Psyllids

Psyllids are leafhopper-like insects that suck phloem sap as both adults and nymphs. Adults are about 1/12 inch (2 mm) long and at rest hold their wings steeply pitched rooflike over the abdomen. Over 160 psyllid species occur in California. Note that Asian citrus psyllid (Diaphorina citri), the vector of the citrus-killing bacterial disease Huanglongbing (Candidatus Liberibacter asiaticus) is a quarantine pest requiring special management. Contact the local county agricultural commissioner for the requirements pertaining to nurseries producing citrus and related hosts of Asian citrus psyllid. See UC IPM Pest Management Guidelines: Citrus for an overview of Asian citrus psyllid.

Eugenia psyllid feeds only on eugenia (Syzygium paniculatum). Feeding by nymphs causes foliage to redden and appear blistered on the upper surface and pitted beneath. Adults are mostly dark brown with a white band around the abdomen. The tiny, golden eggs are laid primarily along the edges of young leaves. Nymphs are orangish to yellow when young and mostly dark brown when older. Psyllids are most abundant when new foliage is produced in the late winter and spring, but reproduction and all psyllid stages can occur year-round.

Ficus leaf-rolling psyllid infests Ficus microcarpa and was first found in California in 2016. It attacks young, newly emerging foliage, causing leaves to roll tightly inward completely or partially from one or both margins. Nymphs are 1/25 inch (1 mm) long and feed within rolled leaves. They are dark grayish-tan initially, becoming brownish to brownish green. Older instars have fringing skirts of long, white, waxy filaments. Adults are 1/20 inch long with a brownish head and brownish-green thorax. The abdomen is green on young adults and changes to brown on older adults. Adults occur mostly outside of rolled leaves and are commonly seen wagging their rear end. As nymphs feed within tightly rolled leaves, this species may be particularly difficult to control without systemic insecticides (e.g., acephate, imidacloprid). For more information see Ficus Leaf-Rolling Psyllid Introduced in Southern California.

Olive psyllid infests mock privet (Phillyrea latifolia), olive (Olea europaea) including fruitless cultivars, and Russian olive (Elaeagnus angustifolia). Adults are mostly tan with a bluish-green abdomen. Nymphs can be difficult to observe because they feed covered in fluffy, white wax they excrete. They produce abundant, white wax on leaves and twigs and cause premature leaf drop. If applying insecticide, target the first generation, typically present during March to April. Olive psyllids are more difficult to control during their second generation (May to June) and later in the season when their waxy deposits and plant damage are most apparent.

Peppertree psyllid feeds only on California pepper tree (Schinus molle), also called Peruvian pepper tree. Adults are pale greenish or tan. Females deposit their tiny eggs on leaf axils and growing tips throughout the year. The orangish nymphs feed on any succulent plant part, causing the plant to form a pit and deform and discolor around where each nymph feeds. One psyllid generation requires only a few weeks during warm weather. The species has multiple generations per year and all life stages can occur throughout the year in coastal areas.

Redgum lerp psyllid infests over two dozen Eucalyptus spp., especially river red gum (E. camaldulensis), flooded gum (E. rudis), and forest red gum (E. tereticornis). Nymphs are brownish, orange, or yellow and produce a roundish cover (lerp), which resembles an armored scale cover. Lerps are whitish, hemispherical caps on leaves that grow up to 1/8 inch in diameter. Nymphs feed beneath a lerp enlarge it as they grow or move and form a new covering. Adults are about 1/8 inch long, slender, and light green, with orangish and yellow blotches.

Females lay tiny, yellowish, ovoid eggs mostly on succulent leaves and shoots. Population increases follow the production of new plant growth, but all psyllid life stages can occur on both new and mature foliage. Redgum lerp psyllid has several generations each year and all stages can be present throughout the year in coastal areas. Because some nymphs form and abandon multiple lerps and the nymphs underneath are commonly parasitized as evidenced by a small rounded hole in the lerp covering, the number of lerps on leaves does not correspond to the actual number of psyllids present. For more information see Pest Notes: Eucalyptus Redgum Lerp.

