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Stephen M. Olson

Inadequate available Ca can cause blossom end rot in watermelons. Many products and materials are marketed to try and help reduce this problem. A 3 X 3 factorial was set up with three soil Ca treatments (none, 1120 kg/ha of dolomite and 1120 kg/ha of qypsum) and three foliar Ca treatments (none, Liqui-Cal at 9.35 L/ha and Foli-Cal at 4.67 L/ha) using both a seeded (2N) and seedless (3N) cultivar. Mehlich-1Ca level prior to planting was 305 ppm. None of the Ca treatments affected leaf or fruit Ca levels. Applied Ca treatments did not affect total yields, fruit weight, or percent soluble solids of the seedless cultivar (Crimson Trio). Yield of `Royal Flush' (2N) was reduced by application of Foli-Cal, but none of the other parameters were affected by the other Ca treatments. Leaf Ca level of `Royal Flush' (3.05%) was almost twice that of `Crimson Trio' (1.59%), while fruit Ca content of `Royal Flush' (0.26%) was lower than that of `Crimson Trio' (0.32%).

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Stephen M. Olson and Joshua H. Freeman

Nine collard (Brassica oleracea acephala group) cultivars were evaluated on six experiments over 4 years to determine how well they performed with respect to yield, plant weight, and bolting tolerance. Experiments covered spring, fall, and winter seasons to determine if one cultivar would be useful for all conditions. ‘Top Pick’, ‘Flash’, and ‘Blue Max’ were found to be the best performing cultivars with respect to yield and plant weight. In general, the hybrid cultivars outperformed the open-pollinated cultivars. Only during one experiment were the cultivars subjected to environmental conditions favorable for bolting, but there were no significant differences in incidence of bolting among the cultivars. Although top-performing cultivars were hybrids, the cost associated with hybrid seed must be considered.

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Stephen M. Olson and Joe W. Noling

Methylbromide is the standard fumigant used for tomato production in Florida. Since it been classified as a category 1 ozone depleter and is to be phased out by 1 Jan 2001 replacement methods of fumigation must be found. Several materials in 1993 were compared to methylbromide in production of `Colonial' tomatoes. These included metham sodium (applied through drip at 3 rates and applied to soil at 935 l·ha-1 and tilled in), dazomet (applied at 2 rates and tilled in), 1,3 dichloropropene + chloropicrin and untreated check. None of the treatments were as effective as methylbromide in reducing root galling by root knot nematodes. Total yields were not affected by treatments even though root system of untreated plants was severely galled. Modifications are to be made for 1994 season and materials added to trial.

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Joshua H. Freeman, Stephen M. Olson, and William M. Stall

Successful fruit set in triploid watermelons [Citrullus lanatus (Thunb.) Matsum. & Nakai] requires a diploid watermelon cultivar, or pollenizer, to be planted nearby as a pollen source. Pollenizer cultivars have been developed to be planted in-row with triploid plants without spacing change, which decreases area per plant. These cultivars have different growth habits, from highly reduced foliage to standard foliage, and it is uncertain how pollenizer growth habit may affect triploid plant growth and yield. Two diploid watermelon pollenizers, ‘Mickylee’ and ‘SP-1’, with markedly different growth habits were planted at five in-row spacings from triploid plants to determine the effect of plant competition on triploid watermelon yield. All treatments used a 1:1 pollenizer to triploid ratio to measure the direct effect of pollenizer growth on associated triploid yields. Experiments were conducted at two locations during Spring 2006 (Quincy and Citra, FL) and one during Fall 2006 (Quincy). Triploid plants paired with ‘Mickylee’ yielded 11.4% (Citra) and 22.4% (Quincy) less weight in the spring and 8.5% less in the fall than plants paired with ‘SP-1’ and also produced fewer fruits per plant. However, the results from the fall trial were not significant. Pollenizer to triploid spacing had a linear effect on yield per plant and fruits per plant, and there was no interaction between pollenizer cultivar and spacing. The use of ‘Mickylee’ as a pollenizer may be an attractive option because of lower seed costs compared with other pollenizers, but these results indicated lower triploid watermelon yields from plants paired with ‘Mickylee’, which is most likely a result of increased plant competition.

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Stephen M. Olson, George J. Hochmuth, and Robert C. Hochmuth

Studies were conducted at the NFREC, Quincy, and AREC, Live Oak, Fla., to compare watermelon {Citrullus lanatus [(Thumb.) Matsum & Nakai]} plant establishment by transplanting and direct-seeding. Cultivars used were `Charleston Gray' in 1984, 1985, 1986, and 1989; `Jubilee' in 1988 and 1989; and `Crimson Sweet' in 1987 to 1990. Early yields were greater with transplants for all three cultivars in all years. With `Charleston Gray', total yields with transplants were higher in 1985 and 1989, but not in 1984 or 1986. The average fruit weights with transplants were also greater in 1985 and 1989 than in 1984 or 1986. With `Jubilee', total yield with transplants was higher in 1989, but not in 1988. Average fruit weight with transplants was greater in 1989 than in 1988. With `Crimson Sweet', total yields were higher with transplants in 1989 and 1990, but not in 1987 or 1988, but fruits were larger with transplanting compared to direct-seeding only in 1990. In all experiments, yields with transplants were never less than those with direct-seeded plants.

