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RESEARCH

Performance of selected phosphite fungicides on greens

Phosphite fungicides provide good results, but one stands above the rest.

Paul Vincelli, Ph.D., and Ed Dixon

For several years, Chipco Signature (active ingredient, fosetyl aluminum or fosetyl-Al) has been used widely in tank-mixes for disease control on creeping bentgrass (Agrostis palustris) putting greens. Periodically, research reports have also shown that certain tankmixes that include Chipco Signature can sometimes provide improved turf grass quality independent of the control of known diseases (9). Reasons for this improved activity are not fully understood, but we postulate that the inert components of the formulation may have some beneficial effect on turf grass physiology, providing some increase in tolerance to environmental stresses under some conditions. The improved stress tolerance sometimes seen with these tank-mixes is not a magic bullet against moderate-to-severe environmental stress under all circumstances.

Figure 1. The spray programs tested were evaluated for dollar spot control (shown above) and turf quality.

Phosphite

When absorbed by plants, fosetyl-Al is broken down to release phosphite ions (P03-) in the plant tissue. (The phosphite ion is sometimes referred to as phosphonate). The way in which the phosphite ion controls disease is complex and still somewhat mysterious. To a degree, phosphite can inhibit growth and sporulation of disease-causing organisms, thus acting as a direct fungal toxin like most other fungicides (1). However, phosphite also can trigger increased biochemical plant defenses (1), which is not typical of most products sold as fungicides. In February 1995, fosetyl-Al came off

patent, and within a short time other phosphite-containing products came to market. Readers are probably familiar with several of the phosphite-type fungicides available in their area. Some phosphite materials currently on the market are sold as fertilizers rather than fungicides; a number of these fertilizers were on the market for years before fosetyl-Al came off patent. (Interestingly, several well-conducted studies raise serious questions about whether the phosphite ion serves as a direct source of 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 of

phosphite-containing fungicides and fertilizers, we initiated a field study in 2003 to test a selection of phosphite fungicides to assess whether they provided equal levels of disease control and maintenance of turf quality (Figure 1). Our expectation was that they would provide essentially equivalent control, but we were surprised to find some differences in performance.

Study design

The site was a soil-based Penncross creeping bentgrass putting green (mowing height 0.188 inch [4.8 millimeters]) at the University of Kentucky Turfgrass Research Center in

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Lexington. The site received nitrogen twice in the autumn and early winter. Before and during the summer test periods, nitrogen and irrigation inputs were minimal in order to provide a moderate level of stress on the turf.

Treatments

All phosphite fungicides tested were used at their full application rate in combination with a half-rate of Chip co 26GT alternating with Daconil Ultrex (referred to below as phosphite fungicide programs; treatments 4-7 in Tables 1 and 2, and treatments 4-9 in Tables 3 and 4). We used half-rates of Chip co 26GT and Daconil Ultrex in order to put the phosphite fungicides through stringent testing conditions. Because we used the contact fungicides at half-rates, another experimental control was the application of half-rates of Chipco 26GT alternating with Daconil Ultrex but without a phosphite fungicide (treatment 3 in all tables). Finally, in 2004 we added another experimental treatment, where we substituted Chip co Aliette for Chipco Signature to test

Controls

A bit of explanation of the treatment design is in order because several treatments serve as experimental controls. Each test included plots treated with water only (treatment 1 in all tables) and plots treated with a spray program expected to provide good disease control. The control spray program, applied every two weeks, was a tank-mix of Chip co Signature plus a full rate of Chipco 26GT, alternating with a tank-mix of Chipco Signature plus a full rate of Daconil Ultrex (treatment 2 in all tables).

the effect of the green dye in Chipco Signature (treatment 5 in Tables 3 and 4), and we added Magellan, another phosphite fungicide (treatment 9 in Tables 3 and 4). Data were collected on the intensity of dollar spot (caused by Sclerotinia homoeocarpa) and brown patch (caused by Rhizoctonia solam), as well as on turf quality (excluding damage from dollar spot). In 2003, we assessed turf quality of annual bluegrass (Poa annua) and creeping bentgrass separately. Weather data from the University of Kentucky Agricultural Weather Center were examined. Selected data are presented in the tables; details of methods and additional data are available in out published reports (4-8).

