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Meador D.P.,Center for Applied Horticultural Research | Fisher P.R.,University of Florida | Guy C.L.,University of Florida | Harmon P.F.,University of Florida | And 2 more authors.
Journal of Environmental Quality | Year: 2016

Petrifilms are dehydrated agar culture plates that have been used to quantify colony forming units (CFU) mL-1 of either aerobic bacteria (Petrifilm-AC) or fungus (Petrifilm-YM), depending on substrate composition. Microbes in irrigation systems can indicate biofilm risk and potential clogging of irrigation emitters. The research objective was to compare counts on Petrifilms versus traditional, hydrated-agar plates using samples collected from recirculated irrigation waters and cultures of isolated known species. The estimated count (in CFU mL-1) from a recirculated irrigation sample after 7 d of incubation on Petrifilm-YM was only 5.5% of the count quantified using sabouraud dextrose agar (SDA) with chloramphenicol after 14 d. In a separate experiment with a known species, Petrifilm-YM did not successfully culture zoospores of Phytophthora cactorum. Isolates of viable P. cactorum zoospores were cultured successfully on potato-dextrose agar (PDA), with comparable counts with a vegetable juice medium supplemented with the antibiotics pimaricin, ampicillin, rifamycin, pentochloronitrobenzene and hymexazol (PARP-H). The quantification of Xanthomonas campestris pv. Begoniaceae on Petrifilm-AC was not significantly different (p < 0.05) than on PDA, but was lower than on Reasoner and Goldrich agar (R2A) or with a hemocytometer. The current formulation of Petrifilm-YM is unlikely to be a useful monitoring method for plant pathogens in irrigation water because of the inability to successfully culture oomycetes. However, Petrifilm-AC was an effective method to quantify bacteria and can provide an easy-to-use on-farm tool to monitor biofilm risk and microbial density. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved. Source

Villavicencio L.E.,Center for Applied Horticultural Research | Villavicencio L.E.,Everris Inc. | Bethke J.A.,University of San Diego | Dahlke B.,Center for Applied Horticultural Research | And 2 more authors.
Journal of Economic Entomology | Year: 2014

The aloe mite, Aceria aloinis Keifer, causes physiological and morphological alterations in species of Aloe L. We conducted three trials to evaluate the potential of various miticides for curative and preventive control of damage caused by A. aloinis. In the first trial, the efficacy of nine miticides against aloe mite damage was assessed without the removal of infected tissue in Aloe reitziiae Reynolds. Although significant reductions in the number of mites and eggs were found due to the treatments, miticide application did not reduce the amount of plant area damaged or damage severity. Once the plants are infected, the irreversible damage by aloe mite progresses. The second trial analyzed the effects of seven miticides on aloe mite damage on Aloe 'Goliath' plants in which the damaged tissue was removed. Reduced damage severity and mite number was observed in all treated plants. To determine if aloe mite damage could be prevented, the effects of six miticides with and without surfactant were tested on uninfected plants of Aloe spinosissima A. Berger in a third trial. Except for chlorfenapyr and fenazaquin, all treatments reduced plant damaged area, damage severity, and the number of mites 60 wk following three miticide applications. The severity index in the second and third trials suggested that all treated plants would be marketable. Our study demonstrated that there were miticides that were effective by contact (carbaryl), translaminar (spiromesifen), and systemic (spirotetramat) action, which can be used to cure and to prevent aloe mite plant damage alone or in combination with cultural practices. © 2014 Entomological Society of America. Source

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