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Abstract

Potassium concentration was highest in the upper 5 cm of medium after leaching with 10 cm H2O, lowest in the middle of the soil column (10 and 15 cm depths), and intermediate at the bottom of the column. Increasing concentrations of applied K (336, 671, and 1007 kg/ha) increased the K level in each medium tested, except 100% sand, and at each depth in the soil column. After leaching, media containing high percentages of sand (75 and 100%) had a lower K concentration at all applied K rates than media containing high percentages of bark (0 and 25% sand). Cation exchange capacity was greater in bark than sand and is probably the most important factor influencing the movement of K in pine bark and sand media.

Open Access
Authors: and

Abstract

Bulk density (BD) of potting media increased as the percentage of sand was increased in the medium. Because of the “fitting” together of particles, volume of medium mixtures was always less than the total volume of the separate components. Particle size distribution was determined most accurately on a volume basis and was used to identify the potting mixtures. The percentage of medium components (bark or sand) retained on any given sieve size could be determined from BD data. Percolation rate, and cation exchange capacity (CEC) declined as the percentage of sand was increased in the potting mixture. CEC was most accurately determined on a volume basis. Increasing the percentage of sand in the potting medium raised pH from 4.1 to 5.4.

Open Access

Abstract

American elm (Ulmus americana L.) and American sycamore (Platanus occidentalis L.) trees were injected in May or June 1974 and 1975 with water solutions of 1,2-dihydro-3,6-pyridazinedione (Maleic hydrazide, MH) and butanedioic acid mono-(2,2-dimethylhydrazide (daminozide). Measurements in 1977 showed sprout length to be significantly reduced by both chemicals applied in 1974. Of the 1975 treatments, only MH-treated sycamore still showed significant sprout length reduction 3 growing seasons after injection. Between April and June 1977, MH and the sodium sait of 2,3:4,6-bis-0-(1-methylethylidene)-α-L-xylo-2-hexulofuranosonic acid (dikegulac) were injected into the trunks of previously topped American sycamore, silver maple (Acer saccharinum L.), red oak (Querem rubra L.), shamel ash (Fraxinus uhdei (Wenz.)Lingelsh), and eucalyptus (Eucalyptus globulus Labill.). Both chemicals significantly reduced regrowth, but high concentrations were generally more effective than were low concentrations of the same chemical. However, high concentrations of dikegulac were likely to cause unfavorable foliar appearance, including leaf distortion and dieback. Regrowth control was generally similar for a species treated with the same chemical at different geographical locations. Average injection cost for a single treatment is estimated at $2 to $3 per tree.

Open Access

Silver reflective plastic mulches were compared with conventional bare ground culture for the reduction of aphids, and mosaic virus diseases as follows: Cucumber Mosaic, Watermelon Mosaic I and II, Zucchini Yellows Mosaic, and Squash Mosaic. Silver plastic mulch produced higher marketable yields than the bare ground treatments. Other colors (white, yellow, and black plastic with yellow edges) of plastic mulch treatments were intermediate in their effects on aphid population and virus disease reduction. Silver reflective mulch alone and silver reflective mulch with insecticide were superior to other colors of plastic mulch in reducing aphid populations. Silver reflective plastic mulch, with or without insecticide, resulted in 10-13 days delay in the onset of the above mentioned mosaic disease.

Free access

The ability of two tomato cultivars, Lycopersicon esculentum cv. VFNTCherry (chill sensitive) and L. esculentum × L. pimpinellifollim cv. New York 280 (chill tolerant) to acclimate to low temperature storage at 2 °C were compared following prior temperature preconditioning. The activities of catalase, peroxidase, and superoxide dismutase and electrolyte leakage were monitored during a 15-day preconditioning period. Low temperature preconditioning reduced membrane damage in both fruit. In contrast, high temperature preconditioning accelerated the rate of leakage in VFNT, while fruit of NY 280 remained relatively undamaged. Low temperature preconditioning stimulated a 4-fold increase in catalase and peroxidase activities in fruit of NY280. High-temperature preconditioning appeared only to benefit fruit of NY280. Regardless of pretreatment, no significant change in superoxide dismutase activities were observed for either cultivar. These findings suggest that the ability to acclimate to low temperature stress may correlate with increased levels of catalase and peroxidase.

Free access

Abstract

Water solutions of commercial formulations of growth regulators were pressure-injected into the trunks of topped American elm (Ulmus americana L.) trees in June to evaluate their ability to reduce sprout regrowth. Regrowth was significantly reduced by methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (chlorflurenol), N-[4-methyl-3-[[(trifluoromethyl)sulfonyl]amino] = phenyl]acetamide (fluoridamid), l,2-dihydro-3,6-pyridazine-dione (maleic hydrazide), succinic acid,2,2-dimethylhydrazide (daminozide) and 2,3,5-triiodobenzoic acid (TIBA); α-cyclopropyl-α-(4-methoxypenyl)-5-pyrimidine = methanol (ancymidol) and (2-chloroethyl)trimethyl-ammonium chloride (chlormequat) were ineffective. Some undesirable effects on the tree and foliage were observed. Maleic hydrazide (MH) and daminozide (SADH) were selected for additional field tests at 3 concentration levels on topped American elm and American sycamore (Platanus occidentalis L.). Regrowth was significantly reduced and foliage condition was acceptable for the high concentration of SADH and the low concentration of MH. Successive measurements in both experiments showed that sprout regrowth was reduced by an amount equivalent to at least 1 year of growth during the first 2 seasons following treatment.

Open Access

Fusarium wilt of tomato (Solanum lycopersicum), caused by fungal pathogen Fusarium oxysporum f. sp. lycopersici (Fol), is one of the most important diseases in tomato production. Three races of the pathogen are described, and race-specific resistance genes have been applied in commercial tomato cultivars for controlling the disease. Race 3 (Fol3) threatens tomato production in many regions around the world, and novel resistance resources could expand the diversity and durability of Fol resistance. The wild tomato species, Solanum pennellii, is reported to harbor broad resistance to Fol and was the source of two known Fol3 resistance genes. In this study, we evaluated 42 S. pennellii accessions for resistance to each fusarium wilt race. F1 plants, developed from crossing each accession with the Fol3 susceptible line ‘Suncoast’, were evaluated for Fol3 resistance, and BC1F1 plants were screened to determine the likelihood that Fol3 resistance was based on a novel locus (loci). Nearly all accessions showed resistance to Fol3, and many accessions were resistant to all races. Evaluation of F1 plants indicated a dominant resistance effect to Fol3 from most accessions. Genetic analysis indicated 24 accessions are expected to contain one or more novel Fol3 resistance loci other than an allele near the I-3 locus. To investigate genetic structure of the S. pennellii accessions used in this study, we genotyped all 42 accessions using genotyping by sequencing. Approximately 20% of the single nucleotide polymorphism (SNP) loci were heterozygous across accessions, likely due to the outcrossing nature of the species. Genetic structure analysis at 49,120 unique SNP loci across accessions identified small but obvious genetic differentiations.

Open Access