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  • Author or Editor: M.A. Ellis x
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A commercially available serological assay kit (flow-through enzyme-linked immunosorbent assay, Phytophthora F kit) was compared to a culture-plate method for detecting Phytophthora spp. in apparently diseased (phytophthora root rot) and apparently healthy red raspberry (Rubus idaeus subsp. strigosus Michx.) plants. During 4 years of testing, 46 tests were conducted on apparently diseased roots. All diseased plants gave a strong positive reaction, a result indicating that Phytophthora spp. were present. Of the 46 plants that tested positive, Phytophthora spp. were recovered from all but one using a selective medium for Phytophthora and the culture-plate method. When the same test was conducted on 27 apparently healthy plants, all had a negative reaction for the presence of Phytophthora except one sample, which had a slight positive reaction. No Phytophthora spp. were isolated from any apparently healthy plants. Our results indicate that the serological test kit enables rapid, dependable, on-site diagnosis of raspberry phytophthora root rot.

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Water use efficiencies of five irrigation methods on dry onions (Allium cepa L.) were compared in a two-year field study. The methods were: 1) graded furrows where water was measured into the upper end of the furrows and excess water was measured as it ran out the lower end; 2) level furrow where water was held in short, level furrows until infiltrated into the ground; 3) sprinkler; 4) trickle; and 5) trickle three times per week. Efficiency of water use (tonne per hectare per millimeter) was least with graded furrows and the same for the other four treatments in 1983, whereas there were no efficiency differences in 1984. Treatment differences in yield among onion grades occurred both years, but no differences in total yields among treatments for either year. The results do not justify the expense of conversion from existing furrow irrigation systems to pressurized systems for water savings on a uniform, heavy-textured soil where good-quality water is used.

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Hand thinning is a necessary and costly management practice in peach (Prunus persica) production. Stone fruit producers are finding it increasingly difficult to find a workforce to manually thin fruit crops, and the cost of farm labor is increasing. A new “hybrid” string thinner prototype designed to adjust crop load in vase or angled tree canopies was evaluated in processing and fresh fruit plantings in varying production systems in four U.S. growing regions in 2009. Data were uniformly collected across regions to determine blossom removal rate, fruit set, labor required for follow-up green fruit hand thinning, fruit size distribution at harvest, yield, and economic impact. String thinner trials with the variable tree forms demonstrated reduced labor costs compared with hand-thinned controls and increased crop value due to a larger distribution of fruit in marketable and higher market value sizes. Blossom removal ranged from 17% to 56%, hand thinning requirement was reduced by 19% to 100%, and fruit yield and size distribution improved in at least one string-thinning treatment per experiment. Net economic impact at optimum tractor and spindle speeds was $462 to $1490 and $264 to $934 per acre for processing and fresh market peaches, respectively. Case study interviews of growers who thinned a total of 154 acres indicated that commercial adoption of string-thinning technology would likely have positive impacts on the work place environment.

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