Control of Pythium, Phytophthora andRhizoctonia in pot and bedding plants

This factsheet describes the symptoms of Pythium, Phytophthora and Rhizoctonia diseases in bedding and potplants, the biology of the causal organisms and a management strategy for disease control.

By Tim O’Neill and Kim Green, ADAS

Factsheet 17/04

Pot and bedding plants

HorticulturalDevelopmentCouncil

Bradbourne House

East Malling

Kent ME19 6DZ

T: 01732 848383

F: 01732 848498

E: hdc@hdc.org.uk

1 Characteristic collapse of seedlings (lobelia) due to Pythium; note the white growth of Pythium

at the edge of the bare patches

Action pointsNursery hygiene• Use fresh growing media, straight

from the bag, bale or covered bunker.

• Use new trays and pots, especiallyfor propagation.

• Regularly clean and disinfect waterstorage tanks and irrigation linesand ensure water tanks are covered.

• Use mains or treated irrigationwater and check at the point ofapplication several times each yearfor contamination by Pythium.

• Eliminate standing water and treatleaks in roofs.

• Regularly change or sterilise capillarymatting.Discard contaminatedmatting.

• Remove plant debris fromglasshouse benches, floors andpropagation beds and dispose of itoutside of the glasshouse.

• Regularly clean and disinfectbenches, floors, tools, trays andtrolleys especially after an outbreakof a root disease.

• Control shore and sciarid flypopulations.

Control during production• Carefully inspect cuttings and plug

plants before planting; reject anywith symptoms of root disease.

• Good growing conditions includingcorrect growing medium nutrientlevels and pH, regular watering andfree-draining compost will minimiserisk of root disease. Mostimportantly, avoid over-watering andgrowth checks.

• Regularly monitor plants for thepresence of disease. Where diseased

plants occur, promptly remove andcarefully dispose of them in acovered skip or bin.

• Where there is a significant diseaserisk, use a preventative fungicidespray programme.

BackgroundPythium is generally the most commoncause of root rot and is particularlytroublesome during propagation. Inrecent years, with the advent of plugproduction, Pythium damping-off ofseedlings has become less common.It is most damaging on cuttings andyoung plants, although mature plantsof certain crops (eg monstera,pelargonium, poinsettia) can also beseverely affected. A recent HDC

project (PC 97a) revealed pathogenicPythium species to be widespread onmany nurseries growing ornamentals.

Phytophthora is less frequent thanPythium but often causes more severedamage. Root and crown rot of matureplants is a common symptom. Certainpot plants (eg dieffenbachia, gloxinia,kalanchoe, primula, saintpaulia) arenotably susceptible. Pythium andPhytophthora are closely related,belonging to a group of fungal-likemicro-organisms. They are both

favoured by abundant moisture, aresimilar in their sensitivity tofungicides, and share other commonfeatures. They will therefore bediscussed together in some sectionsof this factsheet.

Rhizoctonia has a wide host rangeand commonly causes damping-offand wirestem of seedlings and stembase damage to cuttings and youngplants. Mature plants are generallyless susceptible.

3 Phytophthora often causes more severe damage than Pythium as seen here where Phytophthora root rot has caused wilting and plant collapse

of cineraria

IntroductionSeveral soil-borne fungi and fungal-like micro-organisms are responsiblefor economically important root, stembase and crown rot diseases ofbedding and pot plants. The fungimost commonly involved are speciesof Pythium, Phytophthora andRhizoctonia. Pythium alone in beddingand pot plants is estimated to causelosses valued at £5.5 million annually,largely due to reductions in plantquality. Within intensive productionsystems, these pathogens can soonbuild up, causing serious losses andquality issues.

2 Collapse (damping off) of Iobelia plugs due to Pythium infection

Table 1Some bedding and pot plantsparticularly susceptible to Pythium

Bedding plants (seedlings)AntirrhinumAlyssumCallistephusLobeliaNemesiaTagetes

Pot plantsCyclamenFuchsiaMonsteraPelargoniumPileaPoinsettia

Bedding plantsCallistephusCinerariaDianthusNemesiaPetuniaTagetesViolaMatthiolaSalvia

Pot plants (foliage)DieffenbachiaHederaPeperoniaSpathiphyllumZantedeschia

Pot plants (flowering)BellisBegoniaCalceolariaCapsicumCinerariaExacumFuchsiaGerberaGloxinia (Sinningia)ImpatiensKalanchoePelargoniumPeperoniaPoinsettiaPrimulaSaintpauliaSchlumbergeraSolanum

Table 2Some bedding and pot plants particularly susceptible to Phytophthoraroot rot

4 Pythium root rot on poinsettia – affected

roots are grey coloured and fall away easily

5 Pelargonium showing Pythium stem base

rot (black leg)

SymptomsThe symptoms caused by Pythiumand Phytophthora are not usuallysufficiently characteristic for reliablevisual diagnosis to be made. Seekexpert help where there is doubt.

