glasshouse conditions were infected by Mycosphaerella citri , an ascomycete causing “greasy spot” ( Fig. 1G ) ( Farr et al., 1989 ; Timmer et al., 2000 ). This disease produces characteristic black fruiting structures (pseudothecia) in leaf tissues, whole
Kenneth R. Summy and Christopher R. Little
Ed Stover, Chris Wilson, Dominick Scotto, and Masoud Salyani
Parts I and II of this series revealed substantial opportunities for improving spraying of Indian River citrus (Citrus spp.). In this segment of our work we develop guidelines for growers to select the spray parameters providing an optimal balance between efficiency and efficacy while minimizing environmental contamination.
It is proposed that these guidelines could be codified in a simple expert system to make them easier to use. We propose that understanding limiting conditions may be the key to choosing spray options. Wind is a major factor influencing spray deposition and offtarget drift. Based on weather records, wind speeds below 5 mph (8.0 km·h-1) are only routinely observed from 2000 HR until 0800 HR, making night spraying a good choice for low-volume applications. The importance of adjusting sprayer set-up for individual groves is demonstrated, with economic estimates of the cost of failing to make these adjustments. Routine use of careful sprayer adjustments is also likely to reduce off-target drift. Improvements in equipment and spray chemicals are also discussed. Use of non-orchard buffer areas and/or windbreaks appear to offer considerable opportunity for reducing off-site spray movement.
Ed Stover, Dominick Scotto, Chris Wilson, and Masoud Salyani
Foliar application of spray materials is an integral component of commercial citrus production. An intensive assessment of spray application practices has been stimulated by low fruit value and increased concern about potential surface water contamination in the Indian River citrus region of Florida. Many publications report research results regarding distribution of spray materials within orchards and off-target deposition, but interpretation is challenging because so many factors influence spray results, and integrating this information into practical recommendations is difficult. Canopy geometry and density are prominent factors contributing to variable deposition and spray drift. Environmental factors such as temperature, relative humidity, wind speed, and wind direction also greatly influence spray deposition and drift, and substantial changes can occur within seconds. In addition the physical and/or mechanical set up of the sprayer interact significantly with the other factors. A better understanding of these interactions should help growers optimize spray effectiveness and efficiency while reducing potential off-target effects.
Donald N. Maynard and Donald L. Hopkins
Watermelon (Citrullus lanatus [Thunb.] Matsum & Nakai) fruit are affected by a number of preharvest disorders that may limit their marketability and thereby restrict economic returns to growers. Pathogenic diseases discussed include bacterial rind necrosis (Erwinia sp.), bacterial fruit blotch [Acidovorax avenae subsp. citrulli (Schaad et al.) Willems et al.], anthracnose [Colletotrichum orbiculare (Berk & Mont.) Arx. syn. C. legenarium (Pass.) Ellis & Halst], gummy stem blight/black rot [Didymella bryoniae (Auersw.) Rehm], and phytophthora fruit rot (Phytophthora capsici Leonian). One insect-mediated disorder, rindworm damage is discussed. Physiological disorders considered are blossom-end rot, bottleneck, and sunburn. Additionally, cross stitch, greasy spot, and target cluster, disorders of unknown origin are discussed. Each defect is shown in color for easy identification.
James J. Ferguson, Fedro S. Zazueta, and Juan I. Valiente
Fungal diseases have their greatest impact on citrus in Florida by reducing tree vigor, fruit yield, and quality. Given the complex etiology of these diseases, this software was developed to facilitate diagnosis of symptoms and to explain the dynamics of Alternaria brown spot of mandarins, greasy spot, melanose, Phytophthora brown rot, post-bloom fruit drop, and sour orange scab. CITPATH includes a diagnostic key to identify symptoms of the major fungal diseases of citrus foliage and fruit in Florida and a hypertext program containing a description and graphic display of symptoms, maps of geographic occurrence, diagrams of disease development, and management strategies. Users can also consult a list of citrus cultivars susceptible to specific diseases and a reciprocal list of diseases affecting specific cultivars. Chemical control methods are discussed briefly with reference to the current Florida Citrus Spray Guide, a hardcopy of which is included with the software purchase. Developed for commercial growers, county extension programs, citrus horticulture classes, and master gardeners, this software is available on CD-ROM disks containing other citrus databases and as a separate disk for MS-DOS-based computers.
Annelle W.B. Holder, Winston Elibox, Christopher Avey, and Pathmanathan Umaharan
the vascular system of anthurium leaves via natural openings (stomata and hydathodes) or wounds ( Prior et al., 1985 ). Early foliar symptoms of BLS are characterized by small, angular, greasy spots on the lower surface of leaves near veins and leaf
Annelle W.B. Holder, Winston Elibox, and Pathmanathan Umaharan
on the pathogenic variation of A . anthurii . The causal agent of BLS enters the vascular system of anthurium leaves via natural openings (stomata and hydathodes) or wounds ( Prior et al., 1985 ). Early foliar symptoms are small, angular, greasy
Vladimir Orbović, Diann Achor, and James P. Syvertsen
Copper (Cu) is an important component of the fungicide programs that are used for control of many important diseases of citrus. Copper-based fungicides, used either alone or with spray oil, can successfully control greasy spot, melanose, citrus