The effect of wind stress on growth, net CO2 assimilation (A), and leaf water potential of eighteen-month-old, containerized carambola (Averrhoa carambola cv. Arkin) and seedling sugar apple (Annona squamosa) trees was investigated. In a glasshouse, trees were exposed to fan-generated wind speeds of 0 (control), 4 (low wind; LW), or 7 (high wind; HW) m sec-1 for 4 hr/day (1000-1400 hr) for 30 days. No differences in A, stomatal conductance, transpiration, and fresh and dry wt of mature carambola or sugar apple leaves or shoots were observed among treatments. In contrast, as wind speed increased, fresh wt of immature carambola leaves and shoots decreased. For carambola and sugar apple, no significant relationship was found between mid-day leaf water potentials and wind speed. However, after 30 days, leaf water potential of carambola subjected to HW (-1.2 MPa) was lower than those of LW (-1.1 MPa) and control (-1.1 MPa) trees. For sugar apple, leaf water potential of control trees was generally higher than those of trees in the LW and HW treatments. The data indicate that exposure to wind speeds of 4 or 7 m sec-1 for as little as 4 hr/day for 30 days reduces new leaf and shoot growth of carambola trees.
R. Núñez-Elisea, J.H. Crane, and M.L. Caldeira
Panicles of `Kohala' longan (Dimocarpus longan Lour.) trees often retain more than 250 fruit, which results in small fruit (<10 g) of reduced market value. During 1997 and 1998, we conducted experiments to increase fruit size in commercial groves. Trees flowered and fruited normally in 1997, but very scarcely and late in 1998. In 1997, treatments consisted of panicle pruning (clipping off half of the panicle) and/or removal of entire panicles (50% per tree) when young fruits were 5 or 10 mm in diameter. Control trees were left intact. The number of fruit per panicle varied greatly within trees. Panicles (pruned or intact) with <125 fruit generally developed fruit >15 g (32–33 mm equatorial diameter). Total soluble solid content of mature fruit generally decreased with increasing fruit size. Removing whole panicles did not increase average fruit size in remaining intact panicles, suggesting that panicles were fed primarily by leaves within the same branch. In 1998, treatments consisted of applications of GA3 and/or CPPU (a synthetic cytokinin) when fruits were 6 to 9 mm in diameter. Panicles were not pruned since they generally had <150 fruit. Control panicles were not sprayed. There was no consistent effect of treatments on average fruit weight, and no treatment significantly increased fruit size in relation to controls. These preliminary results indicate that other factors besides current fruit set, such as previous fruit load of a branch, branch position (exposure to sunlight and/or wind, and proximity to major limbs), and the amount/age of leaves, may influence the fruiting potential of individual branches.
Jonathan H. Crane, Bruce Schaffer, and Richard J. Campbell
Jonathan H. Crane, Bruce Schaffer, and Richard J. Campbell
Southern Florida has experienced numerous hurricanes, of which Hurricane Andrew was the most recent. Six years after this storm, nearly one-third of the 8093 ha of tropical fruit that existed in Miami–Dade County before the storm has never been replanted. The damage, reaction, and recovery from the storm varied among fruit species. The effect of heat stress and high light intensity was minimal on avocado, `Tahiti' lime, carambola, mamey sapote, guava, sapodilla, and longan. In contrast, mango trees experienced severe heat stress. Root damage caused by toppling and subsequent re-setting of sugar apple, atemoya, mango, and grafted `Tahiti' lime trees was severe; thus, trees not re-set were less likely to recover than trees left toppled or leaning. The extent and rate of recovery from hurricane-related wind stress also varied among species. Avocado, carambola, guava, and longan refoliated within 3 to 4 weeks after Hurricane Andrew. In contrast, mango, sugar apple, and atemoya trees went through two or more cycles of refoliating and dying back until tree death occurred. Iron and nitrogen deficiencies were common for mango, sugar apple, atemoya, and guava. Other consequences of hurricanes in south Florida include increased weed and vine growth and increased susceptibility to drought stress and insect infestations. Recovery to prehurricane crop production levels has varied among crops. For example, avocado and carambola production is near and exceeds pre-1992 levels, respectively. In contrast, `Tahiti' lime and mango production are about 20% pre-1992 levels. The long-term effect of the most recent hurricane on fruit production in south Florida has been a change in the crop species and/or cultivars planted.
M.B. Thomas, H.W. Beck, J.H. Crane, J.J. Ferguson, and J.W. Noling
A computer-based diagnostic system that can assist commercial producers, extension agents, and homeowners in the diagnosis of diseases, disorders, and pest damage for citrus, avocado, `Tahiti' lime, mango, carambola, lychee, and papaya was developed. The program was written in C++ and runs under MS-DOS. The system design was based on the diagnostic reasoning process of experts by identifying the location of symptoms, tree vigor, and occurrence within a grove. Full-screen color images link symptoms to possible diseases, disorders, and/or pest damage. Users can also refer to expert knowledge, graphic displays, pop-up menus, dialogue boxes, and retrieve information via hypertext from extension publications as well as current control methods. The program is available on CD-ROM, contains over 800 digital color images, and includes a glossary of terms.
