Pest 5 - Psyllids on Calistemon spp.

This infestation of a species of psyllids that specifically targets callistemon was found at the Botanic Gardens during our Monday sessions. Psyllids belong to the Family Psyllidae, Order Hemiptera and have sucking mouthparts. 

Appearance : The adult insects are small (less than 4mm in length) and look like miniature cicadas.  Adults have two pairs of wings but they are not strong fliers. They are often hard to see because they jump actively. The nymphs of Lerp insects produce a shell-like covering, which gives rise to their name Lerps. The coverings are commonly white in colour, but are highly variable. Some species do not have protective covers. Psyllids are free-living and do not produce lerp coverings but secrete a white powdery wax for protection. 

Damage : The signs of damage to the callistemon is discoloured reddish and yellow patches on leaves, in some areas like blisters, due to the sucking of the nymphs and adults and the toxic saliva . In heavy attacks, infested leaves may fall prematurely. In other plants, some species can produce honeydew which gives rise to the formation of sooty mould. In the case of the callistemon pictured, the nymphs have settled on the undersurface of the leaves, with feeding causing circular lumps on the upper surface and corresponding depressions on the lower surface, with the scale-like insect inside. 

Host : In this case Calistemon spp. but lerp insects can attack other native trees, especially eucalyptus. Each species of lerps are usually quite specific in what native trees they attack. 

Life Cycle : Gradual metamorphosis with several generations within a season. Nymphs usually go through several stages before shedding its exoskeleton to form the winged adult stage. The overwintering of lerps and psyllids is unknown. Spread is usually only to adjacent plants as the adults can't fly far. 

Control : usually a tree can survive an onslaught the first time and nothing need be done. Birds and other predators feed on lerp insects. Pictured below is a predatory beetle.

With repeat attacks that severely weaken a tree it might be worth considering removing that tree and replacing it with a less susceptible species. Only councils have suitable equipment to handle appropriate insecticides which must be systemic (contact sprays are ineffective due to the lerp coverings). For valuable trees, injections of systemic dimethoate (Rogor) could be considered. 

Reference :  Kerruish, A-151

                     McMaugh, pg. 196