At least six psyllid species infest eucalyptus in California, but some psyllids strongly prefer or are only found on certain Eucalyptus spp. For example, lemongum psyllid (Cryptoneossa triangula) and spottedgum lerp psyllid (Eucalyptolyma maideni) are abundant only on Eucalyptus citriodora and E. maculata.

Similar to aphids, psyllids suck phloem sap and excrete sticky honeydew that attracts ants and induces the growth of blackish sooty mold. High psyllid populations can slow plant growth and cause premature leaf drop. Eugenia psyllid and peppertree psyllid nymphs cause foliage to form pitlike depressions where they feed; infested leaves discolor and appear distorted. Nymphs of redgum lerp psyllid foul leaf surfaces with their caplike waxy covering. Olive psyllid covers foliage and green stems with flocculent, white wax.

Biological and cultural controls and insecticide application can manage pest psyllids.

Natural enemies of psyllids include brown lacewings, green lacewings, lady beetles, and minute pirate bugs. Especially important are tiny parasitic wasps with maggotlike larvae that feed inside and mummify and kill psyllid nymphs. Natural enemies provide good biological control of eugenia psyllid and peppertree psyllid in landscape situations. The introduced Tamarixia schina wasp leaves a roundish emergence hole in peppertree psyllid nymphs it has killed. These emergence holes can be observed by examining the parasitized nymphs under leaves. Eugenia psyllid nymphs are commonly parasitized by the Tamarixia dahlsteni wasp. In coastal areas an introduced parasitic wasp, Psyllaephagus bliteus, substantially reduces the abundance of redgum lerp psyllid, but the parasites is less effective in interior locations that experience hot summers.

To take advantage of biological control, avoid the application of broad-spectrum, persistent insecticides for all pests in the crop. When insecticide is warranted choose the selective, semi-selective, and short persistence pesticides as identified in Relative Toxicities of Pesticides Used in Floriculture and Nurseries to Natural Enemies and Honey Bees. Control ants that harass or kill the parasites and predators of pest insects. Control dust that interferes with the ability of natural enemies to locate and kill pests. See Protecting Natural Enemies and Pollinators for more suggestions.

The crop species grown determines whether psyllids can become a problem. For lists of eucalyptus species that are lightly or not at all infested by psyllids in comparison with those highly infested and damage by these pests, consult Pest Notes: Eucalyptus Redgum Lerp Psyllid.

Provide plants optimal cultural care to improve their tolerance of pest damage. Avoid frequent irrigation of hosts of olive psyllid to the extent compatible with desired crop growth, and provide good soil drainage.

If eugenia are regularly sheared (e.g., grown as topiary plants), well-timed pruning of new growth removes a substantial portion of the psyllid population, and in combination with parasite conservation and the application of compatible insecticides can greatly improve plant appearance. Prune terminals after maximum spring growth appears or about 3 weeks after the first peak in adult psyllid density as determined by weekly branch beating, foliage inspection, or sticky trapping. Leave eugenia clippings as mulch near the shrubs for at least 3 weeks to allow parasites within psyllid nymphs to emerge. About 1 week after shearing tips, inspect plants; if psyllids are present spray them with one of the organically acceptable insecticides or an insect growth regulator (IGR). Repeat the shear, monitor, and spray strategy through the growing season as warranted according to plant growth and psyllid abundance.

Biological and cultural controls are organically acceptable management methods. Some formulations of the botanicals azadirachtin (Azatin), neem oil, and pyrethrins without piperonyl butoxide (PyGanic), and potassium salts of fatty acids (insecticidal soap) are organically acceptable.

Visually inspect hosts on a regular basis to detect psyllids and other pests. Beat or shake sample plant parts over an insect-collecting surface to detect psyllids and some of their important natural enemies. Yellow sticky cards are useful to detect psyllid presence, migration into growing areas, and whether the abundance of psyllids appears to be increasing or decreasing. See Establishing Action Thresholds, Monitoring with Sticky Traps, MONITORING WITH STICKY TRAPS, and Sticky Trap Monitoring of Insect Pests for more information.

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