Performance of selected phosphite fungicides on greens - GCSAA

<strong>Performance</strong> <strong>of</strong> <strong>selected</strong><strong>phosphite</strong> <strong>fungicides</strong> on greensPhosphite <strong>fungicides</strong> provide good results, but one stands above the rest.RESEARCHPaul Vincelli, Ph.D., and Ed DixonFor several years, Chipco Signature (activeingredient, fosetyl aluminum or fosetyl-Al) hasbeen used widely in tank-mixes for diseasecontrol on creeping bentgrass (Agrostis palustris)putting greens. Periodically, researchreports have also shown that certain tankmixesthat include Chipco Signature cansometimes provide improved turfgrass qualityindependent <strong>of</strong> the control <strong>of</strong> known diseases(9). Reasons for this improved activity are notfully understood, but we postulate that theinert components <strong>of</strong> the formulation mayhave some beneficial effect on turfgrass physiology,providing some increase in tolerance toenvironmental stresses under some conditions.The improved stress tolerance sometimes seenwith these tank-mixes is not a magic bulletagainst moderate-to-severe environmentalstress under all circumstances.Figure 1. The spray programs tested were evaluated for dollar spot control (shown above) and turf quality.Photo courtesy <strong>of</strong> Paul VincelliPhosphiteWhen absorbed by plants, fosetyl-Al isbroken down to release <strong>phosphite</strong> ions (PO3 - )in the plant tissue. (The <strong>phosphite</strong> ion issometimes referred to as phosphonate). Theway in which the <strong>phosphite</strong> ion controls diseaseis complex and still somewhat mysterious.To a degree, <strong>phosphite</strong> can inhibit growth andsporulation <strong>of</strong> disease-causing organisms,thus acting as a direct fungal toxin like mostother <strong>fungicides</strong> (1). However, <strong>phosphite</strong> alsocan trigger increased biochemical plantdefenses (1), which is not typical <strong>of</strong> mostproducts sold as <strong>fungicides</strong>.In February 1995, fosetyl-Al came <strong>of</strong>fpatent, and within a short time other <strong>phosphite</strong>-containingproducts came to market.Readers are probably familiar with several <strong>of</strong>the <strong>phosphite</strong>-type <strong>fungicides</strong> available in theirarea. Some <strong>phosphite</strong> materials currently onthe market are sold as fertilizers rather than<strong>fungicides</strong>; a number <strong>of</strong> these fertilizers wereon the market for years before fosetyl-Al came<strong>of</strong>f patent. (Interestingly, several well-conductedstudies raise serious questions aboutwhether the <strong>phosphite</strong> ion serves as a directsource <strong>of</strong> phosphorous nutrition to plants[2,3]. Some authors believe it may even be an“anti-fertilizer” where phosphorus is low [3].)Given the growth in the availability <strong>of</strong><strong>phosphite</strong>-containing <strong>fungicides</strong> and fertilizers,we initiated a field study in 2003 to testa selection <strong>of</strong> <strong>phosphite</strong> <strong>fungicides</strong> to assesswhether they provided equal levels <strong>of</strong> diseasecontrol and maintenance <strong>of</strong> turf quality(Figure 1). Our expectation was that theywould provide essentially equivalent control,but we were surprised to find some differencesin performance.Study designThe site was a soil-based Penncross creepingbentgrass putting green (mowing height0.188 inch [4.8 millimeters]) at the University<strong>of</strong> Kentucky Turfgrass Research Center inJuly 2005GCM 77

