New Zealand

Powdery scab situation

Powdery scab of potato is a serious disease in New Zealand, of importance in seed, fresh vegetable and processing potato production. The disease has become increasingly important in the past for several possible reasons: powdery scab occurs more widely than previously; mercury seed dips were withdrawn from use; Irrigation which favours tuber infection, is increasingly used; increased intensity of potato production has reduced the length of crop rotations; use of cultivars susceptible to powdery scab has increased; washing of table potatoes before sale, making tuber lesions more noticeable, is more common; and there has possibly been confusion in diagnosis between powdery scab and common scab.
Research on the disease was first concentrated on control and detection. All available potato cultivars were been exposed to heavily infested soil, and cultivars with powdery scab reactions ranging form highly susceptible to very resistant have been identified. Each cultivar has been tested in field conditions over at least two growing seasons. Growers can use results of these trials to make informed cultivar choices in relation to the disease. The cultivar Gladiator, which was recently released from the Crop&Food Research potato breeding programme (leader Russel Genet), is very resistant to the disease.

Research on chemical control of powdery scab has identified a number of chemicals (including formaldehyde, sulfur, mancozeb, dichlorophen-Na, cyprodinil, fluazinam, flusulfamide) which can reduce infection in progeny tubers after application to infected seed tubers or as in-furrow preplanting treatments of infested field soils. In cases of severe infestation in soil, control of the disease with chemicals dramatically increased yield of marketable tubers and occasionally increased total yield.

DNA technology have been investigated for the development of sensitive methods of detection of Spongospora subterranea, and to differentiate between common and powdery scab pathogens.
Recently occurrence potato mop top virus in some places has put the disease in the spotlight.
Research in New Zealand is being funded from government research funds, by the New Zealand Vegetable and Potato Growers' Federation, by several chemical companies and by seed potato merchants.

Research today

Plant and Food Research, Lincoln, works on the following projects:
- they provide advisory services to Potato industry (disease diagnosis, especially the scab test)
- Screening of Plant and Food Research early potato breeding lines against Spongospora subterranea
- Survey of Potato cyst nematodes
For further information please contact Farhat Shah (e-mail address below)


A new initiative by Iain Kirkwood of Potatoes New Zealand - International Potato Research Partnership and collaborative framework - wants to build collaboration and teamwork between researchers internationally, and hence improve efficiency in research resource use.



Contact addresses

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Last update: January, 2025