This is an abbreviated text only. See our publications order form for the full text or contact your State Nursery Industry Association - to buy a copy of the full book, published by the Nursery & Garden Industry Australia, Sydney.
These Guidelines endeavour to describe industry 'Best Practice' for production nurseries and manufacturers of growing media. They have been divided into four major sections:
The prevention of root diseases, particularly those caused by Phytophthora spp. is a major consideration as, once contracted, most cannot be eradicated in a commercial or end-use situation. Root rot prevention relies on a complete package of strategies which is successfully operated only when the life cycles of the pathogens are fully understood.
Where a root rot outbreak occurs in a nursery set up with what appears to be the full complement of cultural and physical barriers to the completion of pathogen life cycles, the cause is almost invariably due to a lack of staff or operator training. There will be annual scientific testing of the effectiveness of hygiene practices at the direction of the Technical Officer.
Reticulated (town) water and water from deep bores and clean roof catchments should not require treatment. The pH and EC of all water sources must be checked and recorded at least once per month. Water from surface supplies, springs, effluents, or water testing positive for the presence of root-rot organisms must be disinfested by one or several of the approved methods.
A minimum contact period between water and chlorine and bromine at their lowest biocidal concentrations (2-5 ppm) is 20 mins. A case may exist for reduced contact time, if concentrations are higher (8-10 ppm), but experimental proof is required. Adequate records of water disinfestation treatments must be maintained. The minimal requirements for chlorination or chloro-bromination treatments is once per month recording of; pH of water before treatment, free chlorine concentration at start of contact time, contact time, free chlorine concentration at end of contact time (residual).
For more detail on options for disinfestation of water see 'The Nursery Papers' on chloro-bromination, ozone, chlorine dioxide and UV radiation. See Appendix 5 of the full book for an example recording sheet. The Technical Officer can require a greater degree of testing. Record requirements for other disinfestation treatments will be recommended by the Technical Officer.
The subsequent storage of treated water requires facilities and procedures that do not allow for contamination by untreated water, soil, plant debris, dust and animal movement.
Routine disinfestation of propagating media. There is no requirement to routinely disinfest materials generally considered to be free of major plant pathogens or those from a source consistently testing free of specified pathogens. Experience indicates that perlite, vermiculite and properly composted and correctly stored pine barks prepared on clean surfaces, are most often free of the most common pathogens occurring in propagating facilities, (Pythium spp, Rhizoctonia solani, Fusarium spp, Cylindrocladium spp, Phytophthora spp, Chalara spp and Botrytis spp). Experience also indicates that contaminated propagules, tools, containers, preparation surfaces, water and dust and splashed or windborne inoculum present a much greater risk.
River sand presents a significant risk of carrying Pythium, Rhizoctonia, nematodes and Phytophthora and must be treated or regularly tested and found free of specified pathogens.
Disinfestation of media. Media or media components which present a risk of contamination must be treated by an approved method. More detailed information is provided in Appendix 3 of the full book. Adequate records of all disinfestation treatments, including date, amount treated, method used and results, must be kept.
Mixing of media. Media mixing areas (if media are not to be subsequently treated) must be situated on surfaces and in areas which both shed and exclude runoff water and exclude contamination by tracked soil and other possibly contaminated materials.
Storage of media. Media need to be stored in facilities which effectively prevent infestation or reinfestation by root rot organisms. As such, all media and media components which are already treated, or do not need treatment are to be stored on surfaces and in areas which both shed and exclude runoff water and exclude contamination by soil and other possibly contaminated materials. Alternatively, media can be stored in bins, trailers and trolleys.
Different types of media should be stored separately to avoid possible cross contamination. More specific information is provided in Appendix 3. All storage surfaces must be suited to easy cleaning between batches. Where the possibility of disease risk occurs, the site must be assayed for the presence of soilborne plant pathogens. Storage areas for approved and/or treated media must be effectively separated from areas used to store possibly contaminated media.
Transport of media. Treated media and media determined as being free of specified pathogens must not be contaminated during handling and transport. Equipment used to transport media must be washed and disinfected between loads, if the vehicle is also exposed to unapproved media or media components.
