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- Author or Editor: Louise Ferguson x
Hydrogen cyanamide (H2CN2) has been shown to effectively substitute for lack of chill in a number of species. A 2% H2CN2 solution was applied 24 Feb. 1996 to 24 female Pistacia vera cv. Kerman trees, 6 each on P. atlantica, P. integerrima, and P. atlantica × P. integerrima, hybrid after a season of inadequate chill (<600 hours < 0.5°C). The trees on Atlantica rootstocks were unaffected by the H2CN2 application. Trees on the other two rootstocks produced significantly higher yields after treatment with H2CN2. The primary effect of the H2CN2 appears to have been to significantly decrease the percentage of blank (empty) nuts.
Pistachios are the single most-successful plant introduction to the United States in the 20th century. Part of this success is due to the alternative production practices that have made this crop more economical to grow. Controlled deficit irrigation (CDI) can produce 25% savings in irrigation water with no adverse effects. Reclaimed drainage water can be used for in-season irrigation up to 6 dS/m. Nitrogen applications can be adjusted for crop load and alternate bearing. Foliar sprays of boron, copper, and zinc can replace heavy ground applications to alleviated these micronutrient deficiencies. Some early season insect damage can be tolerated due to the tree's ability to compensate for the damage by filling a higher percentage of the remaining nuts, Maintaining a clean orchard floor can limit some insect pests. Mechanical pruning has been demonstrated to be cheaper and cause no loss in yield. Foliar fungal diseases can be partially controlled by limiting trajectory angle, frequency, and duration of irrigation or by using buried drip irrigation systems. Soil-borne fungal diseases and nematode damage are controlled by using resistant rootstocks.
For California pomology, it is ideal to communicate and disseminate information electronically because of its large size and diversity of fruit and nut crops. In support of statewide extension, the Fruit & Nut Research and Information Center's World Wide Web site 9 http://pom44.ucdavis.edu) focuses on providing information and links for temperate, subtropical and tropical fruits and nuts and keeping all interested persons well informed about University of California research and outreach activities. The Internet has been proven ideal for its user friendliness and rapid dissemination of current information. The Center supports this electronic change for growers and industry by collaborative projects with industry and involving Internet education and demonstrations at short courses, symposia, and educational days throughout the state. By this outreach to fruit and nut crop industries, the needs of the growers can be addressed. Also, it is important to address interdisciplinary cooperation and efficiency in the Agricultural Experiment Station and Cooperative Extension programs, especially in view of the recent reduction in staff and resources. By creating electronic listserv groups for each crop through the Center, extension specialists and farm advisors have the ability for increased communication. A more visible and active focal point —both within and outside the University—for research and outreach activities related to fruit and nut production, handling, processing, marketing and consumption has been created since the Center was established in Dec. 1995.
Currently, the California pistachio industry relies upon 4 rootstock; Pistacia integerrima, P. atlantica and 2 different hybrids of P. atlantica × P. integerrima. Although observations have been made, no trials have established the relative cold tolerances of these rootstock. The above four rootstock were planted in June, 1989, in Shasta County, California. Each rootstock was repeated once within the 100 replications of the randomized complete block experimental design. The trees were unbudded. The lowest winter temperature of 14°F (-24°C) occurred in February, 1990. When the trees were rated for damage in April, 1990, P. atlantica displayed only 3% mild tip burn damage compared to 56% tip burn for P. atlantica × P. integerrima (commercially known as UCB #1), 79% tip burn for P. atlantica × P. integerrima (commercially known as Pioneer Gold I) and 95% severe dieback for P. integerrima. Five superior P. integerrima rootstooks, with no damage, were identified.
Currently, the California pistachio industry relies on four rootstocks: two species and two interspecific hybrids—P. atlantica, P. integerrima, P. integerrima × P. atlantica, and P. atlantica × P. integerrima. The first three are open-pollinated, the last is the result of a closed pollination. The objective of these long-term trials is to compare rootstock behavior in the three major pistachio-producing regions of California. Three trials of 100 replications consisting of one of each of the four rootstocks were established in the three major growing regions of California in 1988. All the rootstocks in all three locations were budded with buds from the same female and male trees. Thus, all differences in performance are the result of rootstock or local climate. Results thus far demonstrate that rootstocks with P. atlantica as the maternal parent are more cold tolerant; more efficient in boron, zinc, and copper uptake; less vigorous; less precocious; and more susceptible to V. dahliae than rootstocks with P. integerrima as the maternal parent. The results also demonstrate that pistachios in California's southern San Joaquin Valley will bear 1 year ahead of pistachios in the central San Joaquin Valley or the northern Sacramento Valley. Trees on rootstocks with P. integerrima parentage also bear earlier than trees on P. atlantica and have higher yield efficiencies. All are colonized by vesicular–arbuscular mycorrhizae.
