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.
Naomi Hirsch and Louise Ferguson
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.
Louise Ferguson and R. Buchner
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.
Louise Ferguson and Robert Beede
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.
Louise Ferguson and Steven R. Grattan
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.
James A. Wolpert and Louise Ferguson
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.
Louise Ferguson and Sergio Castro Garcia
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.
Louise Ferguson, Lynne Epstein and Robert H. Beede
Four pistachio rootstocks, Pistacia atlantica, P. integerrima, and two selections of the same interspecific hybridization, P. atlantica, P. atlantica × P. integerrima (A.K.A. PGII and UCB #1) budded with P.vera, P. vera cv. Kerman females have been evaluated since 1989 in three locations in California's central San Joaquin Valley. Thus far, Atlantica is the most cold tolerant, followed by the interspecific hybrids and Integerrima. Integerrima and UCB no. 1 have produced significantly more clusters and nuts per tree, but all rootstocks have produced the same numbers of nuts per cluster. Trees on no.1 and Integerrima rootstocks also have produced significantly more kilograms of nuts per trunk cross sectional area than Atlantica and PGII. UCB #1 and Integerrima also are significantly more tolerant of the soilborne fungus Verticillium dahl. All rootstocks are equally infected with three species vesicular–arbuscular mycorrhizzae. Two seasons of irrigation with water up to 8.00 dS·m–2, have not affected rootstock performance or yield. UCB #1, Integerrima, and PGII all require supplemental boron, zinc, and copper nutrition for good production. Thus far, Integerrima is the best rootstock for soils with verticillium infestations unless winter temperatures are frequently below freezing. UCB #1 is the best rootstock for locations with cold winters.
Patrick H. Brown, Louise Ferguson and Geno Picchioni
The uptake and distribution of foliar and soil applied boron has been followed in a seven year old pistachio orchard by utilizing 10B isotope dilution techniques and ICP-MS determination. In conjunction with these uptake studies, in-vivo and in-vitro measurements of pollination and fruit set have been used to determine the role of boron in flowering and fruit set.
Foliar applications of boron (1, 2.5 and 5 kg/400 l) resulted in improved fruit set when compared to control trees receiving no supplemental B even when tissue B levels in these control trees appeared adequate (>60 μg/g dwt). Results indicate that B applied to male trees in the late dormant phase (february) is effective in enhancing in-vitro pollen germination by as much as 50%. Movement of B into flower buds and fruit clusters was verified using 10B techniques thus demonstrating the potential usefulness of this technique in correcting incipient B deficiency. A possible role of B in the flowering and fruiting process is discussed.