Approved media suppliers. Media components other than; those generally accepted as being pathogen-free (for instance perlite, vermiculite, expanded polystyrene), or consistently testing free of specified pathogens, or which are routinely disinfested by any of the approved methods already described, must be from an approved source. An approved source is an accredited supplier of pathogen-tested materials (Appendix 1 of the full book has the details).
Reuse of media. Media may be reused, but only on the following conditions: a) media to be reused must be disinfested in an approved manner (App. 3), b) prior to disinfestation, media to be reused must be stored on a site well separated from storage sites of new or treated media ingredients, c) treated recycled media will be pathogen-tested by the Technical Officer on a six monthly basis.
Motherstock plants must be monitored for pests and diseases and treated as appropriate with plant protection chemicals to decrease the possibility of pests and diseases entering propagation facilities. Where motherstock is inground, good drainage is essential.
Seeds must either be collected from the plants or if collected from the ground, treated in a manner approved by the Technical Officer. This could include the use of a suitable heat disinfestation procedure or chemical treatment, depending on the nature of the material.
Cuttings must be obtained, where possible, from parts of the plant not contaminated by soil splash. Mulching is recommended to minimise contamination of the lower part of the plant with soil.
Divisions must come from motherstock free of pests, weeds and diseases.
Benches used to plant or prepare plant propagules need to be constructed of non-porous materials or covered with non-porous materials which are cleaned at least daily but preferably between batches of media or propagules.
Washing the surfaces, with 2000ppm quaternary ammonium chloride solution, prior to disinfestation is essential. Disinfectants commonly in use include quaternary ammonium chlorides, heat, chlorine solutions, and methylated spirits (70%). Disinfectants may be approved or recommended by the Technical Officer, if there is documented information on their effectiveness.
All tools need to be treated between batches of media or after use, by first scrubbing or pressure cleaning, with 2000ppm quaternary ammonium chloride solution, and then using an acceptable disinfectant.
Where contamination of footwear may have occurred; either it should be cleaned and then disinfected, or changed at different work stations. Methods of disinfestation should be in compliance with health regulations in each state. Waterproof footwear is required. Regularly replenished and cleaned footbaths may be essential in some situations (for instance at entries to in-ground sites).
Vehicles from possibly contaminated sites which enter clean sites should be first scrubbed or pressure cleaned, using for example quaternary ammonium chlorides and then disinfected using any of the approved surface disinfectants. It is ideal however, to restrict the passage of possibly contaminated or regularly contaminated vehicles into production or media preparation sites.
Access to in-ground stock areas and propagation facilities must be restricted to all but essential traffic. Propagation areas must not be thoroughfares for staff or materials involved in materials and plant handling operations unrelated to propagation.
Discarded plants and spilt media are to be accumulated in specially allocated containers and removed on a frequent basis. Plants with difficult to control pests (eg silver leaf whitefly) and diseases should be removed promptly from the production area - delays cause an accelerated spread of pests and disease.
Propagating facilities. Although sealed surfaces are preferable, gravel is permitted on paths and under benches where the ground is well drained and the aggregate coarse (10-25 mm diameter) and at least 75 mm deep. However disease organisms such as Botrytis spp can become a problem in older facilities where gravel is used. Floors should be washed and treated or drenched with disinfectant solutions on a frequent basis. Plant debris must not be placed on the floor. Dead and diseased plants and propagules should be placed directly into specially allocated containers (Section 1.1.9).
Production facilities. Pathways adjacent to containerised plant production facilities should be sealed using bitumen or concrete or by the use of coarse gravel (10 mm - 25 mm diameter) on a consolidated graded surface at a depth of at least 75 mm. Pooling is as unacceptable on pathways as it is on surfaces used for plant production. Roadways adjacent to production facilities must be properly drained and consolidated, and preferably sealed. Dust from roads should not enter production or propagating areas.
Plants or propagules entering the nursery should be from NIASA Accredited suppliers or if from unaccredited sources need to be placed in a specially designated quarantine area and carefully monitored for pests and diseases. The period of quarantine is dependent on whether the plants are to be disease tested or not. If not disease tested, the plants should not be removed from quarantine into production areas for at least four weeks. After their removal they should be clearly marked and monitoring continued.
