Psyllids Feeding on a Citrus Tree Leaf (IMAGE) Boyce Thompson Institute Caption Asian citrus psyllids feed on a citrus tree. The psyllids deposit a bacterium in the sap that causes citrus greening disease, a scourge to the citrus industries in Florida and California, worth a combined $17 billion. Credit Image credit: BTI Usage Restrictions Must use proper credit. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.