On July 27, Dr. Beth Grafton-Cardwell held an earwig field day at Lindcove featuring the work of visiting Spanish student Carla Romeu Dalmau.  Earwigs can be a pest of new citrus plantings when they feed on the flush growth and occasionally damage citrus fruit just after petal fall.  Carla has shown that the flush damage occurs in the spring but not the summer and that adults are efficient predators of various insect pests including California red scales, aphids and collembola.  Thus, they are not always a pest but sometimes a beneficial.  While Carla is heading back to Spain soon, the Grafton-Cardwell research team will continue to study earwigs and develop management tools.

Dr. Beth Grafton-Cardwell, with the help of assistants Sara, Jennifer and Jamie, is releasing earwigs into the blue arena surrounding this young citrus tree.  The purpose of the release is to study the level of damage earwigs cause to young citrus at various times of the year. 

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. 

Dr. William Cheung is conducting tests at Lindcove REC to profile the response of a Washington navel orange tree infected with citrus tristeza virus (CTV) compared to an uninfected tree.  A mobile sensor employing differential mobility spectrometry (DMS) records and analyzes the biogenic volatile organic compound (BVOC) signature emitted from the infected and noninfected plants.  The DMS BVOC analysis is designed to be an initial screening tool for rapid sampling of pathogens in citrus.  Studies are also underway in Florida to determine the citrus plant response to the bacterium Candidatus Liberibacter spp., the causal agent of the Huanglongbing disease (HLB).  Dr. Cheung is working in Professor Cristina Davis’ group (Dept.  of Mechanical and Aerospace Engineering, UC Davis)  in collaboration with Professor  Abhaya Dandekar (Dept. of Plant Sciences, UC Davis) and Professor Oliver Fiehn, (Genomic Core, UC Davis).