Search Results

You are looking at 11 - 20 of 50 items for

  • Author or Editor: A.A. Powell x
  • Refine by Access: User-accessible Content x
Clear All Modify Search
Free access

Charles A. Powell and Peter J. Stoffella

Mature-green and mature-red tomato (Lycopersicon esculentum Mill.) fruit were harvested from spring- and fall-grown plants infested with sweet potato whitefly (SPWF; Bemisia tabaci Gennadins). The mature-green fruit were either ripened at 20 to 22C or cold-stored at 10 to 13C for 3 weeks and then were allowed to ripen at 20 to 22C. There was no significant difference in the appearance of either external or internal tomato irregular ripening (TIR) symptoms between the two storage–ripening regimes or in the appearance of internal TIR symptoms among the two storage regimes and vine-ripened tomatoes. Thus, removing the tomatoes from the SPWF during ripening does not reduce TIR symptoms. About half of the mature-green tomatoes, ripened with or without cold storage (10 to 13C), developed no external TIR symptoms, but about half of these tomatoes had internal TIR symptoms. About one-third of the tomatoes developed external symptoms during ripening, but these symptoms disappeared after ripening was complete. A high percentage (71%) of these tomatoes with external symptoms also had internal symptoms. The remaining tomatoes developed external TIR that did not disappear, and almost all of these tomatoes had internal symptoms. These data suggest that culling tomatoes that develop external TIR during ripening will reduce but not eliminate tomatoes with internal TIR from the fresh-fruit market.

Free access

Arlie A. Powell, James Pitts, and Bobby Boozer

Early flowering of peach in the southeastern United States can result in annual crop loss as a result of late winter-early spring freezes. In peach and other prunus, a fall application of ethephon delays flowering several days; however, delayed harvest and smaller fruit size of certain varieties may occur. Hydrogen cyanamide replaces the late stage of chilling in peach but can also advance bloom and harvest date while maintaing or enhancing fruit size. A randomized complete-block experimental design using 13-year old `Surecrop' trees was used to evaluate whether hydrogen cyanamide could offset the delayed harvest and smaller fruit size disadvantages of using ethephon without advancing bloom dates. Treatment combinations of ethephon (at 20%, 50%, and 90% of required chilling) and hydrogen cyanamide (at 90% to 100% of required chilling) were applied as whole-tree foliar sprays to near point of drip. Although not significant, there were trends toward hydrogen cyanamide overcoming both smaller fruit size and delayed harvest induced by ethephon. This agrees with an earlier study using `Redhaven'. Dormex negated the late flowering effects of ethephon applied at 20% chilling but did not cause flowering earlier than the control.

Free access

Arlie A. Powell, James Pitts, and Bobby Boozer

Early flowering of peach in the Southeast can result in annual crop loss as a result of late winter—early spring freezes. It has been shown in peach and other Prunus that a fall application of ethephon delays flowering several days. However, delayed harvest and smaller fruit size of certain varieties may occur. Hydrogen cyanamide replaces lack of chilling in peach but can also advance harvest date and possibly enhance or maintain fruit size. A randomized complete-block experimental design using 12-year-old `Redhaven' trees was used to evaluate whether hydrogen cyanamide could offset the delayed harvest and smaller fruit size disadvantages of using ethephon without advancing bloom dates. Treatment combinations of ethephon (at 20%, 50%, and 90% of required chilling) and hydrogen cyanamide (at 90% to 100% of required chilling) were applied as whole-tree foliar sprays to near point of drip. Although nonsignificant, there were trends toward hydrogen cyanamide overcoming both smaller fruit size and delayed harvest induced by ethephon.

Free access

Arlie A. Powell, James Pitts, and Robert Boozer

Early flowering of peach in the southeastern U.S. often results in some annual crop loss as a result of late winter–early spring freezes. It has been shown in peach and other prunus that a fall application of ethephon delays flowering 4 to 7 days and possibly affords increased bud hardiness. However, delayed harvest and smaller fruit size of certain varieties may occur. Hydrogen cyanamide replaces lack of chilling in peach, but can also advance harvest date and possibly enhance or maintain fruit size. A randomized complete-block experimental design was used to evaluate whether hydrogen cyanamide could offset the delayed harvest and smaller fruit size disadvantages of using ethephon without advancing bloom dates over a 3-year period. Treatment combinations of ethephon (at 20%, 50%, and 90% of required chilling) and hydrogen cyanamide (at 90% to 100% of required chilling) were applied as whole-tree foliar sprays to near point of drip. Results exhibited a possible trend toward hydrogen cyanamide overcoming smaller fruit size and delayed harvest.

Free access

Charles A. Powell, Robert R. Pelosi, and Phyllis A. Rundell

None of 4190 sweet orange [Citrus sinensis (L.) Osb.] nursery trees of `Hamlin', `Midsweet', `Navel', and `Valencia' sampled from five Florida citrus nurseries were infected with a decline-inducing isolate of citrus tristeza virus (CTV) as judged by enzyme-linked immunosorbent assay (ELISA) using isolate-specific monoclonal antibodies. Two of the nurseries had a relatively high level of infection (37% to 100% of composite samples containing tissue from 10 trees) with nondecline-inducing (mild) isolates of CTV, depending on the cultivar. Three of the nurseries had a lower incidence of mild CTV (0% to 22% of 10 tree composite samples). No nursery was CTV-free. ELISA of individual trees used as budwood sources by the nurseries revealed that one tree out of 260 tested contained decline-inducing CTV, and 83 contained mild CTV. These results suggest that the budwood certification program adopted in 1997 has virtually eliminated decline-inducing CTV from commercial budwood supplies.

