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Nebijin fungicide as part of an Integrated Disease
Management Strategy of Potato Powdery Scab
Darren Faire, Northern Regional Manager, Etec Crop
Solutions
Infection of potato tubers by powdery scab (Spongospora subterranean) results in the development of surface lesions, seriously reducing tuber quality. On processing potatoes these lesions are unwanted because they require extra skin removal operations. Potatoes severely infected with powdery scab (PS) will also shrink and lose weight while in storage. Not only are the consequences of infection serious for fresh and process potatoes but seed potatoes with PS become commercially unacceptable for establishment of any new crops because the disease can be transmitted on infected and infested seed potatoes. In addition to the harmful effects on potato quality recent research has indicated that PS can reduce host plant growth. When compared with uninfected plants, those with PS infected roots used less water, had disrupted nutrient uptake and produced less dry matter, with smaller shoots and fewer leaves (Falloon, 2009).
PS of potatoes was first positively identified in New Zealand in 1909. Originally considered of minor importance PS has become a significant disease of potatoes not only in many of the world’s cool/temperate regions but also in hot and dry climates where irrigation is applied. Those countries reporting an increased incidence and spread of PS include; Brazil, Argentina, USA, China, Israel, Portugal, Albania, Germany and Switzerland. Those countries were PS has recently been reported as having established itself include; Alaska, Pakistan, Costa Rica, South Korea and Malta. It is highly likely that in the past PS has gone unrecognized and underestimated. It is widely accepted that PS thrives in cool, wet and heavy soils but its growing incidence is being reported in regions that are predominantly hot and dry, so what’s believed to be driving the increase in PS distribution and severity? Factors such as intensification of potato production with short rotation cycles, increasing use of susceptible cultivars, more frequent use of irrigation to maximize crop productivity and the discontinuation of broad spectrum chemical seed treatments are all contributing to varying degrees.
Like many soil borne pathogens PS is difficult to control. The disease is capable of surviving in the soil for long periods of time, with one severe outbreak in New Zealand being recorded in a field that had not grown a potato crop in 12 years. PS survives in the soil as a resting spore and also through infection cycles on alternative hosts (Falloon, 2008). At present the best strategy to employ to manage PS is one that incorporates a suite of management techniques such as careful cultivar selection, irrigation scheduling and planting dates, crop rotation and field choice. Long rotations are desirable to reduce the likelihood of PS spore survival and there is some limited research to suggest that growing potatoes in land that has grown vegetable brassica’s may result in less PS than if the rotation crop had been grass/clover or cereals (Falloon, 2008). Free draining soils are desirable as they are less likely to encourage PS development than soils with high water retention.
As part of an overall management programme growers should incorporate NEBIJIN® fungicide (flusulfamide). NEBIJIN, applied as a post plant in furrow treatment has proven itself effective for reducing PS; and New Zealand potato growers are fortunate to be amongst one, of a small number of countries where NEBIJIN is registered and available for this use. The development of Amistar® in furrow technology has contributed considerably to the ease of which growers can apply NEBIJIN (along with Amistar to provide control of a wider disease spectrum). Best practice is to apply NEBIJIN at 4-8ml / 100 mtr of bed plus Du-Wett® superspreader at 100ml per 100 L water to assist with soil coverage. Because NEBIJIN does not provide activity against common scab or Rhizoctonia always apply in conjunction with Amistar.
Please contact your Pukekohe Growers Supplies representative for further information on NEBIJIN or Darren Faire, Etec Crop Solutions 021 392 740 or dfaire@etec.co.nz
Lincoln University Powdery Scab Trial Results, 1996.
All treatments applied in furrow, soil artificially infected with powdery scab. Potato variety-Agria
Nebijin is a registered Trademark of Mitsui Chemicals Inc.
®Amistar is a trademark of a Syngenta Group Company.
®Du-Wett is a Trademark of Elliott Chemicals Limited.
Nebijin is registered pursuant to the ACVM Act, 1997 No. P5603
Falloon, R. (2008). Control of Powdery Scab of Potato: Towards Integrated Disease Management. American Journal of Potato Research. 85: 253-260.
Falloon, R.E. and Merz, U. (2009). Review: Powdery Scab of Potato – Increased Knowledge of Pathogen Biology and Disease Epidemiology for Effective Disease Management. Potato Research, 52: 17-37.
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