Richard N. Raid

Influence of cultivar and amendment of soil with calcium silicate slag on foliar disease development and yield of sugar-cane

Abstract Puccinia melanocephala H. Syd. & P. Syd., the causal agent of sugar-cane rust, was significantly influenced by cultivar selection but was not affected by soil amendment with calcium silicate slag at a rate of 6.7 t ha−1. However, severity of ringspot (Leptosphaeria sacchari Breda de Hann) was reduced with slag application. Across five cultivars, slag application reduced ringspot severities by an average of 67%. A significant cultivar effect and slag × cultivar interaction also were observed with respect to ringspot severity. Sugar-cane (interspecific hybrids of Saccharum spp.) yields were increased with addition of slag by averages of 17.2 and 21.8% across five cultivars during 1989 and 1990, respectively. Similar increases were observed for total sugar yields. Enhanced resistance to foliar diseases such as ringspot may partially explain yield increases obtained with application of calcium silicate slag to soils low in plant-available silicon.

An outbreak of bacterial spot of lettuce in Florida caused by Xanthomonas campestris pv. vitians

A widespread and damaging outbreak of a leaf spot disease of lettuce occurred in the 1992-93 winter vegetable season in southern Florida. Individual leaf lesions were dark brown to black, water-soaked, and greasy in appearance. A yellow-pigmented bacterium was consistently isolated. All 1992-93 lettuce strains and reference strains produced symptoms in greenhouse test plants that were identical to those seen in the field. Disease reactions generally were more severe in cos and butterhead lettuce than in crisphead. Strains were gram-negative rods, and negative for glucose fermentation, nitrate reduction, urease production, and utilization of asparagine as a sole source of carbon an dnitrogen. Aesculin was hydrolyzed, gelatin was liquefied, and proteolysis occurred in litmus milk. Cellular fatty acid profiles matched well to library database strains of Xanthomonas campestris pv. vitians

First Report of Downy Mildew Caused by a Peronospora sp. on Basil in Florida and the United States

Basil is grown as a specialty crop in greenhouse and field production in Florida and other regions of the United States. Downy mildew on basil (Ocimum basilicum) was detected from four production sites (Collier, Hendry, Miami-Dade, and Palm Beach counties) in south Florida in the fall of 2007, and within months, it was also found in west-central north Florida (Hillsborough County). Incidence reached nearly 100% on some of the affected crops and caused complete yield losses on basil grown both in the field for fresh market and potted herbs market. Symptoms developed during transit on basil that appeared symptomless at harvest. Symptoms initially appeared as yellowing on the lower leaves that was typically delineated by the veins, although in some cases the entire leaf area of the leaf surface was affected. A gray, fuzzy growth was apparent on the abaxial leaf surface. Microscopic observation detected dichotomous branching, hyaline sporangiophores (220 to 750 × 4 to 9 μm) bearing single sporangia. Sporangia were light brown, ovoid to slightly ellipsoid, and measured 14 to 15 × 15 to 18 μm. Oospores were not observed. Leaves of potted basil plants and coleus (Solenostemon scutellarioides) were inoculated with a suspension containing 1 × 105 sporangia/ml and sprayed till runoff (approximately 15 ml per plant) with a hand-held pressurized aerosol canister. Plants were covered with a plastic bag for 24 h and maintained in the greenhouse under ambient conditions. Noninoculated plants served as controls. After 7 days, symptoms typical of downy mildew occurred only on the inoculated basil plants and sporulation was confirmed microscopically. The internal transcribed spacer regions of an isolate collected in Hendry County were sequenced bidirectionally. The consensus sequence was deposited into GenBank (Accession No. FJ346561). Sequence data matched (100% homology) with a Peronospora sp. reported on sweet basil in Switzerland (GenBank Accession No. AY884605) and was similar (99% homology) to an isolate (GenBank Accession No. DQ523586) reported on coleus, although inoculation to coleus failed to confirm pathogenicity on this host. The sequence data also distinguished the isolate from P. lamii (87% homology) previously reported to occur on basil. The pathogen was identified as a Peronospora sp. based on morphological characteristics and sequencing homology (1-3). References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) S. Francis. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 688. CMI, Kew, England, 1981. (3) A. McLeod et al. Plant Dis. 90:1115, 2006.

Basil Downy Mildew (Peronospora belbahrii): Discoveries and Challenges Relative to Its Control

Basil (Ocimum spp.) is one of the most economically important and widely grown herbs in the world. Basil downy mildew, caused by Peronospora belbahrii, has become an important disease in sweet basil (O. basilicum) production worldwide in the past decade. Global sweet basil production is at significant risk to basil downy mildew because of the lack of genetic resistance and the ability of the pathogen to be distributed on infested seed. Controlling the disease is challenging and consequently many crops have been lost. In the past few years, plant breeding efforts have been made to identify germplasm that can be used to introduce downy mildew resistance genes into commercial sweet basils while ensuring that resistant plants have the correct phenotype, aroma, and tastes needed for market acceptability. Fungicide efficacy studies have been conducted to evaluate current and newly developed conventional and organic fungicides for its management with limited success. This review explores the current efforts and progress being made in understanding basil downy mildew and its control.