RESEARCHLexington. The site received nitrogentwice in the autumn and early winter.Before and during the summer test periods,nitrogen and irrigation inputs were minimalin order to provide a moderate level <strong>of</strong> stresson the turf.ControlsA bit <strong>of</strong> explanation <strong>of</strong> the treatmentdesign is in order because several treatmentsserve as experimental controls. Each testincluded plots treated with water only (treatment1 in all tables) and plots treated with aspray program expected to provide good diseasecontrol. The control spray program,applied every two weeks, was a tank-mix <strong>of</strong>Chipco Signature plus a full rate <strong>of</strong> Chipco26GT, alternating with a tank-mix <strong>of</strong> ChipcoSignature plus a full rate <strong>of</strong> Daconil Ultrex(treatment 2 in all tables).TreatmentsAll <strong>phosphite</strong> <strong>fungicides</strong> tested were usedat their full application rate in combinationwith a half-rate <strong>of</strong> Chipco 26GT alternatingwith Daconil Ultrex (referred to below as<strong>phosphite</strong> fungicide programs; treatments 4-7 inTables 1 and 2, and treatments 4-9 in Tables3 and 4). We used half-rates <strong>of</strong> Chipco 26GTand Daconil Ultrex in order to put the <strong>phosphite</strong><strong>fungicides</strong> through stringent testingconditions.Because we used the contact <strong>fungicides</strong>at half-rates, another experimental controlwas the application <strong>of</strong> half-rates <strong>of</strong> Chipco26GT alternating with Daconil Ultrex butwithout a <strong>phosphite</strong> fungicide (treatment 3 inall tables).Finally, in 2004 we added another experimentaltreatment, where we substitutedChipco Aliette for Chipco Signature to testthe effect <strong>of</strong> the green dye in ChipcoSignature (treatment 5 in Tables 3 and 4),and we added Magellan, another <strong>phosphite</strong>fungicide (treatment 9 in Tables 3 and 4).Data were collected on the intensity<strong>of</strong> dollar spot (caused by Sclerotinia homoeocarpa)and brown patch (caused byRhizoctonia solani), as well as on turf quality(excluding damage from dollar spot). In2003, we assessed turf quality <strong>of</strong> annualbluegrass (Poa annua) and creeping bentgrassseparately. Weather data from the University<strong>of</strong> Kentucky Agricultural Weather Centerwere examined. Selected data are presentedin the tables; details <strong>of</strong> methods and additionaldata are available in our publishedreports (4-8).2003 resultsAll <strong>of</strong> the <strong>phosphite</strong> fungicide programs2003 DOLLAR SPOT CONTROLNo. <strong>of</strong> dollar spot infection centers/plot †Treatment and rate/1,000 square feet* June 10 June 17 July 2 July 15 July 30Experimental controls1. Water 14.3 a 37.3 a 38.3 a 72.0 a 57.3 a2a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 4 fluid ounces alternated with2b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 3.2 ounces 2.7 b-e 0.0 f 0.0 c 0.3 cd 0.0 i3a. Chipco 26GT 2SC 2 fluid ounces alternated with3b. Daconil Ultrex 82.5WDG 1.6 ounces 2.0 cde 1.0 def 0.0 c 0.7 cd 5.7 cdePhosphite fungicide programs4a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with4b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 0.7 de 0.3 ef 0.0 c 0.0 d 1.7 ghi5a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with5b. Resyst 45.8% 5 fluid ounces + Daconil Ultrex 82.5 WDG 1.6 ounces 3.7 a-d 1.3 def 1.0 bc 1.0 cd 7.7 b-e6a. Vital 4.2L 6 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with6b. Vital 4.2L 6 fluid ounces + Concorde 82.5WDG 1.6 ounces 1.3 cde 1.0 def 0.7 bc 2.0 c 10.0 be7a. Alude 5.17L 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with7b. Alude 5.17L 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 3.0 b-e 1.3 def 0.0 c 1.0 cd 9.3 bcd*Applications <strong>of</strong> the two tank-mixes were alternated at two-week intervals between May 28 and July 23.†Means within the same column followed by the same letter are not significantly different.Table 1. Dollar spot control, 2003 test.78 GCMJuly 2005