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Josh H. Freeman, Stephen M. Olson, and Eileen A. Kabelka

In the Spring and Fall 2006, the pollen viability of four diploid watermelon pollenizers was evaluated in Quincy, FL. Triploid watermelon plants [Citrullus lanatus (Thunb.) Matsum. & Nakai.] do not produce sufficient viable pollen to pollenize themselves and a diploid cultivar must be interplanted as a pollen source. Recent studies have illustrated differences in triploid watermelon yields as a result of the pollenizer cultivar used. The viability of the pollen produced by pollenizer cultivars may greatly influence the fruit set and fruit quality in the triploid watermelon crop. Pollen samples were taken from ‘Companion’, ‘Jenny’, ‘Mickylee’, and ‘SP-1’ and were stained to determine their viability. There were no significant differences in pollen viability among cultivars and all cultivars had high average viability. Pollen viability was never lower than 95% for any cultivar. This study indicates that pollen viability of the cultivars evaluated should not influence their effectiveness as pollenizers.

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Dan O. Chellemi, Stephen M. Olson, and John W. Scott

Five strains of Pseudomonas solanacearum, collected from northwest Florida tomato fields, were inoculated onto 23 tomato (Lycopersicon esculentum) genotypes and one tomatillo (Physalis ixocarpa) genotype using a stem puncture technique. The strains represented a diverse group based upon pathogenic aggressiveness and profiles of their fatty acid content. Resistance was evaluated by comparing the response of each genotype to susceptible controls consisting of L. esculentum cv Bonny Best and Sunny. A differential response by the genotypes to the individual strains was observed. Germplasm from Hawaii (H7997 and H7998) exhibited some resistance to one of the strains while germplasm from Taiwan (CL 5915-93-1-0-C-1) was moderately resistant to another strain. However, no genotype was resistant to all five strains tested.

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Joshua I. Adkins, Joshua H. Freeman, and Stephen M. Olson

Diploid watermelon (Citrullus lanatus) pollenizers are planted within triploid watermelon fields to provide viable pollen for triploid fruit set. In recent years, pollenizer cultivars with desirable characteristics for planting in-row with triploid watermelons have been commercially available. The degree of plant competition from in-row pollenizers grown in the commercially common arrangement where pollenizers are placed equidistant from neighboring triploid plants has not been reported. Field experiments were conducted in 2005, 2006, and 2007 in Quincy, FL, to examine the competitive impact of in-row pollenizers grown equidistant from neighboring triploid plants. Four ratios of pollenizers-to-triploids: 1:1, 1:2, 1:3, and 1:4 were used to provide various levels of pollenizer competition. No significant difference in yield based on the weight or number of fruit per triploid plant resulted from the varied pollenizer ratios. Therefore, pollenizers grown in-row at an equidistant spacing from the neighboring triploid plants had no competitive impact on the yield of the triploid watermelon crop.

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John W. Scott, Stephen M. Olson, and Jerry A. Bartz

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Peter C. Andersen, Stephen M. Olson, M. Timur Momol, and Joshua H. Freeman

Tomato spotted wilt (TSW) is caused by a Tospovirus [tomato spotted wilt virus (TSVW)] and is vectored by thrips. TSW is a major impediment to tomato production worldwide and has been identified as the most significant limitation in the southeastern United States. The objectives of this study were to quantify the impact of polyethylene mulch type (black, metalized, Heat stripe, and Sonoco printed) and insecticide (alternating applications of spinosad and methamidophos) on midafternoon soil temperature under the mulch, reflected photosynthetic photon flux (PPF), vegetative growth, flower number, incidence of TSW, yield, and fruit quality of ‘FL-47’ tomato (Solanum lycopersicum L.). Midafternoon soil temperature during April and May (10-cm depth) averaged 2 to 4 °C higher under black mulch compared with the other mulches. The reflectance of PPF was highest for metalized mulch (up to two-thirds of PPF in full sunlight) followed by Heat stripe, Sonoco printed, and black mulch. In the presence of a full plant canopy, PPF reflectance was greatly reduced. The incidence of TSW [as determined visually and confirmed by enzyme-linked immunosorbent assay (ELISA)] was very high in 2002 and relatively low in 2003. Stem weight was significantly reduced in the black mulch treatment; however, plant height, leaf weight, or total numbers of flowers were not influenced by mulch type. For both years, the incidence of TSW on black mulch was significantly greater than that of the other mulch treatments for most sampling dates. The application of insecticides reduced percentage TSW on the last two sampling dates in both years. In 2002, but not 2003, yield per hectare was affected by mulch type. In both years, mulch type did not influence yield per plant and percentage marketable fruit, and insecticide applications increased yield per hectare, yield per plant, and percentage marketable fruit.