- Author: Kathy Keatley Garvey
Senior scientist Arnon Dag of the Agricultural Research Organization, Volcani Institute, Israel, will discuss his research at the UC Davis Department of Entomology and Nematology seminar at 4:10 p.m., Monday, Nov. 27 in 122 Briggs Hall.
His seminar, titled "Improving Cross-Pollination in Deciduous Fruit Trees," also will be on Zoom: The Zoom link:
https://ucdavis.zoom.us/j/95882849672.
"Tree crops belonging to the Rosaceae, such as almond, pear, apple, and sweet cherry, depend on cross-pollination by insects to set fruit," Dag says in his abstract. "The primary pollinator of the crops is the honey bee (Apis mellifera). However, due to harsh climatic conditions during flowering, limited movement of bees between cultivars, low preference of the bees for flowers of the target crop, and limited overlap in flowering between the cultivars, pollination is a primary factor limiting yield. Our group has tested multiple approaches to mitigate this problem: Using 'Pollen dispensers,' sequential introduction of beehives to the orchards, selection of honeybee strains with higher preference for the target crop, introduction of bumblebee (Bombus terrestris) colonies and phosphorous fertilization to increase nectar secretion and improve crop-flower attractiveness. I will summarize the effects of those methods on fruit set and yield in apples, almonds, and pears."
A native of Moshav Lachish, Israel, Dag received his bachelor's degree (1990) and master's degree (1992) in life sciences at the Faculty of Life Sciences, Tel Aviv University. His master's thesis: "Improving the Honey Bee Efficiency of Melon Pollination in Greenhouses." He obtained his doctorate in agriculture at the Horticulture, Faculty of Agriculture at Hebrew University of Jerusalem, completing his dissertation on "Pollenizers, Pollinators and Pollination in Mango." He held postdoctoral positions at both Tel Aviv University and the Hebrew University of Jerusalem.
Dag's research interests include fruit tree physiology, olive biology and cultivation, reproductive biology of fruit trees, crop pollination, pomology in semi-arid conditions and "developing guava as an export crop."
He served as an Extension specialist in beekeeping from 1991 to 2003 for the Israeli Ministry of Agriculture.
Seminar coordinator is Brian Johnson, associate professor, UC Davis Department of Entomology and Nematology. For Zoom technical issues, he may be reached at brnjohnson@ucdavis.edu. The list of seminars is posted here.
- Author: Clebson G Goncalves Ph.D.
- Posted by: Gale Perez
In Northern California, Pokeweed (Phytolacca americana L.) has been around for a long time and is typically found in disturbed areas and fallow sites such as: under power lines, wooded areas, fences, pond edges, roadsides, etc. (Figure 1). However, in recent years, organic orchard growers throughout north coast have reported that pokeweed has been invading and contaminating new areas that were not found before.
Pokeweed is a perennial shrub whose shoot tissues die in the winter but exhibits rapid resprout from a large fleshy taproot in the growing season, causing panic among orchard growers. That kind of shrub can grow up to 10 feet tall, and a single plant can produce greater than 7,000 seeds annually. The seeds may survive in the soil for years before germination, and the new infestation occurrences are usually caused by seeds spread via birds.
Pokeweed contamination and management strategies in pear orchards floor have been the topic of discussion among growers, pest control advisers (PCAs), and farm advisors in the Lake County area. Growers typically monitor and control pokeweed in fallow sites to prevent seed production and spread. However, due to the lack of training or an efficient management program, the control is not always carried out timely and adequately, and seeds end up escaping and contaminating new areas.
In organic pear orchards, pokeweed management is difficult due to the limited number of strategies available. Mowing or hand-pulling has been the primary management strategy in organic areas. Young plants may be removed easily by hand at the beginning of the growing season. However, due to the robust taproot system, once established, plants will produce regrowth quickly from mowing, and hand pulling is laborious.
Tarps or fabrics have been used by growers to suppress pokeweed as well; however, once the weed is already established, pokeweed has shown a strong capability to overcome and regrow from those strategies (Figure 2).
The growers have also tried to adopt non-synthetic herbicide products for pokeweed control. Among those available commercial products, the active ingredients, including acetic acid, citric acid, caprylic acid, capric acid, pelargonic acid, Clove oil D-limonene, and others, have been used for the non-selective control of that weed.
Usually, organic herbicides are recommended for weeds in the early stages of growth. For pokeweed already established, organic herbicides have shown poor effectiveness, and growers have reported that pokeweed begins recovery approximately two weeks after treatment application (Figure 3). Preliminary studies have shown that organic herbicides applied to control weeds may require late sequential application due to the non-systemic characteristics of these products.
Where do we go from here?
UC Cooperative Extension - Diversified Agricultural System program, in collaboration with UC IPM, UC Davis experts, and the Pear Advisory Board, has been designed and will conduct field trials during the 2023 and 2024 growing seasons to access long-lasting control of pokeweed in organic orchards using different organic management strategies including mechanical weeding and use of non-systemic herbicides. The primary objective of those trials is to provide California orchard growers and agricultural PCAs with an organic weed management program for long-lasting control of pokeweed on orchards floor.
- Author: Anne Schellman
What is a Deciduous Fruit tree?
