Do your Syzygiums have zits ?
One of the most common pests affecting Syzygium species is the Pimple Psyllid (Trioza Eugeniae).
What are Psyllids?
The adults are small sap sucking insects about 2-4mm long (see picture). After mating, the female psyllid inserts yellow oval shaped egg into the edge of the new leaves. Small nymphs hatch from the eggs and move to the newly expanding leaves, where they feed and develop in pimple or cup shaped pit or gall which is formed by the plant’s response to the psyllids feeding.
Excessive pit formation creates severely distorted or blistered leaves, leaving shoots to appear stunted. Nymphs produce excrement in the form of tiny white pellets, some of which collects on foliage and becomes blackened from sooty mold growth. When mature, the nymphs transform into winged adults.
What plants do Psyllids like?
Pimple Psyllids affect a wide range of Syzygium and Waterhousea species as they prefer plants with a softer leaf surface that they can penetrate. This is why species like the Acmena are not affected. Not all Syzygiums are susceptible such as Syzygium Luehmannii which is not affected and a lot of the cultivars available are resistant to them.
Health also has plays a major part as plants that are stressed and in poor condition are far more susceptible to attack. When I was building a house about 5 years ago I planted a 25lt Lilly Pilly in the backyard that quickly became unhealthy due to the builders activity and neglect. I don’t think there was one leaf that was not pimpled as I also sprayed it once and nursed it back to health. The plant is now 6 metres tall and I have not seen a pimple on it since.
Syzygium Paniculatum is probably the worst affected species.
I still recommend planting Syzygium species as they are gorgeous plants and most of the time are hardly affected as long as you keep your plants healthy.
Some areas are more prone to attack so you may need to select your Syzygium species a little more carefully.
Let’s go to war on Leaf Psyllid!
So, how do we deal with the pesky little pests? When you see the damage it’s generally too late and the damage can’t be reversed. If it’s a mild attack it’s not really going to affect the health of the plant, just spray with white oil and a systemic insecticide spray such as Confidoror – this will kill the nymphs (Systemic sprays are chemicals that will travel through the plant and remain in the plant tissue for a period of time). If it’s a severe attack it’s a good idea to prune the damage out and spray with white oil and Confidor/ Rogor and feed the plant as well as treat with Seasol to improve the health.
They prefer mild temperatures so are less prevalent in the heat of summer and cold winters.
By Warren Downes
Images: Whitney Cranshaw, Colorado State University, Bugwood.org