Don C. Elfving

Suppression of Specific Apple Root Pathogens by Brassica napus Seed Meal Amendment Regardless of Glucosinolate Content

ABSTRACT The impact of Brassica napus seed meal on the microbial complex that incites apple replant disease was evaluated in greenhouse trials. Regardless of glucosinolate content, seed meal amendment at a rate of 0.1% (vol/vol) significantly enhanced growth of apple and suppressed apple root infection by Rhizoctonia spp. and Pratylenchus penetrans. High glucosinolate B. napus cv. Dwarf Essex seed meal amendments did not consistently suppress soil populations of Pythium spp. or apple root infection by this pathogen. Application of a low glucosinolate containing B. napus seed meal at a rate of 1.0% (vol/vol) resulted in a significant increase in recovery of Pythium spp. from apple roots, and a corresponding reduction in apple seedling root biomass. When applied at lower rates, B. napus seed meal amendments enhanced populations of fluorescent Pseudomonas spp., but these bacteria were not recovered from soils amended with seed meal at a rate of 2% (vol/vol). Seed meal amendments resulted in increased soil populations of total bacteria and actinomycetes. B. napus cv. Dwarf Essex seed meal amendments were phytotoxic to apple when applied at a rate of 2% (vol/vol), and phytotoxicity was not diminished when planting was delayed for as long as 12 weeks after application. These findings suggest that B. napus seed meal amendments can be a useful tool in the management of apple replant disease and, in the case of Rhizoctonia spp., that disease control operates through mechanisms other than production of glucosinolate hydrolysis products.

Gibberellins Stimulate Lateral Branch Development in Young Sweet Cherry Trees in the Orchard

Previous studies showed that successful stimulation of lateral branch development from 1-year-old wood in young sweet cherry trees without reliance on pruning could be accomplished if suitable cytokinin- or cytokinin/gibberellic acid-containing products were applied to assure penetration into active tissues. The goal of the trials reported here was to determine the potential for stimulating lateral branching by applying gibberellic acid alone under similar conditions. Three commercially available products containing gibberellic acid were evaluated. Treatments included the isomers GA3, GA4, and GA4 combined with GA7. All gibberellic acid isomer/formulations were similar in their ability to stimulate branching from lateral buds on 1-year-old wood. In one trial, GA4+7 alone was nearly as effective as the cytokinin 6-benzyladenine. Combining the surfactant Pentra-bark with gibberellic acid resulted in successful branch induction without the need to apply gibberellic acid to scoring or nicking cuts in the bark.

Sunburn Browning Decreases At-Harvest Internal Fruit Quality of Apples (Malus domestica Borkh.)

Changes in internal fruit quality associated with increasing severity of sunburn browning of apples were investigated at harvest in five cultivars. Apples were sorted into five classes ranging from no sunburn (Sb-0) to severe sunburn browning (Sb-4). Fruit quality of flesh tissue was compared beneath the sunburned area, the shaded side, and the shoulder side of each apple. All two-way interactive effects (i.e., sunburn classes vs. sides of fruit, sunburn classes vs. cultivars, and cultivars vs. sides of fruit) were significant (P ≤ 0.05) for all fruit quality traits. For the treatment combination of sunburn class and side of fruit, flesh firmness, and soluble solids concentration increased on the sun side, but titratable acidity averaged over cultivars for the sun side generally declined as sunburn severity increased from Sb-1 to Sb-4. Starch cleared more quickly on the shaded and shoulder sides as compared to the sun-exposed side of all fruit with sunburn browning. Starch also generally cleared more rapidly in apples with more severe sunburn browning, suggesting that sunburned apples were more mature than nonsunburned apples harvested on the same day. For the treatment combination of side of fruit and cultivar, the sun side was higher than shade or shoulder sides in firmness and soluble solids concentration for all cultivars when averaged over sunburn classes. Starch index was lowest for the sun side. For the treatment combination of sunburn class and cultivar, firmness, soluble solids concentration, and starch index, when averaged over sides of fruit, generally increased in all cultivars as severity of sunburn increased; titratable acidity decreased.

Zinc in foliage downwind from a tire-burning power plant

Abstract Burning municipal solid waste (MSW) with coal in power plants is becoming more common. Since used tires comprise an appreciable percentage of NSW some power plants are burning chipped tires with coal.Since the rubber in tires may contain up to 5% by weight of zinc as an accelerator activator, possible emission of zinc from such a power plant was studied. Staghorn sumac foliage was collected at increasing distances downwind from the plant and total zinc was determined.

Cadmium and lead concentration in foliage near a municipal refuse incinerator

Abstract Whereas landfilling still remains a necessary means of disposing of municipal solid waste, construction of refuse incineration facilities is increasing in the United States. There is currently much public opposition to building such incinerators because of health concerns about toxicants emitted as particulates and gases from the stacks. Cadmium and lead are typically present at significant levels in refuse incinerator fly ash. In this study these heavy metals were determined in tree foliage sampled at increasing distances in the vicinity of a municipal refuse incineration plant equipped with electrostatic precipitators to reduce emitted particulates. There was a high degree of correlation between diminishing foliar concentration of cadmium and lead and the logarithm of the distance north and south of the incinerator, the only directions in which foliar samples could be collected. Sources of these metals in refuse and factors which affect the magnitude of their deposition on foliage are discussed.

Stimulation of Lateral Branch Development in Young Sweet Cherry Trees in the Orchard Without Bark Injury

The goal of the trials reported here was to determine the potential for replacing physical disruption of the bark layer with appropriate surface-active chemical products added to bioregulator solutions applied to unpruned 1-year-old sweet cherry (Prunus avium L.) shoots to induce lateral branching. Two surfactant products, Pentra-bark (Quest Products Corp., Louisberg, KS.) and Syl-Tac (Wilbur-Ellis Co., Fresno, CA), combined with Promalin (PR, Valent BioSciences, Walnut Creek, CA) and applied to uninjured bark resulted in approximately the same increase in branching as produced by PR applications to scoring or nicking cuts. Surfactant concentrations higher than 1% v/v were usually necessary to produce increased branching. High concentrations of PR were not effective unless supplemented with a surfactant. Painting active solutions in 3–4 cm wide bands every 30 cm was just as effective as painting those solutions along the length of the outward-facing side of 1-year-old shoots. Use of appropriate surfactants to penetrate the bark barrier can eliminate hand labor for cutting the bark, reduce risk of worker injury, and reduce the risk for bacterial canker infection of trees during branch induction on 1-year-old shoots of sweet cherry