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Rodulfo O. Pacumbaba Jr. and Caula A. Beyl

The growing popularity of Asian pears in the open market has generated a need for more information about their fireblight resistance and stress tolerance. In 1994, Alabama A&M Univ. established a large research planting of 10 cultivars of Asian pear on three different rootstocks. The cultivars included Kosui, Korean Giant, 20th Century, Hosui, Shinko, Ichiban Nashi, Shinseiki, Chojuro, Okusankichi, and Shinsui. The three rootstocks used were Pyrus betulaefolia, Pyrus calleryana, and Old Home × Farmingdale 333. The planting was arranged as a randomized complete block replicated 10 times with a total of 300 trees planted. Mortality was scored in late 1995 and data was subjected to Chi-square analysis. Rootstock did have a significant effect on mortality. P. betulaefolia had the lowest frequency of mortality of 11%, with Old Home and P. calleryana at 24% and 31% respectively. Cultivars also had a significant effect on mortality. Korean Giant and Shinseiki had the lowest mortality of 3.33% and 6.67%, respectively. Kosui and Hosui had the highest mortality of 46.67% and 36.67%. Stress conditions that occurred during 1995 and environmental factors that contribute to the development of fireblight were responsible for the mortality of the Asian pear.

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Rodulfo O. Pacumbaba Jr. and Caula A. Beyl

CD-ROM technology, scanners, and image capture software have enabled an alternate approach to determining disease severity. When estimating disease damage, information on disease severity may be as important as information on disease incidence. Disease incidence is the proportion of leaves infected on each tree; disease severity is the number of lesions or amount of tissue damage per tree. The Mielke and Langdon scale was used to determine the incidence of dogwood anthracnose on dogwoods under physiological stress; the CD-ROM system was used to determine the severity of the disease. Dogwood seedlings were exposed to four shade and three water levels for 12 weeks. Leaf images were stored on a photo-CD for image analysis. Water availability at 100% water-holding capacity significantly increased disease severity on dogwood leaves inoculated in vitro. The system allowed detection of a significant effect of water availability on susceptibility of the leaf to dogwood anthracnose that was not detected when incidence of infection was evaluated on a whole-plant basis

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Rodulfo O. Pacumbaba Jr., Catherine Sabota, and Rhonda Britton

Sixty-six perennial ornamental cultivars were established and then grown under low maintenance, intensive weed competition, and severe mowing conditions. These cultivars were evaluated for their potential application for roadside/median beautification. Experimental plots were cleared with Roundup® prior to planting. During the first 3 weeks of establishment, plants were irrigated as needed. Plants were grown for one season, then pruned back to simulate bush-hog mowing. Plants were grown under low maintenance and no weed control conditions for two growing seasons. Plants were evaluated each season for simulated bush-hog damage recovery potential, survivability under severe weed competition, height, and spread. Two-way analysis of variance with repeated measurements showed that height and spread variation had a significant interaction between plant cultivar and time of evaluation. Several Zephyranthes sp. cultivars performed poorly under severe weed competition and mowing damage resulting in a high mortality rate. Cultivars that did perform well for the 2-year evaluation period include Lagerstroemia indica ×fauriei `Natchez,' Lagerstroemia indica ×fauriei `Muskogee,' Vitex agnus-castus `Shoal Creek,' and Myrica cerifera. Rosa × `Chuckles' and Rosa × `Knock Out' cultivars, with their popular showy appearance, performed moderately well and showed high potential for roadside/median beautification applications.