California area citrus is one of the few global citrus growing regions which has not yet been infected with Huanglongbing disease.    (link to wikipedia)

The sticky surfaced yellow card (image above) is hung on citrus trees across Southern California - hoping to collect the vector insect - and be an early warning system for the disease.  

Omniously, last month, an infected plant was found in Hacienda Heights.   That infection may have been due to plant grafting material smuggled in from China and not the northern spread of the disease from Central America.   

If you enjoy a challenge, boy, there is a big challenge here....