Narcissus: Investigation into the benefits of using water disinfection options during HWT

Summary: Hot water treatment (HWT) is used to control pests and diseases, notably stem nemtaodes, bulb scale mites and fusarium. This has been the standard approach for at least 70 years. For most of that time, formalin was added to HWT tanks as a general biocide, however approval for formalin was withdrawn in 2008 which meant that an alternative was required. Work in BOF 61 identified FAM 30 as a viable alternative and this has since become standard practice in the UK. However, FAM 30 is expensive in comparison to formalin and the result has been that growers do not always use it at the required rate. This issue is exasperated since FAM 30 rapidly depletes in tanks under a high bioload. Alternatives have been considered in other studies. Chastagner and Riley (2002) concluded that chlorine dioxide was effective against spread of Fusarium and chlorine dioxide is currently used by American narcissus growers. However, AHDB Horticulture projects BOF 61 and 61a examined a number of alternatives, including chlorine dioxide and did not recommend its use. The use of chlorine dioxide was reviewed in BOF 70 which recommended that further investigations were required before it could be recommended to growers.  Other biocides have been examined, e.g. peroxyacetic acid (Hanks and Linfield, 1999), hydrogen peroxide and UV (Stewart-Wade, 2011) but require further commercial scale testing before they can be recommended. UV has much to recommend it since it is relatively cheap and non-corrosive but its efficacy is very dependant of water clarity which is a problem with high bioload HWT.

Aims and Objective: 

The aim is to identify commercially viable alternatives to current practice, which is FAM 30 (based on iodine).