Pythium on seedlings and cuttingsPythium is most troublesome duringpropagation, attacking virtually allplant species. Seedlings affected byPythium collapse (‘damping-off’) orfail to emerge. Where seedlings aregrown in pots or trays, areas ofaffected plants enlarge leaving barepatches. The seedlings often collapseall in one direction.

Damping-off caused by Pythiumusually progresses from the root tipsupwards whereas damping-off causedby Rhizoctonia solani (see opposite)usually develops from the compostsurface downwards. Damping-off isless common in trays of plug plants,where there is reduced opportunity forspread between seedlings.Nevertheless, occasionally wholetrays of plants are affected, forexample, when plants are past theiroptimum stage for potting on, or havebeen in transit for an extended period.

Cuttings infected with Pythium mayfail to root and develop a basal softrot, eventually leading to plantcollapse. Less severely affectedcuttings may go unnoticed and be

potted on. After potting, infectedplants can develop extensive root rotin wet conditions. These plants will failto make marketable quality.

Pythium root and stem base rot onrooted plantsOn rooted plants, the effect of root rotis often first seen on above-groundparts, being expressed as poorgrowth, yellowing, wilting or evenplant death. This is the result of adebilitated root system. Occasionallyjust the root tips or thin lateral rootsare decayed but more often there is

an extensive root rot affecting thewhole root ball. Affected roots appearwater-soaked, grey or brown andshrivelled. The outer cortex of the rootsometimes falls away easily, leavingjust the central vascular strand.

In non-woody species particularly,the fungus may invade the stem tocause a stem base or crown rot.Plants damaged in this mannerinclude pelargonium and saintpaulia.

A wide range of host plants aresusceptible to Pythium species.Examples of crops that are particularlysusceptible are given in Table 1.

Phytophthora root and stembase rotPhytophthora species most commonlyattack mature plants, causing a rootand ‘foot’ rot. Leaf yellowing andwilting symptoms on above-groundparts are very similar to those causedby Pythium. The disease symptomson the roots are also similar toPythium. The roots become water-soaked, brown or grey in colour, soft,and the cortex is easily removed. Onedifference between the two diseases,however, is the ability of Phytophthorato progress from roots to invade thestem base and cause a visible rot (egsolanum and poinsettia), morefrequently than Pythium.

It is relatively uncommon duringplant establishment, but there areinstances where Phytophthora cancause severe damage eg rotting ofsaintpaulia and gloxinia leaf cuttings.

Comprehensive lists of susceptiblespecies are available in text books; asummary of commonly grownsusceptible crops is given in Table 2.

Rhizoctonia root and stem base rotRhizoctonia solani is commonly foundon many nurseries and affects a widerange of hosts. The fungus causesdamping-off of seedlings, wire-stem,root rot, crown rot and occasionally aleaf and stem blight of cuttings.Generally, it causes a basal stem rotof cuttings and a crown rot of pottedplants more often than a root rot.

Seedlings infected with Rhizoctoniatend to collapse in different directions,compared with Pythium, where thedirection of collapse is more uniform.Aubretia, begonia and impatiens areparticularly susceptible. If olderseedlings become infected, damageusually occurs at soil level as acharacteristic red-brown constrictionon the stem (wire-stem). Seedlingleaves touching the surface of infestedgrowing media are rapidly invaded byR. solani and become water-soakedand rotten.

On cuttings and older plants, attackat the stem base or soil level results ina dry, light brown discolouration thatis sometimes subsequently colonisedby Botrytis cinerea. Cutting-raisedfuchsia, geranium, poinsettia and NewGuinea impatiens are all susceptible toRhizoctonia basal stem rot during orafter rooting. Saintpaulia and Begoniarex may also be affected during 8 Damping-off of aubretia seedlings due to Rhizoctonia; infection is often at compost level

6 Primula brown core (Phytophthora primulae) – characteristic brown staining within roots (left)

and resulting leaf yellowing (right)

7 Phytophthora stem base rot of solanum – this visible rot is seen more frequently than with

Pythium infections

propagation by leaf cuttings. Severelyaffected cuttings of poinsettia may failto root or produce only a poorlydeveloped root system.