Deciduous fruit trees lose their leaves in fall, and include apple, pear, fig, pomegranate, nectarine, cherry, apricot, peach, and plum.
Planting New Trees & Understanding Where Fruit Originates
Sometimes a fruit tree mysteriously dies, and the gardener isn't sure what happened. A common cause is a tree that was planted too deeply. Root and crown rot slowly affect the tree, causing it to die years later. Watch the detailed instructions on how to plant correctly.
It's important to understand how new fruit develops and grows on the tree. Not all deciduous fruit trees produce fruit in the same place. It's important to know this so you don't accidentally cut off fruit spurs and damage your tree's ability to produce fruit. See this video for guidance. https://www.youtube.com/watch?v=-4fgVrf8XHE&t=250s
Publication - Fruit Trees: Planting and Care of Young Trees https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8048
Fruit Trees: Training and Pruning Deciduous Trees https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8057
Keeping New Trees Small – the Fruit Bush Method
Tired of out-of-control fruit trees? If you are planting a new tree, watch this video! It details the Fruit Bush Method, a specific way of keeping fruit trees small. See photos of 5-6' tall fruit trees planted over 30 years ago that continue to produce an ample amount of fruit. https://www.youtube.com/watch?v=ry4YAp6NzdI&t=1s
Pruning Established Trees
Other Helpful Publications
Fruit Trees: Thinning Young Fruit https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8047
What about Citrus Trees?
Citrus trees such as oranges, lemons, grapefruits, lime, and kumquats are evergreen trees and need different care than deciduous trees. It's not recommended to prune citrus trees at the same time as deciduous fruit trees. Wait until spring to prune your tree for size and shape.
We are offering an online class on citrus on January 31, so watch for our registration advertisement in about a week. Locally, we will be teaching at 8 library locations about citrus during March.
/h3>/h3>/h3>/h3>/h3>/h3>- Author: Ed Perry
If you decide to fight them, now is a good time to plan your strategy since the most critical time to protect your fruit from the pest is spring. Warm spring weather causes most of the first generation moths to emerge within a few weeks. The moths may take 6 weeks or more to emerge during a cool spring. Once they have emerged, the codling moths are still affected by temperature. They do not lay eggs or mate when it's below 62°F at sunset or fly when it's 55°F.
The moths emerge from pupae in early spring about the time when fruit trees are in full bloom. Each moth lays 50 to 75 eggs on fruit, twigs, or leaves. Eggs hatch into larvae which tunnel into the young fruit. Inside the fruit, the larvae feed for several weeks, then tunnel to the fruit's surface and search for protected sites such as under tree bark, in branch wounds, weeds, grass or other litter. The larvae changes first to a pupa, then to an adult and repeats the cycle.
You can also trap many larvae under bands. Take a 6-inch wide strip or burlap or corrugated cardboard, wrap it around the trunk several times, then fasten it in place with a loop of wire or twine. If you use corrugated cardboard, the exposed flutes (ridges) must be at least 3/16 of an inch wide and face toward the tree; otherwise, the larvae won't form cocoons in them. Place a band on each tree no later than mind-May. During warm weather remove the band once a week, and during cool weather once every two weeks. Destroy all the larvae and pupae under the band, and then put the band back on the tree. Keep doing this until you've harvested all the fruit.
Insecticidal sprays are usually the most effective means of controlling codling moths. Sprays give best control when you apply them just after a large number of larvae hatch, but before they burrow into the fruit. These times are several days after a period of peak moth flight and vary according to the year and location.
When using any chemical, carefully follow dilution rates and other directions given on the container label. Do not spray within the number of days before harvest indicated on the label. You can read more details about the life cycle of this pest and management, including chemical controls in the UC IPM Pest Notes: Codling Moth.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
- Author: Ben Faber
That's a good question. Some question whether they flourish now. Southern California does not have the landscapes of apples, pears and peaches of Oregon, Michigan, Pennsylvania or even Fresno, but there are nice little niches of persimmon, low chill apple, and even blueberries that thrive in the lower winter chilling environments along the coast and in the south of California.
Here is an example of what might happen to this fruit industry here. A recent, detailed study extrapolate the accumulation of cold periods in Spain over the next 30 years and to the end of the century. This provides growers with important information on the viability of future fruit cultivation in the various Spanish regions, as it allows them to know if there will be the necessary accumulated cold for the fruits to grow correctly or if they should relocate their crops to other areas.
The results obtained show a general reduction in the accumulation of cold in any future period for all the chilling models and scenarios considered. The reduction is especially significant at the end of the century, under the most pessimistic scenario. These results invite us to strongly commit, not only to adapt but also to mitigate climate change, something that would make an important difference. The probable reduction of cold would threaten the viability of some varieties of fruit trees in the near future, especially in regions where there is currently a low accumulation of cold and there are varieties that require a lot of it.
The study can be viewed at:
https://www.nat-hazards-earth-syst-sci.net/19/1087/2019/
Climate change discussions for California can be found at these websites:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=30513
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=28175
An intriguing Santa Barbara apple study grower's observations are worth noting: https://ucanr.edu/blogs/Topics/index.cfm?start=1&tagname=apples
By the way the 'Moor Park' apricot is not from Moorpark, CA, but from England and the variety has never done very well in Moorpark (http://www.ngr.ucdavis.edu/treedetails.cfm?v=997).