Fungicide Sensitivity Monitoring of Alternaria spp. Causing Leaf Spot of Sugarbeet (Beta vulgaris) in the Upper Great Lakes.

Alternaria leaf spot (ALS), caused by Alternaria spp., can occur wherever sugarbeet is grown. Infection by Alternaria spp. and disease management has historically been considered a minor issue in sugarbeet production in the United States. An increase of both incidence and severity in 2016 of ALS high enough to cause yield loss has been observed in Michigan. With a renewed need to consider potential management of this disease, the sensitivity was determined for populations of Alternaria spp. to three classes of fungicides currently labeled for management of leaf spot on sugarbeet, including demethylase inhibitor (DMI), quinone outside inhibitor (QoI), and organo-tin fungicides. Leaves with symptoms of ALS were sampled from sugarbeet fields in east-central Michigan and southwestern Ontario, Canada. Monoconidial isolates were obtained to determine sensitivity to each fungicide class above. A spiral gradient dilution method was used to estimate the fungicide effective concentration (in milligrams per liter) that caused a 50% inhibition of fungal growth in vitro for all isolates. Significant temporal shifts were detected in the frequencies of sensitivity phenotypes to DMI and QoI but not organo-tin fungicides from 2016 through 2017. Individual isolates of Alternaria spp. were recovered with cross-resistance to DMI and multiple resistance to DMI, QoI, and triphenyltin hydroxide fungicides. To our knowledge, this is the first report of a fungus other than Cercospora beticola with resistance to organo-tin fungicides. Fungicide sensitivity monitoring indicates that an effective integrated disease management approach combining fungicide efficacy trials and monitoring pathogen biology is essential for developing effective resistance management recommendations.

Characterizing a novel strain of Bacillus amyloliquefaciens BAC03 for potential biological control application.

AIMS: To identify and characterize a bacterial strain BAC03, evaluate its biological control activity against potato common scab (Streptomyces spp.) and characterize an antimicrobial substance produced by BAC03. METHODS AND RESULTS: Bacterial strain BAC03, isolated from potato common scab suppressive soil, was identified as Bacillus amyloliquefaciens by analysing sequences of fragments of the recA, recN, cheA and gyrA genes. BAC03 displayed an antagonistic activity against Streptomyces spp. on agar plates using a co-culture method. In glasshouse assays, BAC03 applied in potting mix significantly reduced common scab severity (P < 0·05) and potentially increased the growth of potato plants (P < 0·05). An antimicrobial substance extracted from BAC03 by ammonium sulfate precipitation was identified as an LCI protein using liquid chromatography-mass spectrometry. The antimicrobial activity of either a BAC03 liquid culture or the ammonium sulfate precipitate fraction was stable under a wide range of temperatures, and pH levels, as well as following incubation with several chemicals, but was reduced by all proteinases tested. CONCLUSIONS: Bacillus amyloliquefaciens strain BAC03 displayed a strong antimicrobial activity, that is, the suppression of potato common scab, and may potentially enhance the plant growth. LCI protein is associated with some of the antimicrobial activity. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacterial strain BAC03 has the potential to be developed as a commercial biological control agent for potato common scab.

Zinc deficiency in pheasant chicks fed practical diets.

A disease syndrome characterized by abnormal feathering and varus deviation of the tarsometatarsus spontaneously occurred in pheasant chicks fed a practical commercially prepared diet. The addition of supplemental Zn to the commercial diet was effective in alleviating the clinical signs, even though the commercial mix had Zn levels that met the published pheasant chick requirement. Supplemental arginine was ineffective in reducing the severity of the clinical signs. Also, when the diet was mixed in a laboratory setting, pheasant chicks did not develop abnormal feathering and leg bones. Clinical signs caused by feeding the commercial mix were not reproduced by altering dietary calcium and phosphorus levels in the laboratory mix. Neither adding a pellet binder nor removing supplemental Zn from the lab mix produced as severe leg and feather deformities as the commercial mix. Thus, unidentified dietary factors are capable of causing a Zn-deficiency syndrome in pheasant chicks fed practical diets with analyzed Zn levels meeting the required levels.

Sodium requirements, balance and tissue composition of growing pigs.

The sodium requirements, balance, excretion, patterns and composition of some pig tissues were studied in two feeding trials and a balance trial followed by an additional feeding period with terminal tissue composition analysis. The growth of pigs fed a corn-soybean meal diet without added salt was severely restricted. Results confirm that a sodium requirement of .09% of the diet is adequate and that .20% NaCl supplementation is adequate for any natural diet for swine. Diets containing .065% sodium caused about a 25% reduction in growth when fed to 10-kg pigs but no significant reduction when fed to 27-kg pigs. Dietary retention was 96% for pigs fed .032% or .067% sodium. Retention was less per unit gain (gain was greater per unit sodium retention) fo9r pigs fed .032% sodium than for pigs fed .067% or more sodium. Those fed .032% sodium had a greater PCV after 1 week on trial and a smaller plasma sodium concentration after 2 weeks. The terminal tissue analyses showed that the pigs fed the lowest sodium diet had lower concentrations of sodium in plasma, muscle and bone, lower concentrations of chloride in plasma and muscle and a greater plasma potassium concentration. Crystal sodium of bone was not significantly affected.