On more mature plants, root rotscaused by R. solani typically show asdiscrete brown lesions along the rootlength with rotting of the corticaltissues. New root growth can beinhibited.

Crown rot can result either fromprogression of the fungus from theroots, or from direct fungal attack ofthe crown tissue. Crown rots and/orstem base canker occur on begonia,saintpaulia, poinsettia and impatiens,for example. In the canker phase, onolder plants, there is longitudinalcracking of the stem base and a dryappearance. Other symptoms include

leaf yellowing, wilting, poor growthand plant death.

Under warm, humid conditions, thefungal strands of R. solani cansometimes be seen growing over thecompost surface and occasionally aswebbing over leaves.

Some ornamental species recordedas hosts of R. solani are shown inTable 3.

Table 3Some bedding and pot plants particularly susceptible to Rhizoctonia root and basal stem rot

Disease sourcesand spread

Pythium and PhytophthoraThe most common sources of Pythiumand Phytophthora are infected cropdebris, contaminated loam, peat, sand,dust, capillary matting, non-mainswater supplies, water-holding tanks,dirty tools and unsterilised pots/trays.Pythium and Phytophthora are notseed-borne but they may be introducedto a nursery in infected cuttings or plugplants. Adult shore flies and sciaridflies can also provide a means ofintroducing and transmitting Pythium.Both pathogens produce resting sporesthat enable survival for long periods inthe absence of a growing host.

The resting spores are stimulated togerminate by exudates produced byhost plant seeds and roots. Oncegerminated, a mass of swimmingspores are produced that are readilydispersed in flowing or splashingwater during irrigation, or propagationunder mist or in water films on benchesor floors. Rapid spread can occurwhere production is on ebb andflood benches or floors. Aerial spread,

9 Water is often involved in the spread and/or development of root rots caused by species of

Phytophthora and Pythium; note the Phytophthora-affected plants (purpling) at the edge of the

flood-bench

Bedding plants (seedlings)AlyssumAntirrhinumAubretiaCallistephusCheiranthusImpatiensMatthiolaNemesiaSalviaTagetes

Pot plants (flowering)BegoniaCapsicumCinerariaCyclamenFuchsiaGloxiniaLathyrusPelargoniumPeperoniaPoinsettiaPrimulaStreptocarpus

Pot plants (foliage)CissusColeusFicusNephrolepisPhilodendronSyngoniumTradescantia

other than by water-splash ofcontaminated material, does notnormally occur.

RhizoctoniaThe most common sources ofRhizoctonia are: growing mediacontaining unsterilised loam, potsstood directly on infested ground,contaminated peat and dirtycontainers. Cuttings may also have

surface contamination of the fungusparticularly if taken from the stockplant at compost level. Rhizoctoniacan survive from one growing seasonto the next in soil and crop debriseither as resting structures or asthickened fungal strands.

Under favourable conditions,Rhizoctonia can colonise growingmedia through extensive hyphalgrowth and may spread from an

infected plant to healthy neighbouringplants by growth of hyphae betweentouching leaves or stems. The fungusonly very rarely produces spores soaerial spread of the fungus is limited.Although water does not play asimportant a role in the transmissionof Rhizoctonia as for Pythium andPhytophthora, water splash ofcontaminated material can occur.

Conditionsconducive todiseasedevelopment

Pythium and PhytophthoraInfection and spread are favoured byhigh moisture levels in the growingmedium (moisture holding capacitygreater than 70%). In general,infection can occur over a wide rangeof temperatures as long as free wateris present. However, different speciesof Pythium and Phytophthora havewidely ranging temperature optima.For example, some species ofPythium grow well at temperaturesbelow 15°C, whereas others growbest at 25–30°C. For Phytophthora,

there is negligible germination ofresting spores below 10°C and mostspecies tend to be most active in the20–30°C range.

Pythium and Phytophthora are notstrong competitors in soil, survivingmainly as dormant resting structures.These fungi tend to be moreaggressive in sterilised soils or soillessmedia because of lack of competitionfrom other micro-organisms. However,once dormant resting structures ofPythium and Phytophthora arestimulated by exudates from hostplant roots or seeds, the rapidgermination and fast growth rate ofthe fungus enable them to besuccessful invaders of plant roots.

Any cultural factors adverselyaffecting growth, such as over-watering, an excessively high

conductivity level in the growingmedium, high fertilisation rates orsub-optimal temperatures, canpredispose plants to infection.

