Lifeless azaleas and ghostly viburnums, forlorn sentinels of happier times. Thrips have now
abandoned their favourite their food for anything with sap. Never have I seen thrips on Irish
strawberry trees, May bushes, Abelias, Crepe Myrtles or Capital pear trees.
The mild wet winter of 2021 provided ideal conditions for a pest burden in spring.
Continuing mild, this summer has produced an explosion of thrips, aphids and scale. Heavy
frosts are needed this winter to reduce the population. The natural counterbalance for these
pesky bugs are Ladybird beetles and Lacewings.
Unfortunately, most Canberra gardens don’t provide habitat for predator insects.
Consequently, they’re not in sufficient numbers to counterbalance. Even worse, many
gardeners mistake ladybird nymphs for mealy bugs and spray them.
What are thrips? Can we treat them? Can we manage them? Yes!
Adult thrips are 1-2 mm long, live about two months, reaching maturity 14 days after
hatching. Females lay new eggs every few days. Potentially 40 generations over the warmer
months. Different thrips feed on fruits, flowers, shoots and leaves. They destroy crops and
kill plants. Thrips rasp at soft plant tissues, feeding on the sap that bleeds. Smutty poops on
bronzed, desiccated leaves are a tell-tale sign on this viburnum hedge.
Adequate light and air are fundamental to garden health. Thrips thrive in humid, close
conditions. Over-planted gardens that cannot breathe are more susceptible. Hedges with
accumulated leaf litter provide shelter for pests to winter over. In the following pictures an
abelia hedge is growing around a crepe myrtle. Both infested with thrips. We reduced the
overgrown abelia hedge to sticks, doing it much good and removing the food source. Note
how much debris we found inside, ideal conditions for pests, mould and fungi, bad for plant
There are a number of treatments available from soapy water to insecticides. However, Bio solutions give lasting results, especially when habitat plants are part of the garden. Neem oil combined with diatomaceous earth (DE) is effective, this gets the good bugs too.
The best way to prevent thrips (and aphids) from making your garden their smorgasbord is
attract their natural predators. Ladybeetles, lacewings, parasitic wasps etc are very effective
pest managers. Plant diversity is key, especially flowering herbs, Queen Anne’s lace, salvias,
daisies, Elysium, brassica flowers for food. Native native grasses such as spear grass, foxtailed grass, plume grass, kangaroo grass, poas and local natives for habitat. In addition to bees, just two years after planting grasses in my own garden, now have crickets singing,
butterflies, ladybirds everywhere, a paper wasp nest high in a tree, hover flies and praying
mantis, NO aphid or thrips infestation.
Use natural soil improvers such as Seamungus, kelp, volcanic rock minerals, non-commercial
manure, compost, potassium and magnesium supplements, poultry manure for gross feeders
in small quantities. And of course, mulch. Artificial fertilisers force plants to convert nitrogen
into plant sugars which attracts the chewers and suckers.
- Check out the good and bad bugs interactive poster. http://www.goodbugs.org.au/poster.html
- Bio controls suitable for gardens. http://www.goodbugs.org.au/garden.html
- Bugs for Bugs, supplier. http://www.goodbugs.org.au/garden.html
- QLD Gov, beneficial parasites, predators & pathogens.
Recognizing Ladybird & Lacewing larvae
Here are some pictures to help you distinguish between mealy bugs and ladybirds.
Mealy bugs tend to cluster and smut.
Ladybird nymphs are mobile and quite shaggy or spiky, more distinctive generally. Ladybirds and nymphs eat hundreds of thrips, aphids and scale a day.
Lacewings are beneficial insects for your garden
Images are a mix of original photos and stock images, subject to Copyright ©