Investigations into Compost Tea for the Control of Plant Pathogenic Fungi

8/9/2019 Investigations into Compost Tea for the Control of Plant Pathogenic Fungi

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Brinton, Trnkner - Woods End Agrar u. Umwelt Page 1

INVESTIGATIONS INTO LIQUID COMPOST

EXTRACTS (TEAS) FOR THE

CONTROL OF PLANT PATHOGENIC FUNGI

William F. Brinton

Andreas Trnkner 1

(Extract from Biocycle Paper presented in Phoenix, AZ)

Introduction

The potential disease suppressive characteristics of composts is well known

an d is the su bject of increa sing scient ific effort s, dat ing from rep orts a s ear ly as 1973(Hun t et a l, 1973). New int eres t is seen with t he u se of liquid extra cts for disease con-

tr ol. Compost seed-dips an d plan t a nd soil spra ys based on compost a nd oth er plan t

materials have been reported from organic farming literature since from as early as

1924 (Koepf, 1992).

The presence of highly developed microbial communities in the rhizosphere

(root-region) of plan ts h as long been kn own, but a comp ar able flora on th e leaf su rfac-

es has only been more recently recognized. This area of research was first developed

when Las t (1955) an d Ruinen (1956) coined th e term phyllosphere for th e leaf sur face

microbial ha bita t in ana logy with rh izosph ere. With th e organ izat ion of th e first sym-posium on th is ar ea by Preece and Dickinson (1971), th e stage was set for new ap pr e-

ciation of th e m icrobial populat ion of the leaf surface with respect t o host- path ogen

interactions. Eventually, phyllospheric effects moved into the focal point of research

on the biological contr ol of leaf diseases an d emp ha sis on ant ifun gal propert ies of wa-

ter y extra cts of composts is evident from a bout 1986 to th e pr esent (Weltzien, 1986;

Tr nk ner , 1993). Thus, a bout a 30-year incubat ion has been involved in gett ing to

where we a re pr esent ly with a basic un derst an ding of compost tea s to comba t leaf dis-

ease. It is unfort un at e tha t th ere ha s been so litt le scientific inter est in this ar ena u n-

til quite recently. The u ncerta inty a bout form ulat ing proprietar y techn ologies based

on compost is th e most frequent ly cited rea son for t he slow developmen t (Trn kn er,

1993).

1. Support for this research is acknowledged from the Biodynamic Farming and Gardening Association, the

Center for Biomedical Technology (CIBT) and the Wilhelm-Friedrichs University, Bonn

William Brinton is chief scientist, Woods End Research Laboratory and Andreas Trnkner is Associate Prof.

Microbiology, Wilhelm-Friedrichs University, Bonn


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Compos t t eas as herein in tended should not be confused with use of

leacha tes collected off comp ost sites, alth ough th e lat ter m ay also possess nut rien t

an d potentia l fun gicidal properties. It should also not be equa ted with compost hu -

mic extra cts, compost microbial star ters, a nd oth er similar pr epar at ions. Compost

tea s, also called wat ery-compost-extra cts, r efer to a more deliberat e pr oduction of

specific extr acts a nd spr ayin g un dilut ed based on composts of kn own pr operties an d

age (York an d Brint on, 1995). Several different types of na tu ra l spra ys have been

compared with specific compost teas and compost teas do not necessarily always

perform well (OFRF, 1994). This paper will discuss some of the potentials and pit-

falls involved in t his work.

Th e use of compost ext ra cts differ s significa nt ly from th e repor ted use of solid

compost u sed in cont ainer -media to supp ress da mping off and root-fun gal diseases

(Spr ing et al.,1980; Hoitink , 1980). Wat ery comp ost extra cts described in t his pa per

ar e applied directly to plan t su rfaces via convent iona l high-pressur e spra ying ap pa-

ra tu s. The extra cts a ct directly in varying degrees to suppr ess both th e germ inat ion

an d growth of plan t pat hogenic organ isms a nd ar e efficacious for short periods of

time (Ketterer , 1990; Tr nk ner , 1993).

The Needs and Obstacles to Implementing Compost Teas in Agriculture

A num ber of serious a gricultu ra l problems ar eas exist presen tly which a re of

imm ediat e possible cand idat es for applications of comp ost extra cts. These ar e chief-

ly where fungal diseases sta r t an d spread from leaf an d stem surfaces. Examples

are apple scab (Venturia ina equalis), downy a nd powdery m ildew on gra pes (Plas-

mopara viticola, Uncinula necator) an d Botrytis infections of vegetables and small

fru its. Crop da ma ge by these fungal pests in th e US a lone is in t he $-billions/year .