Investigation of Seed Treatments for Management of Bacterial Leaf Spot of Lettuce

Chemical seed treatments were evaluated for efficacy of disinfestation of lettuce seed that had been inoculated with Xanthomonas campestris pv. vitians. Three concentrations of each chemical were evaluated by treating seed lots for 5 or 15 min. In addition, the effects of each seed treatment on seed germination and early plant growth were examined by observing seed germination rates. Bacteria were not detected when seed were treated with 3 or 5% hydrogen peroxide for 5 or 15 min. Treatment of seed with 0.52% sodium hypochlorite was relatively ineffective at 5 and 15 min. When sodium hypochlorite was used at a 1% concentration for 15 min, the level of bacterial infestation was reduced to 2%. Suspensions of copper hydroxide plus mancozeb also reduced seedborne inoculum to ≤2%. Treatment of seed with copper hydroxide alone, benzoyl peroxide, or calcium peroxide did not reduce seed infestation levels significantly. Seed germination rates were 90% or greater for the majority of seed treatments tested in laboratory assays. Hydrogen peroxide treatments at a concentration of 5% reduced seed germination up to 28% compared with controls. However, no significant differences in germination were observed among control treatments (noninoculated, nontreated seed and inoculated, nontreated seed) and any of the chemical seed treatments when seed were sown in a pasteurized soil mix in the greenhouse.

Temporal InsTabIlITy of agrIculTural HabITaT reduces reproducTIve success of barn owls (TyTo AlbA)

ABSTRACT. Birds are generally unable to predict future changes in habitat condition when selecting nesting locations, and few studies have investigated the effect on birds of shifting habitat quality within nesting seasons. Anthropogenically influenced habitats such as agricultural landscapes are often associated with large shifts in quality that turn initially good habitat into poor habitat. We examined whether daily survival rates of Barn Owl (Tyto alba) nests in an agricultural landscape were influenced negatively by temporal instability in habitat conditions resulting from crop harvest. Although most nesting attempts by Barn Owls in our study area were initiated before the onset of harvest, fields adjacent to the majority of active nest boxes were harvested at some point during nesting attempts. Overall nest survivorship, as well as survivorship of individual nestlings within broods, was lower following harvest, likely because of associated declines in the abundance of rodents, the primary food source of Barn Owls. Nestlings in nests surrounded by harvested fields were generally lighter before fledging than young in nests surrounded by standing sugarcane and their associated dense rodent populations. Although instability of habitat quality in our study area was associated with reduced survivorship of individual Barn Owl nests, a population-level effect is unlikely given the overall fecundity of the population.

First report of powdery mildew of parsley caused by Erysiphe heraclei in Florida.

Parsley (Petroselinum crispum (Mill.) Nym. ex A.W. Hill) is an important leaf crop in the Everglades Agricultural Area of southern Florida. During the spring of 2005 and 2006, disease signs and symptoms resembling those incited by powdery mildew were observed on parsley at a commercial vegetable farm located 15 km east of Belle Glade. Symptoms consisted of leaf chlorosis, particularly in the dense lower canopy, and desiccation of affected tissue. A dense, white-to-light gray fungal growth was visible macroscopically on the surface of affected leaf tissue. Microscopic examinations revealed ectophytic hyphae with lobed appressoria and hyaline, straight conidiophores bearing single conidia. Conidia were short-cylindrical to cylindrical, measured 33 to 44 μm long and 13 to 16 μm wide, and lacked fibrosin bodies. Conidiophore foot cells were also cylindrical, straight, and measured 27 to 37 × 9 to 10 μm. Ascocarps of the teleomorph were not observed. The fungus closely matched the description of Erysiphe heraclei DC, a pathogen previously reported as attacking parsley on the U.S. West Coast (1,2). Pathogenicity was verified by inoculating adaxial leaf surfaces of 12 plants (cv. Dark Green Italian) with conidia collected from infected tissue by using a small brush. Inoculated plants and 12 noninoculated plants were lightly misted, held in a moist chamber for 48 h (22°C), and then incubated in a growth chamber for 4 weeks at 22°C with a photoperiod of 16 h. Symptoms that developed on inoculated plants were similar to those observed in the field, with no symptoms evident on the controls treated in a similar manner. To our knowledge, this is the first report of powdery mildew on parsley in Florida, even though parsley has been grown in the area for at least six decades. Noted as being somewhat unique among fungal pathogens because it favors dry rather than moist climatic conditions, it is probably no coincidence that powdery mildew was observed both years during the month of April, the height of Floridas dry season. The fact that monthly rainfall totals of 22 and 35 mm were recorded during April of 2004 and 2005, respectfully, well below the historical average of 72 mm, may have been a contributing influence. Glawe et al. (1), in issuing a first report of E. heraclei on carrots and parsley in the state of Washington and observing ascocarps on carrot tissue, mentioned the prospect of contaminated seed serving as a potential source of dissemination. Although they did not observe the teleomorph on parsley, prospects for its occurrence seem likely. With the bulk of parsley seed planted in Florida being produced in Washington, Oregon, or California, the observations reported herein may provide credence to such a hypothesis. References: (1) D. A. Glawe et al. Online publication. doi:10.1094/PHP-2005-0114-01-HN. Plant Health Progress, 2005. (2) S. T. Koike and G. S. Saenz. Plant Dis. 78:1219, 1994.

