AgXtra undertaking surveillance of of recovery in bushfire affected areas

11 August 2020

Bushfires left a trail of destruction across the state during late spring and summer, with tens of thousands of hectares burnt, including many cropping properties.

So what is the lasting impact on the fire grounds in terms of the numbers of crop pests and diseases in the following season and how quickly can beneficial insects re-establish themselves?

The GRDC has funded a 12-month project to answer this, comparing the population dynamics in burnt and unaffected areas at seven sites on Kangaroo Island and Yorke Peninsula.

RELATED:Lessons from past help with YP fire recovery

AgXtra senior research officer Julianne Farrell, who is leading the project, says they expect to develop some effective post-fire management strategies to assist growers in the management of scorched paddocks.

“Most of the growers we are dealing with have never experienced such widespread and hot fires,” she said.

“Data gained from a project that tracks the recolonisation of burned areas by invertebrate and vertebrate crop pests and soil organisms as well as beneficial insects will be invaluable for future farm management plans.”

Four sites near Edithburgh that were devastated by fire on November 19 and 20, and three sites in the middle of KI burnt in January will be monitored by AgXtra.

At the start of the project, soil samples were taken at the seven sites, which are being analysed by SARDI for soil-borne pests and diseases.

This will be repeated again after harvest.

RELATED: KI fire frustration lingers, calls to change native vegetation laws

AgXtra has established pitfall and sticky traps in burnt and unaffected cereal and pulse stubbles, and unburnt green bridge areas nearby, which are being collected monthly and the catch counted and identified.

These traplines have been established both parallel and perpendicular to the fire scar.

As expected, there have been less beneficial species counted in burnt areas due to the absence of vegetation and prey species.

But Mrs Farrell says in the unaffected areas, she has been surprised by how diverse the population was of parasitoid wasps, honey bees, hover flies, spiders, moths, carabid and ladybird beetles.

Mrs Farrell says they have already observed some changes in diversity and species present in the first few months.

“Over summer, there were no snails, but prior to sowing we had quite a few snails in the pitfall traps and in the months prior to sowing, the big black Egyptian beetles, which were active in both burnt and unaffected areas, have disappeared,” she said.

She says the main insects on the sticky traps so far have been flies, but as the crops develop, she expects to see more aphids and other flying pests.

Other invertebrate pests under investigation include black Portuguese millipedes and European earwigs.

The YP sites are also being monitored for mice, while on KI, live-capture traps are being used to check for the presence of endangered KI dunnarts – a mouse-sized native marsupial which can be found near crops in uncleared bush areas on the west of the Island.

Trap lines in a burnt wheat stubble.
Trap lines in a burnt wheat stubble.

GRDC research to fill knowledge gap
GRDC southern crop protection manager Ruth Peek is hopeful the project can deliver some positives out of the devastating bushfire season.

“We are keen to assess the impact of bushfires on crop pests and diseases to discover if they re-establish in the landscape post-fire and if they do, just how quickly they return and to what extent,” she said.

There has been some surveillance on fire grounds after SA bushfires in the past, but Mrs Peek says there is a gap in the information available.

“After the Pinery fire, the GRDC supported ‘Farming after Fires’ workshops for growers in the area and from that, soils and soil conservation was a focus, but there was a real gap in pest and disease knowledge,” she said.

“Fire is being used by growers to control disease, especially windrow burning to suppress diseases and pests, so could the recent fires on the Yorke Peninsula have a significant impact in the problem of snails?”

Mrs Peek is hopeful the GRDC will be able to provide growers with management recommendations after the research results are in.

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