Progress 09/15/01 to 09/30/05
Outputs
In this project, we tested reduced-risk and biofungicides and the Melcast melon disease forecaster as alternatives to weekly applications of the standard fungicides mancozeb and chlorothalonil. Three experiments were done in multiple locations during 2002 to 2004 to test control of foliar fungal diseases on muskmelon (Cucumis melo ssp. melo cv. Athena). Six reduced-risk fungicides were evaluated against Alternaria leaf blight (caused by Alternaria cucumerina). Sonata, Serenade, Milsana, and Actigard were alternated with chlorothalonil and Messenger and OxiDate were applied with a half rate of chlorothalonil. Control treatments were chlorothalonil alone applied biweekly and chlorothalonil alone at half rate applied weekly to determine its contribution to disease control within spray programs. All fungicide treatments significantly reduced Alternaria leaf blight two of four trials. No reduced-risk treatments differed significantly from the standard fungicide program of
mancozeb followed by chlorothalonil. The trial in Indiana, 2003, was the only trial in which any reduced-risk fungicide (Actigard and Sonata in this case) rotated with Echo reduced disease beyond the reduction observed with chlorothalonil alone. Actigard significantly reduced weight of marketable fruit compared to the nonsprayed control in three of four trials in 2002. In one of two trials, all reduced-risk fungicides also reduced gummy stem blight (caused by Didymella bryoniae) compared to the nonsprayed control. The effects of using harpin, azoxystrobin, Melcast, and combinations of these alternatives with chlorothalonil were evaluated in five trials against Alternaria leaf blight, gummy stem blight, or downy mildew (caused by Pseudoperonospora cubense). In both Georgia and Maryland, azoxystrobin rotated with chlorothalonil on a Melcast schedule was not effective against gummy stem blight; however, the Alternaria leaf blight model of Melcast was used instead of the gummy stem blight
model. Against downy mildew, chlorothalonil applied according to Melcast scheduling and azoxystrobin alternated with chlorothalonil on a weekly schedule usually did not differ from chlorothalonil applied weekly. Applications of harpin had no effect on any disease, but increased yield of fruit by 10 to 12% in one trial in South Carolina. In 2004 Serenade (Bacillus subtilis), chlorothalonil, Pristine (boscalid plus pyraclostrobin) and Quadris (azoxystrobin) were evaluated in four locations. All products were applied weekly; additional applications of Pristine alternated with Echo and Echo alone were scheduled by Melcast. Serenade applied weekly reduced disease severity compared to the nonsprayed control in IN and MD but not GA and NC. Serenade alternated with Echo was more effective than Serenade applied weekly in GA, NC, and MD, but these two treatments performed similarly in IN. Control with Melcast did not differ from weekly sprays in GA, NC, or MD. Overall, Pristine alternated with
Echo or Echo alone were the most effective treatments against Alternaria leaf blight and Pristine alternated with Echo was the most effective treatment against gummy stem blight.
Impacts
Growers could start the season by using Melcast scheduling to apply fungicides for gummy stem blight or Alternaria leaf blight; these applications also would protect the crop from downy mildew. If downy mildew appeared during the season, the spray schedule could be switched to weekly intervals. Reduced-risk fungicides and biofungicides alternated or mixed with chlorothalonil usually performed similarly to the several conventional control treatments included for comparison. Thus, reduced- risk products did not provide a greater level of control than reduced applications of chlorothalonil. Alternatively, most of the alternative products could be substituted for half of the applications in a weekly spray schedule of chlorothalonil with no loss of disease control. Yield reductions were observed with Actigard applied four times to muskmelon. Pristine provided the most consistent levels of control across locations.
Publications
- A. P. Keinath, G. J. Holmes, D. B. Langston, Jr., D. S. Egel, and K. L. Everts. 2005. Multi-state evaluation of alternatives to chlorothalonil to control foliar diseases on melon. Phytopathology 95:S52.
- D.B. Langston, Jr. 2005. Control of Alternaria leaf spot of muskmelon with biofungicides and reduced-risk fungicides using MELCAST and spray schedules, 2004. Fungicide and Nematicide Tests (online.) Report No. 60:V132. DOI:10.1094/FN60. The American Phytopathological Society, St. Paul, MN.
- G.J. Holmes and M.L. Adams. 2005. Evaluation of Echo and Serenade for control of Alternaria leaf blight of muskmelon, 2004. Fungicide and Nematicide Tests (online.) Report No. 60:V073. DOI:10.1094/FN60. The American Phytopathological Society, St. Paul, MN.
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Progress 01/01/04 to 12/31/04
Outputs
Alternatives to the conventional fungicides chlorothalonil and mancozeb were evaluated against Alternaria leaf blight or gummy stem blight on muskmelon in 15 field experiments in SC, MD, IN, GA, and NC in 2002 and 2003. Actigard reduced yields in four of seven experiments. Addition of Messenger (harpin protein) to chlorothalonil applied with or without Quadris had no effect on disease control in fourteen of the fifteen experiments. Serenade (Bacillus subtilis) alternated with chlorothalonil was the only alternative fungicide that reduced severity of Alternaria compared with chlorothalonil applied biweekly, although this was observed in only one experiment. Based on results from 2002 and 2003, nine treatments and a non-sprayed control were evaluated in 2004 in GA, SC, NC, MD, and IN. Weight, number, and sugar content of marketable fruit did not differ among fungicide treatments. However, significant treatment-by-location interactions were observed for disease control.
