A study of the in vitro sensitivity of 10 isolates of Didymella applanata to copper hydroxide, dithianon, fluazinam, tebuconazole and pyraclostrobin, was conducted. The isolates were derived from diseased raspberry canes sampled during 2013 at five localities in western part of Serbia, known as the main raspberry growing region of the country. Prior to sensitivity testing experimental conditions for radial growth assay were optimized. The results showed that the temperature of 22 °C, oatmeal agar medium and 12/12 hrs light/ darkness light regimen provided the best conditions for sensitivity tests. Most of D. applanata isolates were sensitive to the tested fungicides. The narrowest range of EC50 values was recorded for tebuconazole (1.42-2.66 mg L(-1)). The widest range of EC50 values was obtained for pyraclostrobin, ranging from 0.17 mg L(-1) to 55.33 mg L(-1). The EC50 values for the studied isolates were 39.48-51.19 mg L(-1) for copper hydroxide, 12.12-18.73 mg L(-1) for dithianon and 5.72-42.56 mg L(-1) for fluazinam. According to resistance factor values, all D. applanata isolates were sensitive to copper hydroxide, dithianon and tebuconazole. Among tested isolates, six were highly resistant to pyraclostrobin (RFs in the range of 207.1-325.5) and two moderately resistant to fluazinam (RFs were 3 and 7.4), respectively.
In this work by encapsulation technique we have synthetized three new clove bud essential oil (CEO) Emulsifiable Concentrate (EC) formulations depending on the carrier (synthetic zeolite- F-CSZ, nature zeolite- F-CNZ and gelatin- F-CG). The main idea was to develop an eco-friendly biopesticide that can find use in plant protection as an alternative to the use of conventional pesticides. By encapsulation we wanted to enable water solubility and ensure prolonged efficacy of the essential oil. Biological activity of designed CEO formulations was tested on potato tuber moth Phthorimaea operculella (fumigant mode of action), gray mold fungal pathogen Botrytis cinerea (preserver coatings), and soft rotting bacterial pathogens Pectobacterium carotovorum (subsp. carotovorum and brasiliensis) and Dickeya dianthicola (direct competition). CEO formulations evinced a prolonged action on mortality of P. operculella during the insects’ exposure to the concentration of the emulsions of 40 µL L−1 air. The mortality gradually decreased from a probability of 100% after the first 24 h to 50% after 5 days for F-CSZ or after 4 days for F-CNZ and F-CG. The most promising formulation is F-CSZ enabling activity during 14 days of exposure, while the effect of the other two formulations lasted 10 days. All three formulations produced a strong fungicidal effect against B. cinerea by preventing infection and disease development. The best efficacy was evidenced with F-CSZ (synthetic zeolite as a carrier) showing 100% efficacy when it was used even at the lowest tested concentration of active CEO (1%). The results of in vitro testing against soft rot pathogens determined the MIC value of CEO formulations to be 1% of active CEO. By this research, we present a novel perspective on the use of essential oils as an alternative, environmental biopesticide. CEO formulations can be commercially exploited as a fumigant or preserver coatings to extend the shelf life of stored products or the fresh-fruit market.
Field isolates of Didymella applanata, the causal agent of spur blight of raspberry, were evaluated in vitro for their sensitivity to mancozeb, chlorothalonil, captan, fluopyram, boscalid and difenoconazole. A total of 10 isolates, collected during 2013 at five localities in the major raspberry growing region in Serbia, and characterized as copper hydroxide, dithianon, and tebuconazole (sensitive), pyraclostrobin (sensitive or highly resistant) and fluazinam (sensitive or moderately resistant), were used in this study. The EC50 values for the isolates ranged from 1.33 to 2.88 mg L(-1) for mancozeb, from 3.18 to 6.65 mg L(-1) for chlorothalonil, from 15.75 to 24.69 mg L(-1) for captan and from 1.80 to 8.20 mg L(-1) for fluopyram. The narrowest range of EC50 values was recorded for difenoconazole (0.23-0.49 mg L(-1)), whereas the widest range was obtained for boscalid (4.49-49.25 mg L(-1)). The calculated resistance factors showed that all D. applanata isolates were sensitive to mancozeb, chlorothalonil, captan, and difenoconazole. Four isolates were moderately resistant to boscalid, while three of them were also moderately resistant to fluopyram. This finding of moderately resistant isolates to these SDHI fungicides indicates a possible cross-resistance which should be clarified in further investigations.
SUMMARYThe efficacy of mandipropamid (Revus 250 SC) in controlling Phytophthora infestans in potato was evaluated in field trials. The efficacies of Revus 250 SC in comparison with standard fungicides Quadris (azoxystrobin) were tested in several localities in Serbia (Kasarske Livade, Valjevska Kamenica and Opovo) in 2007 and 2008. Both of the tested fungicides exhibited high efficacy in controlling potato late blight. The differencies in the efficacy of Revus 250 SC (96.3-99.2%) and Quadris (94.1-95.5%) were insignificant. Our experiments showed that the investigated fungicide was highly effective against P. infestans even under high disease pressure.
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