CA1119512A - Biological control of soil borne pathogens - Google Patents

Abstract

????

BIOLOGICAL CONTROL OF SOIL BORNE PATHOGENS

Abstract of the Disclosure A method is described for controlling seedling diseases such as root rot and damping-off, said diseases caused by soil born pathogens of the type including Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, the method of comprising treating the plant, seeds or the soil in which they are to be planted with a fungal microbial antagonist of the Corticium species, such as Corticium sensu lato.

Description

- 1 - 'I 119512-Background of the Invention As an alternative to chemical control of plant pathogens such as bacteria and fungi, the use of natur-ally occurring biological agents provide many advantages.
The use of biologicals should reduce the environmental impact of chemicals as well as providing safety advan-tages to non-target life forms.
The use of microbial antagonists for biological control of plant pathogens can be considered as a specific alternative to chemical control. The antagonist in the natural state normally exists but at levels far too small to produce a beneficial effect. However, it should be possible to use an antagonist which normally is native in such a way as to overcome the soil-borne pathogens by either being present in such numbers as to destroy the pathogen or inhibiting its growth by utilizing its normal food supply. This invention describes the conditions under which soil born pathogens can be controlled by a microbial antagonist. With crops such as sugar beets, soybeans, beans and the like, root rot, crown rot, damping off, and other seedling diseases crease a serious econo-mic problem. Seed treatment or soil amendment with a chemical fungicide such as pentachloronitrobenzine (PCNR) can be effective but the use of naturally occurring bio-logical agents would be desirable.

Detailed Description of the Invention Root rot, damping off and other seedling di-seases are caused by soil borne pathogens such as of the Rhizoctonia, PhYtophthora, PYthium, Fusarium, or Sclerotia species. A fungus, Corticium sensu lato, antagonistic to the noted soil born pathogens has been found to be effective in the biological control of these pathogens.
The fungus can be utilized by coating seeds with it or by using it as a soil amendment.
The antagonistic fungus, characterized by mycelial clamp connections, was isolated from sugar beet residue from western Nebraska. In culture and apparently

-2- 11~951Z
in soil, it produces reddish-brown sclerotia which may help it survive for long periods. The fungus has been identified as Corticium sensu lato, referred to here-after as Corticium.

Example 1 Seed Treatrnent In culture, Corticium parasitized various Rhizoctonia solani isolates. Its potential as a bio-logical control agent was tested by coating seeds with Corticium and determining if these seeds were protected against Rhizoctonia. Fungal material for coating seeds was produced by growing Corticium on a liquid growth medium for 14 days, collecting and air-drying the fungal mat and grinding the material to a desired particle size.
Seeds were coated by dipping them into a methyl cellulose solution and rolling them in ground Corticium of either a coarse or fine particle size. Other seed treatments included methyl cellulose and PCNB coated seeds, and un-treated seed, PCNB being a fungicide active against the _. solani pathogen. These seeds were planted either in unamended greenhouse soils or in soils amended with R.
solani pathogenic to sugar beets. Plant stands recorded after 2 weeks are summarized in Table I. In Rhizoctonia-infested soil, seedling emergence from Corticium- and PCNB-coated seeds was about the same and significantly higher than seedling emergence from untreated and methyl cellulose coated seeds. These results indicate that Corticium and PCNB protected sugar beet seeds from damp-ing-off caused by R. solani.

- 111951'~

T~BLE I

Comparison Between Corticium sensu lato and PCNB as a Sugar Beet Seed Protectant Against ~hizoctonia solani in Soil _________________________________________________________ Seed Percent of Plants Emerged Treatment w/o R. solaniw/R. solani - Untreated 6~abl 5 f Methyl cellulose 47 cd 2 f Corticium coarse mycelium 67a 55bc Corticium fine mycelium 62ab 24 e PCNB (slurr ) 44 d 31 e Y

lvalues followed by the same letter are not significantly different at the 5% level.
Example 2 Corticium was also tested as a soil amendment to control _. solani. Three different soils were amended simultaneously with R. solani plus ground Corticium mycelium, R. solani only, Corticium only, or left unamended. Untreated seeds were planted in these soils immediately after amendments were incorporated and percent seedling emergence was recorded after 2 weeks. Soybean seed and . solanl pathogenic to soybeans were used in sterilized sand and sterilized loam while sugar beet seed and R. solani pathogenic to sugar beets were used in field soil from Western Nebraska. The average percent seedling emergence of 4 successive plantings in these soils are shown in Table II. Higher seedling emergence of soybean and sugar beets resulted from untreated seeds of these 2 crops planted in soils amended with Corticium and R. solani than in soils amended with R. solani only. This indicated that Corticium added to soil protected seeds and seedlings against damping-off caused by . solani.