Treatments did not differ in SC. Fungicides performed identically in GA and NC against Alternaria leaf blight, but dissimilarly in IN against the same disease. Results with gummy stem blight from MD were similar to results in IN. Serenade applied weekly reduced disease severity compared to the nonsprayed control in IN and MD but not in GA and NC. Serenade alternated with Echo (chlorothalonil) was more effective than Serenade applied weekly in GA, NC, and MD, but these two treatments performed similarly in IN. Serenade alternated with Echo did not differ from Quadris alternated with Echo but was less effective than Pristine alternated with Echo in all four locations. Pristine alternated with Echo was more effective than Quadris alternated with Echo or Echo alone in MD and IN but not in NC and GA. However, Echo alone was more effective than Quadris alternated with Echo in NC and GA but not in MD and IN. Applying Echo or Pristine alternated with Echo according to the Melcast disease
forecaster did not differ from weekly sprays in GA, NC, or MD. In IN, control was better when Pristine alternated with Echo was applied weekly rather than according to Melcast. In summary, Pristine alternated with Echo or Echo alone were the most effective treatments against Alternaria leaf blight and Pristine alternated with Echo was the most effective treatment against gummy stem blight. Downy mildew also was present in SC in 2002 and 2003 and in MD in 2004 and became more severe than gummy stem blight in all three experiments.
Impacts
Results of this multi-state research project will assist growers in choosing effective fungicides to manage Alternaria leaf blight and gummy stem blight on muskmelon. The performance of fungicides against downy mildew, another serious disease of muskmelon, also should be considered when selecting fungicides. Pristine alternated with chlorothalonil or chlorothalonil alone were the most effective treatments against Alternaria leaf blight and Pristine alternated with Echo was the most effective treatment against gummy stem blight. Although the biofungicide Serenade was more effective than not spraying, it was less effective than most conventional fungicides. However, Serenade could be used by growers who want to reduce inputs of conventional fungicides. In general, applications of fungicides using Melcast, which is based on weather conditions, were as effective as weekly calendar-based applications.
Publications
- D.B. Langston, Jr. 2004. Control of gummy stem blight of muskmelon with biofungicides and reduced-risk fungicides using MELCAST and spray schedules. Fungic. Nematic. Tests 59:V134.
- A.P. Keinath, V. B. DuBose, W.H. May III, and J.P. Cantrell. 2004. Reduced-risk fungicides rotated or mixed with chlorothalonil to manage downy mildew on muskmelon. Fungic. Nematic. Tests 59:V004.
- A.P. Keinath, V. B. DuBose, W.H. May III, and J.P. Cantrell. 2004. Control of downy mildew on muskmelon with combinations of Echo, Quadris, or Messenger applied weekly or with Melcast. Fungic. Nematic. Tests 59:V005.
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Progress 01/01/03 to 12/31/03
Outputs
Reduced-risk fungicides were tested on muskmelon in seven experiments done in South Carolina, Georgia, Maryland, and Indiana in 2002. The objectives of these experiments were to test reduced-risk fungicides applied in combination or alternation with chlorothalonil to see if growers could reduce the amount of chlorothalonil used. In the first experiment, the same 10 treatments were evaluated in SC, MD, and IN. Treatments included the systemic acquired-resistance products Actigard and Messenger; the biofungicides Serenade, Sonata, and Milsana; and the reduced risk contact fungicide Oxidate. Oxidate and Messenger were applied in combination with a reduced rate of chlorothalonil and the other four reduced-risk fungicides were applied in alternation with the full rate of chlorothalonil. Chlorothalonil applied alone at two rates was included as the controls. In MD, all treatments reduced moderate levels of Alternaria leaf blight and gummy stem blight and there were no
overall differences in yield. Likewise, in SC all treatments reduced downy mildew and increased yield, compared with the nonsprayed control. In IN, all treatments reduced Alternaria leaf blight. In addition, alternating Actigard or Serenade with chlorothalonil was more effective than chlorothalonil applied biweekly. Actigard reduced weight and number of fruit compared with the nonsprayed control in IN. In the second experiment, four alternative fungicide treatments and two application schedules (weekly or Melcast forecasting) were compared to each other and to a nonsprayed control and a mancozeb/chlorothalonil standard. The alternative treatments were chlorothalonil alone or alternated with Messenger and chlorothalonil alternated with Quadris with or without Messenger. In IN and MD, treatments applied according to Melcast were less effective against Alternaria leaf blight than those applied weekly were. In GA, the chlorothalonil/Quadris treatments applied according to Melcast also
were less effective against gummy stem blight than those applied weekly. In SC, chlorothalonil alone was more effective against downy mildew than chlorothalonil alternated with Quadris. In general, there were no yield differences in these experiments, except that plots sprayed with Messenger in SC had slightly higher yields than plots not sprayed with Messenger.
