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Redlegged Resistance: Yorke and North Crops Damaged By Earth Mites


Farmers have been dealt another blow recently, with crops across South Australia infested with a number of redlegged earth mites (RLEM).

Scientifically known as the Halotydeus destructor, these major pests do exactly that; destroy crops by lacerating plant tissue and sucking up the nutrients.

This results in the decelerating of photosynthesis and cell damage, causing a ‘silvering’ or ‘whitening’ appearance which can often be mistaken for frost.

The RLEM feed on ryegrass and cereal crops, and have a penchant for oats. When not wreaking havoc on crops, the mites also feed on a range of weeds including Paterson’s curse, ox-tongue and skeleton weed.

Pesticides have largely been used to help control the mites, however crop producers across the Yorke and North have recorded a rise in resistance to the chemicals.

There are many theories for the increase in resistance; insufficient chemical rotation across the industry, a lack of pesticide education, and disharmony between market and industry objectives.

In light of this, industry leaders have been looking at non-chemical strategies to assist in pest control and long-term sustainability.

Biological control is an area which is currently being investigated. The RLEM have at least 19 recorded predators and one pathogen which have been known to attack them in eastern Australia. These predators include ants, spiders, beetles and other mites and they play an important role in reducing populations.

However, introducing predators can have a slow dispersal and establishment rate. There are also concerns about whether introducing non-native predators will benefit the area overall, or cause more issues.

A more accessible strategy is cultural control and involves participation by all agribusinesses.

The earth mites spend most of their time in soil and cannot travel long distances. Despite this, they travel through soil adhering to livestock and farm machinery. Their movement during summer also occurs through wind gushes, sending eggs across great distances.

Hosing down machinery, rotating crops with non-host crops and weed control can all help reduce mite reproduction and survival rates in the region.

The biggest misconception around these mites is that they only affect crop producers; they have also been found to be directly responsible for reducing pasture palatability to livestock.

The most important thing for farmers during this season is to keep vigilant and stay informed about RLEM control strategies. For more information, see the Resistance Management Strategy For The Redlegged Earth Mite, released by the Grains Research & Development Corporation.

Written by Erin Connellan
Photo source Tom Fisk, Pexels

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