tested provided good control <strong>of</strong> dollar spot(Table 1). Surprisingly, however, we did seedifferences among <strong>phosphite</strong> spray programsin dollar spot control. On most assessmentdates, there was no significant difference indollar spot control achieved by the <strong>phosphite</strong>fungicide programs. On later assessmentdates, small but statistically significant differencesemerged, with Resyst, Vital and Alude(treatments 5-7 in Table 1) all providing lesscontrol than the Chipco Signature program(treatment 4) on July 30, 2003.All <strong>phosphite</strong> fungicide programs tested(treatments 4-7 in Table 2) providedimproved turfgrass quality when compared tothe water-treated control (Table 2) and sometimesdid not differ from one another.However, in 2003, statistically significant differenceswere evident among the <strong>phosphite</strong>fungicide programs, with Resyst, Vital andAlude (treatments 5-7 in Table 2) providingsome reduction in turf quality compared tothe Chipco Signature program (treatment 4)in several assessments. During the testperiod, there were several sustained periods <strong>of</strong>rainfall deficit.2004 resultsDollar spot pressure was less intense in2004 than in 2003. As in 2003, all <strong>phosphite</strong>fungicide programs provided good control <strong>of</strong>dollar spot, with no significant differencesamong <strong>phosphite</strong> fungicide programs onmost assessment dates (Table 3). On July 26,RESEARCH2004, a slight but significant reduction in dollarspot control was observed in the Resyst andAlude programs (treatments 6 and 8, Table 3)as compared to several other <strong>phosphite</strong> fungicideprograms.No consistent, statistically significant differencesin turf quality were observed amongthe various <strong>phosphite</strong> fungicide programstested (treatments 4-9 in Table 4). However,only the Chipco Signature and ChipcoAliette programs (treatments 4 and 5) providedturf quality statistically higher than thewater-treated control (treatment 1) in allassessments. There was no difference in turfquality between the Chipco Signature program(treatment 4) and the Chipco Alietteprogram (treatments 5). The generally mild2003 TURF QUALITY Creeping Poa Overall turfbentgrass † annua † qualityTreatment and rate/1,000 square feet* July 2 July 22 June 25 July 10 June 22 Aug 5Experimental controls1. Water ND ND ND ND 4.7 e 3.3 hi2a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC4 fluid ounces alternated with2b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 3.2 ounces ND ND ND ND 7.7 a 6.3 abc3a. Chipco 26GT 2SC 2 fluid ounces alternated with3b. Daconil Ultrex 82.5WDG 1.6 ounces ND ND ND ND 6.8 abc 4.7 efgPhosphite fungicide programs4a. Chipco Signature 80WG 4 ounces + Chipco 26 GT + 2SC2 fluid ounces alternated with4b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 8.0 a 8.0 a 7.3 a 6.3 a 7.5 a 5.3 b-e5a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC2 fluid ounces alternated with5b. Resyst 45-8%SL 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 7.3 a 6.3 b 5.3 b 4.3 b 6.3 bc 5.0 d-g6a. Vital 4.2L 6 fluid ounces + Chipco 26GT 2SC2 fluid ounces alternated with6b. Vital 4.2L 6 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 7.7 a 6.0 b 5.3 b 5.0 ab 5.7 cde 4.3 fgh7a. Alude 5.17L 5 fluid ounces + Chipco 26GT 2SC2 fluid ounces alternated with7b. Alude 5.17L 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 7.3 a 6.0 b 5.3 b 3.7 b 6.0 bcd 6.7 abNote. Turf quality was scored on a 1-9 scale, where 9 = excellent turf health. Dollar spot damage was excluded from turf-quality assessments.*Applications <strong>of</strong> the two tank-mixes were alternated at two-week intervals between May 28 and July 23.†ND, no data. Means within the same column followed by the same letter are not significantly different.Table 2. Turf quality, 2003 test.July 2005GCM 79

