Pesky Mites…

close up of the pin head sized RLEM

typical RLEM leaf damage

 

Have you noticed some of your young seedlings under attack lately? In the Garden we have a bit of a red legged earthmite problem. They seem to prefer the beetroot seedlings, but have been having a chomp at a few others.

It’s probably to be expected that in the early days of the garden we will run into a few problems because we haven’t yet established conditions for good bugs and healthy plants. It takes time to develop a dynamic living system from a bare paddock!

The red legged earth mite is tiny – about the size of a pin head with a black body and 8 red legs – but it’s scientific name is Halotydeus destructor, which tells you a lot! It was “accidently” released into Australia from South Africa in the early 1900s and is a major pest in broadacre crops and pastures as well as veges. Conventional growers use broad spectrum pesticides which kill the good bugs as well as the bad. The RLEM is starting to develop a resistance to sprays, so biological control agents are being investigated (as well as stronger chemicals!)

The mites normally appear in autumn, with the onset of wet weather and cool temperatures. Drought has meant that we haven’t had a problem for a few years because we haven’t had a decent autumn break. The damage they cause can be confused with frost damage – the leaves get ‘silvering’ or whitish patches because the mites suck out plant sap. They spend most of their time on the soil rather than plants (or hiding under capeweed!).

The best control method is to encourage predatory insects to eat the mites and their eggs. There are around 19 known predators, including other mites, small beetles, spiders and ants. I have found  that heavy frosts can knock the population back as well. You can spray a biological alternative – a general oil based spray such as eco-oil which suffocates the mites, or a potassium soap based spray with garlic and pyrethrum may help.

The other option is to build up the plant’s ability to withstand attack by applying a seaweed spray or foliar fertilser. Some biodynamic growers have found using BD501 (horn silica) has been effective. Reducing harbours for the mites can also help – capeweed and grasses, for example.

This time of year, plants are at a disadvantage because of the cool conditions. Once the weather warms, they will start to have the upper hand over the bugs.

We will be sowing a “good bug mix” in spring. This is a mix of re-seeding annual and perennial flowers that will attract beneficial insects (ladybeetles, hover flies, lace wings, wasps) to control pests such as the RLEM.

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