If they need to be repotted this is permissible but they may not be treated with fungicides or nematicides which mask disease symptoms. It is especially important that the designated quarantine area is situated where drainage water from it is not allowed to enter other propagation or production sites on the nursery.
Containers, plants to be potted, the growing medium and the newly potted plants must not come into contact with possibly contaminated materials or surfaces during potting operations.
The importance of removing disease inoculum from hands, clothes and feet is underrated. Pythium, Fusarium, Rhizoctonia, Chalara, Phytophthora and Cylindrocladium can all be transmitted to benched plants by the use of soiled hands. Good access to hand washing facilities and their routine use is essential in a disease prevention programme. While a hand washing biocide (recommended by State Health Departments) may be necessary in some situations, soap and water used with a brush is usually suitable.
New containers if stored free of soil, plant debris and drainage water contamination, need not be disinfected. Clean and disinfected containers must be stored above floor level.
Used containers must be reasonably cleaned of waste material and then dipped in fresh 1% hypochlorite solution for 20 minutes. Alternatively they can be treated with aerated steam, methyl bromide or other method approved by the Technical Officer (see Appendix 3).
Disinfectant chemicals are dangerous and the nursery must be equipped to use them safely. They must then be handled and stored as per government regulations regarding hazardous chemicals.
The pathogens of most concern are those that are soil and waterborne. Contaminated water, growing media (including soil), surfaces and infected plants are the main elements which allow the continuity of pathogen lifecycles.
In nursery propagation and production sites, the water most likely to be contaminated is drainage water, and the growing medium most likely to be contaminated is that prepared on the nursery or residual on used pots, tools and surfaces on which plants and media are placed. Also bear in mind that water splash is a marvellous way of spreading these diseases and many other diseases as well.
A suitable surface for the handling, propagation and growing of plants is therefore one which isolates them from the above sources of contamination, and it is this need that NIASA is attempting to define and address. There are various elements of risk of contamination in different situations and it is therefore difficult to be didactic about bench and bed specifications, but for the purposes of disease prevention the following recommendations have proved useful.
In many situations the Technical Officer should be given some discretion in the interpretation of these guidelines, as long as they have the necessary technical background, and any changes are approved by their NIASA accreditation committee.
Propagating beds for inground plants. Beds must be freely draining. Footbaths containing regularly replenished disinfectant solutions are necessary at entrances to areas where beds, rather than benches are used. There must be limited access and strictly defined entry points for both vehicular and foot traffic. The area should not be accessible to animals.
Motherstock beds. See Section 1.1.3 Motherstock plants.
Production beds for containerised stock. The surface of the bed and the pathways adjacent to it must prevent contact of the plant, the plant roots or the container, with soil or water contaminated by soil (or media) or water draining from other containers or from any other possibly contaminated sources. Puddling is definitely not permitted.
Coarse gravel or crushed rock covered surfaces have been shown, by broad scale nursery testing, to be effective in disease prevention where the surfaces are consolidated, well drained and the aggregate (screenings of 10 mm and preferably higher diameters) is 75 mm deep (preferably deeper). Weedmat over aggregate may be useful in keeping the material free of crop debris and potting mix spill, and reducing root escape.
Concrete, polythene or bitumen are permitted where; they are covering properly consolidated surfaces, exceptionally good drainage occurs, and all other hygiene practices are excellent. Beds with these surfaces must not pool water and must be separated as much as possible from adjacent production sites in terms of water runoff.
Weed mat over soil represents a significant problem for disease control and is not sufficient.
If a growing surface in a production area is considered to offer a possible risk in terms of root disease prevention, this area must be tested by the Technical Officer. The guidelines for sampling are given in Appendix 2 of the full book.
Fumigation of the soil with methyl bromide and chloropicrin mixtures is recommended prior to surfacing with gravel on contaminated nursery sites where aggregate is not being placed over pathogen free roadbase, and where care is to be taken in preventing contamination.
Benches. Where benches are used, the height requirement is dependent on the type of surface underneath. Benches spanning or adjacent to either properly sealed or aggregate surfaced floors and paths and grown in polyhouses/glasshouses with low precipitation rate irrigation outlets, need not be higher than 30 cm. However, where splash and other methods of contamination are likely to occur, a suitable bench height is 75 cms or higher.
