Horticultural Biosecurity

It has been estimated that plant diseases are responsible for up to a 15% loss in potential farm income. As with livestock, lowering the challenge of pathogenic organisms will reduce the incidence of disease, increasing both output and quality.

This is most important in the greenhouse environment where there is no natural weathering process to reduce the challenge carried over in debris and dust from previous crops. This together with the high intensity of plants greatly increases the risk of disease. Many plant disease organisms survive in plant debris or dust for months or years in a dry state on the floor, the structural framework, tools, implements, grading and packing lines and clothing. Just as it is in intensive livestock housing, greenhouse hygiene is a fundamental requirement for disease control.

Thus the state of hygiene of the greenhouse and its surroundings, weeds, algae, dirty machinery, rubbish piles of prunings and un-saleable produce all have an impact on plant health. Also adjacent field crops of the same plants can present hazards to the greenhouse crops.

Most disease causing organisms are transmitted by vectors. Controlling contamination on these vectors is the key to successful disease control. Some of the potential sources of disease organisms are listed below:

Boots	Trolley tyres	Overhead ornamentals
Commercial peat	Seed	Transplants
Debris on wires	Insects	Trash piles
Dirty seed trays	Tools	Overalls
Dust on structure	Fruit crates	Grading & packing lines
Outside trash piles	Weeds	Well and creek water
Soil	Visitors

One specific chemical formulation with proven efficiency in destroying infective organisms is a powdered stabilized blend of peroxygen compounds, surfactant, organic acid and an inorganic buffer system. FarmCare GB markets this formulation as Viru-Gard. The combination of efficiency, safety and lack of residue concerns makes the use of Viru-Gard an attractive alternative to many of the plant hygiene and disease control chemicals in use today.

Terminal Biosecurity Programme for Greenhouses

The following procedures should be followed for each greenhouse to be disinfected.

 

 

 

 

 

 

 

 

Stage 1: Removal of Equipment and Dry Cleaning

The removal of all gross organic matter is essential as it contains high levels of contamination and is a major source of infection. High levels of soiling will also reduce the efficiency of the cleaning and disinfection process.

• Remove trays, pots, containers and equipment from the area to be disinfected and put to one side for cleaning and sanitising.
• Remove all crop debris, strings etc.
• Do not leave trash piles near the greenhouse as they may contain spores which are carried back into houses on feet and tyres or are blown in by the wind.

Stage 2:Pre-cleaning and Sanitizing

Following any dry cleaning process high levels of infective material will still remain. Cleaning and sanitizing using products with detergent capacity and biocidal activity to remove soiling from the surfaces ensures greasy deposits do not remain on rough surfaces e.g. concrete and wood. Detergent-sanitizers also reduce the time taken to clean by up to 60%, and reduce the spread of disease in washing water. Fluorine should not be used on glass as it etches the surface providing a surface for increased growth of algae and other infectious organisms.

• Use FarmCare Quat-Gard at a dilution of 1:1000.
• Apply with a knapsack sprayer or pressure washer. The pressure washer should be set on a low pressure setting 500psi (35 bars) using a 45° angle jet. The application rate should be 1 litre of solution per square metre of surface area.
• Start at the apex of the roof and work down the walls to the floor paying particular attention to corners and other areas where dirt accumulates. Caked soiling should be brushed if necessary to aid removal.
• Allow surfaces to dry where possible before disinfection.

Stage 3: Water System & Equipment Sanitising

Irrigation water and irrigation lines

All water systems contain some contamination, especially the header tanks where dust and dirt can accumulate. This may allow disease such as Pythium, Fusarium and Phytophthora to pass on from one crop to the next. Viru-Gard will also breakdown bio-films and algae.

Run 1% (1:100) Viru-Gard solution through the pipes or soak them in a bath. Flush irrigation lines with clean water after treatment.

Moveable Equipment

Equipment removed from the house can carry heavy pathogenic contamination and if not thoroughly cleaned can lead to carry over of infection to the new crop.

