showing that mowing frequency influences predator densities in the tree canopy.

No abstract

No abstract

No abstract

Studies of overlapping cohorts in the United States have shown an excess mortality from brain cancer in vinyl chloride (VC)-exposed workers. One plant located in Louisville, Kentucky, is included in many of these studies. We separated this plant from the large US cohort and re-analyzed the mortality experience. Louisville experienced significantly elevated liver (standardized mortality analyses [SMR] = 400) and brain cancer (SMR = 229) mortality. Liver cancer mortality remained significantly elevated (SMR = 344) in the remaining cohort; however, brain cancer mortality was markedly reduced (SMR = 112) when Louisville was removed. In contrast with liver cancer, a preliminary review of work assignments did not suggest that the brain cancer excess was related to VC exposure. The Louisville brain cancer cluster has had a significant impact on the reported literature. Although unrelated to VC, the cause of this cluster remains uncertain.