trifloxystrobin and enilconazole

Calonectria (formerly Cylindrocladium) infection of pot azalea (Rhododendron simsii Planch) is an important disease problem in which usually one or two of the four plants per pot show progressing leaf and especially stem lesions, leading to mortality of the respective plant and rendering the pot unmarketable. This may occur in a later stage of the growing season, leading to significant commercial losses. The main objective of this study was to test a range of fungicides for their efficacy against this pathogen. To test the fungicides, a bioassay was first developed in which mycelium and conidiospores of the pathogen were produced on Potato Dextrose Agar, blended in water, and dilutions of the resulting suspension inoculated at the base of 11-week-old cuttings three weeks after they had been trimmed. Disease progression was monitored up to 7 weeks post inoculation and a disease index on a scale of 0 to 3 was established. In the actual efficacy trial, the following fungicides (with corresponding active ingredient(s)) were tested as preventive treatments: Topsin M 70 WG (thiophanate-methyl), Sporgon (prochloraz), Signum (boscalid+pyraclostrobin), Switch (cyprodinyl+fludioxonil), Flint 50WG (trifloxystrobin), Ortiva Top (azoxystrobin+difenoconazole) and Fungaflor (imazalil). Disease expression started after about 2 weeks, increased approximately 1 index level, and leveled off 5 weeks after inoculation. The best control was observed with Sporgon, Ortiva Top and Signum. Switch produced intermediate effects and insufficient control was observed with Topsin, Flint and Fungaflor. These results explain why specific standard fungicide treatments, such as those with Topsin, fail to control the disease, while they can be effective against a different Calonectria species such as C. pseudonaviculata, the cause of boxwood blight.

Topics: Acetates; Carbamates; Dioxolanes; Fungicides, Industrial; Hypocreales; Imidazoles; Imines; Methacrylates; Plant Diseases; Pyrazoles; Pyrimidines; Rhododendron; Strobilurins; Triazoles

The effectiveness of postharvest dip treatment with trifloxystrobin (TFX) or imazalil (IMZ) was compared for controlling green and blue mold (caused by Penicillium digitatum and Penicillium italicum, respectively) of citrus fruit. Residues retained by fruit were determined as a function of treatment time, dip temperature, and storage conditions. Trials on 'Avana apireno' mandarin oranges artificially inoculated with P. digitatum or P. italicum revealed that treatments with 200 to 600 mg/liter active ingredient TFX at 20 degrees C were less effective than 100 mg/liter TFX at 500C for controlling P. digitatum but equally effective for controlling P. italicum. IMZ treatments with 200 mg/liter IMZ at 20 degrees C or 25 mg/liter IMZ at 50 degrees C resulted in more than 98% reduction of P. digitatum and ca. 93% reduction of P. italicum compared with untreated fruit. Total suppression of pathogens was achieved when higher IMZ doses were applied. Studies on artificially wounded lemons, oranges, clementines, and mandarins revealed that treatment with 100 mg/liter TFX at 50 degrees C effectively controlled decay development (mainly due to P. digitatum) after 7 days of storage at 20 degrees C. These results were confirmed on nonwounded oranges of cv. Tarocco and on grapefruits of cvs. Marsh Seedless and Star Ruby during 3 weeks of simulated quarantine at 1 degrees C, storage (5 weeks at 8 degrees C for oranges and 8 weeks at 11degrees C for grapefruits), and an additional 1 week of simulated marketing conditions at 20 degrees C. IMZ at 50 degrees C was highly effective for controlling decay during storage and the simulated marketing period. TFX treatment at 50 degrees C was as effective as IMZ for controlling decay in most samples. After treatment with 100 mg/liter TFX at 20 degrees C, fungicide residues in 'Tarocco' oranges doubled from 0.15 mg/kg to 0.30 mg/kg when dip time increased from 0.5 to 3 min, whereas when treatments were performed at 50 degrees C TFX residues were not related to dipping time. Residues of TFX were significantly correlated with dip temperature. A 3-min dip treatment at 50 degrees C resulted in a deposition of TFX that was approximately twofold higher than that obtained when treatments were carried out at 20 degrees C.

Topics: Acetates; Citrus; Colony Count, Microbial; Consumer Product Safety; Food Handling; Food Preservation; Fungicides, Industrial; Humans; Imidazoles; Imines; Methacrylates; Penicillium; Pesticide Residues; Strobilurins; Temperature; Time Factors