mb/ - 3 -~119SlZ

In control soils without R. solani, Corticium used either as a seed coating (Table I) or added to the soil (Tablc II) caused no reduction in seedling emergence and many times increased it over controls. Survival of R. solani in soil with Corticium significantly declined in 9 months in the greenhouse when compared to soils with R. solani only.
Corticium survived much better than R. solani during this period.
T~BLE II
.~
Performance of Corticium sensu lato Against Rhizoctonia solani in Three Different Soil Types Average Percent of Soybean or Sugar Beet Plants Emerged in 4 Successive Soil Amendmentl Plantings Sovbean Sugar Beet Sterilized Sterilized Field Sand2 Loam Soil - None 42a 57c 18e Corticium mycelium 54a 66c 37 fg R. solani 12 b 4 d 23ef R. solani +
Corticium mycelium 58a 19 d 50 g lall soil amendments were added simultaneously at the be-ginning of the experiment.
2values followed by the same letter are not significantly different at the 5% level.
Results from extensive greenhouse studies showed that seed decay and seedling blight (damping-off) of sugar beets caused by Rhizoctonia solani is reduced substantially by coating the seed with Corticium. Similar results were obtained when seeds were coated with the antagonistic fungus and planted in a sugar beet field that had a very high amount of _. solani. In greenhouse studies, higher seedling emergence of sugar beets resulted from untreated seeds of soybeans and sugar beets planted in soil simultanc-ously amended with R. solani and the antagonistic mb/ 4 ~1195~2 func3u~s than in .soils amended ~litll R. _olani only. Sur-vival of ~ solln in soil with the anta(3onistic fun(3us signif icantly declined in ~ months in the greenhouse when compared with soils with R. solani only. ~ihen 5 compared as seed treatments or soil amendMents, the fungici(le PCNn and the antac3Oni,tic ruo(Jus y.lve nearly e-lual protection a(3ainst seedling dampiny-of ~ caused by R. solanl but the anta(3onist protection hac3 greater longevi ty .

l~xample _ Greenhouse _rial__eed Treatments The greenhouse studies evaluatinc~ ~seed treat-ments involved the followinc3 treatments with f ield soil from southeastern Nehraska:
15 Treatments:
1. Soil heavily infested with R. solani ancl planted with untreated seed;
2. Same as treatment 1 except seed was coated with Corticium, the antagonistic fungus;
20 3. Same a.s 1 except soil was not infeste(l with 1~. sl)lani;
4. Same as 2 except soil was not infested wi~ . s~ ni.
The yreenhouse trial comprised of 4 treatments was repeated six times with essentially the same results.
Out of 32 seeds for each treatment, plantecl in 4 repli-25 cated pots with 8 seeds/pot, the results sumarized inTable III were obtained. These results are representa-tive of each of the six greenhouse trials.

11195~l2 lAUrr III
Iffcct o~ (`oating ';ugar neet Seed with C_r_ic_um Sensu Lato to R. solani on incidencc of dampinc3-off _/
________________________________________________________ No. o Seedlings Seedling Treatment _merc3ed out of_ _2 seec1s_ _emerc3erlce Soil in~esteci~ith R. solalli 1. Untreatecl seed 1 0.03 2. Seed coated with Corticiurm fungus antagonistic to _. Solani 10 31-Untreated soil (no r~. solani)

