Fruit tissue only was treated with concentrations of 0, 240, 360, 480, 600, 720, 840, and 960 ppm of (2-chloroethyl)methyl bis (phenyl methoxy) silane (CGA 15281) applied to 1/3, 1/2, and 2/3 of the fruit surface. Increased abscission of fruit occurred as ovule length increased from 3.5 mm to 13.3 mm when fruit alone were treated. Foliage sprays of the same concentrations with the fruit protected generally had no effect on fruit or leaf abscission. Application of 0.01 ml droplet of CGA 15281 to the abscission zone, peduncle, and fruit cheek caused little fruit removal, but produced chlorosis of the treated area on the fruit. The data suggest that fruit contact with CGA 15281 is necessary for fruit thinning.
Organic orchards represent a significant and growing component of Washington state agriculture. Comparison studies have shown that organic apple systems can be equally profitable yet more environmentally sustainable than their conventional counterparts. Despite this success, sustainable methods of weed control, fertility, and soil quality stabilization and improvement have remained a challenge. Intensive cultivation is commonly used to control weeds in organic orchards. This can lead to reduced or degraded soil organic matter, structure, water infiltration, aerated pore space, and other soil productivity parameters. In addition, tillage accelerates nutrient cycling and can result in the loss of valuable nutrients from the system. To address the need for sustainable organic methods of weed management, an integrated study of alternative understory management options was established in a newly planted orchard in 2005. Weed control measures included efficient tillage using a Wonder weeder, organically approved herbicide, wood chip mulch, and living cover mulches. Three rates of nitrogen (low, medium, and high) were applied across the Wonder weeder, wood chip, and living cover mulch plots in order to determine ideal N fertility rate. Analyses of total C and N and N-15 in organic fertilizers, soil pools, living cover biomass, and tree leaves are being used to track N and C cycling and partitioning, N-use efficiency, soil quality, and to determine optimal fertility guidelines. Preliminary results indicate intense competition between living mulch understory and orchard trees, and a trade-off may exist between maximizing soil quality and orchard productivity.
This article summarizes the current status of organic vegetable production practices in California. The production of vegetables organically is growing rapidly in California, led in large part by growth in the market demand for organically grown produce. Key aspects of organic vegetable production operations such as certification and farm production planning, soil management, weed management, insect management, and plant disease management involve special practices. Many practices have not been thoroughly researched and the scientific base for some practices is still being developed.
Two distinct syndromes have emerged in some production areas that have caused losses of sweetpotato (Ipomoea batatas) storage roots during postharvest storage: a complex of fungal rots (end rots) progressing from either end of storage roots and a necrotic reaction (internal necrosis) progressing internally from the proximal end of storage roots. This study was conducted in multiple environments to evaluate whether the use of preharvest ethephon application and storage with or without curing after harvest could be used to screen sweetpotato breeding lines for susceptibility/resistance to these two disorders. Treating vines with ethephon 2 weeks before harvest and placing harvested roots directly into storage at 60 °F without curing resulted in the greatest incidence of end rots in each state and there were significant differences in incidence among the sweetpotato genotypes evaluated. However, when ethephon was not used and roots were cured immediately after harvest, the incidence of end rots was low in all the genotypes evaluated except for one breeding line. Incidence and severity of internal necrosis were greatest when ethephon was applied preharvest and roots were cured immediately after harvest, but two cultivars, Hatteras and Covington, had significantly more internal necrosis than all others.