• Where there is a high risk of carry-over of infectious organisms on trays, pots, containers wash or dip them in a 1% (1:100) Viru-Gard solution.
• Where there is a low risk of infective material either soak and scrub equipment in a tank or pressure wash with FarmCare Quat-Gard (at a dilution of 1:250).
• Store equipment where it will not be re-contaminated.

Stage 4: Disinfection

The level of disease organisms, particularly viruses, present after cleaning and sanitizing is still high enough to offer a serious challenge to young or recently introduced plants. The use of a broad spectrum disinfectant active against viruses, bacteria, yeasts, moulds and other pathogenic organisms is essential to complete an effective disease control programme. It is of prime importance to ensure all surfaces are thoroughly wet with disinfectant to break the chain of infection. Dirt floors harbour millions of spores. Laying concrete floors improves hygiene and assists the disinfection process.

• For routine disinfection of glasshouse structures apply 0.5% (1:200) Viru-Gard solution at a rate of 300ml per square metre (1 gallon/150 sq. ft) of surface area. Concrete floors require two passes a 1% solution for routine disinfection.
• Use a knapsack sprayer or pressure washer at 35 bars (300psi) with a 45o spray head.

Stage 5: Fogging and Aerial Disinfection

When the greenhouse has been thoroughly cleaned and disinfected all moveable equipment should be returned. To disinfect inaccessible areas of the house that might have been overlooked, the house should be fogged. It is particularly important to fog any reception and storage area.

• Spray Viru-Gard diluted at 1:100. Spray into the eaves using a very fine mist from a pressure washer or using a mechanical fogger.
• Use at a rate of 1 litre of solution per 100 m³. Fogging with Viru-Gard is safer and more effective than traditional methods of fogging with aldehydes as the greenhouse can be entered soon after fogging limiting downtime to a minimum.

Continuous Protection with Plants in the House

Regular Fogging

To avoid the buildup of pathogens during the growth phase of a crop, routine fogging once a week with Viru-Gard is advised. The Viru-Gard formulation has been proved to be non-phytotoxic.

• Spray Viru-Gard diluted at 1:200. Spray into the eaves using a very fine mist from a pressure washer or using a mechanical fogger.
• Use at a rate of 1 litre of solution per 100 m³. Fogging with Viru-Gard is safer and more effective than traditional methods of fogging with aldehydes as the greenhouse can be entered soon after fogging limiting downtime to a minimum.
  

Site Security

Between applications of the Terminal Disinfection Programme there are many opportunities for introduction of infection to the greenhouse. Measures must be taken to reduce the risk of disease being brought onto the site with visiting vehicles and personnel and minimizing the movement of infective material from house to house.

Visitor Control

The following will help you to avoid pathogens being introduced into your greenhouse or spreading disease from one house to another.

• Access to your greenhouse should be limited
• Transport vehicles should be cleaned and disinfected upon arrival and on departure.
• Require that all visitors wear clean or disposable clothes, overalls, hats, gloves and boots.

Pruning

Prune with a sterilized knife. Use Viru-Gard to sterilize by dipping (not soaking) in a 1.0% solution at the end of each row. Alternatively use a sponge soaked in a Viru-Gard solution.

Foot dips / Disinfectant Soaked Mats

Ensure foot dips or foam Mats are placed at the entrance to each greenhouse.
Fill foot dips with a solution of Viru-Gard diluted 1:100 and replenish twicw weekly or more often if heavily soiled. Ensure that soaked mats remain wet with a 1% Viru-Gard solution.

Hand Hygiene

Dirty or unwashed hands transfer infection. All visitors to the site should be required to wash their hands before entering the site using a germicidal hand soap. All staff should wash their hands before starting work, after breaks and when changing work activities.

Wheel dips

Fill with a solution of Viru-Gard diluted 1:100 and replenish twice weekly or more often if heavily soiled.