Of special concern is the worsening si tuat ion in potato cultur e with Late

Blight causative Phytopthphora infestans showing n ew genotypes with in crea sing

resistance to conventional fungicidal treatments (Dowley, 1981). While chemical

spra ying program s can still resu lt in sat isfactory cont rol, it h as become a subst an -

tia lly more complicat ed and costly und ert ak ing. Su ccessful resea rch an d imp lemen -

ta tion th is area using biocont rols is likely to have extrem ely importa nt agronomic

and economic impacts. Despite this apparent fact, many agricultural officials re-main unconvinced that compost based disease suppression is likely to prove eco-

nomical in the near fut ure an d th ere is cont inued concern tha t spraying live cul-

tu res of ma nu re-based extr acts, which ar e likely to conta in opport un istic pat ho-

gens, m ay be h ygienically problema tic (USDA, pers. comm .).


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Mode of Effects of Compost Extracts

Compost teas exert influence in the so called phyllosphere (plant surface)

th rough a coatin g with actu al live bacteria (NOTE: see ph oto sh owing scann ing elec-

tron microscopic view of leaf su rface sprayed with compost tea) . The principal

agents in the composts extra cts a ppear to be bacteria r epresenting but not neces-sari ly limited t o the genera of Bacillus, Pseud om onas, S erratia, Penicillium , and

Trichoderma (see photo). In examining normal composts, we have found that the

ma jori ty of bacteria in m oderately-mat ur e m aterials a re facultat ive an aerobes or

aerobes. Species such as Enterobacteria, Serratia, Nitrobacter, Pseudomonads, Ba-

cillus, Staphylococcus and various Actinom ycetes are al l present (Droffner et al .

1995). Thus, it seems likely th at ma ny composts possess poten tial disease sup pres-

sive traits.

There is no single mechanism explaining effects of compost extracts against

pa th ogens . To da te, th e effects of compost extra cts ha ve been divided int o severa l cat -egories (Kett erer , 1990; Beicht , 1981;Bud de & Weltzien, 1990):

Inh ibition of spore germina tion

Ant agonism and competition with pat hogens:

Induced resista nce against pat hogens:

The p rima ry source of the effects observed with compost t eas is appa ren tly of

a live, microbiological n at ur e (see bioassa y photos). St erilized or m icron filtered com-

post extra cts usu ally exhibit significan tly redu ced a ctivity against pat hogens (Weltz-

ien, 1986). Th is does not ru le out th at in some cas es ster ile extr acts will possess sup-pressive effects. Th ere is some evidence th at chemicals called siderophores, pseudo-

bactins and pseudomycins produced by Pseudomonas exert a powerful chemical

suppr essive effect of other organ isms (Kloepper , 1980; Poter a, 1994). Ant ibiotics ha ve

been obser ved to be formed by B. subtilis and inhibit the germination and/or growth

of ma ny fun gi. Also, an emer ging field of stu dy is the ar ea of indu ced or a cquired r e-

sistan ce. Ample evidence is being seen th at microbes wheth er pa th ogenic or n ot can

cau se th e induction of plan t int ern al defenses. For exam ple, by inoculat ing cucum ber

leaves with the bacteria Colletotrichum lagenarium , the infected leaves not only be-

cam e resistan t toward C. lagenariu m , but a lso toward a ll oth er pa th ogens of bacterial

and viral natu re. In fact, the concept of induced systemic resistance was coined for

this phenomenon (Kuc et al., 1975). An overview of the use of microbial metabolites

to induce resistance ha s r ecently been presented (Schnbeck an d Dehne, 1986). It

ma y or not be ironic tha t difficulties a nd hygienic concerns about using live extr act

compost sprays are avoided by using metabolites from compost cultures for stimulat-

ing plan t r esistan ce. However, this work is still in its infancy.


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Based on existing information, it is clear that successful use of compost ex-

tr acts for disease cont rol needs to be evalua ted in r elation to specific cultivars an d

specific fun gal pat hogens. In ma ny r eport ed cases pat hogens ha ve been cont rolled

by compost teas to levels similar if not better than conventional fungicidal treat-

men t (Ketter er, 1990; Tr nk ner , 1993) (see Table 5). However, t he findings a lso

suggest th at differen t m odes of prepa ra tion of th e water y compost extra cts ma y be

requ ired to sat isfactorily tr eat differen t diseases un der var ying field circum sta nces.