3. Untreated seed 12 37

4. Seed coated ~ith Corticium antagonis-tic fungus 14 40 a/ The suyar beet seed was of poor quality as only 60%
was viable.
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ ~ _ _ _ ~rom the results of these trials it is apparent that:
1. The fungus Corticium sensu _ato gave good ~rotection to suc3ar beet seeds and seecllings against damping-off caused by R. solani. ~bout 31% of the seedlings emerged from seeds treated with the antagonis-tic fungus and plantecl in soil heavily infested with1~. solani (Table III). Only 0.03% of the seedlings emerged from nontreated seeds plantecl ir- soil infested ~ith _. solani. Seedling emergence from untreated ancl treated seec3 planted in soil free of R. solani was 37%
and 40%, respectively.
2. Seeds treated with Corticium sensu lato and planted in soil free of R. solani consistently gave higher stands tllall untreatec3 seed planted in the same soil. This .suggests that the antagonistic fullyus pro-tccts thc gcrminating ~sce(ls and sccdlill(~i from pathoc3ens othc~r t~lan i~. solal-i.

~119SlZ

~xam~le 4 Greerlhouse Trials Soil ~mendlTlents . ~
Tllree c3ifferent soils, two different Rhizoctonia isolates, and seed of two diferent crop plants were used in this study. Untreated soyhean seed and a soybean iso-late of R. solarli were used in steril.ized sancl and steri-_ _ . . _ lized loam. ~ntrc?ated suyar ~eet ce(l and a su(lar beet isolate of R. solani were usecl in fielcl soil from we.stern ~ebraska. The soils were simultaneously amended with the treatments inclicatecl and plante~ to 4 succes~sive crops of untreated seed. The average percent seedlin~3 elnergence a~ter 2 weeks i shown in Table IV.
Treatments (soil amendments) 1. I~]one 2. Corticium mycelium 3. R. solani 4. R. solani + Corticium mycelium ~ l` IV
Performance of C _t_ ium sensu lato ~gainst ~hi~octonla s_lani in Three Different Soil Types _________________________________________________________ ~verage ~ercent of soyhean or .sugar beet ~lant.s emerged in 4 ___successiv__~a_tln-~s __ __ _ 1/ _ _____oybean _ _ __ ___ Su(3ar Beet Soil amendment- Sterilized Sterilized _ _____ __ ______ ___ Sanc3_ _____Loam __ Fi C? ld Soil None?` 42a2/ 57 c 18 e Corticium mycelium 54a 66 c 38 fq R. solani 12 b 4 d 23 ef R. solani ~ Corticium myc;elium 58a 13 d 50 g _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ . _ _ _ . . _ _ _ _ . _ . ~
1/~11 soil am-ndlllents were aclded simultaneously at the ~e-ginning of the experiment.
2/Vall]cs ~ollowccl hy thc same letter are not si~nificant-ly llifr-~ lt~ t ~ c 5~ lc~v~l.
_________________________________________________________ lli(3hcr seedling emer(3ellce o~ soy~ean ancl sugar beets resulte(l 1rom untreated scec3s o~ these two erops planted in soils amended with Cortieium and R. solani than in soils amended with R. solani only. This indi-eated that _orticium adde(~ to soil proteeted seecls andseec31inys against damping-ofE causec3 by 1~. sc)l<ln_.
Survival of I~. olani in soil with Co icium signifi-eantly deelin~d in 9 morltlls in the greenilouse when eom-. pared with soils with R. _olanl only. Cortieium sur-vived mueh better than _. solani during this period.

Lxample 5 Field Trial ~ sugar beet field was used for this study.
This field had a high ineidenee of R. solani on sugar beets (blaek rot) in 1976. In the trial, sugar beets were planted on September 3 and eounts of seedlin~J
emergenee were made on September 13, 15, 18, and 20.
The sced used had a c3ermination rate of ~,0%. Thrce seed treatments were used.
Treatments ___ _ 1. Seed was not treated.
2. Seed was eoated with the fungus Cortieium, antagonistie to R. solani.
3. Seed was treated with the antagonistie fungus that hacl been ~illecl by steam heat ~ just before ~laeing it on the seed.
1,000 seeds were planted for eaell treatment.
See(31ing emergenee for the above three treat-ments on September 15 was as follows:
Only 15~ of the untreated secds produeed seecl-lings.
~bout 35% of the seeds treated with the antago-nistie funyus ~rodueed seedlin~3s. This is more than twiee the number produeecl by the untreatecl seeds.
The c3eaci anta(3onistic furl~3us (3ave no ~ otection - a~3airls~ I~. _olani. C)rlly 1190 Or tile sccds coated with tl)e dcad allta90rlistiC fU11~3US gave rise to seecllirl~3s.

