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Blair J. Sampson, Stephen J. Stringer, and Donna A. Marshall

We evaluated relationships between floral traits of 23 genotypes of southern blueberries and indices of pollination efficiency (fruit set, fruit abortion, seed number, and berry size) for Osmia ribifloris Cockerell, a manageable solitary bee. Flower size in Vaccinium and presumably ovary size were proportional to berry size, except for the tiny blooms of one V. tenellum clone (NC7808), which produce large commercial-sized berries of ≈2 g. Longer-styled blueberry flowers visited by O. ribifloris produced the heaviest berries with the most seeds. Osmia ribifloris reliably pollinated ‘Climax’ and ‘Tifblue’ rabbiteye blueberries. However, the peculiarly misshapen blooms of ‘Premier’ rabbiteye blueberry receive less pollination from O. ribifloris and yield berries containing 25% fewer seeds. Fruit set for these misshapen ‘Premier’ flowers was equivalent to that of intact flowers indicating that this floral polymorphism would not greatly alter cultivar performance. For seven Vaccinium species, wild and cultivated alike, 80% to 100% of a plant’s fruit production depends on efficient cross-pollination by bees such as O. ribifloris.

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Stephen J. Stringer, Arlen D. Draper, Donna Marshall-Shaw, Blair J. Sampson, and John J. Adamczyk Jr.

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Stephen J. Stringer, Donna A. Marshall, Blair J. Sampson, and James M. Spiers

A study was conducted at the Mississippi State University Agricultural and Forestry Experiment Station (MAFES) McNeil Unit in southern Mississippi to identify promising muscadine grape (Vitis rotundifolia) germplasm for use as parents in the breeding and genetics research program and to develop information on performance for use by growers in the region for cultivar selection decisions. The vineyard was first established in 1992 and was expanded in 1994. Cultivars were evaluated in 2001, 2002, and 2006 for their performance and were found to differ in vigor, resistance to diseases, yield, and fruit quality. Cultivars suitable for winemaking that performed well included Carlos, Doreen, Magnolia, Noble, Regale, Sterling, and Welder. Cultivars intended for the fresh market that produced high yields and high-quality fruit included Alachua, Black Beauty, Darlene, Fry, Ison, Janebell, Nesbit, Polyanna, Sweet Jenny, Summit, and Tara. ‘Dixie’, a multipurpose cultivar, ‘Eudora’, a newly released fresh-market cultivar, and ‘Southern Home’, a multipurpose cultivar with enhanced ornamental value, also performed well at this location.

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Stephen J. Stringer, Donna A. Marshall, James M. Spiers, and Blair J. Sampson

Muscadines are grapes indigenous to the Southeastern United States, and they are highly prized for their unique fruity flavors. Factors including skin color, berry size, skin thickness, flower type, productivity, etc., vary among muscadine grape cultivars, making some cultivars more desirable for fresh market while others are better suited for processing and prodction of juice, jelly, and wine. A muscadine grape research vineyard was established in McNeil, Miss., in 1992 containing 37 named cultivars and numerous breeding lines. Performance of these cultivars was evaluated in 2001–2003 and results of these trials are presented.

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Christopher T. Werle, Karla M. Addesso, Blair J. Sampson, Jason B. Oliver, and John J. Adamczyk

Invasive ambrosia beetles (Coleoptera: Curculionidae) are an important pest problem at ornamental tree nurseries. Available chemical treatments are not completely effective and, due to the length of the beetle dispersal period and insecticide breakdown, repeated treatments can become costly in terms of application expense and nontarget impacts. Additional options are needed to reduce application frequency and to provide an acceptable level of crop protection. Four treatments were tested using ethanol-injected eastern redbud trees at research sites in Mississippi (MS) and Tennessee (TN) over 2 years (2014–15), with the number of new ambrosia beetle galleries compared over time on 1) nontreated control trees, 2) kaolin-treated trees, 3) bifenthrin-treated trees, and 4) kaolin + bifenthrin (k + b)-treated trees. Kaolin-treated trees rapidly lost their coating after rain events and, at 6 days after treatment (DAT) in TN, no differences were detected in the number of beetle galleries between kaolin and nontreated control trees. Kaolin + bifenthrin-treated trees appeared to retain treatment residue longer, but were not better-protected than bifenthrin-treated trees at any time. Further research is needed to determine whether an adjuvant, such as a surfactant, spreader, or sticker, may enhance the modest impact offered by kaolin in our test, or if a reduction in rates of bifenthrin may be allowable.

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Grant T. Kirker, Blair J. Sampson, Cecil T. Pounders, James M. Spiers, and David W. Boyd Jr

Azalea lace bug (ALB), Stephanitis pyrioides (Scott), is an important economic pest of azaleas in the southeastern United States. In this study, 33 commercially available cultivars of evergreen azalea, Rhododendron spp., were evaluated for S. pyrioides feeding preference in both choice and no-choice feeding bioassays. Mean stomatal length and area, which were hypothesized to affect ALB feeding preference, were also measured for each of 33 cultivars and results were correlated with indices of ALB feeding (mean feces) and fecundity (mean eggs). An azalea cultivar, Fourth of July, was least preferred by ALB in both no-choice and choice tests, whereas ‘Watchet’ was most preferred. Cultivars Fourth of July and Delaware Valley White had the smallest mean stomatal areas despite their disparate susceptibilities to ALB feeding. Although stomates through which ALB insert their proboscides vary in size among azalea cultivars, they confer no obvious resistance to ALB feeding preference. Therefore, the mechanism for lace bug resistance in azalea remains elusive.

Open access

Nicolas C. Strange, John K. Moulton, Ernest C. Bernard, William E. Klingeman III, Blair J. Sampson, and Robert N. Trigiano

Helianthus verticillatus Small (whorled sunflower) is a federally endangered plant species found only in the southeastern United States that has potential horticultural value. Evidence suggests that H. verticillatus is self-incompatible and reliant on insect pollination for seed production. However, the identity of probable pollinators is unknown. Floral visitors were collected and identified during Sept. 2017 and Sept. 2018. Thirty-six species of visitors, including 25 hymenopterans, 7 dipterans, 2 lepidopterans, and 2 other insect species, were captured during 7 collection days at a site in Georgia (1 day) and 2 locations in Tennessee (6 days). Within a collection day (0745–1815 hr), there were either five or six discrete half-hour collection periods when insects were captured. Insect visitor activity peaked during the 1145–1215 and 1345–1415 hr periods, and activity was least during the 0745–0845 and 0945–1015 hr periods at all three locations. Visitors were identified by genus and/or species with morphological keys and sequences of the cox-1 mitochondrial gene. The most frequent visitors at all sites were Bombus spp. (bumblebees); Ceratina calcarata (a small carpenter bee species) and members of the halictid bee tribe Augochlorini were the second and third most common visitors at the two Tennessee locations. Helianthus pollen on visitors was identified by microscopic observations and via direct polymerase chain reaction of DNA using Helianthus-specific microsatellites primers. Pollen grains were collected from the most frequent visitors and Apis mellifera (honeybee) and counted using a hemocytometer. Based on the frequency of the insects collected across the three sites and on the mean number of pollen grains carried on the body of the insects, Bombus spp., Halictus ligatus (sweat bee), Agapostemon spp., and Lasioglossum/Dialictus spp., collectively, are the most probable primary pollinators of H. verticillatus.

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Stephen J. Stringer, Donna A. Shaw, Blair J. Sampson, Hamidou F. Sakhanoko, Ebrahiem Babiker, John J. Adamczyk Jr., Mark K. Ehlenfeldt, and Arlen D. Draper