It is conceivable that in the not-too-distant future on-farm laboratories will extract

and prepare enrichment extracts and sterile metabolites from on-farm wastes and

use t hem in pest bio-cont rol program s. New developmen t effort s by our group an d

other s to work out field bioas sa y techn iques su ch as in su ppr ession of growth of Bot-

ryt is by comp ost extra cts (see bioas sa y photo) ma y per mit gr owers t o screen for fun-

gicidal a ctivity pr ior t o costly imp lemen ta tion; however, t his work is far from com-

plete.

Four Step Approach to Making Compost Extracts For Fungicide Sprays

There ar e four sta ges in th e pr ocess of pr epa rin g compost teas: pr epa ra tion, ex-

tr action, filtra tion an d indu ction. Ea ch sta ge has a few specific cond itions. (See photo

of spra y tan k an d orcha rd spr aying at Golden Hooves Far m, CA)

1. P REPARATION STAGE: Fresh compost is blended with t ap water in a

dilut ion ra tio of 1 par t: 5-10 pa rt s (vol/vol). The ideal ra tio must be exper -

iment ally derived. Wooden ba rr els or la rge ta nk s ar e preferred. To be

avoided ar e pest icide/bio-cide ta nk s even if pr evious ly was hed .

2. E XTRACTION: Allow to sta nd at 15-25o C, over 3-8 da ys, stirr ing 2-3

times dur ing th is period. A highly aerobic mix is N OT required. Stirring

is performed either with a rod or r ota ting bar, or a ny kind of pum ping-

agita tion, for a bout 30 minu tes a t ea ch event , during th e life of th e

extract.

3. F ILTRATION: The best a pproach is to decan t from par tway u p fron t he

bott om of th e ta nk an d pass t hr ough a 200 mesh (75-micron) sieve.

Determ ine in adva nce the operat iona l spray rig nozzle sizing so th at

clogging does not occur. To avoid ser ious filtr at ion pr oblems, do n ot st ir

mixtu re within 8 h our s of filtering.

4. IN DUCTION: Apply the extra ct p eriodically at or p rior t o the t imes of

fun gal infection p ressu re u sing convent iona l plant protection spr aying

equipmen t. It is highly advisable to add a wetter /sticker a gent, but it

mu st be pre-screen ed for a nt imicrobial propert ies using a sta nda rd m ico-

bial challenge pr ocedur e.


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Assuming all the proper steps are taken, the most significant factors influ-

encing the effectiveness of watery compost extracts are considered to be the age of

th e compost itself an d th e na tu re of th e sour ce ingred ient s which go int o it. It should

be noted that some wetter-sticker (surfactant) agents commonly used with fungi-

cides have been found to be microbially su ppressive, spoiling th e effects int en ded for

of th e compost tea s. Woods En ds Lab in Mt Vern on Main e an d other microbial labs

like BBC Labora tories in Temp e, Arizona offer a screen ing service to pre-test t hes e

agents .

Farm and Commercial Composts to Combat Fungal Disease

Both far m a nd comm ercial agricultur al composts possess qualities tha t ma y

lend th emselves to disease suppr ession. Given t he a bility of ma ny farm ers t o pro-

du ce th eir own, an d th e likelihood th at some of th ese composts ma y alr ead y possess

fungicidal properties, then more widespread use for biological control is within

sight . However, far ms d eprived of livest ock m ay be t he m ost in n eed of microbiolog-

ically rich composts. Biodiversity studies tabulating biocontrol potentials on vary-

ing far ms a re only recently gett ing under way.

This mu ch being said, it is obvious t ha t wh ile th e th eory of compost t ea d is-

eas e contr ol is easy to gra sp, it is oper at iona lly more difficult . The h eter ogeneit y of

compost source mat erials an d th e lack of sta bility or r elative imm at ur ity of ma ny

comm ercial composts is likely to limit th e u sefulness of this a pproach (Trn kn er,

1993). If comp ost leacha te is subst itu ted for pr epa red comp ost tea s, th ere is no gua r-

antee that it will possess the same properties as a prior batch. Even given a good

comp ost, the impr oper ha nd ling or poor t iming of ap plicat ions could frus tr a te grow-

ers efforts to achieve success in the field. Thus, the need exists to define the quali-

ties tha t ma ke for high value composts an d to determ ine the mea ns of prepa ra tion

an d ap plicat ion n eeded t o achieve consisten t field effects. In Eu rope, emph as is is on

th e u se of th e Dewar Flask met hod (see Biocycle, Nov 1995) to determ ine relat ive

age of the compost (compost n ot older t ha n cat egory IV is u sed). In one stu dy, we

det erm ined th e efficacy of differen tly aged horse ma nu re compost again st Fu sa riu m

wilt of clover seedlings (see Ta ble 1) and foun d 8-week old pr oduct wa s significa nt ly

super ior t o 20 week pr oduct.


