The Effect of Citrus Greening Disease on Insecticide Use: Insights from Florida and Implications for California


Project Description

Background: The Asian citrus psyllid (ACP), Diaphorina citri, is a small aphid-like pest of citrus that functions as a vector of a devastating disease known as citrus greening disease, or Huanglongbing. ACP was first found in Florida in 1998 with the first positive case of citrus greening disease discovered in 2005. By 2007 it was found in all citrus producing counties in Florida leading to devastating consequences.

Despite quarantines on infected counties, the ACP and citrus greening has spread. Non-viral ACP were eventually found in San Diego county, CA in 2008 and the first confirmed case of citrus greening was later found in LA county in March 2012. Statewide detection efforts are now in place in citrus groves and residential areas (maybe you’ve seen the yellow note-card sized “sticky traps” hanging on trees around town). Citrus greening causes the fruit to drop early, be malformed, off-tasting and generally unmarketable. It passes from tree-to-tree in a similar manner as malaria passes person-to-person: once a tree is infected it will infect all psyllids that feed on the tree and those psyllids will in turn infect the other trees they feed on. Currently, infected trees are destroyed because there is no cure. Prevention methods are equally limited with widespread insecticide use being the most common tactic.

Research Project: To date, most research has focused, unsuccessfully, on containing the spread of ACP,developing resistant trees, or discovering biological control agents. Surprisingly, few studies have addressed the economic consequences of citrus greening or the effect of citrus greening on insecticide use in Florida. There have been a few studies, however, that have used data from Florida to anticipate the potential outcomes for California citrus. This research project will address part of this gap. We will ask what the effects of citrus greening are on chemical expenditures and insecticide use in Florida and relate these result to California citrus regions. We will analyze the USDA census of agriculture data before the ACP or citrus greening was found (i.e. 1997) and after citrus greening became endemic (2007). We will use various statistical methods to understand how insecticide use has changed as a result of citrus greening. Interns will experience the research process from start (forming a statistical model and finding/downloading data) to finish (running the model and interpreting the results). Insecticides are not only economically costly, but also have vast unintended consequences on human health, water quality and biodiversity. Thus, understanding how citrus greening effects insecticide use is important for both the economical and ecological sustainability of California and US citrus.

UCSB California NanoSystems Institute