RESEARCHtemperatures in 2004 coupled with mildrainfall deficits <strong>of</strong> short duration resulted inlower levels <strong>of</strong> weather-related stress on theturf than in 2003.ConclusionsThe <strong>phosphite</strong> fungicide programs tested allprovided good control <strong>of</strong> dollar spot and someimprovement in turfgrass quality. However, ourdata revealed unexpected but statistically significantdifferences in both disease control and turfgrassquality among the products tested, especiallyunder more stressful growing conditions.The Chipco Signature program was consistentlyin the top statistical grouping with respect toboth disease control and turfgrass quality. Thedifferences among <strong>phosphite</strong> fungicide programstypically were modest, but small improvementsmay be meaningful given the high aestheticexpectations and the pronounced agronomicstress that can occur on putting greens.Although most <strong>of</strong> these products differslightly in chemistry <strong>of</strong> the active ingredient(different cations associated with the <strong>phosphite</strong>ion, for example), it seems unlikely thatthis would account for the observed differencesin performance. We suspect that the differencesin performance we observed are dueto differences in formulation (inert ingredientsand other aspects <strong>of</strong> formulation, manyaspects <strong>of</strong> which are proprietary). We currentlyare participating in an ongoing multistatestudy led by Erik Ervin, Ph.D., atVirginia Polytechnic Institute, Blacksburg,Va., which we hope will shed some light onthis question.Disclosure statementCleary Chemical Corp. and Regal Chemical providedpartial funding toward the cost <strong>of</strong> conducting the 2003test; funding was not solicited in 2004. Funding was neithersolicited nor received from Bayer Corp. for this study.Literature cited1. Guest, D., and B. Grant. 1991. The complex action <strong>of</strong>phosphonates as antifungal agents. BiologicalReviews 66:159-187.2. Förster, H., J.E. Adaskaveg, D.H. Kim and M.E.Stanghellini. 1998. Effect <strong>of</strong> <strong>phosphite</strong> on tomato andpepper plants and on susceptibility <strong>of</strong> pepper toPhytophthora root and crown rot in hydroponic culture.Plant Disease 82:1165-1170.3. McDonald, A.E., B.R. Grant and W.C. Plaxton. 2001.Phosphite (phosphorous acid): its relevance in theenvironment and agriculture and influence on plantphosphate starvation response. Journal <strong>of</strong> PlantNutrition 24:1505-1519.4. Vincelli, P., E. Dixon, D. Williams and P. Burrus. 2004.Influence <strong>of</strong> spray programs with phosphate <strong>fungicides</strong>on turf quality in a mixed creeping bentgrass/2004 DOLLAR SPOT CONTROLNo. <strong>of</strong> dollar spot infection centers/plot †Treatment and rate/1,000 square feet* June 28 July 6 July 12 July 19 July 26Experimental controls1. Water 16.7 ab 19.7 a 23.7 a 11.0 a 7.7 a2a. Chipco Signature 80WG 4 ounces + Chipco 2SC 4 fluid ounces alternated with2b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 3.2 ounces 0.0 i 0.0 d 0.0 d 0.0 c 0.0 f3a. Chipco 26GT 2SC 2 fluid ounces alternated with3b. Daconil Ultrex 82.5WDG 1.6 ounces 2.3 e-h 0.3 d 1.3 bcd 1.3 bc 2.3 a-ePhosphite fungicide programs4a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with4b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 1.3 f-i 0.0 d 0.0 d 0.0 c 0.7 ef5a. Chipco Aliette 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with5b. Chipco Aliette 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 1.3 e-i 0.0 d 0.3 cd 0.0 c 1.3 def6a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with6b. Resyst 45.8%SL 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 4.3 cde 0.0 d 2.3 bc 0.3 d 4.0 abc7a. Vital 4.2L 6 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with7b. Vital 4.2L 6 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 0.0 i 0.0 d 0.0 d 0.0 c 0.0 f8a. Alude 5.17L 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with8b. Alude 5.17L 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 2.7 d-g 0.0 d 2.3 bc 0.0 c 4.0 abc9a. Magellan 53.5%L 4.1 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with9b. Magellan 53.5%L 4.1 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces. 1.0 ghi 0.3 d 0.0 d 0.0 c 0.3 ef*Applications <strong>of</strong> the two tank-mixes were alternated at two-week intervals between May 20 and July 28.†Means within the same column followed by the same letter are not significantly different.Table 3. Dollar spot control, 2004 test.80 GCMJuly 2005