RhizoctoniaRhizoctonia can grow and causeinfection under a wide range ofenvironmental conditions, however itgenerally grows best in growing mediathat are evenly moist and warm.Research suggests that Rhizoctoniaroot rot increases at growing mediatemperatures of 17–26°C and whenthe growing media is dry.

Factors that delay plant establish-ment or maturation may facilitateRhizoctonia attack. These include slowgermination, sub-optimal temperatures,irregular watering, excessively highnutrient levels or incorrect pH.

11 Rhizoctonia stem base rot of campanula – evenly moist and warm

growing media favours disease spread

10 High moisture levels in the growing medium favour the spread of

Phytophthora and Pythium. Here Phytophthora root rot in kalanchoe has

caused stunted growth, wilt and purpling of leaves (right)

Control strategyBecause of the ability of Pythium,Phytophthora and Rhizoctonia tosurvive for long periods in differentareas of the glasshouse environment,effective disease management isunlikely to be achieved with a singlecontrol method. Use of healthyplanting material and careful nurseryhygiene, together with appropriatefungicide use, are key factors in themanagement of root rots on beddingand pot plants.

Healthy planting material• Cuttings or plants from other

nurseries should be inspectedcarefully for signs of disease. Plantswith symptoms should be rejected.

• Where plants are being raised fromcuttings, use only those with well-developed and healthy-looking rootsystems.

• Where seedlings are being trans-planted,ensure that healthy seedlingsare selected; avoid using seedlingsfrom trays with poor emergence orother signs of damping-off.

Reducing sources of infection• Only use new or thoroughly cleaned

and sterilised pots and containers.Store them where they will not

become contaminated with dust,water or debris. Segregate old andnew pots and trays to prevent anypotential disease cross-contamination.

• It is essential to use new growingmedia from a reliable source and tostore it where it will not becomecontaminated. Growing mediashould be free-draining and notsaturated with water.

Nursery hygiene • Diseased plants and associated

growing media should be removedand discarded into a covered skipor bin (this is particularly importantwith sub-irrigation systems).

• Sand from sand benches and shouldbe regularly changed or disinfected(eg with Jet 5).

• Regularly change or disinfectcapillary matting (eg with Jet 5).Discard old or contaminated matting.

• Regularly clean and disinfect thepropagation, potting and productionareas, including tools, equipment,machinery and benches. Danishtrolleys, production troughs andfloors should also be disinfected.

• Before disinfecting, remove as muchplant debris, dirt, spent media and

dust as possible from glasshousebenches, floors and propagation beds.

• Disinfectants with activity againstPythium and Phytophthora includeJet 5 and sodium hypochlorite.The latter also has activity againstRhizoctonia. Follow the manufac-turers label and use at therecommended rate.

Note: there is a risk of phytotoxicityto plants by root uptake if ahypochlorite residue remains in asand bed or capillary matting, oron another treated surface, wherenew plants are placed.

• Eliminate standing water: treat leaksin roofs and find out why thoseniggling puddles are there and getrid of them. Check irrigation systems,especially overhead spray lines forleaks,drips or application irregularities.

• Encourage good crop hygiene instaff and pay particular attention tofootwear, as Pythium inoculum isreadily transferred from dirty to cleanareas on the soles of shoes. If footbaths are employed at the entrance tosensitive areas of the nursery, ensurethat the sterilant in them is regularlychanged otherwise they may inadver-tently become sources of diseasethemselves. And at all times thereshould definitely be no muddy boots.

12 Cuttings should be inspected carefully for signs of disease: Phytophthora stem and tuber rot of gloxinia leaf cutting, with rot progressing along

leaf mid-rib

Irrigation• Preferably use mains or borehole

water, or otherwise use water froma source where there is minimal riskof pathogen contamination.

• Check irrigation water at the pointof application several times eachyear for contamination by Pythium.Water samples can be sent forlaboratory testing to determine thepresence of Pythium species.

• Regularly clean and disinfect waterstorage tanks and irrigation lines (egwith sodium hypochlorite or Jet 5).Tanks should be covered to preventcontamination.

• Where there is a known higher risk ofpathogen contamination (eg wherewater is collected and recycled),unless this can be minimised byother means, install a facility to treatit prior to use (eg UV-light, chlorinetreatment or slow sand-filtration),particularly in propagation situations.A grower’s guide to slow sandfiltration is available from the HDC.

