Psyllids

Psyllids are jumping plant lice that suck plant juices. 

​Most native psyllid species do not pose a threat to your garden. Local predators tend to keep those populations in check most of the time. Invasive psyllid species are something else altogether.

Asian citrus psyllid (USDA ARS)

Psyllid identification

Psyllids look like tiny cicadas or winged aphids with tubular mouthparts. They have powerful legs and short antennae. Psyllids can be 1/12 to 1/5” long. Adults hold their wings in a roofline position. Nymphs are flattened and look a lot like soft scale insects. Psyllid nymphs commonly produce waxy filaments or covers called lerps using wax and honeydew.

Potato psyllids look like flies (Whitney Cranshaw, Colorado State University, bugwood.org) CC BY 3.0 US

Psyllid lifecycle

Regardless of the species, psyllids start as tiny eggs that hatch and go through five developmental stages or instars. Adult psyllids can fly, but most prefer to jump. If you think you see a psyllid run or fly, it is probably a psocid [SO-sid]. Psocids are beneficial insects that feed on fungi. They have a narrow “neck” and chewing mouthparts. 

Psyllid host plants

As a species, psyllids have strong preferences for particular host plants. While some psyllids will prefer your sweet peppers and chilis, others will go after your peaches and nectarines, others will only feed on  olive or pear trees, and other psyllid species will only feed on potato and tomato plants. 

The invasive Asian citrus psyllid carries huanglongbing,, a deadly citrus disease. Citrus trees infected with huanglongbing must be destroyed and removed by a professional arborist, which is both sad and expensive. These pests, when present, are most active in spring.

Psyllid species most likely to threaten your garden include:

• Asian citrus psyllid (Diaphorina citri)
• Eugenia psyllid (Trioza eugeniae)
• Olive psyllid (Euphyllura olivina)
• Pear psyllid (Psylla pyricola)
• Potato/tomato psyllid (Bactericera cockerelli)

Dozens of psyllid species infest ornamental trees and shrubs, as well. These include the recent invasions of Ficus leaf-rolling psyllids and spotted gum psyllids. On the other hand, some psyllid species are beneficial. The Australian melaleuca psyllid, for example, has been purposefully introduced to Florida to help control paperbark trees, an invasive weed tree.

Damage caused by psyllids

One of the biggest problems associated with psyllids is their poop. After they have robbed your plants of valuable nutrients, they add insult to injury by excreting a large portion of the sap they ate and depositing it on leaves. Sap-sucker poo or honeydew is rich in sugar and other nutrients. Honeydew ends up being food for fungal sooty mold and disease-carrying  ants. 

Psyllid feeding can also spread diseases, such as calico, and zebra chip, and disorders, such as galls, leaf and bud discoloration and deformation, and premature leaf drop. Leaf distortions often look similar to peach leaf curl. Pear psyllids inject fruit with toxins that blacken leaves and fruit skins. Psyllid feeding also creates points of entry for other pests and diseases.

How to control psyllids in the garden

Control psyllids with insecticidal soaps and yellow sticky sheets. Do not use dish soap. Parasitic wasps and pirate bugs feed on psyllids, so avoid using broad-spectrum insecticides. Severely infested plants should be removed and destroyed or thrown in the trash. Usually, simply monitoring plants can make controlling these and other pests much easier.

To prevent invasive psyllids from finding your garden, only buy pest-free plants from reputable nurseries, and place new plants in quarantine.