" lil9512 Dam;)ing-off of suyar beet seeds and seecllings was reduced greatly in a fielc3 with a hi~h amount of R. solani by coatinc~ the seed with Cort _ium. The re-sults from this field trial were comparable to those obtainecl from cJreenhouse stuclies.
The oryanism Corticium sen.su lato appears to be ubiyuitous in soil and has ~een isolated as a single sclerotium. It has isolation inteyrity with respect . to morphology and there has been no evidence toward mutation. In a dry state, a mycelia-sclerotia mixture has maintained viability for one year at 25 deyrees C.
It can be used for scccl coating or soil applications.
The organism is yrown via still culture with yields averaging 12 grams per liter. It is yrown in a potato-dextrose broth made by sliciny 300 grams of potatoes to which is added 50n milliliters (ml.) of distilled water. The potatoes are steamed until soft and the broth is then strained. Distilled water is adcled, if nccc~ssary, to yielcl a volume of 50n ml.
20 grams of dextrose is added to the potato broth which is then sterilized by autoclaviny.
Various conventional techniques can be used in culturing the organism and which can be summarized as Lollows:
a. Flasks - 50 ml. media-still for 14 days;
aeration, 25 degrees C. 30 deyrees C.
or more results in sclerotia.
b. Plates - (100 ml. petri dishes) using

5 ml. depth - still - 3 days. Evaporate to mycelial-sclerotia dry film.
shorter version of the techniquc has becn to grow in flas};s for 2 clays and then pour into plates as thin film and allow to pro--ceed for 4 days more.
Beyinnin(3 at 5 days a dark wine-red cul-turc filtrate is formcd. Thcrc is no hioantayonistic activity in ~~ilt:ra~es.
~fter clryiny of the film, material can he groun(l in a suitable mill.

", lll951Z
c. ~olid culture - rerlite used as the base in 250 ml. flasks: 100 ml. ~erlite and 50 ml. of potato de~trose broth; 25 de-grees C.
S Tl-is microbial antagonist to soil born patho-may be utili~ed eEfectively in divcrsc formulations"
il~cluding the agronomically acceptahle aclj~lvants ancl carriers normally employecd for facilitating the dis-. ;~ersion of active ingredients for agricultural appli-cations, recognizing a known fact that the dosage, formu-lation, mode of application of a pest control a(3ent and other variables may affect its activity in any given appli-cation. Thus, the previously described antagonist may be formulated as a suspension or dispersion, in aqueous or nonaqueous media, as a dust, as a wettable powder, as an emulsifiable concentrate, as a yranule, or as any of several other known types of formulations, depencling on the desired mode of application. These compositions may bc applied as sprays, c]ust, or granules to the see(ls, soil or plant situs against which activity is desired.
In order to provide compositions in the form of dust, granules, water dispersible powders, aqueous c~ispersions, or emulsions and dispersions in organic liquids, the carrier or dilucnt acJcnt in ~such formula-tions may be a finely divided solid, an organic liquid, water, a wetting agent, a dispersing agent, or emulsify-illCJ agent, or any suitable combination of these. General-ly, when liquids and wettable powders are r)repared a con-ditionirlg agent comprisinc3 one or more surface-active agents or surfactants is present in amounts sufficient to render a (~iven com~osition containing the active material, the microorganism, dispersible in water or in oil. The microorganism, the fungi Corticium _ensu lato, is obtained by fermentation procedures. To convert it to a form which will facilitate the preparation oE the fol-lowing described compositions, a slurry is prcr)are(l which i.s thell dLic?d onto a prim.lry, agronolnically ac(el~tc~l)le carrier such as vermiculite, whereby the microorganism -1 1- lll9S12 is adsorbecl onto the carrier. l`he micrOoryanism, ac]sorbed OlltO the earricr, becomes the concclltrate for preparincl the clesired composition. If desire(l, the slurry ean be used as the concentrate for fungal antagonist compositions.
The surface active acJent used in the invention can be a wettiny, dispersinc~ or emulsifyinc3 ayent which will assist dispe~r~sion of the effeetivc comE)osition. The surface-activ~ agent or surfactant can include SUCIl . anionic, cationic anci nonionie agents as have heretofore been generally employed in plant eontrol eompositions o similar types. Suitable surfaee-aetive agents are set forth, for example, in "~etergents ancl Emulsifiers" 1971 Annual by John W. I~leCuteheon, Ine.
In general, 1-10% by weight of the surface-aetive agent will be used in eompositions of this inven-tion and ordinarily the amount of surfaee-aetive agent will range from 1-5% but may even be less than 1% by weiyht.
~dditional surfaee-aetive agents ean be adcled to formulations to inerease the ratio of surfaetants:
aetive incJreciients up to as high as 5:1 by weight. Sueh eomE~ositions may have a yreater bioloyieal efectiveness than can be exE,ectecl when the eomponents are usecl separ-ately. When uscd at hic3her ratios, it it preferrecl that the suraetant be present in the range of one-fifth to five parts surfaetant for eaeh one part of aetive ayent.
~ The following are more detailed formulations exemplifyiny the various eompositions.

