Apple scab, a fungal disease caused by Venturia inaequalis, is considered the most important disease of apple worldwide. The disease can be devastating, causing reduction in yield or making the apples unfit for the market. Currently, the production of marketable fruit from scab susceptible cultivars depends on the repeated applications of fungicides. Scab-resistant apple cultivars, which are genetically immune to apple scab, can offer a biological alternative to fungicide use. `Liberty,' was bred for immunity to apple scab; however, it is not immune to other apple diseases and pests. Research has been conducted during a 3-year project (1996–1998) to determine whether reduced fungicide programs adversely affect overall tree vigor, productivity, and fruit quality. Data collected include tree vigor (TCSA and time of leaf abscission), tree productivity (YE), and fruit quality (fruit firmness and disorders during storage). Results indicate no significant differences between the two treatments (reduced fungicide and no fungicide application) in most of the parameters measured. Based on fruit that were harvested and graded to commercial standards, the estimated gross monetary value of the crop does not show difference between treatments. These results could translate into an economic advantage for growers when one factors in the savings in fungicide purchases. In addition, there are also health and environmental advantages to reduced fungicide usage.
L.P. Berkett, M.E. Garcia, J. Clements, and G. Neff
Gerry Neilsen, Frank Kappel, and Denise Neilsen
Institute Inc., 1989 ). Results and Discussion Tree vigor, yield, and fruit size. Tree vigor was unaffected by the imposition of different crop load treatments for 3 years from 2003 to 2005 as indicated by similar TCSA for thinned and
Laura J. Lehman, Eric Young, and C.R. Unrath
Spur-type or nonspur `Delicious' apple scions on either Malus domestica Borkh. (seedling) or M.26 rootstocks received paclobutrazol foliar sprays in one or two `consecutive years or a soil drench in the year of planting. For each scion, total shoot, root shank, and tree dry weights measured in the 3rd year after planting were suppressed by all treatments. Trees on M.26 put less dry weight into rootstock wood after foliar sprays, but trees on seedling were not similarly affected. No treatment influenced fibrous root dry weight of the spur-type scion on seedling, while all treatments suppressed dry-weight gain of the same scion on M.26. All trees had higher root: shoot ratios and blossom densities 3 years after the soil drench and several had higher ratios after foliar sprays. Chemical name used: ß-[(4-chlorophenyl)methyl] (l,l-dimethylethyl)-l-H-1,2,4-triazole-l-ethanol (paclobutrazol, PB).
M.L. Arpaia, G.S. Bender, and G.W. Witney
A project evaluating the performance of cv. Hass on eight clonal avocado rootstocks—G755A, G755B, G755C, Duke 7 (D7), Borchard (BR), D9, Toro Canyon, and Topa Topa was established in southern California in 1986. Two additional rootstocks, Thomas and G1033, were added in 1987. Of the trees planted in 1986, the BR and D7 rootstocks have consistently had the highest total yields for all rootstocks, whereas the three G755 selections have had the lowest productivity. No differences in productivity between the two rootstocks planted in 1987 have been detected. The influence of rootstock on the magnitude of alternate bearing will be discussed, although the oscillation in yield is greater for the higher-yielding rootstocks. Tree size has been measured throughout the study. The BR selection has consistently produced a larger tree, even though it has continued to have high productivity. There are no consistent differences between the other rootstocks. Yield efficiency, measured as the kg fruit/m3 of canopy volume has been calculated. In selections that are prone to severe alternate bearing, the swing in yield efficiency is also the greatest. The data thus far suggests that a yield efficiency of ≈2.5 kg fruit/m3 canopy volume is the maximum yield possible for California `Hass' avocado.
