Search Results

You are looking at 1 - 10 of 23 items for :

  • Author or Editor: Louise Ferguson x
  • HortScience x
Clear All Modify Search
Author:

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.

Free access
Author:

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.

Free access

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.

Free access

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.

Free access

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.

Free access

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.

Free access

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.

Free access

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.

Free access

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.

Free access

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.

Free access