RESEARCHSCIENCE FOR THE GOLF COURSEdedicated to enriching the environment of golf

Phosphonate products for diseasecontrol and putting green qualityHow does potassium phosphite stack up against fosetyl-AI in controlling Pythium blightand anthracnose basal rot?

Joshua Cook; Peter Landschoot, Ph.D.; and Max Schlossberg, Ph.D.

ethyl phosphonate), the active ingredient inAliette and Chipco Signature fungicides.

All phosphonate fungicides, whetherphosphites or fosetyl-Al, are broken downinto phosphorous acid following plantuptake. Because phosphorous acid is thecompound that controls disease, we com-pared products based on equivalent rates ofphosphorous acid. We did this by determin-ing the molecular weight of phosphorous

TREATMENT RATESTreatment

"Rate/1,000 square feet Rate/hectare

Potassium, phosphate 4.0 ounces 12'~2kilograms,.,Potassium phosphite standard .... 43.6 fluidounces 138.8 liters

"Alude 7.4 fluidounces , :'. 23.6 litersAliette , 5.7 fluidounces 17.4 kilograms

" !

.. , '5.Tfluid ounces 17.4 kilograms,Chipco Signature ,, . ,,,-

Subdue Maxx ,"!;. ,c, 3.2 liters, ~I 1.0 fluidounce

"'.' '." 'W""", ."" ',., •• '. ' mlTable 1. Treatments and rates used in the Pythium bligN'1 anthracnose "and,putting greenrquality phosphonatefungicide studies.'

phosphorous acid are referred to as phos-phites, and phosphite products typicallycontain a mixture of phosphorous acid andpotassium hydroxide (KOH). Phosphite fun-gicides (Alude, Magellan, Vital, Resyst andothers) usually list potassium phosphite ormono- and di-potassium salts of phospho-rous acid as the active ingredient on theproduct label. Esters of phosphorous acid arereferred to as fosetyl-AI or aluminum tris (0-

," ~Figure 1. A Pythium chamber (greenhouse frame covered with plastic) was used to produce conditions necessary forPythium blight development (left). An automatic misting system was used to increase humidity levels (right).

TreatmentsPhosphonate fungicides are made up of

salts or esters of phosphorous acid. Salts of

EDIIO.R'SI. note:

In their previous article ("Sorting outthe phosphonate products," GeM," "November 2005, pp. 73-77), the authors I '

reviewed phosphonate terminology, howphosphonate compounds control disease,.and their role as fertilizers. In this article,they discuss the results of phosphonatefungicide research conducted on Pythiumblight and anthracnose, as well as puttinggreen quality.

Phosphonate products differ in active ingre-dient, formulation, trade name, label terminol-ogy, uses and price. Detailed studies on howthese products perform with respect to diseasecontrol and improving turf quality should helpyou make sound choices on the most appro-priate product(s) for your specific needs. Theobjectives of our research were to determinewhether products made with potassium phos-phite or fosetyl-AI provide similar control ofPythium blight and anthracnose basal rot whenapplied at equivalent rates of phosphorous acid,the active compound for controlling diseases.We also wanted to determine whether productformulation influences disease control. Oursecond objective was to evaluate the effects ofactive ingredient and formulation on puttinggreen quality when applied at equivalent ratesof phosphorous acid.

APril200s1 GeM 93

Pythium blight trialsIn 2004 and 2005, we conducted field

trials to determine whether the active ingre-dients and formulations of different phos-phonate fungicides influence the degree ofcontrol of Pythium blight on creeping bent-grass (Agrostis palustris). We began the tri-als by seeding Penncross creeping bentgrasswithin a greenhouse frame one year beforetreatment application. The turf was mowedthree times each week at a height of 1.0 inch(25.4 millimeters), and the area was fertil-ized and watered to maintain a dense turf.Just before treatment application, the green-house frame was covered with clear polyeth-ylene plastic.

This trial was conducted in the plastic-covered greenhouse frame equipped withan automatic misting system (referred to asa Pythium chamber) to ensure warm, humidconditions necessary for Pythium blightdevelopment in central Pennsylvania (Fig-ure 1). Treatments included the phospho-nate fungicides and other treatments listedin Table 1.

TreatmentsTreatments for Pythium blight, anthracnose

and turf quality trials included a commercialphosphite product (Alude); two fosetyl-AIproducts (Aliette WDC and Chipco Signa-ture); a potassium phosphite standard (madeby mixing reagent-grade phosphorous acidwith water and adjusting the solution to a pHof 6.2 with KOH); and reagent-grade potas-sium phosphate (made by mixing reagent-grade phosphoric acid with KOH to raisethe solution to a pH of 6.2). The potassiumphosphite standard was included as a treat-ment because we knew nothing was added tothe mixture that would enhance the efficacyof the phosphite. Thus, we could evaluate theefficacy of the potassium phosphite withoutinterference from formulation effects.

Potassium phosphate (essentially fertilizerphosphorus) was applied at about the samerate of phosphorus as the potassium phos-phite treatment. This treatment was added toensure that disease suppression was not dueto a phosphorus nutrition effect.

