This report proposes that the delimitation radius for tree surveys around an HLB+ tree be reduced from 400m to 300m. This change is suggested based on the geographic distribution of all trees confirmed to be positive for huanglongbing by March 2020, based on a methodology previously used by the CPDPC to make operational decisions.
Residential buffer zones around commercial citrus can be treated by CDFA with insecticides to suppress Asian citrus psyllid populations only if 90% of growers in that region apply insecticides within a designated 3-week window. While useful, this threshold created logistical difficulties and a new criterion for treatment was explored.
As a part of DATOC's report on exposure to CLas in Southern California residential areas, DATOC was asked to evaluate exposure over smaller geographic scales. We also evaluated the changes in infection density in the most recent detections.
DATOC compiled available research to help the CPDPC advise growers on how they should respond to an HLB find in or near their commercial grove. This was the basis of the "Best Management Practices in Response to Huanglongbing in California Citrus", approved by the CPDPC and published on CitrusInsider.org.
The CDFA action plan previously called for sampling 25% of an orchard should HLB be found within 400m. Best available evidence indicated that would be inefficient. DATOC suggested an evidence-based replacement plan, which was approved in March 2019.
The DATOC expert panel feels strongly that the find of a single Asian citrus psyllid (ACP) in an area which is not generally infested and eradication is still being attempted should trigger a treatment area around the detection that is never less than a 400 m radius.
The presence of ACP in California has been tracked by various programs and projects for several years. This analysis will construct a time series for various California regions since the start of these activities.