Jeannette Warnert, Public Info. The four infected trees, which were removed Tuesday, Sept. 23, were not part of the UC Citrus Clonal Protection Program Foundation Block, a collection of about 200 varieties of citrus trees that are California's primary source of virus-tested budwood.
Nurseries use the budwood to grow new citrus trees for farmers.
Citrus tristeza virus is widespread in Southern California, Mexico and most other parts of the world where citrus is grown. The disease is caused by several strains of the virus, some stronger than others, which are transmitted from tree to tree by feeding aphids. Symptoms can include light green foliage, poor growth, leaf drop, reduced yield, poor fruit quality and tree death. However, in trees grown on tolerant rootstocks, certain strains of the virus cause no visible signs of decline. The tristeza virus was first detected in San Joaquin Valley orchards about 40 years ago.