Subdue Maxx was applied at the label-recommended rate for Pythium blight con-trol (1.0 fluid ounce/I,OOO square feet or 3.2liters/hectare) for comparison with phospho-nate. This rate of Subdue Maxx has providedexcellent control of Pythium blight in ourPythium chambers during previous studies.

the range given for Pythium blight control onthe fungicide labels and for anthracnose con-trol on the Chipco Signature label (Table 1).

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100

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80

Figure 2. The effect of phosphonate fungicides on Pythium blight development of Penncross creeping bentgrass in2004. Disease is expressed as the percentage of blighted turf. Bars above columns indicate the level of statisticalsignificance.

PYTHIUMVS. FUNGICIDES, 2004

Figure 3. Effect of phosphonate fungicides on Pythium blight development of Penncross creeping bentgrass in2005. Disease is expressed as the percentage of blighted turf. Bars above columns indicate the level of statisticalsignificance.

94 GeM I April2006

PYTHIUMVS. FUNGICIDES, 2005

acid in each product and adjusting the prod-uct rates accordingly. The rates of all of thephosphonate fungicide treatments fell within

RESEARCH

ANTHRACNOSEVS.PHOSPHONATERate/1,000 Disease severity (0-10)t

Treatment square feet Rate/hectare July 5,2005

Control 1'liI - - 5.5 abl

Potassium phosphate11)

12.2 kilograms 6.3 a ,;4.0 ounces

7.4 fluid ounces""

Alude 23.6 liters 'I 4.5 bc

Aliette 5.7ounces 17.4 kilograms 4.5 bc"-Potassium phosphite standard 43.6 fluid ounces 138.8 liters , " 3.5 cd

." ,

Chipco Signature 5.7 ounces 17.4 kilograms ~!O dm

tAnthracnose basal rot disease severity ratings based on a ,0-10 scale, where 0 = no disease and 1,0::: severedisease symptoms.tOata means within the same colurnn that a.re followed by the same letter are not significantly different from'one another.

,

" "', '"

I. I" '"Table 2. Treatment, application rate and anthracnose. basal rot disease-severity ratings for the 2005anthracnose phosphonate fungicide trial. Five treatment applications were made at two-week intervals beforethe July 5 rating date.

"

Figure 4. Plots showing the effects of potassium phosphitestandard or Hl03 (left), Chipco Signature (center), andpotassium phosphate or Hl04 (right) on symptom develop-ment of Pythium blight of creeping bentgrass.

Treatments were applied once on Aug. 30,2004, and again on July 18, 2005. Followingtreatment application, the open ends of thePythium chamber were closed, and inoculumof Pythium aphaniderrnatum was applied tothe test area. Temperature and humidity werecontrolled with vents that could be opened andclosed and an automatic misting system. At theend of each trial, all plots were evaluated for thepercentage of area exhibiting blighted turE

ResultsResults showed that Pythium blight disease

was more severe in 2005 than in 2004, prob-ably as a result of higher chamber tempera-tures in 2005 (Figures 2, 3). In 2004, phos-phonate fungicides (including the potassiumphosphite standard) provided good (>95%)control, whereas in 2005, the same treatmentsshowed only 70% to 84% control. Despiteseasonal differences in overall Pythium blightcontrol, no statistically significant differencesoccurred among the phosphonate fungicidesin either year of the study. This indicates thatproducts with phosphites and fosetyl-AI asactive ingredients provide similar Pythiumblight control (Figure 4). Results also suggestthat the formulation of individual productsdo not appear to have any advantage withrespect to Pythium blight control.

The potassium phosphate treatment andthe untreated control had no effect on dis-ease, indicating that phosphorus nutritionwas not responsible for Pythium blight con-trol. Subdue Maxx provided significantlybetter control than all treatments on creepingbentgrass in 2005, but did not differ from thephosphonate fungicides in 2004.

Trials conducted in the Pythium cham-ber represent a severe test for fungicide per-formance, and are better for measuring rela-

tive differences among fungicides than formeasuring the actual degree of control in thefield.

Anthracnose and putting greenquality trials

In 2004 and 2005, we conducted field tri-als on a putting green to determine whetheractive ingredient and formulation of differ-ent phosphonate fungicides influence controlof anthracnose basal rot and putting greenquality. The trials were conducted on an 8-year-old mixed stand of Providence creepingbentgrass and annual bluegrass (Poa annua)growing in an 80 :20 root-zone mix andmaintained as a putting green. A minimalamount of nitrogen was applied to the trialarea to encourage development of anthrac-nose. Treatments (Table 2) were similarto those in the Pythium blight trial, exceptthat there was no Subdue Maxx treatment.All treatments were applied every two weeksbeginning on May 21 and ending Aug. 13 in2004; and beginning May 4 and ending July29, 2005, for a total of seven applications ineach year. Anthracnose disease ratings wereassessed visually using a 0 to 10 scale, with10 indicating severe disease and 0 indicat-ing no disease. Because very little disease wasevident on the test area in 2004, only resultsfrom 2005 are discussed in this article. Put-ting green quality was rated every two weeks,just before treatment application, on a scaleof 0 to 10, with 10 indicating excellent turfquality and 0 indicating very poor quality.