~.xample 6 ~ettable Powders Wettable powders are water-dispersible eompo-sitions eontaininy the aetive material, an inert solid extender, ancl one or more surfaetants to provide rapi(]
wetting and to prevent heavy floceulations wherl sus-pcnclccl in watcr.

` 1~1951Z

l'he inert extenders which are preferred for use in the wettable powders of this invcntion containing the active compounds are of mineral origin.
Extenders suitable for the wettable powder formu-lations of this invention are the natural clays, diatomaceous earth and synthetic mineral fillers derived from silica and silicate. Most preferred fillers for this invention are kaolinites, attapulgite clay, montmorillonite clays, synthetic silicas, synthetic magnesium silicate and calcium sulfate dihydrate.
Among the more preferred surfactants are the nonionic and anionic types. They are most suitable for the preparation of dry, wettable products of this invention and dispersants.
Occasionally a liquid, nonionic compound which is primarily an emulsifier, may serve as both wetter and dispersant.
Most preferred wetting agents are alkylbenzene and alkylnapthalene sulfonates, sulfated fatty alcohols, amines or acid amides, long chain esters of sodium isethionate, esters of sodium sulfosuccinate, sulfated or sulfonated vegetable oils, and ditertiary acetylenic glycols. Preferred dispersants are methyl cellulose, polyvinyl alcohol, lignin sulfonates, polymeric alkylnapthalene sulfonates, sodium napthalene sulfonates, polymethylene bisnap'nthalene sulfonate and sodium-N-methyl-N-(long chain acid) taurates.
Wetting and dispersing agents in these preferred wettable powder compositions of the invention are usually present at concentrations of from about 0.5 weight percent to 5 weight percent. The inert extender then completes the formulation. Where needed, 0.1 weight percent of the extendcr may be replaced by a corrosion inhibitor or an antifoaming agent or both.

,, mb/ - 12 -111951'~
Thus, wettable powder formulations of the invention will contain from about 25 to 90 weight percent active material, from 0.5 to 2.0 percent wetting agent, from 0.25 to 5.0 weight percent dispersant, and from 9.25 to 74.25 weight percent inert extender, as these terms are described above.

mb/ - 12a -1~1951Z

~`~h('11 ~:h(` ~ et:tat)le p0W!ler C0ntCli11s a C(>rrOSiO!1 inhibit(>r or a1l a1ltifol1ninc3 IC3ent or botll, thi eorrosion inhibi~or shoull not e-xeeed about l pcreellt of thc e~)n~
sition, and the a1ltitoamin~3 agc?nt shoulc3 not exeeecl a!~ut 0.5 1ereent t>y weic311t o~ tlle eomposition, botll rer)1a:in~3 e(~uivalellt amc)ullts of t,lle inert e~t.ellc3er.

