Performance of selected phosphite fungicides on greens - GCSAA

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