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Table 1: Effects of extracts made from various ly aged ho rse man ure

compo st on infect ion rate of clover seed l ings

wi t h Fusari um cu l morum

Compost of varying organ ic ma ter ials such as leaves, yar d debris an d str aw,

can sh ow var ying disea se supp ress iveness, with a loss of th e ability after a s litt le as

3 month s of agin g. Comp osts conta inin g ma nu res (horse and da iry) ha ve sh own sig-

nifican t an tifun gal propert ies in some cases up to 9-12 m onth s of age (Dit tm er,

1990).

In an oth er st udy we compa re t he efficacy of var ious extr acts pr epar ed from

differin g subst ra tes (Table 2). Recen tly, some biosolids compost extr acts h ave been

found t o possess some fungista tic poten tials aga inst t he fungu s B. cinerea tha t af-

fects bedding plan ts (Warn er, 1995).

Pr eservat ion of compost t ea effects is problema tic, since th ey mu st be used

within one-week or less of the extraction. However, in one set of studies, the an-

tipa th ogenic effectivenes s was lengt hen ed thr ough drying th e comp ost pr ior to stor-

age and the natural fungicidal propert ies were el ici ted later af ter remoistening

(Dittm er, 1991; Tr nk ner , 1995, personal comm un ication). The disea se supp ress ion

char acter istics of comp ost teas h as so far n ot been considered t o ha ve a r elat ionsh ip

to pH or oth er chem ical tr ait s, an d is definitively as sociat ed with facult at ive an aer -

obes more t ha n str ict a erobes and can be dependent on t he n atu re of th e compost

subst ra te (see Table 2).

Age of

compost

Infection

index

a

a. treatments followed by the same letter are not significantly

different at P 0.05

8 weeks 0.53 a

12 weeks 0.61 a

20 weeks 0.78 b


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Table 2: Influe nce of various natu ral substrates on th e infect ion

of Tomat oes exposed t o Fusari um oxysporum

* treatments followed by the same letter are not significantly different at P 0.05 by Duncans test

after Trnkner, 1993.

Solid Compost vs. Liquid Extracts

In a ddition t o comp ost tea s, th ere is cons idera ble basis for soil applicat ions of

macro amounts of finished compost. Compost is well known for imparting suppres-

siveness dir ectly to th e soil (Kloepper , 1980). In a ddit ion, t ria ls ha ve shown signif-

ican t differen ces in a nt iphytopath ogenic effects between composts, green ma nu res

and l ivestock manures. In one study, soils receiving composts over three years

showed increa sing an tipat hogenic tr aits again st S . trifoliorum , with some ins ta nces

of 100% contr ol. Soils receiving fresh green was te a nd non-comp osted livestock m a-nu res over t he sa me per iod in cont ra st gave no pat hogen reduction (Ditt mer , 1991).

In other words, use of solid compost applied directly to soils or container media

should not be cur ta iled even when compost tea s ar e available.

The d ifferen ce between th e use of soil-ap plied composts a nd wat ery comp ost

extracts can perha ps best be summ arized in th at th e teas give immediate but very

short-term control of surface spreading pathogens, while soil composts act more

slowly over a longer period of tim e an d requ ire mu ch lar ger am ount s. For long term

effects in solid med ia, it is not un usu al th at a t very least 5% by volum e an d often a s

mu ch as 40% comp ost in th e seedling mix ar e requ ired t o brin g about effective dis-eas e contr ol (Bud de & Weltzien, 1990). In cont ra st, a wh ole hecta re of vineyar d can

be covered wit h ext ra ct prep ar ed from only less t ha n 100 k ilos of comp ost (York &

Brinton, 1995).

Substra te for E xtract Infection index0.5 g inoculu m

Control Soil, Ap-Horizon 0.91 d*

Bark humus 0.64 a

CommercialYardwaste Compost

0.78 c

Prepared Soil:clay:peat+fer t ilizer 0.72 b

Horse Manure compost 0.60 a


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Seed Dips or Seed-Baths with Compost Teas

Seeds dips with ma nu re composts h ave long been a dvocat ed by biodynamic

far mer s in Eu rope. Cur ren t resea rch shows the su ppressive effects of th e teas a s dip

ar e appa ren t with cont rol ofPythium on alfalfa (Tab le 3). It is clear t ha t increa sed us e

by farmers of seed-baths should and could be made as a substitute for conventionalseed coat ings with quest iona ble fun gicides such as Cap ta n.