rxam~>le 7 _ _ _ _ . _ _ _ _ ~usts _ Dusts are 3c?n.se powcler eompositionc, whieh are intende~-] Lor ap~ eation in ciry form. nuSt~S are eharae-terizec3 by their free-[lowinc3 and rapi`3 settling proper-ties so that they are not readily winc1t)-)rll to areas where their presenee is not desirecl. ~hey eontain pri-marily an active inc3redient an~ a dense, ~ree-flo~7in~3, solid exten(ler. Thcir performanee is sometimes aidecl by the inelusio1l of a wettin3 a(3e1lt ancl eonvenienee in manufaeture Lrequently demandci the ine1usion of an inc-rt absorptive ~3rinc]in(3 aic].
The wettable powder as deseribecl above ean also b~ u.e-1 in the preC)aration oL dust,. ~1hilc ,ueh wettahlc powders ecln be used direetly in dust ~orm, it is rnore advantac3c-ou.s to dilute them by blen-1inJ with the dense 3uit dilueilt. In this manner, (]is~er.iin1 a(JentC;l eorro-sion inhieitors, anl alltifoarn ayents may also be used as comporlel~ts o[ a c1ust.
I`huc, the duit eompciitio1ls oF thi-. invention ean eomprise ~rom al)o1lt 0.5 to 20.0 wei~3ht peree1lt aetive in3rcdiellt, 5 to 25 weigllt pcrecnt ~iller, () to 1.0 wei(~ht prreerl~: wf?ttirlg a~3ent and ~rom about 30 to 90 weight per-c(-nt den;e, fr(~e-~lowinc3 exten(3er, aci thcsc t--rms ar u~ec31,(rein. ~ueh dust: I:ormulatiolls ean eortain, in a,3ditic)ll, mi.nor amoullts o~ di.spersant~ci, corrosic>ll in-hibitoLs, an(1 a1ltio;lm a(3ents 3erive(1 Lrom the wetta,le ~,;w<ler-; use(l t-~ make t11e dust.

--I ,,--F,xanl~le ~
~mulsif_able O_ls Emulsifiable oils are usually solutions of sus-pensions of active material in nonwater miscible solvents together with a surfactant anc3/or emulsifier.
For compositions of thi~s invention, emulsi~iable oil compositions can be made by mixing the active ingredi-ent with an orc3anie solvent and surfactallt. Suitable solvents for the compositions o~ this inventioll are chlorinated solvents, water immiscible ethers, esters, or ketones alone or in admixture with arolnatic hydrocar-bons. Suitable surfactants are those ionic or nonionic agents known to the art as emulsitying agents.
~mulsifying agents most suitable for the emul-sifiable oil compositions of this invention are long chainalkyl or mercaptan polyethoxy alcohols, alkylaryl poly-etiloxy alcohols, sorbitan fatty acid esters, polyoxy-ethylene ethers with sorbitan fatty aci-3 esters, poly-ethylene glycol esters with ~atty rosin acids, ~atty alkylol amide condensates, calcium and amine salts of fatty aleohol sul~ates, oil soluble petroleum sulfon(~tes, or preferably mixtures of these emulsifying agents. Such emulsifying agents shoulc3 comprise from about 1 to 10 weigllt percent of tlle total eomposition. ~s described above, however, up to 5 parts of emulsifyinc~ agent for eaeh part of active ingredient ean be used.
Thus, emulsifiable oil eompositions of the present invention ean eonsist of from about 10 to 50 weight percent aetive ingredients, about ~0 to 32 perccnt solvents, and about 1 to 10 weight percent emulsifier, as these terms are defined and used above.

~_a~le_~
Granules ~,ranules are~ physically stable, particulate c(~m~-O~.itions c~>llt:a;n;rlg Illycelium~ sclerotia ~"- spores ol ~h;s inVelltiOn whicl~ adl~eL-( to or uL-c~(3i~ ril)u~e-1 Lhrough a basic matriY~ Or a coherellt, inert carrier with lll~SiZ

microscopic dimensions. In ordcr to aid leaching of the active ingredient from the granule, a surfactant can be present.
The inert carrier is preferably of mineral origin, and suitable carriers are natural clays, some pyrophyllites and vermiculite. Suitable wetting agents can be anionic or nonionic.
For the granule composition of this invention, most suitable carriers are of two types. The first are porous, absorptive pre-formed granules, such as preformed and screened granular attapulgite or heat expanded, granular, screened vermiculite. On either of these, a suspension of the active agent can be sprayed and will be absorbed at concentrations up to 25 weight percent of the total weight.
The second type are initially powdered ]caoline clays, hydrated attapulgite or bentonite clays in the form of sodium, calcium or magnesium bentonites. Water-soluble salts such as sodium salts may also be present to aid in the disintegration of the granules in the presence of moisture. These ingredients are blended with the active components to give mixtures that are granulated, followed by drying to yield formulations with the active component distributed uniformly throughout the mass. Such granules can also be made with 25 to 30 weight percent active component but more frequently a concentration of about 10 weight percent is desired for optimum distribution. The granular compositions of this invention are believed to be most useful in a size range of 15-30 mesh.
The most suitable wetting agents for the granular compositions of this invention depend upon the type of granule used. When pre-formed granules are sprayed with active material in liquid form, the most suitable wetting ., ~ mb/ - 15 -~ll95~Z