Pest control• As potential disease vectors, the

occurrence of shore flies and sciaridflies should be kept to a minimum.For control of shore flies, avoidanceis the best strategy; use hygienemeasures to reduce algal growth onsubstrates such as capillary matting,as this is the main food source.Routine control of sciarid flies isoften necessary on susceptiblehosts such as poinsettias and thiscan be achieved using biologicalcontrol within an IPM programme(See HDC Factsheet 08/02 foroptions).

Cultural control during production• Regular inspection of plant roots

may provide advance detection ofroot rot problems.

• Avoid checking the growth of youngplants – good growing conditionsincluding correct growing mediumnutrient levels and pH, will minimisethe potential for these diseasesto establish.

• The growing medium should be welldrained, and irrigation should beapplied only as needed to avoid

prolonged periods of saturation,eg using well managed trickle orsub-irrigation.

• Fertilisers should be appliedaccording to plant requirements foradequate growth.

• Plants, especially seedlings, shouldbe grown at temperatures conduciveto optimum growth and development.

• Manage the aerial environment tominimise surface wetness andperiods of high humidity.

• With flood irrigation, accuratecontrol of depth and duration of

flooding, combined with disinfectionof the empty floor or benchbetween crops, is important toreduce root disease risk.

Use of fungicides• Where there is a significant disease

risk, use a preventative fungicideprogramme.

• Alternate fungicides from differentgroups, and according to labelinstructions, in order to avoid thebuild up of resistant pathogen strains.

13 & 14 Adult sciarid fly (top) and shore fly (bottom) are potential vectors of disease and should

be kept to a minimum

Table 4Fungicide products with label approval for use on protected and outdoor bedding and pot plants and activityagainst Phytophthora and Pythium

Fungicide group

Thiadiazole

Phosphonate

Carbamate

Active ingredient

Etridiazole

Fosetyl-aluminium

Propamocarbhydrochloride

Product

StandonEtridiazole 35

Terrazole 35 WP

Aliette 80 WG

IT Fosetyl-AL

Standon Fosetyl-AL80 WG

Filex

Proplant

Phytophthora

Level of disease control

Pythium

( )

( )

( )

Comment

Label approval. Donot use on gloxiniaor pansy.

Label approval. Donot use on gloxiniaor pansy.

Label approval.

Label approval.

Label approval.

Label approval.

Label approval.

Fungicide useFungicide products with labelapproval for use on bedding and potplants against Pythium, Phytophthoraand Rhizoctonia are shown in Tables 4and 5.

Fungicide applicationEffective protection against Pythiumand Phytophthora requires thefungicide to be thoroughly and evenlyincorporated throughout the growingmedium. This can be achieved eitherby thoroughly mixing an etridiazoleproduct directly with the growing mediajust prior to use, or using this productor fosetyl aluminium or propamocarbhydrochloride, as a drench to thesurface. Drench treatment is usuallybest started immediately after stickingor potting. Where there is continuingrisk of attack, additional fungicideapplications will be required. For protection against Rhizoctonia,

the fungicide may only needincorporation into a shallow surfacezone (1–2 cm deep). Plants are mostvulnerable to stem and root rot attackwhen young, and become progres-sively less so as they mature. Earlytreatments are very important. Wherethere is a continuing risk of attack,additional applications will berequired. Basilex, Cleancrop Curveand Delsene 50 Flo are permitted asdrench treatments, whilst Amistar andiprodione products are permitted assprays. Note that application ofBasilex is not permitted by hand-heldequipment.

Fungicide resistanceIntensive use of certain fungicidesincreases the risk of selecting outstrains of fungal pathogens that areresistant. These fungicides thenbecome much less effective orcompletely ineffective. This hasoccurred with certain fungicides that

have been used in the past forcontrolling Pythium and Phytophthoraon pot and bedding plants but whichare no longer available (eg Pythiumspecies resistant to furalaxyl, theactive ingredient in Fongarid).

To minimise the development ofresistant strains of the pathogen,select products from two or moredifferent fungicide ‘groups’ for alternatesprays. Use no more than two spraysof the same fungicide, or fungicide‘group,’ in sequence, then use acompletely different fungicide group.

The fungicides currently approvedand widely used for several years forcontrolling these pathogens(etridiazole in Terrazole 35WP, fosetylaluminium in Aliette 80WG andpropamocarb hydrochloride in Filex)have not to date given rise to aresistance problem.Currently, effective fungicidal controlof Rhizoctonia on pot and beddingplants in the UK is very largely

control

( ) partial control

Note:

All products should be incoporated throughly

and evenly into the compost or applied as a

drench to the compost surface, according to

the label recommendation.