Free access

C.A. Powell, A. Hadidi, and J.M. Halbrendt

The ability of 32P-labeled transcribed cRNA probes to detect tomato ringspot virus (TmRSV) RNA in nucleic acid extracts from roots, bark, and leaves of nectarine (Prunus persica [L.] Batsch) trees with the Prunus stem-pitting disease was assessed and compared with detection of TmRSV antigen by enzyme-linked immunosorbent assay (ELISA) in the same tissues. Neither TmRSV-specific nucleic acid nor antigen was detected in nectarine leaf tissue. ELISA detected TmRSV antigen in root extracts from 71% of the diseased trees, while dot hybridization detected virus-specific nucleic acid in 18% of the same samples. However, ELISA detected TmRSV antigen in only 47% of bark extracts; whereas TmRSV-specific nucleic acid was detected in 100% of the bark extracts from samples collected at or near the soil line. When nucleic acid extracts from bark were prepared from various locations on diseased trees and tested for TmRSV-specific nucleic acid by dot hybridization, there was an almost perfect correlation between the presence of stem-pitting symptoms and the detection of TmRSV nucleic acid. Detection of TmRSV RNA from the bark tissue of rootstock suckers from TmRSV-infected `Delicious'/MM.lO6 apple (Malus × domestica Borkh.) trees was unsuccessful using dot hybridization. The viral RNA, however, was usually detected in either leaf or root tissue of these same trees.

Free access

Charles A. Powell, Mark A. Ritenour, and Robert C. Bullock

The trunk diameter of ‘Valencia’ sweet orange trees tested with seven insect control strategies was measured annually for the first 5 years after planting. Yield data (marketable fruit per tree) were collected after the fourth and fifth years. The insect control treatments were Admire (imidacloprid) applied at 12, 6, 3, or 2-month intervals; Temik (aldicarb) applied annually; Meta-Systox-R (oxydemeton-methyl) applied annually; or no insect control. Trunk diameter was significantly increased by Temik treatment at 1 and 2 years after planting. Six annual applications of Admire (at 2-month intervals) significantly increased trunk diameter 2 years after planting. None of the other treatments affected trunk diameters compared with the control. There were no trunk diameter differences among treatments at 3, 4, or 5 years after planting. Both Temik applied annually and Admire applied every other month or every 3 months significantly increased yield.

Free access

Charles A. Powell, Phyllis A. Rundell, and Robert R. Pelosi

Bark chips from six container-grown citrus trees, infected with nondecline-inducing citrus tristeza virus (CTV) isolates and maintained in a vector-free greenhouse for 10 years, 15 commercial grapefruit (Citrus paradisi Macf.) trees, and 16 commercial sweet orange [C. sinensis (L.) Osbeck] trees were used to inoculate three indicator plants each of `Madam Vinous' sweet orange [C. sinensis (L.) Osbeck], sour orange (C. aurantium L.), `Duncan' grapefruit (C. paradisi Macf.), `Mexican' lime [C. aurantifolia (Christm.)], Swingle citrumelo [C. paradisi Macf. × Poncirus trifoliota (L.) Raf.], and sour orange grafted with `Hamlin' sweet orange [C. sinensis (L.) Osbeck]. All plants providing bark chips had repeatedly tested positive by enzyme-linked immunosorbent assay (ELISA) for CTV [reacted with monoclonal antibody (MAb) 17G11], but tested negative for Florida decline-inducing isolates of CTV (did not react with MAb MCA13). After 6 months in vector-free greenhouses, all in oculated trees (except Swingle citrumelo, which is considered CTV resistant) were positive for CTV by 17G11 ELISA. In addition, some indicator plants inoculated from nine (two container, two commercial grapefruit, and five commercial orange trees) of the 37 bark chip source trees also were positive for decline-inducing CTV by MCA13 ELISA. Some of these positive indicators also showed vein-clearing symptoms characteristic of infection with a severe isolate of CTV. No control, noninoculated indicators in the same greenhouse, became infected with either decline-inducing or nondecline-inducing CTV. These results indicate that decline-inducing isolates of CTV can be present as a minor component of a mixture at levels undetectable by ELISA, and that these decline-inducing isolates can become detectable by ELISA and sometimes by symptoms when inoculated into indicator plants.

Free access

Arlie A. Powell, Robert T. Boozer, and James A. Pitts

Phenological studies were conducted over a 3-year period beginning in Winter 1993–94 to relate flowering and fruiting stages of peach to heat accumulation [growing degree hours (GDH)]. Mature trees of `Loring' and `Redhaven' peach in the same orchard were used annually. Some variation from year to year was apparent in GDH levels related to 50% flower and other stages of development. Major sources for this variation appear to be timing and severity of pruning, tree vigor, and shoot diameter. Temperature predict models were used successfully to properly forecast GDH accumulation and and various flowering and fruiting stages once rest was satisfied.