The bench surface should preferably be free draining (for example galvanised mesh) and easily disinfested. However solid surfaces or benches, and those used for capillary watering systems are permitted but only; where all other hygiene practices are exceptionally good, and plants grown on them routinely test free of specified pathogens.
Hanging baskets and double benches are allowed in growing areas providing all other hygiene practices adhere to the guidelines.
NIASA Accreditation of in-ground production sites is permissible, where the production sites have tested free of soilborne pathogens. Long term disease freedom of in-ground sites has been proven possible but only where great care has been taken to quarantine these sites effectively. This can be expensive but has been very cost effective where the aim has been the supply of plants free of specified pathogens.
The NIASA accreditation of in-ground production sites is very dependent on comprehensive site sampling and this may involve additional expense to the applicant. There will be annual scientific testing of the effectiveness of hygiene practices at the direction of the Technical Officer. Sites contaminated by pathogens may be adequately disinfected with properly applied fumigants, for instance, methyl bromide or a recommended substitute. This has been very effective in the long term eradication of Phytophthora spp, but less effective with Fusarium spp. in many situations. Long term success depends on effective quarantine of the site after treatment.
In all cases, the area must be well drained. Where the soil type is heavy and consequently, internal drainage is restricted, a raised bed system must be developed. All water from adjacent areas must be deflected from the production area and roadways. The production site needs to be broken up into as many discretely drained blocks as possible. In this manner, if infection does occur, it can be restricted to a limited part of the nursery.
Surface drains need to be properly graded, stabilised and run freely. Vehicle access to production sites needs to be limited. The growing area needs to be fenced to prevent the access of animals and vehicles, which may carry soil infested with weeds and disease organisms.
Growing media and media components supplied to the nursery must be free of weeds and weed propagules. Media storage and mixing areas must be free of weeds and weed propagules. Propagation areas and production areas must be free of weeds. Weeds must be suppressed on the general nursery site, even when outside of the immediate production area.
1.2.2 Insects & other pests, Integrated Pest Management (IPM)
IPM should be applied wherever feasible and must be an aim for all businesses for information on practicing IPM). As with the control of diseases and weeds, it is expected that the control of insects, mites and other pests on accredited nursery sites will be of a high level of effectiveness. The responsible use of and minimal dependence upon crop protection chemicals is a major consideration of NIASA.
Note that tolerance levels for a number of specified insects could be required, particularly where these pests are also covered in interstate quarantine guidelines. Examples include; whiteflys, European red mite, western flower thrips, melon thrips, palm weevil borer, whitegrubs, Argentine ant, Black vine weevil, palm leaf beetle, scale and mealy bug.
1.2.3 The prevention and control of pathogens, other than those causing root and crown rots
Pathogens should be prevented from entering the site where possible and if not, managed to levels which allow the sale of a high quality product. Pathogen tested motherstock should be used wherever possible. Freedom from and testing for quarantinable pests and diseases may be mandatory in the future.
Equipment. Application equipment must be suited to the task, be calibrated regularly and kept in good working order. Records of calibration and maintenance of all equipment must be kept. Staff operating the equipment must have access to adequate and properly used measuring devices and safety equipment.
Personnel. Persons responsible for crop protection procedures must demonstrate an adequate knowledge of;
pest and disease diagnosis and control,
crop hygiene,
safe use of plant protection chemicals,
the principles of Integrated Pest Management.
The person responsible must hold a current 'National Farm Chemical Users Course' certificate or its equivalent.
Plant protection chemical storage and mixing facilities. These must meet the minimum requirements of the relevant government regulations. Pest, disease and weed control programmes. These must be capable of controlling correctly diagnosed or identified target organisms without causing significant damage due to plant protection chemical induced phytotoxicities. IPM should be applied wherever feasible and must be an aim for all businesses.
Plant protection chemical drift and contamination. The method of equipment use, the choice of equipment and the plant protection chemicals used must all be chosen on features which reduce the escape of agricultural chemicals from the production site, and minimise environmental impact.
