During the spring of 2013, all 12,000+ trees at the Lindcove Research and Extension Center were tested for citrus tristeza virus (CTV). This week, LREC staff treated and removed 36 CTV-infected trees. The CTV strains found at LREC have been mild, causing few if any symptoms in the trees.  However, infected tree removal ensures the research plots are free of disease that could potentially affect the conclusions of the research.  

Lindcove REC has a small block of mature Manzanilla and Sevillano olive trees.  In past years the trees have been used for olive fruit fly research and mechanical harvester field trials, but now are currently being used by Dr. Carol Lovatt, Professor of Botany and Plant Sciences at UC Riverside, and Dr. Elizabeth Fichtner, UCCE Farm Advisor in Tulare County.  Their research is investigating the physiological mechanism underlying alternate bearing in olive with the goal of utilizing plant growth regulator treatments for mitigation of alternate bearing. 

The alternate bearing cycle in table olive results in a heavy crop one year followed by a light crop the next year.  Alternate bearing is disadvantageous to growers and processors because it affects the total annual yield of the crop and the average fruit size.  The first goal of the project is to better understand the nature and timing of fruit’s inhibition of vegetative shoot growth and return bloom in olive.  To achieve this goal, the research team collects olive shoots throughout the season and excises buds in the laboratory for analysis of expression of floral genes, natural plant growth regulator production, and visualization of floral and vegetative bud development.  Understanding the timing of floral bud development in olive will allow growers to effectively time plant growth regulator treatments on mature trees to counteract or eliminate the alternate bearing cycle. 

Field trials evaluating the systemic uptake of neonicotinoid insecticides into citrus trees are in their third year of evaluation at Lindcove REC.  Dr. Frank Byrne (right) and Richard Aubert (left) from the Department of Entomology (UC Riverside) are mixing up a batch of Belay insecticide to be applied to mature Parent navel orange trees.  One strategy is to apply the insecticide under the tree as a soil drench and another strategy is to apply it as a trunk spray.  Belay, which is not yet registered for citrus, is in the neonicotinoid class of insecticides, which are recommended insecticides for control of Asian citrus psyllid.  Dr. Byrne is comparing the two methods of application to see how they affect the rate of uptake of the chemical and what level of protection from the Asian citrus psyllid is imparted to the tree.

Citrus germplasm and nursery stock production have been through dramatic changes the last few years in California.  The CCPP Foundation Operations at LREC after 51 years of outdoor production have transitioned into protective structures.  CCPP and industry have been always in close collaboration.  As part of the continuing efforts to improve and optimize the budwood production schemes and protocol the CCPP invited nurserymen with experience in the new nursery technologies to visit CCPP and discuss ideas about the LREC Foundation Operations.

The visit was successful and very productive. Similar visits will be planned in the future as needed and as specific questions arise and different industry and scientific expertise is required. The CCPP has been inviting all stakeholders to its Foundation Operations for decades now during the annual Foundation and Evaluation Block Walkthrough.  It appears however that a different visitation model will be required under the new and upcoming quarantine and compliance regulations for the CCPP Protected Foundation Blocks.  This first visit with nurserymen may very well evolve to become a new type of “Undercover CCPP Walkthrough”.

---- Georgios Vidalakis, Director, Citrus Clonal Protection Program