RESEARCHResults

Anthracnose symptoms developed rap-idly on the test site during early July 2005,and the test was evaluated on July 5 after fivetreatment applications had been made. Noneof the phosphonate fungicides completelycontrolled anthracnose, but the Chip co Sig-nature and potassium phosphite standardtreatments had significantly less disease thanthe untreated control. Chip co Signature per-formed better than Aliette (both were appliedat the same rate of fosetyl-AI), indicating thatthe formulation of Chip co Signature may beenhancing disease control. The potassiumphosphite standard showed significantly lessdisease than the untreated control, indicatingthat this compound may have some benefit insuppressing anthracnose under certain con-ditions. With respect to anthracnose, noneof the other treatments differed significantlyfrom the untreated control. Although theseresults are interesting, we would like to pointout that data from anthracnose trials oftenvary from region to region and from year toyear. Nevertheless, we now have justificationfor conducting more extensive anthracnosetrials with phosphonate fungicides.

The results for putting green qualitywere similar to the anthracnose results, withthe Chip co Signature treatment providingslightly better quality than other treatmentson most rating dates during 2004 and 2005(Figure 5). The other phosphonate treatmentsusually provided better putting green qualitythan the potassium phosphate treatment and

April 20061 GeM 95

may have been partially a result of residualpigment from the Chipco Signature formula-tion; however, we attempted to minimize thiseffect by taking ratings two weeks after treat-ments were applied.

Other phosphonate fungicides providedimproved putting green quality at certain timesduring the test when compared to the control,but not as much as Chipco Signature. Cur-rently, we are unsure of why phosphonate fun-gicides improve putting green quality. Qualityimprovement does not appear to be a phospho-rus nutrition effect, but may be partially dueto a reduction of minor pathogens present inputting green turf. More-detailed research mayshed light on how some phosphonate fungi-cides improve turf quality, and provide insightsinto the environmental and management con-ditions under which this may occur.

the phosphorous acid does not have a stronginhibitory effect on the causal pathogen,Colletotrichum graminicola.

Chipco Signature also provided slightlybetter putting green quality than all otherphosphonate treatments in 2004 and 2005.Although the improvement in putting greenquality may have been partly due to anthrac-nose control, Chipco Signature plots weregreener and appeared healthier (fewer brownand thin areas) than other treatments onmost ratings dates. The enhanced green-up

HE..BESEABCIlI says ...

> We compared products made with potassium phosphite or .fosetyl-AI to determine whetherthey provide similar control of Pythium blight and anthracnose basal rot when applied atequivalent rates of phosphorous acid and to determine whether product formulation influencesdisease control.

> Products with phosphites and fosetyl-AI as active ingredients provided similar control ofPythium blight, and formulation of individual products did not appear to have any effect.

> The potassium phosphate treatment had no effect on Pythium blight control.> The Chipco Signature and potassium phosphite standard treatments had significantly less

anthracnose than the untreated control. We concluded that the formulation of Chipco Signatureis a factor in anthracnose control.

> Chipco Signature provided slightly better putting green quality than all other phosphonatetreatments in 2004 and 2005.

the untreated control during both years, butthe response was not as strong as the responseto Chipco Signature.

ConclusionsThe objectives of our study were to deter-

mine whether products made with potassiumphosphite or fosetyl-AI provide similar con-trol of Pythium blight and anthracnose basalrot, as well as enhanced putting green quality,when applied at equivalent rates of phospho-rous acid. Although levels of overall Pythiumblight control varied between 2004 and 2005,no differences were found among phospho-nate treatments in either year, regardless ofactive ingredient or formulation. Chipco Sig-nature and the potassium phosphite standardprovided some control of anthracnose, butcomplete control was not achieved.

Chipco Signature performed better thanAliette, a product containing fosetyl-Al,which was applied at the same rate of activeingredient as Chip co Signature. Based onthis observation, we concluded that the for-mulation of Chipco Signature played animportant role in suppressing this disease.It is not surprising that most phosphonateproducts did not have a pronounced effect onanthracnose, given that our laboratory stud-ies (not discussed in this article) show that

RESEARCH

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FundingThe Pennsylvania Turfgrass Council, Cleary Chemical

Corp. and Bayer Environmental Science provided fundingfor this study.

AcknowledgmentsWe thank Wakar Uddin, Ph.D., and Michael Soika for

advice, isolates and equipment used in conducting thePythium blight trials .

Figure 5. Turf-quality ratings of a creeping bentgrass/annual bluegrass putting green with an untreated control andplots treated with Aliette, Alude and Chipco Signature. Turf quality was rated on a scale of 0-10, where 10 was thehighest-quality turf.

96 GeM I April2006

Dates

5/4 5/18 6/1 6/15 6/29 7/13 7/27 8/10 Joshua Cook is a graduate research technologist, PeterLandschoot (pjl1@psu.edu) is a professor of turfgrassscience and Max Schlossberg is an assistant professorof turfgrass nutrition and soil fertility in the department ofcrop and soil sciences at Penn State University, UniversityPark, Pa.