Annual Treatments for Aphids are Reducing Tristeza Virus at Lindcove

Each year, with funding provided by the California Citrus Nursery Board, we test every tree at Lindcove for citrus tristeza virus (CTV), a disease that is spread by aphids.  While the infected trees are symptomless, we remove them so that infections do not affect the research results of the various trials being conducted at LREC.  For many years, the average number of trees removed was 3 per year.  In 2007 and 2008 we had a sudden increase in the number of infected trees (52 and 83 infected trees removed in those two years) because of the increasing incidence of CTV in the commercial orchards surrounding LREC.  We recognized that removing this many trees each year would soon wreck havoc on the research trials and we requested assistance from the Tulare County Pest Control District.  They responded to the need for reducing the rate of spread of CTV onto LREC, by voting to provide funding to treat for aphids every spring and fall in a 2 mile radius around LREC.  The other San Joaquin Valley pest control districts have added a portion of their funding to the treatment program as well.  We are pleased to report that the incidence of CTV at LREC has been declining since the aphid treatment program was started in 2008 to: 52 trees (2009), 20 trees (2010) and 12 trees (2011).  Aphid control is reducing the spread of CTV, which is reducing the number of CTV-infected trees and so sustaining the excellent research program at LREC.