Effect of Fertilization on Resistance of Captiva St. Augustinegrass to Southern Chinch Bugs (Hemiptera: Blissidae) and Gray Leaf Spot Disease

‘Captiva’ is a recently released variety of St. Augustinegrass which is resistant to the southern chinch bug, Blissus insularis Barber. We tested to determine if fertilization of Captiva influenced its resistance to the insect and/or disease incidence. Tissue nitrogen and phosphorus content increased in plants with increasing fertilization levels. Fertilization did not have a significant effect on Captiva resistance to southern chinch bug as measured by adult survival. However, incidence and severity of gray leaf spot disease, Pyricularia grisea (Cooke) Sacc., increased with increasing fertilization.

SEASONAL FLIGHT OF PLECIA NEARCTICA (DIPTERA:BIBIONIDAE) IN SOUTHERN FLORIDA

The lovebug, Plecia nearctica Hardy, is a serious nuisance to motorists traveling in southern states. The insects are smashed against windshields obscuring vision and cars may overheat when radiators become clogged. The smashed insects also damage car paint if the body fluids are not removed soon after contact (Callahan and Denmark 1973). The insect was first described by Hardy (1940) from Galveston, Texas, who reported it to be widely spread, but more common in Texas and Louisiana than other Gulf Coast states. It has now progressed to all states bordering on the Gulf of Mexico, as well as Georgia, South Carolina, and parts of Central America. It was first collected in Florida in 1949 and today is found throughout Florida (Denmark and Mead 1992). Adult flights of lovebugs have been reported to occur primarily during May and September in different areas of the insects range (Hetrick 1970; Callahan and Denmark 1973; Buschman 1976; Thornhill 1976; Callahan 1985). However, in spite of these previous reports, no data have ever been presented actually showing seasonal flights of the lovebugs. Our objective was to determine seasonal flight patterns of P nearctica in southern Florida. Additional data on temporal sychronony of flights at different locations are also presented. Yellow sticky traps (Pherocon AM, no bait) made by Trece Inc., Salinas, California and baited with anethole (Cherry 1998) were used to monitor adult flights of lovebugs. Sampling was conducted by putting out 15 new sticky traps each month at approximately mid-month. These 15 traps were located at three different locations (5 traps/ location) to provide data on temporal synchrony between locations. One location was the Everglades Research and Education Center (location one), University of Florida, located near Belle Glade, Florida. The other two locations were located approximately 24 km southwest of the research center (location two) and 31 km east of the research center (location three). All three locations were located within Palm Beach County, Florida, and surrounded by agricultural lands (sugarcane, rice, vegetables). Traps at each location were placed 250 m apart in a straight line (i.e. a one km transect) adjacent roads. Each trap was hung one m above the ground on a metal rod and had a sponge (3 x 3 x 3 cm) containing 5 ml of anethole wedged into it. All 15 traps were hung and baited on the same day and collected seven days later. The seven day exposure period was used to avoid short term inclement weather factors such as rain, extreme winds, etc. that might greatly reduce adult catches within a shorter trap exposure time. Traps were collected by wrapping each trap in clear cellophane in the field. Lovebugs on each trap were counted by microscopic identification in a laboratory. A sample of lovebug adults collected on the traps during different major flight periods (May, September, December) was sent to Dr. Gary Steck, Division of Plant Industry, Gainesville, Florida who corroborated that the insects were P nearctica. Statistical analysis was conducted by SAS (1996). Temporal synchrony of adult flights between locations was determined by multiple correlation using the total number of adults caught each month at each location. Differences in mean numbers of adults caught at each location during different months were determined by using Tukeys test. A figure to visually show the overall seasonal flight pattern of the lovebugs is also presented. Although different numbers of lovebugs were observed between locations (Table 1), there was temporal synchrony in flight between locations. Multiple correlation of

Effect of Planting Date and Density on Insect Pests of Sweet Sorghum Grown for Biofuel in Southern Florida

Abstract There is much research and resource currently being invested in sweet sorghum, Sorghum bicolor L. Moench, for biofuel in southern Florida. The objective of this study was to determine the effect of planting date and density on insect pests of the crop in southern Florida. Emergent damage was primarily caused by fall armyworms, Spodoptera frugiperda (J.E. Smith), and to a lesser extent by the lesser cornstalk borer, Elasmopalpus lignosellus Zeller. Damage at heading was caused by different species of stink bugs (Heteroptera: Pentatomidae). Both emergent damage and numbers of stink bugs at heading varied significantly between planting dates. Correlation analysis showed that planting density had no to little effect on percentage damage by insects to emerging or heading sweet sorghum. Estimated ethanol yield was highest in the first crop of the early planting and decreased thereafter. No consistent effect of planting density or row configuration on yield was shown.