Disinfection of Paths, Roadways and Areas around Houses

Keep paths and areas around houses clear of trash piles as these are a potent source of infection. Spores are carried back into houses on feet and tyres or are blown in on the wind. Spray these areas regularly with a 1:100 dilution of Viru-Gard at a rate of 300ml per square metre.

Clothing

Wash clothing weekly and hang out to dry. Mosaic virus can persist for years, in unwashed overalls stored in the dark.

No Smoking

Tobacco products may contain Tobacco Mosaic Virus (TMV)

Ornamentals in Vegetable Greenhouses

Ornamentals such as grapevines, figs, oleanders, and hanging baskets harbour whitefly, thrips, nematodes and disease organisms. Do not grow these plants in a vegetable greenhouse.

Viru-Gard horticultural efficacy

A summary of independent efficacy data for the formulation of Viru-Gard is shown below:

Organism	Disease	Crop	Effective Dilution
Alternaria solani	Early Blight	tomato	1:200
Botrytis cinerea	Grey Mould	several	1:200
Clavibacter michiganensis michiganensis	Bacterial Canker	tomato	1:500
Clavibacter michiganensis sepedonicus	Bacterial Canker	potato	1:100
Collectotrichum coccodes	Black Dot Root Rot	tomato	1:200
Didymella bryoniae	Gummy Stem Blight	cucumber	1:200
Epicoccum nigrum spores	Grass Fungus	grass	1:200
Erwinia amylovora	Fireblight	apple	1:250
Erwinia carotovora atroseptica	Bacterial Stem Rot	tomato	1:100
Fusarium moniliforme	Fusarium Leafspot	-	1:50
Fusarium oxysporum lycopersici	Fusarium Wilt	tomato	1:200
Fusarium oxysporum radicis-lycopersici	Fusarium Crown & Root Rot	tomato	1:200
Fusarium solani	Pepper Fruit and Stem Rot	pepper	1:500
Geotrichum cutaneum	-	-	1:25
Penicillium italicum	Root rot	citrus	1:100
Penicillium italicum	-	citrus	1:100
Penicillium oxalicum	Penicillium Stem Rot	cucumber	1:100
Pepper Mild Mottle Virus	fresh dried leaves and roots	pepper	1:20
Pepper Mild Mottle Virus	glass	pepper	1:50
Pepper Mild Mottle Virus	concrete	pepper	1:20
Pepper Mild Mottle Virus	knives	pepper	1:50
Phomopsis sclerotinoides	Black Root Rot	cucumber	1:200
Phytopthora cactorum	-	apples	1:100
Pithomyces chartarum	-	grass	1:100
Pithomyces chartarum spores	-	grass	1:400
potex virus	Potatox X Disease	potato / tobacco	1:100
Pseudomonas syringae	Bacterial Speck	pepper	1:500
Pseudomonas syringiae syringiae	Bacterial Blast	plums, cherries	1:250
Pseudomonas solanacearum	Brown rot	apples	1:800
Pseudomonas solanacearum	Bacterial wilt	potatoes	1:800
Pseudomonas viridiflava	Bud Rot	kiwi fruit	1:250
Pyrenochaeta lycopersici	Corky Root Rot	tomato	1:200
Pythium aphanidermatum	Pythium Damping-off	several	1:500
Pythium sp	Pythium Damping-off	several	1:50
Rhizoctonia solani	Rhizoctonia damping off	several	1:200
Sclerotinia sclerotiorum	White Mould	several	1:200
Thielaviopsis basicola	Root Rot	tomato	1:500
Verticillium dahliae	Verticilium Wilt	tomato	1:500
Verticillium dahliae	Verticilium Wilt		1:50
Xanthomonas campestris	Citrus canker	Various citrus fruits inc. Orange, Lemon, Lime & Grapefruit	1:100
Xanthomonas campestris	Bacterial Spot	cabbage	1:500