New hygiene protocols will reduce disease and
save on control costs!
| A recent review of current knowledge of hygiene procedures for the control of plant pathogens showed that chemical fumigation and heat treatments are still the most reliable methods for the control of all plant pathogens. Chemical disinfectants only appear to be effective on a far narrower range of pathogens and more work on their use is required. New Best Practice protocols based on the review and featuring the use of double treatments are listed. |
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Why bother with nursery hygiene? I’ve never had a problem before!
This is an attitude which many people learn to regret the hard way, it’s amazing just how quickly disease can spread in a nursery ! There are many who have lost the majority of their plants due to the spread of diseases such as Phytophthora root rot, Fusarium rot, Sclerotium rot, black rot and many other diseases.
Many diseases, once established in a nursery are a source of on-going problems as they are often difficult to eradicate because they reside in soil, on nursery surfaces, equipment, in water or on alternate hosts from which they can spread and re-infect new nursery plants. An example of this is where one gram of dust taken from a glasshouse used for carnation production had 1 200 spores of Fusarium oxysporum f.sp. dianthi, the cause of Fusarium wilt. Similarly, a researcher recently recovered ten Phytophthora cinnamomi propagules from five drops of waste water collected from a single pot containing an infected azalea plant. Nursery hygiene is truly an ounce of prevention which could save a pound of cure.
Stop diseases from spreading
Always keep in mind how pathogens spread! Transfer of plant pathogens from diseased to healthy plants is often assisted by nursery practices. Pathogens may be brought into a nursery on infected plants or contaminated materials and spread from them by air, water, soil, growing media, plant material, tools or clothing.
Spread of disease within the nursery is helped by many factors, such as close spacing of plants, overhead irrigation, grafting and pruning operations. Any recycled water requires disinfestation but even with disinfected water, overhead irrigation may spread, via water splash, bacteria or fungal spores which are produced on infected plants. Similarly, water will carry root pathogens from infected plants to healthy plants in ebb and flow or capillary mat systems. A residual disinfectant in the water will lessen the chance of disease spread.
A major method of limiting spread of disease is to disinfect nursery surfaces that come into contact with potentially diseased plants. Such surfaces include cutting tools, work benches, floors, walls, plant containers, nursery equipment such as trolleys, trays, and vehicles. In general, it has found that clean surfaces are much more effectively disinfected than surfaces with adhering dirt, plant material or potting mix. Therefore it is recommended to thoroughly clean surfaces before the application of disinfestation treatments.
New research
The recent literature shows that there is insufficient knowledge on the efficacy of disinfectants commonly used in nurseries to provide reliable guidelines for the adequate control of plant pathogens contaminating propagating and cutting tools, nursery benches, paths and other surfaces. Further work on surface disinfestation, funded by HRDC, is being undertaken by the Institute for Horticultural Development and NSW Agriculture.
Best Current Disinfestation Protocols
(Based on the best available information in July 1997. For specific disease problems contact your plant pathology service.)
Knives and other cutting instruments
Step 1 Scrub clean using plastic ‘scratchies’ and 2000ppm quat (quaternary ammonium compounds) solution, (make sure no dried sap remains),
Step 2 Dip cutting surfaces in fresh 2% sodium hypochlorite solution for 1 minute,
Step 3 Rinse in clean disinfected water to remove excess chemical (a squirt bottle may be useful).
Plastic containers and trays
Step 1 Scrub clean using 2000ppm quat solution to remove media and plant debris,
Step 2 Dip in fresh 1% sodium hypochlorite solution for 20 minutes.
or Steam-treat at 60oC /30 minutes.
Hands
Option 1 Use disposable gloves and change them between operations.
Option 2 Wash hands thoroughly between operations using Savlon or Dettol soap.
Wooden stakes and similar materials
Heat treatment (60oC /30 minutes) materials must be well separated. There are no effective alternatives.
Footwear
Option 1 Change footwear and use only designated footwear in the working area.
Option 2 Scrub clean with a brush and 2000ppm quat solution for at least 30 sec.
Tools, spades, bobcat buckets etc:
Option 1 Scrub clean with a brush and 2000ppm quat solution
Option 2 Pressure clean with a 2000ppm quat solution
Disinfestation methods - a review
Heat: Steam heating of potting mix and used containers for 60oC /30 minutes is a safe and efficient way controlling a broad range of pathogens. The timing of treatment should begin when the centre of the potting mix or load of containers reaches 60oC.
Quaternary ammonium compounds (quats): Quats have been shown to be more effective than phenolic compounds for control of P. cinnamomi. on surfaces. In general, quaternary ammonium compounds (quats), have shown incomplete control against Thielaviopsis basicola, Phytophthora cinnamomi and viruses.
Sodium hypochlorite solutions: These are effective against a wide range of pathogens, inactivating orchid virus particles 2% a.i. and ORSV at 15% a.i., CEV on budding knives was inactivated at 0.26% a.i. /1 sec but at 0.26% a.i., failed to control ToMV on shears. Most fungal and bacterial pathogens are killed on contact with chlorine but resistant fungal structures such as sclerotes may not be killed.
Where pathogens have colonised peat or plant tissues, sodium hypochlorite is ineffective as a disinfectant. In peat debris colonised by plant pathogenic fungi, sodium hypochlorite failed to control Verticillium dahliae or Phomopsis sclerotiodes at 10% a.i./60 min or Didymella bryoniae at 10% a.i./10 minutes. These findings are important for the development of effective protocols for the disinfection of plant containers and emphasise that quick dip treatments do not disinfect surfaces.
The bottom line
Preventing the spread of disease results in fewer disease outbreaks and a reduced need for the use of agricultural chemicals. Nursery operators should review their hygiene protocols against this latest review as current practices may be inadequate.
Further reading
Disinfestation Protocols for the Nursery Industry - A literature Review, (booklet), Mebalds M., M, Tregea, W. and van der Linden, A. (1997). Report for HRDC Project NY612. Available from HRDC.
Nursery Industry Accreditation Scheme Australia (NIASA) Best Practice Guidelines, (booklet), NIAA 1997.
Practical Guidelines for Nursery Hygiene, (booklet), Goss, O.M. (1983). Australian Nurseryman’s Association (now NIAA) Sydney. Available from NIAA.
Acknowledgements
The current protocols were formulated at a workshop involving nursery operators ;John Bunker, Greg Daley & John Lawrence,
Industry development officers ; John McDonald, Hans Kosmer & Ian Atkinson,
Plant pathologists; Gordon Stovold, Keith Bodman & Martin Mebalds. The review and workshop were funded by the nursery industry product levy and HRDC.