2003 results

All of the phosphite fungicide programs

2003 DOLLAR SPOT CONTROL

No. of dollar spot infection centers/plott Treatment and rate/1 ,000 square feet* June 10 June 17

July 2

July 15

July 30

Experimental controls 1. Water 2a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 4 fluid ounces alternated with 2b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 3.2 ounces 3a. Chipco 26GT 2SC 2 fluid ounces alternated with 3b. Daconil Ultrex 82.5WDG 1.6 ounces

Phosphite fungicide programs 4a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 4b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 5a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 3.7 a-d 1.3 def 1.0 bc 1.0 cd 7.7 b-e

14.3 a

37.3 a

38.3 a

72.0 a

57.3 a

2.7 b-e

0.0 f

0.0 c

0.3 cd

0.0 i

2.0 cde

1.0 def

0.0 c

0.7 cd

5.7 cde

0.7 de

0.3 ef

0.0 c

0.0 d

1.7 ghi

5b. Resyst 45.8% 5 fluid ounces + Daconil Ultrex 82.5 WDG 1.6 ounces 6a. Vital 4.2L 6 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 6b. 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 be

7a. Alude 5.17L 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 7b. 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 of the two tank-mixes were alternated at two-week intervals between May 28 and July 23. tMeans within the same column followed by the same letter are not significantly different. Table 1. Dollar spot control, 2003 test.

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tested provided good control of dollar spot (Table 1). Surprisingly, however, we did see differences among phosphite spray programs in dollar spot control. On most assessment dates, there was no significant difference in dollar spot control achieved by the phosphite fungicide programs. On later assessment dates, small but statistically significant differences emerged, with Resyst, Vital and Alude (treatments 5-7 in Table 1) all providing less control than the Chipco Signature program (treatment 4) on July 30,2003. All phosphite fungicide programs tested (treatments 4-7 in Table 2) provided improved turf grass quality when compared to the water-treated control (Table 2) and sometimes did not differ from one another. However, in 2003, statistically significant differences were evident among the phosphite fungicide programs, with Resyst, Vital and Alude (treatments 5-7 in Table 2) providing some reduction in turf quality compared to the Chipco Signature program (treatment 4) in several assessments. During the test period, there were several sustained periods of rainfall deficit. 2004, a slight but significant reduction in dollar spot control was observed in the Resyst and Alude programs (treatments 6 and 8, Table 3) as compared to several other phosphite fungicide programs. No consistent, statistically significant differences in turf quality were observed among the various phosphite fungicide programs tested (treatments 4-9 in Table 4). However, only the Chipco Signature and Chipco Aliette programs (treatments 4 and 5) provided turf quality statistically higher than the water-treated control (treatment 1) in all assessments. There was no difference in turf quality between the Chipco Signature program (treatment 4) and the Chipco Aliette program (treatments 5). The generally mild

2004 results

Dollar spot pressure was less intense in 2004 than in 2003. As in 2003, all phosphite fungicide programs provided good control of dollar spot, with no significant differences among phosphite fungicide programs on most assessment dates (Table 3). On July 26,

2003 TURF QUALITY

Treatment and rate/1,OOO square feet* Experimental controls

Creeping bentgrasst July 2 July 22

Poa annuat

June 25 July 10

Overall turf quality June 22 Aug 5

1. Water 2a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 4 fluid ounces alternated with 2b. Chipco Signature 80WG 4 ounces + Oaconil Ultrex 82.5WOG 3.2 ounces 3a. Chipco 26GT 2SC 2 fluid ounces alternated with 3b. Oaconil Ultrex 82.5WOG 1.6 ounces

Phosphite fungicide programs

NO

NO

NO

NO

4.7 e

3.3 hi

NO

NO

NO

NO

7.7 a

6.3 abc

NO

NO

NO

NO

6.8 abc 4.7 efg

4a. Chipco Signature 80WG 4 ounces 2 fluidounces alternated with

+

Chipco 26 GT

+

2SC

8.0 a 8.0 a 7.3 a 6.3 a 7.5 a 5.3 b-e

4b. Chipco Signature 80WG 4 ounces + Oaconil Ultrex 82.5WOG 1.6 ounces 5a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with

5b. Resyst 45-8%SL

5 fluidounces

+

Oaconil Ultrex 82.5WOG

1.6 ounces

7.3 a

6.3 b

5.3 b

4.3 b

6.3 bc

5.0 d-g

6a. Vital4.2L 6 fluidounces + Chipco 26GT 2SC 2 fluidounces alternated with 6b. Vital4.2L 6 fluidounces + Oaconil Ultrex 82.5WOG 7a. Alude 5.17L 5 fluidounces + Chipco 26GT 2SC 2 fluidounces alternated with 7b. Alude 5.17L 5 fluidounces + Oaconil Ultrex 82.5WOG