R. Nuñez-Elisea, B. Schaffer, M. Zekri, S.K. O'Hair, and J.H. Crane
Tropical fruit trees in southern Florida are grown in porous, oolitic limestone soil that has very low organic matter content and water-holding capacity. Thus, trees require frequent irrigation during dry periods. In these soils, a quantitative basis for monitoring soil water content to determine when and how much to irrigate has been lacking. Multi-sensor capacitance probes (EnviroSCAN™, Sentek, Australia) were installed in commercial carambola, lime, and avocado orchards to continuously monitor changes in soil water content at depths of 10, 20, 30, and 50 cm. Eight probes were installed per orchard. Volumetric soil water content was recorded at 15-min intervals with a solar-powered datalogger. Results were downloaded to a laptop computer twice a week. Monitoring the rate of soil water depletion (evapotranspiration) allowed irrigation before the onset of water stress. The time at which soil reached field capacity could be determined after each irrigation (or rain) event. Soil water tension was recorded periodically using low-tension (0–40 cbars) tensiometers placed adjacent to selected capacitance probes at 10- and 30-cm depths. Soil water tension was better correlated with volumetric soil water content at a 10-cm depth than at 30-cm depth. Using multi-sensor capacitance probes is a highly accurate, although relatively expensive, method of monitoring soil water content for scheduling irrigation in tropical fruit orchards. Whereas tensiometers require periodic maintenance, the multi-sensor capacitance probe system has been virtually maintenance free. The correlation between soil water content and soil water tension obtained in situ indicates that tensiometers are a less precise, but considerably cheaper, alternative for scheduling irrigation in tropical fruit orchards in southern Florida.
Michael B. Thomas, Jonathan H. Crane, James J. Ferguson, Howard W. Beck, and Joseph W. Noling
The TFRUIT·Xpert and CIT·Xpert computerbased diagnostic programs can quickly assist commercial producers, extension agents, and homeowners in the diagnosis of diseases, insect pest problems and physiological disorders. The CIT·Xpert system focuses on citrus (Citrus spp.), whereas the TFRUIT·Xpert system focuses on avocado (Persea americana Mill.), carambola (Averrhoa carambola L.), lychee (Litchi chinensis Sonn.), mango (Mangifera indica L.), papaya (Carica papaya L.), and `Tahiti' lime (Citrus latifolia Tan.). The systems were developed in cooperation with research and extension specialists with expertise in the area of diagnosing diseases, disorders, and pest problems of citrus and tropical fruit. The systems' methodology reproduces the diagnostic reasoning process of these experts. Reviews of extension and research literature and 35-mm color slide images were completed to obtain representative information and slide images illustrative of diseases, disorders, and pest problems specific to Florida. The diagnostic programs operate under Microsoft-Windows. Full-screen color images are linked to symptoms (87 for CIT·Xpert and 167 for TFRUIT·Xpert) of diseases, disorders, and insect pest problems of citrus and tropical fruit, respectively. Users can also refer to summary documents and retrieve management information from the Univ. of Florida's Institute of Food and Agricultural Sciences extension publications through hypertext links. The programs are available separately on CD-ROM and each contains over 150 digital color images of symptoms.
Marcio Eduardo Canto Pereira, Steven A. Sargent, Charles A. Sims, Donald J. Huber, Celso Luiz Moretti, and Jonathan H. Crane
The ethylene inhibitor 1-methylcyclopropene (1-MCP) delays ripening of avocado (Persea americana) and many other fruits, but there are few reports of the influence of this ethylene inhibitor on sensory attributes. The objective of this study was to evaluate the effects of aqueous 1-MCP on fruit ripening and sensory attributes of ‘Beta’ avocado, a Guatemalan-West Indian hybrid. Treatment with aqueous 1-MCP at 2.77 μmol·L−1 (150 μg·L−1) for 1 minute effectively delayed ripening by 6 days, delaying the onset of climacteric and lowering respiration rates as compared with control. Treated fruit had greener peel and firmer pulp when ripe, and untrained sensory panelists could not detect differences in texture, flavor, and overall liking between treated and untreated fruit. Immersion of ‘Beta’ avocado in aqueous 1-MCP extended the shelf life to 14 days at 20 °C and 84% relative humidity, an increase of 6 days (75%) as compared with untreated fruit, without compromising sensory acceptability. This technology has the potential to permit shipment of these fruit to more distant markets than currently possible.
A. H. Lange, J. C. Crane, W. B. Fischer, K. O. Roberts, and C. L. Elmore
A number of pre-emergence soil residual herbicides were tested at 2 locations on varieties of young peach, plum, cherry, pear and walnut rootstocks. The greatest variation in response resulted from differences in location. Important differences in varietal response were also obtained with the various herbicides in light soils. Simazine appeared sufficiently safe to trees in heavier soil but gave variable weed control. Diuron gave about the same degree of weed control but more safety than simazine on young trees. Of the uracil herbicides tested, DP-733 was the least toxic to the fruit tree species tested, while bromacil and isocil were generally the most toxic, except to peach trees. Of the commercial uracil herbicides, only DP-732 (terbacil) was of sufficient interest for further study.