Tree Infected with HLB Found in Riverside, California

Len Wilcox California Corner, HLB Management


The California Department of Food and Agriculture (CDFA) stated last week that a second tree has tested positive for HLB disease, also known as citrus greening, in Riverside County. Due to being in a previously identified detection area, the tree had been tested several times previously but had not shown indications of the disease. The CDFA is in the process of removing the HLB-positive tree.

In addition to removing the tree, CDFA has pulled samples from all other citrus trees on the property for testing and is in the process of beginning treatment of all host plants within 400 meters of the detection site.

The tree was located on a site where the first detection in the county was found back in 2017. CDFA had tested the trees on that site five different times since that first detection. All tests had negative results before the positive test last week. This is a perfect example of one of the major issues with controlling HLB: Infected trees may not test positive for the disease for several years.

Since this new detection occurred on the same property as a previous find, there will not be a change to the current HLB quarantine area or Asian citrus psyllid quarantine zones.

For more information, visit Citrus growers and pest control advisers in Riverside County can also contact Alan Washburn, grower liaison, at or 951-683-2392 with questions or to seek recommendations on how to protect their orchards.