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18th July 2017

New research untangling the nematode knot

New research untangling the nematode knot

Sweet potato growers have shown their eagerness for new insights into controlling the costly problem of root-knot nematodes (RKN) following a treatment assessment trial by CQUniversity Australia and the Department of Agriculture and Fisheries.

More than 50 Bundaberg-region growers, as well as state and national industry representatives, recently turned out to inspect the progress of the research trial which is critically reviewing the effectiveness of the control methods still available to growers.

This follows the removal from market in recent years of a number of chemical nematicides due to concerns about toxicity impacting on human and environmental health.

It is estimated that root-knot nematodes cause more than $100 million per annum losses to Australian agriculture, with sweet potato growers among the hardest hit.

“In the Bundaberg region, where 80% of Australia’s sweet potato supply is grown intensively as a high value crop, yield losses as a result of RKN infestation in untreated fields may be as high as 57%,” CQUniversity researcher Dr. Yujuan (Jady) Li said.

“The removal of nematicide products and the tightening restrictions of nematicide use in agriculture pose a significant threat to the future of the Australian sweet potato industry, with growers now urgently requiring access to new effective and reliable treatment products.”

The research team was led by CQUniversity’s Dr. Yujuan (Jady) Li, and was comprised of CQUniversity research student Upamali Peiris and technician Karli Groves, and Queensland Department of Agriculture and Fisheries technical officer Rachael Langenbaker, with support provided by the Australian Sweetpotato Growers with the trial conducted at the Zunker family’s Windhum Farms at Bundaberg.

The products trialled included three chemicals, Tervigo, Vydate and Nimitz; and two organic products, Nemguard and Compost-Aid applied with Soil-Set.

The crop was harvested and assessed for nematode damage at 160 days after planting of the Orleans variety of sweet potato.

“Overall, the three chemical products provided the most effective and reliable control of the pest, however their effectiveness varied based on soil nematode numbers, with greater protection provided in areas of low nematode pressure,” Dr. Li said.

“Of the three chemicals, Nimitz provided the highest and most consistent control in this trial, followed by Vydate and Tervigo respectively.

“The two organic products performed similarly well under low nematode pressure, however the effectiveness of both was below average in areas with higher nematode numbers.

“Compared to the chemical products, the effectiveness of both organic products was lower regardless of nematode numbers.”

The results of the 6-month trial present a complex picture of the variability faced by producers when determining the most suitable control product for their crop.

“In this first step to providing growers with a wider range of options for protecting their crop from the damage of RKN, the results indicate that effective control will be reliant on many factors, most notably soil nematode numbers,” Dr. Li said.

“The results of this trial will help to guide growers in their search for nematode protection, however more research will be required to provide understanding into the causes of such variability in product performances.”

The next stage of the research will investigate the causes of this variability, with further products and applications rates to be tested before best practice recommendations can be made to growers.