Greenhouse studies examined the effects of an aquatic herbicide (fluridone) in irrigation water on four vegetable crops growing on two soils. Tests on Fuquay loamy sand (0.3% humic matter) and Portsmouth fine sandy loam (4.1% humic matter) examined fluridone concentrations ≤250 μg·L−1. Injury to sweet corn (Zea may L.), cucumber (Cucumis sativus L.), bell pepper (Capsicum annum L.), and tomato (Lycopersicon esculentum L.) on these soils varied with soil type and stage of plant growth. Seedlings or new transplants were more susceptible to fluridone damage than older plants. All plants showed more injury on Fuquay loamy sand, which had the lowest humic matter content. Injury to cucumber occurred only to seedlings exposed to 250 μg·L−1 on the Fuquay loamy sand. Bell pepper was the most sensitive crop to fluridone. The “no observed effects level” below which no significant injury of a crop occurred over both soil types and both stages of crop maturity was 5 μg·L−1 for sweet corn, bell pepper, and tomato and 100 μg·L−1 for cucumber.
Stratford H. Kay, Ross B. Leidy, and David W. Monks
Stratford H. Kay, David W. Monks, and Ross B. Leidy
In 1992, we initiated a study to determine the effects of fluridone in irrigation water applied to container-grown azaleas. Azaleas (Rhododendron indicum L. `George Tabor') were grown in containers with a 3 pine bark: 1 sand mixture and were irrigated daily for 5 weeks (except weekends) with solutions containing fluridone concentrations ≤2000 g·L−1. The threshold for appearance of visible injury symptoms (bleaching of new growth) was 250 g·L−1 at 5 and 12 weeks after treatment initiation. Visible symptoms did not appear until at least 35 days after treatments began. No statistically significant injury occurred to azaleas treated with solutions containing fluridone concentrations <250 g·L−1. This treatment rate was well above the maximum fluridone concentration (<90 g·L-1) normally occurring in ponds immediately following fluridone application. It appears unlikely that even long-term irrigation of `George Tabor' azaleas from fluridone-treated ponds would cause any significant injury.
Robert D. Belding, Sylvia M. Blankenship, Eric Young, and Ross B. Leidy
Variation in amount and composition of epicuticular wax among several apple (Malus ×domestica Borkh.) cultivars was characterized by gas chromatography, thin-layer chromatography, and gas chromatography-mass spectroscopy. Across cultivars, wax mass ranged from 366 to 1038 μg·cm-2. Wax mass decreased during the 30 days before harvest. Ursolic acid accounted for 32% to 70% of the hydrocarbons that make up the epicuticular wax. Alkanes, predominantly 29-carbon nonacosane, comprised 16.6% to 49%. Primary alcohols of the hydrocarbons ranged from 0% to 14.6% of the epicuticular wax. Secondary alcohols of the hydrocarbons were the most cultivar specific, making up 20.4% of the epicuticular wax in `Delicious' and only 1.9% `Golden Delicious' strains. Aldehydes and ketones of the hydrocarbons represented a small amount of total wax, ranging from 0% and 6.0%. Percentage of primary alcohol in the epicuticular wax increased as fruit developed. Other components showed no distinct trends with fruit development. Examination of the ultrastructure of cuticular wax using scanning electron microscopy revealed structural differences among cultivars.