Search Results
Abstract
Rooted twig cuttings of ‘Jefferson’ peach [Prunus persica (L.) Batsch] infected or noninfected with phony peach disease were divided into nonphony, medium phony, and severe phony based on symptoms and on Fastidious, gram-negative, xylemlimited bacteria (PPXLB) counts. During the dormant season, the rooted plants were subjected to cold treatments of -11.7°, -14.4°, -17.9°, -20.0°, and -21.6°C in cold chambers. Plants with higher PPXLB counts exhibited more cold injury than plants with lower counts.
Bumblebees (Bombus spp.) are important pollinators of mostly self-sterile rabbiteye blueberry (Vaccinium ashei Reade). Annual bee colonies start from solitary overwintered queens who emerge in near-synchrony with rabbiteye blueberry bloom. Although colony populations may reach several hundred individuals by midsummer, in early spring most Bombus visiting rabbiteye blueberry are queens reared the previous season. Thus, practices that encourage production of queens in summer may increase populations of blueberry pollinators the next spring. In south Georgia, midsummer shortages of nectar-yielding plants may nutritionally limit queen production, and cultured bee forages may help overcome this deficiency. Candidate plants must not compete with the crop for pollinators, and they must be attractive to bees, easy to grow, vigorous, and non-invasive. In 3 years of trials, the following plants have shown promise as supplemental bumblebee forages in south Georgia: Althea (Hibiscus syriacus), abelia (Abelia ×grandifolia), vitex (Vitex agnuscastus), red clover (Trifolium pratense perenne), Mexican heather (Cuphea hyssopifolia), monkey grass (Liriope muscari), summer sweet (Clethra alnifolia), and giant sunflower (Helianthus giganteus).
Observations in controlled field experiments over 5 years indicated that imidacloprid, applied as a soil drench around the trunks of peach (Prunus persica), nectarine (P. persica var. nectarine) and japanese plum (P. salicinia) trees at planting and in the early spring and mid-summer for two subsequent seasons (0.7 g/tree a.i.), slowed the development of symptoms of phony peach disease (PPD) and plum leaf scald (PLS) (Xylella fastidiosa) in the trees. After 3.5 years, the percentage of peach trees showing PPD symptoms was 8.5% for the imidacloprid-treated trees compared to 34.3% for untreated trees. After 4.5 years, the percentage of peach trees showing PPD symptoms was 13.1% in the treated trees and 71.4% in the untreated trees. After 3.5 years, nectarine trees in untreated and treated plots showed PPD symptoms in 8.3% and 0.9% of the trees, respectively. After 4.5 years, PPD symptoms in nectarine were found in 32.3% of the untreated trees and 8.5% of the treated trees. Development of PLS disease in plum was also slowed by the trunk drench with imidacloprid in two japanese plum varieties. After 3.5 years, dieback was observed in 55% of the twigs of untreated and 23% of the twigs of treated trees of `Au Rosa' plum and 33% of the twigs of untreated and 12% of the twigs of treated trees of `Santa Rosa' plum.
The purpose of this three-way cooperative project is to develop new fresh-market peach and nectarine varieties in the 400 to 650 chill hour range for the early season shipping market. Since 1990, >3000 seedlings have been evaluated, resulting in 48 selections. Additionally, several hundred selections from other programs have been evaluated. `Sunsplash', an attractive, early season, 400 chill hour nectarine, was released in 1993 as a result of this cooperative effort. A novel aspect of the program has been the use of non-melting flesh parents for the purpose of improving handling characteristics. Selections include both yellow- and white-flesh types, peaches and nectarines. Some may be adapted for use in other production areas and are available for testing under non-propagation agreement. Evaluation summaries of selections and standards will be presented.
Abstract
Softwood cuttings taken from phony peach disease-infected and uninfected trees of ‘Jefferson’ peach [Prunus persica (L.) Batsch] produced 80% or more well-rooted cuttings with no significant difference (5% level) between phony and non-phony cuttings.
Abstract
Application of 960 ppm (2-chIoroethyl)methylbis(phenylmethoxy)silane (CGA-15281) substantially inhibited carbon transport into young fruit of peach [Prunus persica (L.) Batsch] 4 to 5 days before visual symptoms of senescence occurred. Carbon transport was unaffected 4.25 hours after treatment, but was greatly reduced after 24 hours. Reduced carbon transport continued through 144 hours following CGA-15281 application.
Abstract
CGA-15281 applied in the fall delayed bloom in peach (Prunus persica L. Batsch) by 4–9 days without damage to the trees. The length of the delay was cultivar and concentration dependent. Fall ethephon applications (500 ppm) damaged trees severely, but delayed bloom 10–18 days, whereas 125 or 250 ppm ethephon caused little tree damage and delayed bloom 3–5 days. Bloom delay from application of ethylene-generating compounds resulted from both prolonging rest and slow bud development once rest was complete. Daminozide applied in January caused bloom delay in 1983 but not in 1984. Silver nitrate had little effect on bloom delay or blossom density at any time of application. Dimethipin and merphos applications in late summer caused defoliation and reduced blossom density, but did not affect date of bloom. Thidiazuron did not induce defoliation or delay in bloom, but greatly reduced blossom density. Chemical names used: (2-chloroethyl)methylbis(phenylmethoxy)silane (CGA-15281); (2-chloroethyl) phosphonic acid (ethephon); butanedioic acid mono (2,2-dimethylhydrazide (daminozide); 2,3-dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetraoxide (dimethipin); N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron); Tributyl phosphorotrithioite (merphos).
Abstract
Semihardwood peach [Prunus persica (L.) Batsch] cuttings were successfully rooted when the bases and tops were misted intermittently with water. Rooting was not affected by cultivar or type of cutting (basal vs. terminal). Closer proximity of the bases of the cuttings to the mist line and overhead misting improved rooting percentage.