About three or four months ago I got really busy at work and didn’t have time to look after my garden properly for a few weeks. As I was watering the garden one evening, I realised that some red and black bugs were perched on my Kiwi plant (Actinidia deliciosa ‘Hayward’). The more I looked, the more I realised the bugs were everywhere. Swaying on the silverbeet, sunbaking on the fig leaves, taking a siesta on the pumpkins. I had a vague recollection that they were called shield bugs or something similar, but through a little bit of googling I realised that they were Harlequin Bugs (Dindymus versicolor).
I didn’t realise that they were sucking the sap of the plants and vegetables until far too late in the game, by which time they had destroyed a sizeable amount of my tomato crop and nearly killed my Kiwi plant. After researching the causes of the outbreak, I realised that I had created a brilliant playground for them, as they danced merrily amongst the stack of wood and iron in one corner of the garden and the bountiful weeds (including Mallow (Malva sp.) and grasses) along the fences and edges of the vegie beds, and drank to their hearts content from all of the fruit and vegetables I’d grown especially for them. A bit aghast, I rapidly cleaned up all the weeds in the backyard and moved the pile of wood and iron into the shed. I made up a solution of detergent and water in a spray bottle (according to Peter Cundall’s recommendation) and went on the attack. I felt pretty terrible killing the bugs since I had been responsible for their proliferation, and also knowing they are native to south-eastern Australia. It also gave me the heebie-jeebies playing the part of the looming destructive giant coming after them as they tried valiantly to scurry underneath a leaf or branch out of my view. After making myself watch and analyse the death of a few of the bugs as they dragged themselves through the detergent and then turned on their backs with their little legs clasped to their bodies, the spray seemed to kill them quite quickly by blocking their breathing tubes (within a few seconds if I sprayed them so they were completely covered in detergent) so was a fairly humane solution. I used an environmental dishwashing detergent to try to minimise harm to the soil. I kept up the targeted spraying every day for two or three weeks, particularly in the morning when the bugs were sunning themselves on top of the leaves. The numbers of bugs got fewer and fewer, but I was still worried about my kiwi plant. For some reason the bugs loved this plant and although they disappeared from everywhere else in the garden they kept appearing on the Kiwi. I would spray all the bugs on the plant each day only to find three or four on it again the next day. The plant had quickly gone from a thriving vine to just a stem with a few browned leaves attached. I had intended to transplant the Kiwi as soon as the summer heat passed and the autumn break came, so did this a few weeks ago. Even after I transplanted it, I kept finding Harlequin Bugs on the plant; somehow the bugs sniffed out their favourite food source even though it was in a new location. Strangely, I only ever found bugs on the female Kiwi plant. They were never really on the male Kiwi plant at all. My female Kiwi plant now looks terrible. I am hoping that by next spring the plant will have somehow survived, got over the shock of the transplant and the bug attack, and will have sufficient root stock to regrow. The Harlequin bugs have hibernated for the winter, but now I am aware of the problem I will be straight on to them when they emerge next spring before they have a chance to get out of control again, and will be much more diligent at keeping the weeds in check.
Gippsland gardener’s blog has some great info as well.
So, the key lessons I’ve learnt are:
- To avoid an outbreak of Harlequin Bugs, keep the garden very tidy. Remove weeds and piles of wood/rubbish.
- Harlequin Bugs spend winter underneath piles of wood or other shelter, and spend the spring/summer sucking the sap of plants. They may look innocuous, but they can cause a lot of damage to plants and fruit and vegetable crops.
- An effective organic control method is to spray individual bugs with a strong mix of dishwasher detergent and water. Keep spraying every day until the population has disappeared.