RESEARCHPoa annua soil-based green, 2003. Fungicide andNematicide Tests 59:T009.5. Vincelli, P., E. Dixon, D. Williams and P. Burrus. 2004.Efficacy <strong>of</strong> <strong>fungicides</strong> for control <strong>of</strong> dollar spot in amixed creeping bentgrass/Poa annua soil-basedgreen, 2003. Fungicide and Nematicide Tests59:T019.6. Vincelli, P., E. Dixon, D. Williams and P. Burrus. 2004.Influence <strong>of</strong> <strong>fungicides</strong> on turf quality in a mixedcreeping bentgrass/Poa annua soil-based green,2003. Fungicide and Nematicide Tests 59:T020.7. Vincelli, P., E. Dixon, D. Williams and P. Burrus 2005.Influence <strong>of</strong> spray programs with <strong>phosphite</strong> <strong>fungicides</strong>on turf quality in a mixed creepingbentgrass/Poa annua soil-based green, 2004.Fungicide and Nematicide Tests (in press).8. Vincelli, P., E. Dixon, D. Williams and P. Burrus. 2005.Efficacy <strong>of</strong> <strong>fungicides</strong> for control <strong>of</strong> dollar spot in amixed creeping bentgrass/Poa annua soil-basedgreen, 2004. Fungicide and Nematicide Tests (inpress).9. Vincelli, P., J. Doney and D. Williams. 1998. Effects <strong>of</strong><strong>fungicides</strong> on turf quality <strong>of</strong> creeping bentgrass,1997. Fungicide and Nematicide Tests 53:451.THE RESEARCH says . . .Paul Vincelli, Ph.D. (pvincell@uky.edu), is an Extensionpr<strong>of</strong>essor and Ed Dixon is a research analyst in thedepartment <strong>of</strong> plant pathology at the University <strong>of</strong>Kentucky, Lexington.➤ This study compared programs using Chipco Signature, Chipco Aliette, Daconil Ultrex,Alude, Resyst, Vital and Magellan.➤ Compared to the water-treated control, all the <strong>phosphite</strong> <strong>fungicides</strong> provided good dollarspot control in both years and improved turfgrass quality in the more stressful year, but theChipco Signature program was consistently in the top statistical grouping in all assessments.➤ We do not know why these differences in performance occurred, but we suspect that inertingredients and other aspects <strong>of</strong> the formulation may be the cause.2004 TURF QUALITYOverall turf quality †Treatment and rate/1,000 square feet* July 27 July 28 Aug 2Experimental controls1. Water 4.8 e 3.3 c 5.2 e2a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 4 fluid ounces alternated with2b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 3.2 ounces 7.0 ab 7.3 a 7.0 abc3a. Chipco 26GT 2SC 2 fluid ounces alternated with3b. Daconil Ultrex 82.5WDG 1.6 ounces 5.3 cde 4.3 bc 5.5 dePhosphite fungicide programs4a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with4b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 6.3 a-d 6.3 ab 6.7 a-d5a. Chipco Aliette 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with5b. Chipco Aliette 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 7.0 ab 7.0 a 7.0 abc6a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with6b. Resyst 45.8%SL 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 5.8 b-e 4.7 bc 5.5 de7a. Vital 4.2L 6 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with7b. Vital 4.2L 6 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 6.0 a-e 5.7 ab 6.3 a-e8a. Alude 5.17L 5 fluid ounces + Chipco 26GT 2Sc 2 fluid ounces alternated with8b. Alude 5.17L 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 5.3 cde 4.7 bc 5.5 de9a. Magellan 53.5%L 4.1 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with9b. Magellan 53.5%L 4.1 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 5.8 b-e 4.7 bc 5.7 cdeNote. Turf quality was scored on a 1-9 scale, where 9 = excellent turf health. Dollar spot damage was excluded from turf-quality assessments.*Applications <strong>of</strong> the two tank-mixes were alternated at two-week intervals between May 20 and July 28.†Means within the same column followed by the same letter are not significantly different.Table 4. Turf quality, 2004 test.July 2005GCM 81