1.6 ounces

7.7

a

6.0 b

5.3 b

5.0 ab

5.7 cde 4.3 fgh

1.6 ounces

7.3

a

6.0 b

5.3 b

3.7 b

6.0 bcd 6.7 ab

Note. Turf Quality was scored on a 1-9 scale, where 9 = excellent turf health. Dollar spot damage was excluded from turf-qualityassessments. *Applications of the two tank-mixes were alternated at two-week intervals between May 28 and July 23. IND, no data. Means within the same column followed by the same letterare not significantlydifferent.

Table 2. Turf quality,2003 test.

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temperatures in 2004 coupled with mild rainfall deficits of short duration resulted in lower levels of weather-related stress on the turf than in 2003. may be meaningful given the high aesthetic expectations and the pronounced agronomic stress that can occur on putting greens. Although most of these products differ slightly in chemistry of the active ingredient (different cations associated with the phosphite ion, for example), it seems unlikely that this would account for the observed differences in performance. We suspect that the differences in performance we observed are due to differences in formulation (inert ingredients and other aspects of formulation, many aspects of which are proprietary). We currently are participating in an ongoing multistate study led by Erik Ervin, Ph.D., at Virginia Polytechnic Institute, Blacksburg, Va., which we hope will shed some light on this question.

Disclosure statement Cleary Chemical Corp. and Regal Chemical provided partial funding toward the cost of conducting the 2003 test; funding was not solicited in 2004. Funding was neither solicited nor received from Bayer Corp. for this study. Literature cited 1. Guest, D., and B. Grant. 1991. The complex action of phosphonates as antifungal agents. Biological Reviews 66:159-187. 2. Forster, H., J.E. Adaskaveg, D.H. Kim and M.E. Stanghellini. 1998. Effect of phosphite on tomato and pepper plants and on susceptibility of pepper to Phytophthora root and crown rot in hydroponic culture. Plant Disease 82:1165-1170. 3. McDonald, A.E., B.R. Grant and Plaxton. 2001. Phosphite (phosphorous acid): its relevance in the environment and agriculture and influence on plant phosphate starvation response. Journal of Plant Nutrition 24:1505-1519. 4. Vincelli, P.,E. Dixon, D. Williams and P.Burrus. 2004. Influence of spray programs with phosphate fungicides on turf quality in a mixed creeping bentgrass/

Conclusions

The phosphite fungicide programs tested all provided good control of dollar spot and some improvement in turfgrass quality. However, our data revealed unexpected but statisticallysignificant differencesin both diseasecontrol and turlgrass quality among the products tested, especially under more stressful growing conditions. The Chipco Signature program was consistendy in the top statistical grouping with respect to both disease control and turfgrass quality. The differencesamong phosphite fungicide programs typically were modest, but small improvements

we.

2004 DOLLAR SPOT CONTROL

Treatment and rate/1,000 square feet* Experimental controls 1. Water 2a. Chipco Signature 80WG 4 ounces + Chipco 2SC 4 fluid ounces alternated with 2b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 3.2 ounces 3a. Chipco 26GT 2SC 2 fluid ounces alternated with 3b. Daconil Ultrex 82.5WDG 1.6 ounces Phosphite fungicide programs 4a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 4b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces . 5a. Chipco Alietle 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 5b. Chipco Alietle 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 6a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 6b. Resyst 45.8%SL 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 7a. Vital 4.2L 6 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 7b. Vital 4.2L 6 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 8a. Alude 5.17l 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 8b. Alude 5.17L 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 9a. Magellan 53.5%l 4.1 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 9b. Magellan 53.5%L 4.1 fluid ounces + Daconil.Ultrex 82.5WDG 1.6 ounces.

*Applications of the two tank-mixes were alternated at tWo-week intervals between May 20 and July 28. tMeans within the same column followed by the same letter are not significantly different. Table 3. Dollar spot control, 2004 test.

