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Alan R. Biggs

The proportion of spurs blooming on `McIntosh' apples (Malus domestica Borkh.) was reduced significantly in 1986 and 1988, but not in 1987, following seasonal programs of six bitertanol or flusilazole treatments applied at two and three rates, respectively. The fungicides were not associated with any visible phytotoxic effect nor was shoot length reduced by any fungicide treatment. In two of three experiments conducted in May and June 1986, transpiration was reduced by the low rate of flusilazole and the high rate of bitertanol relative to both the captan and nonsprayed trees. In all three experiments, flusilazole at 1.4 g a.i./100 liter was associated with transiently reduced transpiration rates, lasting a minimum of 48 hours, relative to the nonsprayed control. Fungicides affected the diffusive resistance of apple leaves in all three experiments; however, there were no consistent treatment effects on diffusive resistance among the three experiments.

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Alan R. Biggs and Stephen S. Miller

Twenty-three apple (Malus ×domestica Borkh.) cultivars were tested in the field and laboratory for their relative susceptibility to the white rot pathogen, Botryosphaeria dothidea. Wounded fruit were inoculated in the field at 2 to 3 weeks preharvest with mycelium from 14- to 21-day-old cultures. In the laboratory, detached fruit were similarly inoculated. Fruit were rated for relative susceptibility to the fungus with two criteria: disease severity of attached fruit in the field based on lesion growth (mm/degree-day) and disease severity of detached fruit in laboratory inoculations of wounded fruit (mean lesion diameter after 5 days). Based on the laboratory and field data from 2 years of study, cultivars were classified into three relative susceptibility groups: most susceptible: `Fortune' and `Pristine'; moderately susceptible: `Golden Supreme', `Creston', `Ginger Gold', `Sansa', `Golden Delicious', `Senshu', `Orin', `Sunrise', `GoldRush', `Arlet', `Braeburn', `Cameo', `Enterprise', `Fuji', `Shizuka', `Gala Supreme', and NY 75414; and least susceptible: `Honeycrisp', `Yataka', `Suncrisp', and `PioneerMac'. Compared to previous cultivar rankings, the results of the present study indicate that some new apple cultivars from the first NE-183 planting show greater resistance to Botryosphaeria dothidea than current standard cultivars.

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Alan R. Biggs and Stephen S. Miller

Twenty-three apple (Malus ×domestica) cultivars were tested in the field and laboratory for their relative susceptibility to the black rot pathogen, Botryosphaeria obtusa. Wounded fruit were inoculated in the field at 2 to 3 weeks preharvest with mycelium from 14- to 21-day-old cultures. In the laboratory, detached fruit were inoculated similarly. Fruit were rated for relative susceptibility to the fungus by determining disease severity of attached fruit in the field based on lesion growth (mm/degree-day) and detached fruit in laboratory inoculations of wounded fruit (mean lesion diameter after 4 days). Based on the laboratory and field data from two growing seasons, cultivars were classified into three relative susceptibility groups—most susceptible: `Orin', `Pristine', and Sunrise'; moderately susceptible: `Suncrisp', `Ginger Gold', `Senshu', `Honeycrisp', `PioneerMac', `Fortune', NY75414, `Arlet', `Golden Supreme', `Shizuka', `Cameo', `Sansa', and `Yataka'; and least susceptible: `Creston', `Golden Delicious', `Enterprise', `Gala Supreme', `Braeburn', `GoldRush', and `Fuji'. Compared to previous cultivar rankings, the results of the present study indicate that no new apple cultivars from the first NE-183 planting show greater resistance to Botryosphaeria obtusa than current standard cultivars.

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Alan R. Biggs and Gregory M. Peck

Three separate experiments were conducted to test standard calcium chloride salt (CaCl2) rates and several new formulations of calcium (Ca) for amelioration of bitter pit, a Ca-related physiological disorder that affects fruit of many apple (Malus ×domestica) cultivars, including the popular cultivar Honeycrisp. Even small amounts of bitter pit damage make apples unmarketable. We evaluated various formulations of Ca to compare their effectiveness in controlling bitter pit, including proprietary Ca products (InCa™, Sysstem-Cal™, Vigor-Cal™, XD10, and XD505) with and without antitranspirant. Calcium chloride is the most common Ca product used to reduce bitter pit incidence, but it has negative impacts, such as phytotoxicity and corrosiveness. Of the products that were tested in 2011, XD10 at the high rate and XD505 are candidates for future study. In 2012, both the CaCl2 and XD10 treatments had lower bitter pit severity than the nontreated control, but only the CaCl2 treatments had a lower total percentage of fruit with bitter pit compared with the control. The antitranspirant reduced bitter pit incidence in one of three treatments. Full season Ca treatments and higher rates (up to 23.5 lb/acre per season of elemental Ca) are needed to significantly reduce bitter pit incidence in ‘Honeycrisp’ apples in the mid-Atlantic United States.

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Emily E. Hoover, Richard P. Marini, Emily Tepe, Wesley R. Autio, Alan R. Biggs, Jon M. Clements, Robert M. Crassweller, Daniel D. Foster, Melanie J. Foster, Peter M. Hirst, Diane Doud Miller, Michael L. Parker, Gregory M. Peck, Jozsef Racsko, Terence L. Robinson and Michele R. Warmund

Researchers have collected a considerable amount of data relating to apple (Malus ×domestica) cultivars and rootstocks over the past 30 years, but much of this information is not easily accessible. The long-term goal of our working group is to increase access to this information using online technology available through eXtension. In eXtension, researchers and extension personnel are developing a community of practice (CoP) to increase the quality and amount of online information for individuals interested in our work [referred to as a community of interest (CoI)]. For this project, our CoI is broadly defined as commercial apple producers, nursery professionals, county extension educators, Extension Master Gardeners, home gardeners, and consumers. Our CoP is developing diverse educational tools, with the goals of increasing productivity, profitability, and sustainability for commercial apple production. Additionally, we will provide other members of our CoI access to research-based, reliable information on the culture of apples. We chose to begin our focus on cultivars and rootstocks adapted to the eastern United States and will add other U.S. regions as our resources and interest in our project grows.