sneaky stinkers
Be alert for destructive citrus bugs that change colour as they mature, writes MARTYN ROBINSON
This story starts in late winter or early spring, when you might notice clusters of small, lime-green bugs with a black spot on their backs infesting your citrus. A few weeks later, the green bugs disappear, and small groups of bright orange bugs appear all over the tree. Some leaves are a bit withered and the fruit, if any, doesn’t look as good as you’d hoped. After another few weeks, most of the orange-coloured bugs have gone, to be replaced by largish brown bugs and the tree looks just as bad, if not worse. These seemingly different bugs are all stages in the life cycle of one species − the bronze orange bug (Musgraveia sulciventris). Also known as stink bugs, they can shoot a stream of unpleasant-smelling fluid into your face and eyes, so always wear eye protection when dealing with them.
So why the colour change? Well, the bugs develop their protective fluid from the sap of the plants they feed on and, when they hatch, they don’t have a good defensive arsenal, so they start life camouflaged to avoid detection. As they grow, their ability to squirt the unpleasant fluid also develops, and they advertise this with the bright orange colour that says to would-be predators (or gardeners): don’t touch! While there are no warning colours in the brown, adult stage, they are usually in among a group of brightly coloured younger siblings and have an added defence − they now have wings, so they can fly.
If you can rid the tree of most of the green bugs, you have a head start. As they turn orange, they are better able to protect themselves but are also easier to see. Wearing glasses, brush them off the tree and crush them. Adults can be dealt with the same way, but many will fly off to return later or invade your neighbour’s trees. Last summer’s severe heat killed them all in our area but, inevitably, an adult will fly in from elsewhere and start the cycle again.
Martyn gardens mainly on Sydney’s Northern Beaches