As part of our coverage of California Invasive Species Action Week, today we focus on a pair of invasive species that “work” together: an insect called the Asian citrus psyllid and the plant disease it can spread, huanglongbing.

Our long-time readers will know that we write about these pests quite a bit. That's because this pest pair has the potential of causing profound economic harm to the California citrus industry. So please read on and found out what you can do to help.

The Basics

The Asian citrus psyllid (ACP) is a very small flying insect that feeds on citrus plants...

San Luis Obispo County has seen more than 20 detections of Asian citrus psyllid (ACP) since January 2018, according to Citrus Insider. The majority of these invasive insects have been found in the backyards of residential properties in the city of Nipomo.

If you haven't yet heard about this insect, Asian citrus psyllids can carry and spread the incurable citrus disease huanglongbing, also called HLB or citrus greening disease. Citrus trees infected with HLB develop mottled leaves and produce misshapen fruit that stays green and tastes bitter. There is currently no treatment for the disease, which usually kills trees within three to five years.

Due to these ACP finds, citrus growers in SLO County are on high alert,...

Brown Rot

Monitor for this disease by checking for damaged fruit on your tree, as well as fruit in storage. Sometimes affected fruit develops a pungent odor and can ruin fruit held in storage. See the UC IPM web page on Brown Rot to learn more.

Citrus Leafminer

If you see what look like small “tunnels” on your citrus...