Kuo-Tan Li, Jim Syvertsen, and Jacqueline Burns
The shedding of leaves, branches, flowers, and young fruit; scuffing of bark; and exposed roots that are caused by trunk or canopy shakers during harvest appears to be unavoidable, but generally does not reduce long-term yields. Nonetheless, such visible injuries have limited the widespread adoption of mechanical harvesting in Florida's citrus industry. We determined if such physical injuries caused by a properly operated trunk shaker resulted in any physiological injures or any consequent decline in vigor and productivity of well-managed, healthy citrus trees. We continuously monitored various physiological indexes in mature `Hamlin' and `Valencia' orange trees annually harvested by hand or by a linear-type trunk shaker with various shaking durations. Trunk shaking did not reduce return bloom, fruit set, young fruit growth, or canopy and root growth. There was a correlation between the seasonal timing of a simulated bark injury and recovery from the injury. Although some root exposure was frequently observed during trunk shaking, leaf water relations and fine root growth were unaffected. There was no difference in leaf dry weight per area and leaf nitrogen among treatments. Mechanical and hand harvesting in late season `Valencia' during full bloom removed similar amounts of flowers. However, immature fruit were removed by trunk shaking when `Valencia' were harvested after mid-May, and the number of young fruit removal increased with shaking duration and fruit size. The loss of young fruit for the next crop remains a major problem of mechanical harvesting in late harvest `Valencia'.
Chenping Zhou, Ruiting Chen, Yaqiang Sun, He Wang, Yi Wang, Ting Wu, Xinzhong Zhang, Xuefeng Xu, and Zhenhai Han
above the bars indicate a significant difference at P < 0.05. Table 1. P values of main effects of tree vigor, leaf photosynthesis, the numbers of flower, and fruit-set in apple trees between girdling treatments and bridge grafting produced using a
D. Michael Glenn and Michael J. Newell
Excessive vegetative growth in peach (Prunus persica) causes canopy shading that reduces fruit bud initiation in the canopy interior and increases pruning costs and time. Sod competition can reduce pruning but may also reduce yield. The objective of the present study was to measure the effects of increased sod competition [2- vs. 8-ft-wide vegetation-free areas (VFA)] on yield and quality of irrigated peach. Total pruning weight was reduced by sod competition in the first 4 of 7 cropping years. Subsequent years indicated no effect on vegetative growth due to sod competition. Annual increase in trunk cross-sectional area was reduced by sod competition in the first year of cropping and unaffected in subsequent years. Canopy development was reduced by sod competition in the first 2 years of cropping, which increased photosynthetically active radiation transmission through the canopy and increased fruit red color in the first year. The width of the VFA did not alter the relationship between total fruit number and total yield in any year; however, the total number of fruit per tree was reduced in all years and total yield was reduced in 6 of 7 years. Results suggest that dormant season pruning was removing a higher percentage of the crop bearing wood from the 2-ft VFA compared with the 8-ft VFA treatment, resulting in reduced yield per unit of dormant pruning. This indicates that pruning practices must be modified to leave more bearing wood in mature trees to maintain yield potential when sod competition is used to control vegetative growth.
D.M. Glenn, T. Tworkoski, R. Scorza, and S.S. Miller
The lack of dwarfing rootstocks for peach has led to cultural and genetic approaches that reduce tree size and vegetative growth to establish high-density plantings. The objectives of the study were to evaluate the interactions of pruning strategies, groundcover management, tree densities, and peach (Prunus persica) architecture combined in eight peach production systems on components of yield and economic value. The use of sod management reduced pruning time and costs, but the reduction of crop load reduced net return. High-density plantings in large vegetation-free areas (VFAs) had greater economic return than low-density plantings.
consumption of mango fruit. However, ‘Aikou’ has strong tree vigor, so it is likely to be higher than ‘Irwin’. Furthermore, this cultivar needs more exposure to light for coloring the peel than does ‘Irwin’. Another problem with pot cultivation is that the
John Cline, Gerry Neilsen, Eugene Hogue, Shawn Kuchta, and Denise Neilsen
the burning of wood wastes, cereal, and hay straw, these materials have become available in large quantities. This increased availability has coincided with reports of increased tree vigor and yield associated with mulching in orchard trials ( Merwin