Table 3: Effect of various seed treatments on incidence of Pythium on

alfal fa se edl ings a f ter 6 days ge rminat ion

A significant in creas e of compost usa ge in Ca lifornia vineya rds ha s been noted

(Fetzer , 1995). As an overview, we have surveyed resea rch tr ials condu cted in Europe

employing various ma nu re compost extr acts in cases involving comm on fun gal pests

of gra pes (Table 4). The da ta indicat e sat isfactory to excellent cont rol in man y cas es.

Seed treat ment

Pr oport ion (%) of Pyth ium -infected a lfalfa seed lings incompost seeding substr at e

Steamed Untrea tedIn fected soil

cover

Untrea ted 6 a* 17 a 43 a

Soaked in Wat erfor 1 hour

4 ab 23 b 36 b

Soaked in Compostextract,1 hour

1 c 6 c 15 c


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Table 4: Prepa rat ion, use a nd results of com post

extracts for reduc ing grape fungi (Trn kn er, 1992)

In virtu ally all the viticultur e cases, the significan t reduction of the pest inquestion has been observed in conjunction with a yield increase. The results for each

individua l trial ha ve been pr eviously reported (Tr nk ner , 1992).

Compost Extracts Compared to Standard Fungicides

How does compost tea per form compar ed to common fun gicides? We examin ed

res ear ch which concern ed itself with H orse manu re comp ost tea effects over two yea rs

versus sulfur an d convent iona l fun gicide on gra pes (Table 5 see a lso Ph oto).

Ta ble 5: S p ra y e ffe cts o n d ow n y m ild ew ( P l a s m o p a r a v i t i c o l a ) in cid en ce o n

w ho le gra pe s in the Ahr-Valley (Kettere r, 1990).

* Treatments followed by the same letter are not significantly different at P 0.05 by Duncans test

800-1,500 liters/ha sprayed each time for 12 intervals over the season

Gra pe Disease Cau sat ive Agent

Plasmoparaviticola Botrytiscinerea Pseudopezizatracheiphila Uncinulanecator

Compost Tea Type: Horse Dairy Horse Horse

Extract Rat io 1: 9 1: 4 1: 10 1: 3

Extract Time 3 days 7 d 7-14 d 3 d

Spraying In terva l 8 - 14 d 7 - 10 d 12 d 10 d

Disease Reduct ion 90 % 48 % 55 % 94 %

TREATMENTBerr y Infection I nd ex (%)

light infectionseason

Hea vy infectionseason

CONTROL 10.5 b* 83.5 a

Wet table Sulfur 16.5 a

Sulfur + Compost Extract 3.0 c

Compost Extract 3.5 c 20.0 c

Standard Fungicide 2.0 c 7.5 c


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In both a light and heavy infection year, composts performed very well and re-

su lted in significan t reduction over contr ols, and did not differ significan tly from st an -

dar d fun gicides.

These an d other results u nderscore the significan t effects tha t properly pre-

pa red comp ost teas can a chieve when us ed in subst itu tion for, or in conjunction with,sta nda rd fungicide cont rol program s. Increa sed resear ch an d tr ials in t he field is like-

ly to promote th is valu e-ad ded composting on an even br oader scale in agricult ur e.

SELECTED REFERENCES FOR COMPOST EXTRACT STUDIES

Brin ton, W.F. (1994), Use of Compost Teas for Fu nga l Pa th ogen Cont rol. Biodyna micsVol. 3

Beicht , W. (1981) Indu ction of Resista nce in P lan ts by Microbial Met abolites. Disser-ta tion, U niversity Ha nn over.

