- Author: Chris M. Webb
A team of scientists from the Agricultural Research Service of the U.S. Department of Agriculture and the University of Florida’s Indian River Research and Education Center are studying the use of periwinkle (Catharanthus roseus) to fight Huanglongbing (HLB). HLB is a bacterial disease that threatens citrus crops worldwide. The bacteria is spread by the Asian Citrus Psyllid.
The scientists infect the periwinkle plants with HLB and then run experiments on the diseased plants in an effort to find a way to return the plants to good health. They have used nutrient and soil treatments to regenerate infected plants and have placed cuttings in chemical compounds to search for HLB treatments.
Further information on this research and more can be found in the May 2010 edition of the Topics in Subtropics Newsletter on our website.
Yellowing leaves is one symptom of HLB
Periwinkle shows promise for solutions
to problems caused by HLB
- Author: Chris M. Webb
Our office is offering a smart irrigation scheduling and monitoring tour and seminar for commercial fruit tree growers on Thursday, April 29 from 12:30-4:30 pm.
Topics will include:
- Implications of irrigation management for nitrogen and phosphorus leaching
- Computer-controlled irrigation
- Irrigation system upgrades
- Improved efficiency
- Irrigation soil sensors
This education opportunity will be translated simultaneously into Spanish.
Education credits for Los Angeles Region and the Central Coast Ag Waiver
will be provided.
Please register in advance to ensure your participation by calling Maren
Mochizuki at 805-645-1467 or by email mmochizuki@ucdavis.edu. Additional details can be found here.
- Author: Chris M. Webb
The Asian Citrus Psyllid (ACP) continues its advance through Southern California. This is an extremely destructive pest. The disease it carries is capable of destroying citrus trees, orchards, and related industries.
An ACP Task Force has been formed in Ventura County. Top priority is to reduce the spread of the psyllid, which in turn will reduce the spread of disease. Your help is needed to stop this pest. You can help in the following ways:
- Do not bring citrus trees, other plants, or fruit into the state from other counties, states, or countries.
- If you have citrus on your property, please check regularly (at least monthly) for signs of infestation. Details on what to look for can be found here.
- Encourage your friends, neighbors and relatives to do the same
- A suspected ACP infestation should be reported immediately to the CDFA hotline at 800.491.1899, or your county agricultural commissioner. The Ventura County Agricultural Commissioner can be reached at 805.933.2926
The Ventura County ACP-HLB task force will be conducting a workshop on February 25, 2010 designed for growers and pest-control advisors. More information about the workshop can be found here.
Our office has outreach materials available to help spread the word. Please contact us if you would like some.
Psyllid eggs and nymphs tucked into crevices and folds.
Asian Citrus Psyllid nymph
Asian Citrus Psyllid adult
- Author: Chris M. Webb
Some of the most popular handouts at our garden display at the Ventura County Government Center is Fruit Trees: Planting and care of young trees. This publication can be downloaded for free here.
Other related topics are also available at no cost are:
Fruit trees: Thinning Young Fruit
Fruit trees: Training and Pruning Deciduous Trees
Fruit Trees: Pruning Overgrown Deciduous Trees
Additional pruning resources can be found in our previous Deciduous fruit tree pruning post and Winter tasks for backyard deciduous fruit trees.
- Author: Chris M. Webb
Today Ventura County Cooperative Extension Farm Advisor, Ben Faber shares some of his knowledge of citrus with us.
Citrus leaves appear wilted or flaccid during periods of low temperature. This is a natural protective response to freezing temperatures and does not mean the leaves have been frozen. Leaves will be firm and brittle and often curled when frozen. Leaves become flaccid after thawing, and if the injury is not too great, they gradually regain turgor and recover, leaving however, dark flecks on the leaves. Seriously frozen leaves collapse, dry out, and remain on the tree. Foliage form recent flushes are most susceptible to this damage. If twigs or wood have been seriously damaged, the frozen leaves may remain on the tree for several weeks. If the twigs and wood have not been damaged severely, the leaves are rapidly shed. Trees losing their leaves rapidly is often a good sign and is not, as many growers believe a sign of extensive damage.
Cold damage to the twigs appears as water soaking or discoloration. In older branches and trunks it appears as splitting or loosening of bark where the cambium has been killed. Bark may curl and dry with many small cracks. Dead patches of bark may occur in various locations on limbs and trunk. Sensitivity to frost is dependent upon many variables. In general, mandarins are the most cold hardy followed by sweet orange and grapefruit. Lemons are very frost sensitive with Eureka decidedly more sensitive than Lisbon. Limes are the least cold hardy. Healthy trees are more tolerant than stressed ones. The rootstock also imparts sensitivity onto the scion. Injury to the foliage and to young trees may be immediately recognizable but the true extent of the damage to larger branches, trunks, and rootstocks may not appear for on to four months following the freeze. No attempt should be made to prune or even assess damage from the frost until spring when new growth appears.