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Abstract
The severe freeze of January 12–14, 1981 gave Florida Fruit Crops Extension faculty some serious challenges and unique opportunities in ensuing months. Record-breaking low temperatures throughout peninsular Florida severely damaged much of Florida’s citrus and growers were faced with many problems dealing with rehabilitation and care of frozen fruit and trees. Within 24 hours after the severity of the freeze was apparent, Extension faculty of the University of Florida's Department of Fruit Crops had formulated a massive state-wide effort of intensive Extension to help growers cope with their problems. This paper outlines the procedure used to formulate this educational program.
Abstract
Florida has a unique training program for 4-H youths with interest in citrus. Extension specialists in the Department of Fruit Crops, county extension personnel and industry leaders cooperate in an annual Junior Citrus Institute held at 4-H Camp Cloverleaf near Lake Placid. Here, outstanding 4-H members spend a week learning horticultural operations such as fertilizing, spraying, pruning and cultivation, as well as nursery practices.
Abstract
The effectiveness of intermittent and constant microsprinkler irrigation, compared with no irrigation, for freeze protection of young ‘Hamlin’ orange trees [Citrus sinensis (L.) Osb.], was studied during radiative and advective freezes in 198586. All tree trunks were wrapped with fiberglass insulation to reduce evaporative cooling. Intermittent irrigation of 5 min on and 10 or 15 min off maintained trunk temperatures under the wrap above critical values during radiative and advective freezes at air temperatures of — 7.1°C. However, trunk temperatures above the wrap decreased to below air temperatures due to evaporative cooling when using intermittent treatments during advective conditions. Trunk temperatures were highest for constant irrigation, intermediate for intermittent, and lowest for unirrigated wrapped trees; yet, survival was similar for all treatments. Nevertheless, intermittent irrigation provided acceptable freeze protection to the lower trunk using one-fourth as much water as constant irrigation and may allow citrus growers more flexibility in using irrigation for freeze protection of young citrus trees.
Bacteriophages specific to Xanthomonas campestris pv. pelargonii (Xcp), the causal agent of bacterial blight of geranium, Pelargonium ×hortorum L.H. Bailey, were isolated from soil and sludge samples from Florida, California, Minnesota, and Utah. Sixteen phages were evaluated for their potential to lyse 21 Xcp strains collected from around the world. The Xcp strains varied in their susceptibility to the phage isolates with 4 to 14 phages producing a lytic or highly virulent reaction. A mixture of five h-mutants was developed from phages that exhibited the broadest host-ranges and tested against the same Xcp strains. The h-mutant phage mixture lysed all 21 Xcp strains. Three experiments were designed to determine the efficacy of using a mixture of four h-mutant phages to control the spread of the bacterial blight pathogen on potted and seedling geraniums under greenhouse conditions. Plants surrounding diseased inoculated plants were treated with a phage mixture at 5 × 108 pfu/mL daily, biweekly, or triweekly, or treated with Phyton-27®, at 2.0 mL·L-1 every 10 or 14 days. In potted geraniums, daily foliar sprays of the phage mixture had reduced disease incidence and severity by 50% and 75%, respectively, relative to control plants after 6 weeks. In two plug experiments, the phage mixture applied daily also had reduced disease incidence and severity by 69% and 86%, and 85% and 92%, respectively, when compared with controls after 5 weeks. In all three experiments, disease incidence and severity were less for plants treated daily with phages than for those treated less frequently with phages or with Phyton-27®. Chemical name used: copper sulfate pentahydrate (Phyton-27®).
A mixture of host-range mutant (h-mutant) bacteriophages specific for tomato race 1 (T1) and race 3 (T3) of the bacterial spot pathogen, Xanthomonas campestris pv. vesicatoria (Doidge) Dye was evaluated for biological control of bacterial spot on `Sunbeam' tomato (Lycopersicon esculentum Mill.) transplants and field-grown plants for two seasons (Fall 1997 and Fall 1998). Foliar applications of bacteriophages were compared with similar applications of water (control) and of copper/mancozeb bactericides, the commonly used chemical control strategy for tomato seedling and field production. In 1997, the incidence of bacterial spot on greenhouse-grown seedlings was reduced from 40.5% (control) to 5.5% or 0.9% for bactericide- or bacteriophage-treated plants, respectively. In 1998, the incidence of bacterial spot was 17.4% on control plants vs. 5.5% and 2.7% for bactericide- and bacteriophage-treated plants, respectively, although these differences were not statistically significant at P ≤ 0.05. Applications of bacteriophages to field-grown tomatoes decreased disease severity as measured by the area under the disease progress curve (AUDPC) by 17.5% (1997) and 16.8% (1998) compared with untreated control plants. Preharvest plant vigor ratings, taken twice during each field season, were higher in the bacteriophage-treated plants than in either bactericide-treated plants or nontreated controls except for the early vigor rating in 1998. Use of bacteriophages increased total weight of extra-large fruit 14.9% (1997) and 24.2% (1998) relative to that of nontreated control plants, and 37.8% (1997) and 23.9% (1998) relative to that of plants treated with the chemical bactericides. Chemical names used: manganese, zinc, carboxyethylene bis dithiocarbamate (mancozeb).
Abstract
Research in the Institute of Food and Agricultural Sciences (IFAS) has developed production techniques whereby oranges can be produced for approximately 30-35¢ per 90 lb. box (40.8 kg). However, a 1968 survey has indicated that many growers had costs several times this figure. To counteract this, extension specialists at the University of Florida developed a “Program for Economical Citrus Production.” A research-documented text with an extensive bibliography and a series of charts with duplicate 35 mm colored slides for group presentation was prepared. Extension citrus agents received packages of the text material along with intensive training in each segment of the program. This text material is now used in a unified, statewide program whereby all extension personnel concerned with citrus can conduct intensive programs on specialized topics.