As one of the oldest continuously produced tree crops in the world, it is ironic that table olive (Olea europaea) production has benefitted from few technological innovations, including harvesting. Two harvesting technologies, trunk shaking and canopy contact, have been identified. In a 2013 trial, a prototype canopy contact harvester successfully harvested 92% of a 5.3-ton/acre mechanically pruned crop, vs. 81% for a 12.8-ton/acre hand-pruned control crop in a 19-year-old, 13 × 26-ft grove, spaced at 139 trees/acre and adapted for mechanical harvesting with 6 years of mechanical topping and hedging. About 85% of the hand-pruned olives were cannable vs. 86% of the mechanically pruned olives. Over the 6 years of mechanical pruning, the mechanically pruned trees averaged an annual 4.2 tons/acre vs. 5.3 tons/acre with hand-pruned trees. Again in 2013, this same canopy contact harvester achieved 81% final harvester efficiency with a 5.8-ton/acre crop in a 12-year-old, 12 × 18-ft, 202-tree/acre, mechanically pruned hedgerow grove vs. 80% efficiency for a 5.17-ton/acre crop with hand-pruned hedgerow trees. Similarly, no significant differences in the percentage of cannable olives, fruit size distribution, or value per ton was produced by the pruning treatments. In this trial in which both hand and mechanical pruning were used to produce a hedgerow, the hand-pruned trees averaged 3.7 tons/acre vs. 4.3 tons/acre for mechanically pruned trees. In a commercial trial in 2012, the trunk-shaking harvester achieved 77% average harvester efficiency in a 40-acre, 180-tree/acre grove, with a 4-ton/acre crop prepared with both hand and mechanical pruning. These ongoing trials indicate that adapting groves with mechanical pruning does not decrease average annual yields and can produce table olive groves that can be mechanically harvested at a cost and speed that is competitive with hand harvesting.
There are two ways salinity can damage citrus: direct injury due to specific ions, and osmotic effects. Specific ion toxicities are due to accumulation of sodium, chloride, and/or boron in the tissue to damaging levels. The damage is visible as foliar chlorosis and necrosis and, if severe enough, will affect orchard productivity. These ion accumulations occur in two ways. The first, more controllable and less frequent method, is direct foliar uptake. Avoiding irrigation methods that wet the foliage can easily eliminate this form of specific ion damage. The second way specific ion toxicity can occur is via root uptake. Certain varieties or rootstocks are better able to exclude the uptake and translocation of these potentially damaging ions to the shoot and are more tolerant of salinity. The effect of specific ions, singly and in combination, on plant nutrient status can also be considered a specific ion effect. The second way salinity damages citrus is osmotic effects. Osmotic effects are caused not by specific ions but by the total concentration of salt in the soil solution produced by the combination of soil salinity, irrigation water quality, and fertilization. Most plants have a threshold concentration value above which yields decline. The arid climates that produce high quality fresh citrus fruit are also the climates that exacerbate the salt concentration in soil solution that produces the osmotic effects. Osmotic effects can be slow, subtle, and often indistinguishable from water stress. With the exception of periodic leaching, it is difficult to control osmotic effects and the cumulative effects on woody plants are not easily mitigated. This review summarizes recent research for both forms of salinity damage: specific ion toxicity and osmotic effects.
Alternate bearing in pistachio (Pistacia vera L.) is correlated with crop load; a heavy crop on l-year-old wood appears to cause abscission of inflorescence buds on current wood. Defruiting heavily bearing trees before or during the period of nut growth stopped inflorescence bud loss. This relationship between crop and bud loss was affected by the fruiting status of neighboring shoots. Large defruited branches (> 5.5cm diameter). in fruiting trees had bud retention values (50% to 65%) equivalent to fully defruited control trees, but smaller branches showed reduced bud retention levels. Bud retention was increased 2- to 6-fold in small branches when neighboring branches were defruited. Nitrogen concentration of leaves in late August was positively correlated with the final bud retention percentage and inversely correlated with defruiting date.
Several experimental procedures were used to evaluate the influence of solar radiation on insect infestations in Calimyma and Adriatic variety figs (Ficus carica L.). Direct sunlight eliminated infesting insects and prevented further infestation of ripe figs drying on the ground for at least 10 days. Placement in the shade resulted in 12% insect infestation in figs within 3 days. Figs that fell naturally into sunlit areas contained almost no insects, whereas 31% of figs that fell into dense shade were infested. While ripening figs were still attached to trees, the level of insect infestation was 50% higher on the shady north side than the sunny south south side. The insect pests most frequently encountered in these experiments were nitidulid beetles and their larvae. Disease incidence was not affected by degree of exposure. We propose that cultural techniques to maximize exposure of ripening and drying figs to solar radiation could be developed as important pest management tools.
Currently, 94% of California fig production is dried or otherwise processed, but there is interest in expanding fresh fig sales. Since cultivars dominating the industry were largely selected for dried fig use, the fig collection of the National Clonal Germplasm Repository (NCGR) in Winters, Calif., was screened for traits of interest in fresh fruit production. For some traits, the bearing collection of 137 accessions was screened, while for most traits, data was collected on a core group of 30 accessions. While current commercial cultivars feature flavors of honey or caramel, some NCGR accessions have bright fruity flavors, reminiscent of berries or citrus, as well as noticeable acidity. Considerable variation was observed for time of maturity. Breba (figs on previous year's wood ripe in June/July) production was markedly greater in `King' than in any other core-group genotype, with ≈3× more fruit per branch than the next most breba-productive variety and 8× higher than the commercial standards. Earliness of ripening in the large collection was most pronounced in `Yellow Neches', `Orphan', and `Santa Cruz Dark', with 3× as many ripe fruit per tree in early August as the earliest commercial standard. Several commercial standards scored among the varieties with greatest late-season production (≈200 fruit per tree ripe after mid-September), comparing favorably with `Zidi', `Panachee', and `Ischia Black', among others. The SSC at commercial ripeness ranged from 13% to 19%, and SSC at tree-ripeness averaged 30% higher than in commercially ripe fruit. Several accessions were observed to have fruit traits that might also contribute to sustained quality through market channels.