Impacts
Under moderate disease pressure, several alternative fungicides applied in alternation with chlorothalonil were more effective than chlorothalonil applied biweekly, meaning that combining the two fungicides had an additive effect. It may be possible to substitute some alternative fungicides for up to one-half of the typical chlorothalonil applications. Actigard reduced yields of muskmelon compared with the nonsprayed control in one of three experiments. Because of this, it is not likely that this fungicide will be registered for use on cucurbits. Melcast intervals were too long to provide the same level of control as 7-day spray intervals. Melcast thresholds may need to be adjusted on muskmelon.
Publications
- Keinath, A. P., DuBose, V. B., May, W. H. III, and Cantrell, J. P. 2003. Use of biofungicides and reduced-risk fungicides rotated with chlorothalonil to control downy mildew on muskmelon. Fungicide Nematic. Tests 58:V024.
- Keinath, A. P., DuBose, V. B., May, W. H. III, and Cantrell, J. P. 2003. Alternatives to mancozeb for managing foliar diseases on muskmelon in Charleston, SC. Fungicide Nematic. Tests 58:V029.
- Langston, D.B., Mitchell, B.R., Griffeth, L.A., Carpenter, D.B., and Harrison, W.E. 2003. Control of Alternaria leaf spot of muskmelon with biofungicides and reduced-risk fungicides alternated with chlorothalonil. Fungicide Nematic. Tests 58:V082.
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Progress 01/01/02 to 12/31/02
Outputs
Reduced-risk fungicides were tested on muskmelon in eight experiments conducted in South Carolina, Georgia, Maryland, and Indiana in 2002. The objectives of these experiments were to test reduced-risk fungicides applied in combination or alternation with chlorothalonil to see if growers could reduce the amount of chlorothalonil used. In the first experiment, the same 10 treatments were evaluated at each location. Treatments included the systemic acquired resistance products Actigard and Messenger; the biofungicides Serenade, Sonata, and Milsana; and the reduced risk contact fungicide Oxidate. Oxidate and Messenger were applied in combination with a reduced rate of chlorothalonil and the other four reduced-risk fungicides were applied in alternation with the full rate of chlorothalonil. Chlorothalonil applied alone at two rates was included as the controls. In Georgia and Maryland, severity of Alternaria leaf blight was low and all treatments reduced disease compared
with the nonsprayed control. There were no differences in control between alternative treatments and chlorothalonil applied alone. At both locations, Actigard alternated with chlorothalonil reduced weight of fruit compared with chlorothalonil alone and with the nonsprayed control. In Indiana, severity of gummy stem blight was low and all treatments except Milsana alternated with chlorothalonil reduced disease. However, Oxidate, Sonata, and Milsana alternated with chlorothalonil and chlorothalonil applied weekly alone increased yields compared with the nonsprayed control. In South Carolina, all treatments reduced downy mildew. For unknown reasons, chlorothalonil applied biweekly was more effective than Actigard, Milsana, Serenade, and Oxidate alternated with chlorothalonil. All sprayed treatments increased yield compared with the nonsprayed control except Actigard alternated with chlorothalonil. In the second experiment, four alternative fungicide treatments and two application
schedules (weekly or Melcast forecasting) were compared to each other and to a nonsprayed control and a mancozeb/chlorothalonil standard. The alternative treatments were chlorothalonil alone or alternated with Messenger and/or Quadris. In South Carolina, alternating Quadris with chlorothalonil was less effective against gummy stem blight than chlorothalonil alone. Treatments that received eight fungicide applications scheduled with Melcast had less downy mildew than treatments that received seven weekly fungicide sprays, regardless of the fungicide mix used. In Maryland, alternating Quadris with chlorothalonil was more effective against Alternaria leaf blight than chlorothalonil alone. In Indiana, all treatments except Messenger plus Quadris alternated with chlorothalonil on a weekly schedule reduced gummy stem blight. In general, treatments did not affect yields in these experiments.
Impacts
Under low disease pressure, alternative fungicides applied in alternation with chlorothalonil were as effective as standard protectant fungicides applied weekly. However, chlorothalonil applied biweekly also was just as effective and would cost less than also applying an alternative fungicide in addition. Additional work is needed to see how alternative fungicides perform under higher disease pressure. Actigard reduced yields of muskmelon compared with the nonsprayed control in three of the four experiments.
Publications
- No publications reported this period
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Progress 09/15/01 to 12/31/01
Outputs
This project was awarded after the field research season for muskmelon had ended. The principle investigators held a conference call and exchanged electronic messages to plan and coordinate field experiments for spring 2001.
Impacts
This project will develop disease management strategies that use fewer applications of B2 carcinogenic fungicides. Worker and consumer exposure to fungicides and potential environmental damage will decrease when these strategies are adopted by growers.
Publications
- No publications reported this period
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