Ventura County UCCE Farm Advisor Ben Faber shares with us some of his citrus tree knowledge.

Heat affects different types and varieties of citrus differently. Heat determines when fruit ripens and how sweet it will be.  Grapefruit has one of the highest heat requirements of all citrus.  Grown along the coast it will be sour, but in the Central Valley it can be decidedly sweet.  A Pixie mandarin along the coast will be 6-8 weeks later in ripening than the Valley and will hang on the tree much longer.  Acid fruits like lemon and ‘Bearss’ lime have low heat requirements and are well adapted to the coast.  The everblooming characteristics of lemons and limes are accentuated along the coast where there may be continuous cropping with lemon blooms year round.

High temperatures can have a negative effect on citrus.  Coastal citrus may suddenly drop fruit when temperatures swing from the cool 60’s to the 90’s as often happens with Santa Ana conditions.  Sudden warm weather can cause fruit to split, induce flower and leaf drop, and cause sudden burn to both the fruit and tree.  These problems are compounded by dry soil moisture and problems can be reduced if there is adequate moisture present during the heat wave.  In hot environments, some citrus like navels produce less fruit.

Lemons

The Ventura County UCCE website includes a history section. One fun and educational part of the section is the History of Ventura and Oxnard slide show, put together by our own Steve Griffin.

The photos cover the mid 1800’s through the early 1900’s. Agriculture’s prominence in early county life is clear. While looking at photos of both cities downtown areas 100 years ago and more it is interesting to see what remains and what has changed.

The slide show is best viewed through the internet explorer browser and can be found by following this link.

In addition to the online photos, our office has many other historical photos not yet online. They cover larger sections of the county and include: 4-H meetings with women in long skirts and ruffled shirts, lush fields in places that have houses for decades, photos of old research and irrigation projects, and generally show that while much has changed, much remains the same.

These photos are available for viewing. Please contact our office if interested to set up an appointment.

I am sorry to have to report that we have another potential ecological and economic disaster coming our way. Much like the Asian Citrus Psyllid and Huanglongbing disease, this new threat is also a pest-disease complex.

Laurel Wilt Disease (LW) is caused by a fungus, which is carried by the Redbay Ambrosia Beetle (RAB). These beetles typically attack trees under stress (e.g. drought). The beetle bores into a tree carrying the fungus. The fungus in turn digests the wood disrupting the flow of water and nutrients.  As the tree weakens it becomes more attractive to the RAB and is used for brood rearing and is attacked in mass. It only takes one beetle to cause the infection. Once a tree is infected it takes about 6 months to collapse. Unfortunately one of the hosts for the RAB is the avocado tree.

The initial detection of this disease in the US was found May 2002 in Port Wentworth (Savannah), Georgia. It has spread mainly along the coast of South Carolina, Georgia and Florida as of 2008.  It is currently in the avocado orchards around Miami.

Much research is being done to help stop this destructive disease. While resistant trees are the subject of much of the research, we can all do our part to help stop the spread of the disease. This can be done in the following ways:

• Report any suspicious laurel trees to CDFA
• Voluntarily remove and destroy the tree
• Don’t move any symptomatic host wood from a site
• Don’t chip dead wood and use it as mulch around the yard
• For now, don’t purchase or obtain native Lauracae plants and avocado trees from an area known positive for the RAB-LW
• Leaving the tree in place will increase the RAB-LW infestations throughout your local area.
• Controlling the beetle may be impractical in the home landscape – it only takes 1 beetle to infest a tree.

Current control strategies are as follows:

Options for dooryard avocado trees

• Cut and burn the tree – not recommended because of the danger of burning and the requirement for burn permits, and various ordinances of local, state and federal agencies.
• Cut the tree down to the ground.
  • Pile the wood or chip the wood of the tree, pile it on top of the tree stump and tarp this pile of wood to the ground; essentially composting the infested remains of the tree in-place
  • Adding biosolids (e.g., manure), fertilizer, and water will speed the decomposition process
  • Spray your chainsaws with bleach and water to disinfect it against the possibility of spreading LW fungus to other susceptible host trees.

The Ventura County UCCE website has many great sources of information for home gardeners. One of them is the Santa Barbara Coastal Gardener. This garden column provides answers and information on home, garden and landscape problems. It was created by Frank Laemmlen Ph.D., Farm Advisor Emeritus in the Santa Barbara County Cooperative Extension Office. The original column was in question and answer format with one or more questions answered in each issue. We have separated each topic and have listed them as fact sheets.

The information is divided into the following major categories: home, landscape, and vegetables & fruit. The variety of subjects covered is vast. The landscape section even has a list of deer resistant/tolerant plants.  From time to time, our office receives quite a few calls about how to keep landscapes intact from deer. This and much more can be found by clicking here, or by clicking on the home gardening button on our home page.

There have been two earlier posting on this blog about the Asian Citrus Psyllid (ACP)and the potential crippling impact for citrus in California caused by the Huanglongbing vector (aka citrus greening disease) this insect carries. Please read the Introduction to the Asian Citrus Psyllid and Asian Citrus Psyllid: Lessons from Florida for additional information about this pest.

We are entering the time of year in which the ACP becomes most active. Make sure to check your trees regularly for signs of this insect. The Introduction to the Asian Citrus Psyllid post provides detailed photos and descriptions of how to determine if this species is on your trees. If you see this psyllid, call the California Department of Food and Agriculture at 1-800-491-1899 right away.

I recently asked Ventura County UCCE Farm Advisor Ben Faber what I should share about the ACP. He said to remind people how important it is to make sure to declare plant items when crossing the border. It is people who are spreading this around.

Recently UC Agriculture and Natural Resources’ News and Information group released a video demonstrating for the general public how to detect Asian Citrus psyllids on their garden trees. The video is available at:

http://news.ucanr.org/newsstorymain.cfm?story=1233

In addition, our office has a supply of bookmarks that contain photos and instructions for identifying both ACP and trees struck by Huanglongbing. They are available in both English and Spanish. Please contact our office if you would like some.

ACP infestation




ACP feeding damage



Distorted leaves from ACP