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  • Dalrymple Jennings posted an update 3 weeks, 1 day ago

    ua in China. M. decidua is a horticultural plant which belongs to the protected and endangered tree species. This finding is important to alert growers to realize the proper management of this disease during species protection and cultivar extension.Anthracnose fruit rot (AFR) and Botrytis fruit rot (BFR) are primary diseases affecting strawberry, which typically drive fungicide applications throughout the growing season. The Strawberry Advisory System (StAS), a disease forecasting tool, was originally developed in Florida to better time fungicide sprays by monitoring AFR and BFR infection risk based on leaf wetness and temperature input in real-time. Thirteen field trials were conducted in Maryland and Virginia between 2017 and 2019 to evaluate the StAS performance in the Mid-Atlantic region. As a result, 55%, 18%, and 31% fewer sprays were recorded on average in the model-based StAS treatment compared with the grower standard treatment in 2017, 2018, and 2019, respectively. Marketable yield, as well as AFR and BFR incidence were largely comparable between the two treatments. However, poor disease control occurred during the StAS treatment in four trials in 2017, presumably due to a missed fungicide spray during a high-risk infection event and attributable to heavy rainfall that led to impassable fields. The implementation of the StAS may be further challenged by the employment of floating row covers that are essential for growing strawberries in plasticulture systems in open-fields in the Mid-Atlantic region. Preliminary results indicated that row covers can alter canopy-level microclimatic conditions, possibly increasing the risk for disease occurrence. Overall, the StAS can be a valuable tool for Mid-Atlantic growers to control AFR and BFR, but sprays may need to be promptly applied when consecutive or heavy rainfalls are predicted, especially for highly susceptible cultivars. Complications in disease forecasting and management arising from the use of row covers need to be further addressed in this region due to its highly diverse climate.Natamycin is a biofungicide that was recently registered for postharvest use on citrus and stone fruits in the United States. It has been used as a food preservative for many decades, with no resistance ever observed to date. The objective of this study was to determine baseline sensitivities for mycelial growth of 43 to 72 isolates of seven postharvest pathogens to natamycin and the resistance potential of Penicillium digitatum. Mean effective concentrations to inhibit mycelial growth by 50% (EC50 values), as determined by the spiral gradient method, were 0.90 μg/ml for Alternaria alternata, 0.76 μg/ml for Botrytis cinerea, 3.20 μg/ml for Geotrichum citri-aurantii, 0.17 μg/ml for Monilinia fructicola, 1.54 μg/ml for Penicillium digitatum, 1.14 μg/ml for P. expansum, and 0.48 μg/ml for Rhizopus stolonifer. Distributions of EC50 values for each pathogen were unimodal and mostly normal with no outliers detected. Natamycin was also inhibitory to spore germination with values for five of the species similar to those for mycelial growth. Microscopically, natamycin generally arrested spores at the pre-germination swelling stage. Mass platings of conidial mixtures of ten isolates of P. digitatum were inoculated on agar media with 2.5-log radial concentration gradients of natamycin or fludioxonil, and platings of G. citri-aurantii were executed on media amended with natamycin or propiconazole. No resistant isolates were observed for both species to natamycin or for G. citri-aurantii to propiconazole, whereas a resistance frequency of 4.5 x 10-6 to 3.1 x 10-6 was calculated for P. digitatum to fludioxonil. The wide spectrum of activity against different fungal pathogens and a low resistance potential support the registration of natamycin as a postharvest treatment and its integration into an integrated pest management program with other practices including sanitation and rotation of other fungicides with different modes of action.Fusarium head blight (FHB), caused mainly by Fusarium graminearum, is best controlled with demethylation inhibitor (DMI) fungicides during flowering. Romidepsin inhibitor However, the use of premixes of DMI and quinone outside inhibitor (QoI) fungicides to control FHB has increased in Brazil. Data on FHB severity and wheat yields measured in field experiments conducted in Brazil were gathered from both peer- and non-peer-reviewed sources published from 2000 to 2018. After applying selection criteria, 73 field trials from 35 bibliographic sources were identified, among which 50% of the data were obtained from cooperative network trials conducted after 2011. To be included in the analysis, a DMI+QoI premixes or tebuconazole (TEB) were tested in at least 14 trials and three years. Four premixes met the criteria. Estimates of percent control (and respective 95% confidence interval) by a network model fitted to the log of the treatment means ranged from 44.1% (pyraclostrobin + metconazole applied once; 32.4 to 53.7) to 64.3% (pyraclostrobin + metconazole; 58.4 to 69.3); the latter not differing from TEB (59.9%, 53.6 to 65.3). Yield response was statistically similar for pyraclostrobin + metconazole (532.1 kg/ha, 441 to 623) and trifloxystrobin + prothioconazole (494.9 kg/ha, 385 to 551), and both differed statistically from a group composed of TEB (448.2 kg/ha, 342 to 554), trifloxystrobin + TEB (468.2 kg/ha, 385 to 551), azoxystrobin + TEB (462.4 kg/ha, 366 to 558) and pyraclostrobin + metconazole applied once (413.7 kg/ha, 308 to 518). The two categories of FHB index (7% cut off) and yield (3,000 kg/ha cut off), both in the non-treated check, did not explain the heterogeneity in the estimates. Two sequential sprays of TEB or one spray of pyraclostrobin + metconazole as management choices are likely more profitable than DIM+QoI premixes sprayed twice during flowering considering only the fungicide effects on yield.Fusarium basal rot (FBR) is particularly problematic to Allium producers worldwide. In Vietnam, information on the profile of FBR is scarce, despite the presence of Fusarium spp. in Allium plants has long been recorded. In the present study, a total of 180 isolates of Fusarium spp. were recovered from Allium bulbs/plants showing symptoms of FBR in 34 commercial Allium fields around Da Lat, Lam Dong (Vietnam). These isolates were identified to the species level by using sequencing the ITS region and the translation elongation factor 1α (TEF-1α) gene. F. oxysporum was found to be most prevalent (81%) in samples from all locations and Allium varieties, followed by F. solani (15%) and F. proliferatum (4%) which was only found in onion (Allium cepa L.). Pathogenicity tests on onion seedlings (56 isolates) and mini bulbs (10 isolates) indicated that onion can be infected by all these species, but that the virulence varied greatly between isolates. Moreover, isolates that were virulent on seedlings were sometimes not virulent on bulbs and vice versa, which points to a specialization of isolates for the host phenology.

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