Spring is here and that means new growth on your plants and multiplying insects looking for homes on that new growth. Australian Brush Cherry (Eugenia or Szygium) are hosts to the Eugenia Psyllid adults, eggs, and nymphs (crawlers). Psyllids suck plant juices, produce sticky honeydew which attracts sooty mold and distort and discolor new leaf growth, eventually causing defoliation and die back.
To help prevent infestation, avoid excessive irrigation and unnecessary fertilization which will cause soft new foliage that promotes increased populations of the psyllids.
Controlling these pests requires diligent observations of their life cycle. Beneficial parasitic wasps have been released in California to control the psyllid population and now occur naturally throughout the state. None are available for purchase and release so you’re going on “hope & a prayer” that these critters will find your Eugenias to provide the control you desire. If you notice the insects on your plants, prune the terminal branches after spring growth to remove any psyllid eggs or nymphs and leave the clippings as mulch. These critters will die on the cut foliage. Do this in 3 week cycles or as long as you see adult psyllids. Clipping affected leaves is the only way to eliminate the damaged foliage.
Use Yellow Sticky Traps to monitor the number of adult psyllids and help determine the most effective time to spray or shear the new growth tips.
Chemical control may be needed in certain circumstances or when damaged leaves cannot be tolerated. Products such as neem oil, insecticidal soap and horticultural oil provide temporary control of the psyllid population through direct contact with the spray. Infested new growth must be thoroughly covered with the insecticide spray. This is the preferred treatment early in the season while waiting for the beneficial parasitic wasps to attack.
When you notice a sharp increase in adult numbers on the Yellow Sticky Traps, treat with an insecticide to kill the eggs and nymphs before damage occurs. Systemic insecticides are the most practical for controlling psyllids in large trees, hedges, shrubs or clumped groups of plants.
Imidacloprid, found in Bayer Advanced Garden Tree & Shrub Insect Control or Bonide Tree & Shrub Insect Control, can be applied in late winter or spring before the populations begin to multiply. Use as a foliar spray or soil drench, following package directions. Malathion, a broad-spectrum insecticide, can also be used but know that it can kill many natural enemies. Be cautious when using pesticides; follow all package directions and wear protective clothing and goggles. Overuse of pesticides can contaminate urban surface water runoff and municipal wastewater.