Records. Complete records of the chemicals used, the rates, the dates of application, the approximate volumes (or weights) applied, the section of the nursery sprayed and/or the crops treated, and the name of the spray operator, must be maintained (See Appendix 5 for an example recording sheet). Application equipment used, safety equipment worn and results of treatment, including damage, should also be recorded.
Removal of contaminated materials. Prompt removal and/or disinfestation of contaminated plants and other materials can reduce the incidence of plant disease by up to 80%. Many plant protection chemicals cannot achieve this reduction. Therefore the site must be kept free of possibly contaminated materials including plants, potting mix and crop residues.
Water quality. The quality of the various supplies of irrigation water available to the nursery must be of a known analysis, to determine its possible effects on the quality of stock produced. The pH and EC of all water sources must be checked and recorded at least once per month. See Appendix 5 for an example recording sheet. Where the water source is of poor quality water, with for example excessive suspended materials or high iron content, treatment practices must be capable of ensuring the production of quality plants.
Irrigation. Irrigation equipment and practice must suit the needs of the crop in terms of the uniform distribution of water and effective irrigation scheduling. See the book 'Nursery Industry Water Management - Best Practice Guidelines - Australia 1997' published by NGIA for a full coverage of irrigation best practice.
Waste water, particularly that containing fertilisers and/or plant protection chemicals, should be minimal in volume, preferably reused or recycled, or alternatively disposed of by an approved discharge system. See the book 'Nursery Industry Water Management - Best Practice Guidelines - Australia 1997' published by NGIA for a full coverage of waste water best practice.
Growing media should have a suitable range of physical properties in terms of water holding capacity, aeration and drainage. Plants requiring a hardening-off period should be able to be placed under a modified watering regime.
Humidity. The humidity of atmospheres maintained in nursery structures should not continually exceed levels beyond which plant health becomes a persistent problem (over 85%, except in propagation houses).
The physiological and physical damage sustained by plants should be, where necessary, minimised by the use of suitably constructed windbreaks. Windbreaks and other methods of dust control must be employed where applicable.
The crops should be grown under light regimes suited to the needs of the species. Where necessary, facilities should exist to acclimatise plants to light levels used by the purchaser. Light levels in the dispatch area and in the transport process should not exceed the tolerance of indoor plants.
Temperature extremes should not regularly exceed the tolerance range of the majority of crops grown. In the event of an environmental control failure (for example, with low precipitation frost mitigation, greenhouse cooling or greenhouse heating), the nursery operator must be prepared to grow-on the damaged plants for a period sufficient to guarantee both quality and continued plant vitality.
The operator should demonstrate a thorough knowledge of crop nutrition. Enough information on the nutritional practice of the business should be relayed to the Technical Officer to demonstrate that the operator consistently uses an effective programme. Practices should minimise nutrient leaching.
All growing media must be tested for pH and EC, using the Australian Standard methods, either at the time of delivery or just prior to use. Adequate records including date, batch number, volume, pH and EC must be kept. See Appendix 5 for an example recording sheet.
The operator needs to supply the outgoing produce with the nutritional reserves required to maintain the plants for long enough to meet the needs of the purchaser. An assessment of the nutritional status of plants ready for sale will be made by the Technical Officer.
Structures should be adequately maintained, safe and comfortable to work in during periods of peak staff activity, and suited to their design purposes.
The roots of many plants when removed from the container will need some attention at planting out. The degree of attention is related to several factors, not the least of these being the size of the container, the vigour of the plant and the time that the plant has been occupying the container. It is therefore the amount of attention that has to be paid to remedial root treatment and the estimated post transplant success of the plant that need to be used as yard sticks in evaluating this aspect of plant quality. Consider the following rating system;
A small amount of teasing required - no root trimming.
Teasing with a small amount of root trimming.
A considerable amount of teasing and root pruning - the plant has a reasonable chance of establishment when planted.
Heavy root pruning and teasing required. The chance of plant survival and satisfactory establishment greatly reduced.
Root binding has reached the point where the plant should be rejected and destroyed.
If more than 10% of plants ready for sale in the nursery are in the last two categories, the applicant should be informed that this is unacceptable for the purposes of NIASA.
Nursery & Garden Industry