No. of dollar spot infection centers/plott June 28 July 6 JUly 12 July 19 July 26

16.7 ab

19.7 a

23.7 a

11.0 a

7.7 a

0.0 i

0.0 d

0.0 d

0.0 e

0.0 f

2.3 e-h

0.3 d

1.3 bcd

1.3 bc

2.3 a-e

1.3 f-i

0.0 d

0.0 d

0.0 c

0.7 ef

1.3 e-i

0.0 d

0.3 cd

0.0 c

1.3 def

4.3 cde

0.0 d

2.3 be

0.3 d

4.0 abe

0.0 i

0.0 d

0.0 d

0.0 c

0.0 f

2.7 d-g

0.0 d

2.3 bc

0.0 c

4.0 abc

1.0 ghi

0.3 d

0.0 d

0.0 c

0.3 ef

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RESEARCH

5. Poa annua soil-based green, 2003. Fungicide and Nematicide Tests 59:T009. Vincelli, P.,E. Dixon, D.Williams and P. Burrus. 2004. Efficacy of fungicides for control of dollar spot in a mixed creeping bentgrasslPoa annua soil-based green, 2003. Fungicide and Nematicide Tests 59:T019. Vincelli, P., E. Dixon, D.Williams and P. Burrus. 2004. Influence of fungicides on turf quality in a mixed creeping bentgrassl Poa annua soil-based green, 2003. Fungicide and Nematicide Tests 59:T020. Vincelli, P.,E. Dixon, D.Williams and P.Burrus 2005. Influence of spray programs with phosphite fungicides on turf quality in a mixed creeping bentgrasslPoa annua soil-based green, 2004. Fungicide and Nematicide Tests (in press). Vincelli, P., E. Dixon, D.Williams and P. Burrus. 2005. Efficacy of fungicides for control of dollar spot in a mixed creeping bentgrasslpoa annua soil-based green, 2004. Fungicide and Nematicide Tests (in press). 9. Vincelli, P., J. Doney and D.Williams. 1998. Effects of fungicides on turf quality of creeping bentgrass, 1997. Fungicide and Nematicide Tests 53:451. Paul Vincelli, Ph.D. ([email protected]), is an Extension professor and Ed Dixon is a research analyst in the department of plant pathology at the University of Kentucky, Lexington.

6.

EJlESEABCHI---------, says ...

~ This study compared programs using Chipco Signature, Chipco Aliette, Daconil Ultrex, Alude, Resyst,Vital and Magellan. ~ Compared to the water-treated control, all the phosphite fungicides provided good dollar spot control in both years and improved turfgrass quality in the more stressful year, but the Chipco 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 inert ingredients and other aspects of the formulation may be the cause.

7.

8.

2004 TURF QUALITY

Overall turf qualityt Treatment and rate/1,000 square feet* Experimental controls 1. Water 2a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 4 fluid ounces alternated with 2b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 3.2 ounces 3a. Chipco 26GT 2SC 2 fluid ounces alternated with 3b. Daconil Ultrex 82.5WDG 1.6 ounces Phosphite fungicide programs 4a. Chipco Signature 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 4b. Chipco Signature 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 5a. Chipco Aliette 80WG 4 ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 5b. Chipco Aliette 80WG 4 ounces + Daconil Ultrex 82.5WDG 1.6 ounces 6a. Resyst 45.8%SL 5 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 6b. Resyst 45.8%SL 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 7a. Vital 4.2L 6 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 7b. Vital 4.2L 6 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 8a. Alude 5.17L 5 fluid ounces + Chipco 26GT 2Sc 2 fluid ounces alternated with 8b. Alude 5.17L 5 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 9a. Magellan 53.5%L 4.1 fluid ounces + Chipco 26GT 2SC 2 fluid ounces alternated with 9b. Magellan 53.5%L 4.1 fluid ounces + Daconil Ultrex 82.5WDG 1.6 ounces 4.8 e

3.3

July 27

July 28

Aug 2

c

5.2 e

7.0 ab

7.3 a

7.0 abc

5.3 cde

4.3 bc

5.5 de

6.3 a-d

6.3 ab

6.7 a-d

7.0 ab

7.0 a

7.0 abc

5.8 b-e

4.7 bc

5.5 de

6.0 a-e

5.7 ab

6.3 a-e

5.3 cde

4.7 bc

5.5 de

5.8 b-e

4.7 bc

5.7 cde

Note. Turf quality was scored on a 1-9 scale, where 9 = excellent turf health. Dollar spot damage was excluded from turf-quality assessments. *Applications of the two tank-mixes were alternated at two-week intervals between May 20 and July 28. tMeans within the same column followed by the same letter are not significantly different. Table 4. Turf quality, 2004 test.

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