Table 5Fungicide products with approval for use on protected and outdoor bedding and pot plants and activityagainst Rhizoctonia

Fungicide group

Benzimidazole (MBC)

Dicarboximide

Organo-phosphorus

Strobilurin (QoI)

Activeingredient

Carbendazim

Iprodione

Tolclofos-methyl

Azoxystrobin

Product

Cleancrop Curve

Delsene 50 Flo

Rovral WP

Cleancrop Gavotte WP

IT Iprodione

Ipromex 50% WP

Standon Iprodione 50WP

Basilex

Amistar

Level of diseasecontrol

( )

( )

( )

( )

( )

( )

( )

Comment

SOLA 1213/04. Apply as adrench treatment.

SOLA 1004/04. Apply as adrench treatment.

Extrapolation under LTAEUfrom various crops. Use as afoliar spray; not approved as agrowing medium drenchtreatment.

As for Rovral WP.

As for Rovral WP.

As for Rovral WP.

As for Rovral WP.

Label approval. Apply as adrench treatment. Use byhand-held equipment is notpermitted. Do not use onheathers. An organo-phosphorus pesticide.

Permitted by LTAEU fromvarious SOLAs (eg 1684/01protected ornamentals or1041/01, outdoor andprotected celery. The latterallows up to 4 applications percrop). Use as a foliar sprayneeds to be high volume.

• The Long Term Arrangements for Extension of Use

(LTAEU) allow extrapolation of use from a label

approval or SOLA to use on an ornamental crop

at grower’s own risk. However, use must be in

a similar manner and rate as that specified on the

label or Specific Off-Label instructions; be cautious

as some treatments may prove to be phytotoxic.

• Contact the Pesticide Safety Directorate

Information Service (01904 640500 or visit

www.pesticides.gov.uk) or seek other

professional advice if in doubt about which

fungicide products are permissible on bedding

and pot plants or how to correctly use them.

• Some products recently widely used for root

disease control (eg Bavistin DF) are no longer

produced, although some stocks may still

be available.

• Always follow label recommendations, including

rate of use, and check the range of ornamentals

listed that can be safely treated. Where a product

is to be used widely on a crop for the first time,

test treat a few plants first to check for crop safety.

control

( ) partial control

reliant on azoxystrobin (Amistar) andtolclofos-methyl (Basilex). The latter isnot permitted by hand-held equipment.Instances of resistance to tolclofos-methyl have been very rare and noneconfirmed in the UK.

For further advice on strategies tominimise the risk of selecting resistantpathogen strains, see the FRAG-UKTechnical leaflet: FungicidalResistance, which can be downloadedfrom www.pesticides.gov.uk.

Biocontrol and the use of diseasesuppressive growing mediaThere is continuing interest in the

development of disease suppressivegrowing media. These may utilisebiocontrol agents, such as species ofthe fungus Trichoderma, which maydevelop during composting orsuppressive substances leached frombark such as phenolics. There are alsoproducts being marketed, eg compostteas, which claim to enhance thevigour and health of plant growth, andthereby strengthen the plant’sresistance to disease attack. Althoughthere is limited information on thereliability of such methods undernursery conditions and in comparisonwith fungicides, some results have

been promising. HDC project HNS125 is assessing the potential ofcompost teas for improving crophealth and growth in hardyornamentals.

Further informationBall Field Guide to Diseases ofGreenhouse Ornamentals by MargaretL Daughtrey and A R Chase (ISBN: 0-9626796-3-1).www.ballpublishing.com.

AcknowledgementsWayne Brough (ADAS Horticulture),Stuart Coutts and Andrew Fuller aregratefully acknowledged for help inreviewing the text.

HDC project PC 97a, Ornamentals:Sources of Pythium inoculum,fungicide resistance and efficacy ofsurface sterilants, Final report May2001.

HDC Diseases and Pests of BeddingPlants, Identification Cards.

Diseases of greenhouse plants by J TFletcher (ISBN 0-582-44263-X).Longman.

Further information: A full copy of the final

report for HDC project PC 97a is available from

the HDC office (01732 848383).

December 2004

Whilst publications issued under the auspices

of the HDC are prepared from the best available

information, neither the authors or the HDC can

accept any responsibility for inaccuracy or

liability for loss, damage or injury from the appli-

cation of any concept or procedure discussed.

© 2004 Horticultural Development Council.

No part of this publication may be reproduced in

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sion of the Horticultural Development Council.

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