Budde, K. an d Weltzien, H .C. (1990) The u se of compost extr acts a nd subst ra tes forcombating Erysiphe graminis( in German ) , 6th Intern at iona l Symposium onGra in Diseases, Ha lle, 5-9 Nov 1990, Pa rt II, 527-528

Dittm er, U. (1991) Un ter suchu ngen zu den Wirku ngen des Kompostierun gsprozessesun d zum Antipa th ogenen P oten tial von Komposten gegen Sclerotnia spp. undPseud ocercosporella herpotrichoides [Investiga tions in to th e effects of th e com-posting process and on t he a nt ipat hogenic effects of composts on S clerotnia tri-foliorum , S clerotinia sclerotiorum und Pseudocercosporella herpotrichoides]Disserta tion, U niv. Bonn

Ditt mer , U. et al. (1990) Der Einfluss der Kompostieru ng von Kompostsu bst ra ten u nd

wsserigen Kompostextrakten auf verschiedene Pflanzenkrankheitserreger,[The influen ce of comp ost subst ra tes an d compost extra cts on var ious plan t dis-eases], Gesunde Pflanze 42: 219-235

Droffner , M.L, W. F. Brint on an d E . Evan s (1995). Evidence for th e P rominence ofWell Characterized Mesophyllic Bacteria in Thermophilic (50-70oC) Comp ost-ing E nvironmen ts. Bioma ss Bioener gy 8: 191-195.

Gross-Spangenberg, A. et al. (1993) Ein neues biologisches Verfahren zur Verrin-gerun g des new organic met hod for trea ting ap ple scab], in Zerger, U. (Ed.),Forschung im kologischen Landbau, SL-Reprints, 42: 238-243

Fet zer, J (1995) personal com m un ication . Ceago Vineyard s, Ukiah , CA

Hoitink, H.A.J . (1980) Composted Bar k: a lightweight medium with fun gicidal p rop-ert ies. Plant Disease 64:561-565

Hu nt , P.G., Sma rt , G.C. & C.F. En o (1973) Sting N ema tode, Belonolainus logicau da-tus, immotility indu ced by extra cts of composted mu nicipal r efuse. J rn l. Nem-atol. 5:60-63

Ketterer, N. (1990) Untersuchungen zur Wirkung von Kompostextrakten auf den


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Blatt befall der Kar toffel und Toma te du rch Phytophth ora infestans sowie au fden Befall der Weinr ebe dur ch Plasm opara viticola, Pseudopeziza tracheiphilaund Un cinu la necator, [Research into the effect of compost extracts on potatoan d tomato leaf infections thr ough P. infestan s a s well as the incidences ofgrap e diseases] Doctoral Dissert at ion, U niv. Bonn

Ketterer, N. and Weltzien, H.C. (1988) Wirkung von Kompost- und Mikroorganis-men -Extr ak ten au f den Befall der Kart offel durch Phytophth ora infestans, [Ef-fects of compost extracts and microorganisms on incidences ofP. infestans inpotatoes], Comm. . Biol. Bundesanst. Land- und Forstwirtsch.: 245:346 (ab-stract)

Koepf, H.H. (1992) Biodyna mic Fa rm ing: Principles an d P ra cticeAnt hr o. Press, NY

Kloepper , J .W. et a l. (1980) Pseudomonas siderophores: A mechanism explaining dis-ease su ppr essive soils. Cur ren t Microbiology 4:317-320

Kuc, J., Shockley, g. and Kear ney, k., 1975: Pr otection of cucumber again st Colletot-richum legenar ium by Colletotrichum lagen ar ium. Ph ysiol. Pl. Pat hol. 7, 195-

199.

Last , F.T., 1955: Seasona l incidence of Sporobolomyces on cerea l leaves. Tra nsa c-t ions Br it. Micol. Soc. 38, 221-239.

Magdoff, F . (1996) personal communication , Un iversity of Vermont , Dept of Pla nt an dSoil Science

OFRF (1994) Californ ia Organ ic Fa rm ing Resear ch F oun dat ion, Newsletter on Fu nd-ed P rojects 1993-94 Includin g Biocont rol and Compost Tea P rojects

Potera, C. (1994) From Bacteria: A new weapon against fungal infection. Science265:p605

Pr eece, T.F. an d Dickinson, C.H., 1971: Ecology of Leaf Sur face Microorgan isms.Academic Pr ess, London, 640p.

Ruinen , J ., 1956: Occur ren ce of Beijerinckia species in th e ph yllospher e. Natu re 177,220-221.

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Sam erski, C. an d Weltzien, H.C. (1988) (in Germa n) Unter suchu ngen zum Wirk un gs-mecha nismu s von Kompostextra kten im Pa th osystem Zuckerr be - Echt er Me-hltau , (Investigations into th e mecha nism for compost extract effects onSphaerotheca fuliginea in su gar beets ), Z.PflKra nk h.P flSchut z, 95: 176-181

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Documents

Investigations into Compost Tea for the Control of Plant Pathogenic Fungi