Efficacy of Natural Compounds to Suppress Sprouting and Fusarium Dry Rot in Potatoes

Sprout and disease growth are ongoing concerns in stored potatoes.  Reducing the rate and extent of both sprouting and disease can increase profit margins and allow the industry to produce a quality potato year round at a reasonable cost.  Although there is a highly effective product,  available in North America for sprout control in stored potatoes (CIPC – chlorpropham), there are concerns that this product; a) leaves residues which are a potential concern for consumers and b) is not suitable for use on seed potatoes or even in the vicinity of seed potatoes.  This product is only available to licensed applications and is not suited for use by small scale or hobby growers. At present, there are no products registered for control of fungal diseases like Fusarium dry rot in stored potatoes.   This project evaluated the potential to use the volatile compounds produced by a range of plants to control sprouting and disease development in stored potato.  Potatoes (cv. Norland) were treated with the natural products in sealable 18L plastic containers.  The products tested were; purified S-(-)-carvone) and R- (-)-carvone, dill weed, ground cloves, clove oil, garlic powder, diallyl disulfide extracted from onion, ground peppermint or peppermint oil.  The liquid treatments were applied to filter paper disks attached to the lid of the plastic container, while the dried plant products were sprinkled over the potatoes. Each tuber was inoculated with Fusarium sambucinum (primary causal organism for dry rot in potato) just prior to treatment with the plant products.   The potatoes were exposed to the treatments for 14 days at room temperature.  After 14 days, the treatments were removed and the potatoes were held for another 14 days under the same conditions.  Sprout suppression and incidence of Fusarium dry rot were evaluated 14 and 28 days after the treatment.  A taste panel evaluated the impact of the various treatments on the flavor of the potatoes immediately after treatment and again after the 14 day holding period.  Diallyl disulphide and carvone completely suppressed sprouting during the 14 day treatment period and slowed sprouting during the 14 day holding period.  Garlic powder, peppermint oil and ground cloves also suppressed sprouting.  None of the treatments provided any degree of control of Fusarium dry rot.  Some of the treatments significantly altered the flavour of the potatoes.  The altered flavor was considered desirable by some taste panelists and undesirable by others.