In The Garden with Brownie
ARE you a lover of paw paws? If you are – and there’s a lot of you (us) – it’s just become that little bit harder to grow your own in the backyard, with the rapid spread of a new exotic pest taking hold across Southeast Queensland.
Called the Papaya mealybug, this fluffy white sap sucker was first detected in Darwin in 2023, and in late 2024, it showed up in Brisbane.
Not only does it affect papaya (or paw paw), but it can also have a devastating effect on frangipanis and hibiscus. But it can also infest the likes of avocado, capsicum, cherry, eggplant, grapefruit, guava, mango, peas, pomegranate, sweet potato, and tomato.
It looks very similar to the standard garden variety mealybug – so white, fluffy, oval-shaped, and about the size of a grain of rice. However, their difference is that they can breed much more rapidly than the common mealybug and end up covering whole fruits, leaves, and stems.
They cover the plant with a very sticky white wax, as well as producing copious amounts of honeydew on which sooty mould grows, reducing photosynthesis. In high infestations, the papaya mealybug causes deformation and stunting of new growth, yellowing and dropping of leaves, and early fruit drop. Ultimately, the entire host plant may die.
In Darwin, the Northern Territory government has been trialling the release of a predatory native ladybird that eats the mealybug. So far, the results have been promising, but the vast number of ladybirds that will need to be bred and released will pose a significant hurdle in gaining the upper hand over the pest.
In the meantime, authorities here are asking gardeners to keep an eye out for the Papaya mealybug and report any suspect individuals to Biosecurity Queensland by calling 132523 or through their online portal www.daf.qld.gov.au/contact/report-a-biosecurity-pest-or-disease.
But the poor old paw paw and frangipani are both already impacted by serious fungal diseases in our gardens.
Paw paw is well known to be affected by a common disease called anthracnose – a fungal infection causing black spotting on the leaves and fruit. Managing this fungal problem involves removing infected material early and disposing of it in your bin (not your compost). After this, a regular spray with a copper-based anti-fungal treatment or wettable sulfur is recommended.
If maturing fruits have early signs of spotting, you can pick them, submerge them in moderately hot water (about 50 degrees is OK) for 10 minutes. This heating will kill the fungal spores and stop the black marks from growing larger. Then they can be ripened on your kitchen bench.
Nearly all frangipani trees are now impacted by the yellow Frangipani rust (a fungal disease). Over the summer months, when the humidity increases, the leaves of frangipani trees show a tendency to be covered with little yellow and brown spots, which is how this fungal rust pest presents itself.
The infection reduces the vigour of the leaves, weakening the plant and damaging the stems. Again, the key to managing the disease is hygiene – collect infected leaves (including those that have fallen) and dispose of them in the rubbish bin.
You can also spray with a copper-based fungicide product, but it’s preferable that you start this before the rust shows itself as a preventative measure.
Some days it just feels like Mother Nature is not on our side when it comes to pests and diseases in the garden. But a little bit of vigilance, prevention, management, and control can make sure you’re not plagued to the point of distraction by these exotic pests.