Red-shouldered beetles

OLYMPUS DIGITAL CAMERA The warm, dry weather has enouraged this small native beetle (Monolepta australis) to move into gardens. As their common name suggests, these yellow beetles have a bright red stripe across their shoulders and a red spot on their wings. They arrive in a large swarm and choose one or two stressed plants to feed on. We have noticed that they frequently choose plants with white flowers. Although these beetles are only 6mm long, their sheer numbers enable them to skeletonise small to medium shrubs in a very short time before moving on to another property. Monoleptas are difficult to control because sprays that will kill the beetles will also kill beneficial insects visiting plants at the same time.
If the plant being attacked is not too large, you can get rid of these beetles by using a stick to knock them into a container of soapy water. Because of their fondness for the colour white, many beetles will drown themselves in a white container full of water left near the target shrub. (Don’t add soap to this water or it will kill bees that stop by for a drink.) The only way to protect your garden from attack by these beetles is to keep shrubs watered during dry spells, and keep the garden surface mulched to prevent moisture loss through evaporation.

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9 Responses to Red-shouldered beetles

  1. Many thanks for the information mentioned above. I have a beautiful passion fruit vine that was attacked one night last week after rain. I have never witnessed such devastation.
    I shall put out white containers filled with water and see what happens; as a Naturopath I do not use chemical sprays.

  2. Anthea Lorking says:

    We live in the Mid North Coast and I have had these horrible little monster strip our rather large 35 foot Peppercorn Tree over night, I know it will come back as this is the third year we have had them come for a visit. After their feast on the Pepper tree they have now completely striped the five Crepe Myrtles and they did look so lovely, also have removed all the red flowers off the Chinese Pompom tree…….What a mess the garden looks at the moment…..We find that they seem to come in when we have extreme heat then the on coming of a severe storm, which it is about to happen this afternoon or evening…..Hope they will all drown nasty little pests!!!!!
    I agree. Aussie gardens would be much happier without these voracious little beetles. – Lyn

  3. Jen Gunn says:

    These beetles are attacking a little tree in my garden for the third time. I’m wondering if they are back because they laid eggs somewhere, or if they just swarm. It has to be the former. Rang a local gardening guru on a radio programme and got no help. Out to try the white plastic container! Thanks!
    Hi Jen, these little beetles attack particular stressed plants. Whether they are attracted by particular pheromones given off by the plants, I don’t know. They used to always attack a white rose bush the previous owners had planted on shallow gravelly soil. Since we replaced it with lavender, they haven’t been back. You haven’t said what type of tree it is. I’d look up care and conditions required for that tree and see if you can relieve its stress. – Lyn

  4. Anne-Marie Ladegaard says:

    We live on the NSW Mid North Coast and currently have swarms of these beetles in our garden, much to my dismay! None of our trees and shrubs are particularly stressed, but they have attacked all the bottlebrush flowers, lili pili flowers and new growth, the pink crepe myrtle is badly attacked and they have also started on tomatoes and the huge Lavender Star Flower vine (Grewia). They are everywhere and very little one can do, sadly, without affecting the many good bugs and frogs in the garden! They first came 3 years ago and each year there are more and more of them, despite prevention methods! I will try the white container method just to see what happens!
    Fortunately, Anne-Marie, we have not had to deal with these pests in the numbers that you are enduring. The Queensland DPI states: “Of the summer legumes, soybeans, navy beans and mungbeans are particularly attractive hosts. Other crops include cotton, sugarcane and pasture grasses. Larvae feed underground on the roots of sugarcane and pasture grasses.” Are there host plants for larvae growing nearby? I hope the white containers work for you. Remember to remove the dead bodies regularly. Let me know how you get on. – Lyn

  5. Michael Fowler says:

    very interesting comments about the little bugs
    we also live on the mid north coast and this is the fourth year that they have destroyed foilage on some of my plants and trees
    they are currently devouring my large peppercorn tree but seem to be spreading to other plants such as my geishas I am trying to control them by spraying with fly spray which is quite effective.
    there are thousands of them so control is difficult As i said. these bugs have previously consumed large amounts of foilage in my garden but usually around christmas time While the little blighters did visit at christmas this year this is the first time that they have appeared at this time of the year. anyway. so far I have managed to save my trees from total destruction but it has been a lot of hard work

    The extreme weather events that are becoming more common place stress on plants and they can’t produce their normal pest-deterrent pheromones. Sadly, I think we will have to expect more pest attacks as the climate changes. – Lyn

  6. Tristan Mules says:

    Thhey hammer white cedars, completely strip them.

  7. Susan Stewart says:

    Most healthy plants recover quite well. It is a concern that gardeners may be using chemicals that will kill beneficial insects – unfortunately resulting in much more serious problems long-term. Swarming numbers like this suggest a system out of balance, perhaps amplified by changing climatic patterns. The eggs are laid in damp soil, so one strategy could be to spray the soil around plants with organic eco-oil.

    Thanks for your suggestion, Susan.

  8. Angela says:

    I live on the Atherton Tablelands. These bugs don’t seem to pick a particular season to attack now as I have had a swarm for a week currently. They attack my orange and mandarin trees as well as others. It is upsetting to the point of heartbreaking. The trees are not stressed prior to the attack but of course being full of white buds the bugs go crazy for them. My peaches don’t stand a chance either. 2 trees of fruit gone to them for yet another year. I was seriously thinking about chopping the peaches out altogether 6 months ago but decided to give it just 1 more year! My thoughts now are to use some cheap cans of insect spray in just the mandarins (they are my most important at this stage) as I think that I can be more accurate with that than say pyrethrin. I have never sprayed them before but this year they have hit a nerve and I have had enough! They white buckets have not worked for me ever. Of the 10 bugs that drown about 1000 (of course who knows how many are there) will be above happily destroying everything! My property is surrounded by hundreds of acres of cattle pasture so trying to target the eggs is a no go. A system out of balance for sure.

    Hi Angela, I don’t know what to advise you with those beetles in plague proportions as they usually only target particular plants that are stressed. You say your trees are not stressed, but have you checked your soil pH. A pH out of the healthy range prevents plants absorbing nutrients and trace elements that allow them to produce their own pest repellents. Also, you could give your trees seaweed extract tea at weak black tea strength as a foliage spray. This contains a range of essential trace elements and a good supply of potassium that strengthens cell walls. If you must resort to spraying, check the Australian Pesticides & Veterinary Medicines Authority chemical database and permit database for chemicals registered or approved under permit to treat this pest on the target crop in your State/location. Always read the label. Always observe withholding periods. – Lyn

  9. Ian Stanton says:

    Hi all; we live on the mid north coast NSW and have had similar experiences;
    I found that common fly spray used at night does a very good job of killing these beetles especially when in plague proportions

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