agents are nonionic, liquid wetters miscible with the solvent. These are more gencrally known in the art as emulsifiers and comprise alkylaryl polyether alcohols, alkyl polyether alcohols, polyoxyethylene sorbitan mb/ - 15a -~S~

11195:12 fatty acid esters, polyethylene glycol esters with fatty or rosin acids, fatty alkylol amide concentrates, oil soluble petroleum or vegetable oil sulfonates, or mix-tures of these. Such agents will usually comprise up to about 5 weight percent of the total composition.
When the active ingredient is first mixed with a powdered carrier and subsequently granulated, liquid nonionic wetters can still be used, but it is usually preferable to incorporate at the mixing stage, one of the solid, powdered anionic wetting agents such as those previously listed for the wettable powders. Such agents should comprise about O to 2 weight percent of the total composition.
Thus, the preferred granular formulations of this invention comprise about 5 to 30 weight percent active material, about O to 5 weight percent wetting agent, and about 65 to 95 percent inert mineral carrier, as these terms are used herein.

Claims (12)

the embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows:

1. A microbial antagonist concentrate for the preparation of compositions effective to control soil borne pathogens selected from the group consisting of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said concentrate comprising the microorganism Corticium sensu lato adsorbed on an agronomically accep-table carrier.

2. The concentrate of Claim 1 wherein the soil borne pathogen is Rhizoctonia solani.

3. A microbial antagonist concentrate for the preparation of compositions effective to control soil borne pathogens selected from the group consisting of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said concentrate comprising a slurry of the microorganism Corticium sensu lato.

4. A microbial antagonist composition for the control of soil borne pathogens selected from the group consisting of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said composition compris-ing the microorganism Corticium sensu lato and an agro-nomically acceptable carrier.

5. The concentrate of Claim 4 wherein the soil borne pathogen is Rhizoctonia solani.

6. A wettable powder composition useful in the control of soil borne pathogens selected from the group consisting of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said composition com-prising:
25-90% of the microorganism Corticium sensu lato, 0.5-2% of a wetting agent, 0.25-5% of a dispersant, and 9-75% inert extender.

7. A dust composition useful in the control of soil borne pathogens selected from the (group consist-ing of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said composition comprising:
0.5-20% of the microorganism Corticium sensu lato, 5-25% of a dense filler, 0-1% of a wetting agent, and 30-90% of an extender.

8. An emulsifiable oil composition useful in the control of soil borne pathogens selected from the group consisting of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said composition compris-ing:
10-50% of the microorganism Corticium sensu lato, 40-82% of a suitable solvent, and 1-10% of an emulsifier.

9. A granule composition useful in the con-trol of soil borne pathogens selected from the group consisting of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said composition comprising:
5-30% of the microorganism Corticium sensu lato, 0-5% of a wetting agent, and 65-95% of an inert carrier.

10. A method for controlling the growth of soil borne pathogens selected from the group consisting of Rhizoctonia, Phytophthora, Pythium, Fusarium or Sclerotia species, said method comprising exposing the said pathogen to a microorganism comprising Corticium sensu lato.

11. A method of protecting crops selected from the group consisting of sugar beets, soybeans and beans from seedling diseases caused by soil borne pathogens se-lected from the group consisting of Rhizoctonia, Phyto-phthora, Pythium, Fusarium or Sclerotia species, said method comprising coating the seeds of said crops with a microbial antagonist to said pathogen comprising the microorganism Corticium sensu lato or adding said micro-bial antagonist to the soil in which said seeds are planted.

12. The method of Claim 11 wherein the soil borne pathogen is Rhizoctonia solani.