Pests That Threaten Citrus Trees of Southern California

Few places in the world are more hospitable to citrus trees than Southern California. But unfortunately, even in a place with a nearly ideal climate for these fruit-bearing trees, the trees must still survive amid a variety of insects and other pests. In fact, while these pests and parasites threaten the citrus trees growing in residential yards, they pose an even greater threat to our state’s important commercial citrus industry. 

Accordingly, residents, commercial growers, and property managers must familiarize themselves with some of the most notable citrus pests and the symptoms they cause. This will allow for prompt treatment, or, when necessary, removal of the afflicted trees. 

We’ll discuss four of the most dangerous and common citrus pests below. 

Asian Citrus Psyllid (Diaphorina citri)

The Asian citrus psyllid is undoubtedly the gravest threat that faces California citrus trees. These tiny six-legged critters are originally native to southeast Asia, but they eventually reached U.S. shores and have established populations throughout southern California. 

The feeding activities of these insects cause moderate damage to the trees, usually manifesting as contorted leaves at the ends of young shoots. But they actually present an even greater threat: Asian citrus psyllids are one of the only vectors for citrus greening disease – a devastating bacterial pathogen of citrus trees. 

Citrus Leaf Miner (Phyllocnistis citrella)

The citrus leaf miner is another invasive species, originally native to southeast Asia. It also has another trait in common with the Asian citrus psyllid: It can cause distorted, contorted leaves to appear on afflicted trees. Fortunately, while citrus leaf miners may reduce a given tree’s vigor, they rarely cause afflicted trees to die outright. This highlights the importance of having citrus pests positively identified at the first sign of their presence. 

Citrus leaf miner larvae tunnel under the surface of citrus tree leaves. This damages the leaves, which means they can’t photosynthesize effectively, thereby causing the tree considerable stress. Leaf miners can be identified by noting the winding “mines” they create inside leaves, which generally have a dark center. This dark coloration is caused by the larvae’s droppings (frass). 

California Red Scale (Aonidiella aurantii)

California red scale is another exotic pest, but this one has been around for a lot longer than the Asian citrus psyllid or the citrus leaf miner. Unlike the psyllid, which was first found in the U.S. in 1998, and the leaf miner, which first appeared in California in the early 2000s, California red scale has been in the country since the civil war. 

These tiny red insects can cause fairly significant damage to citrus trees, including leaf drop, the production of misshapen leaves, and bark splitting. In severe cases, this pest can cause the death of infected citrus trees.  

Citrus Thrips (Scirtothrips citri)

Citrus thrips can cause quite a bit of damage to citrus trees, but they rarely cause the death of those that are afflicted. However, they can severely damage a growing crop, so they’re of extreme importance to commercial growers (as well as homeowners who simply want healthy fruit crops). 

Citrus thrips are very small insects, who are relatively easily identified by noting their yellow-orange coloration and fringed wings. Their feeding activities cause damage to the citrus fruits themselves, as they can leave silver-colored scars on the surface of the fruit. It is the second-instar life stage that causes the bulk of the damage, as these insects typically feed beneath the calyx of the growing citrus fruits.  


Remember that it is important to take citrus pests seriously and spring into immediate action whenever they’re suspected of being present. This will help limit the damage caused and give your trees the best chance of recovery. 

If you observe citrus pests or symptoms that hint at their presence, give your friends at Evergreen Arborist Consultants a call. One of our certified arborists will visit your property, inspect your trees and recommend a mitigation strategy.