Progress 10/01/01 to 09/30/06
Outputs
Objectives: 1. Characterize combined effects of (a) density of plants and (b) the proportion of each of the constituent crops species on the productivity of a biculture of summer squash and cucumber. 2. Characterize effects of the proportion of each of the constituent crop species on increase of squash powdery mildew in a biculture summer squash and cucumber. Results: Fields were planted to mixed populations of summer squash and cucumber with varying proportions of each species and varying densities over three years. Each year, individual plants in plots were monitored for disease symptoms and at fruit maturation yield results were recorded.
Impacts
Results of this research will be used to develop predictive models of powdery mildew disease progression under varying production conditions including plant stand density and mixed crop stands.
Publications
- No publications reported this period
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Progress 10/01/04 to 09/30/05
Outputs
Combined effects of (a) overall density of plants and (b) the relative density of the two constituent crop species on the productivity of a bicultural of summer squash and cucumber have been evaluated. Data are being analyzed to estimate (a) optimal overall density, (b) optimal relative density, and (c) rates of change in productivity with respect to changes in overall density and relative density.
Impacts
The results will improve understanding of competition between squash and cucumber and could aid in the development of environmentally-sound control methods for diseases of these crops.
Publications
- No publications reported this period
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Progress 10/01/03 to 09/30/04
Outputs
No activity for this period.
Impacts
This project will improve understanding of the potential role of polyculture in managing foliar diseases of vegetables.
Publications
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Progress 10/01/02 to 09/30/03
Outputs
Polyculture (the mixing of plant genotypes in space or time) could be one of the few, effective biological alternatives to pesticides for the management of foliar diseases of cucurbit vegetables. In 2003, combined effects of (a) overall density of plants and (b) the relative density of the two constituent crop species on squash powdery mildew in a biculture of summer squash and cucumber were evaluated. A field experiment was established at Lane, Oklahoma. An experimental unit consisted of one plot (6 m x 8 m) containing three rows of plants. A complete factorial arrangement of four levels of overall density (0.6, 1.2, 2.4, and 4.8 plants/m2) and five levels of relative density (0, 44, 55, 66, and 100% cucumber plants) were randomized to plots in each of three replicate blocks. The severity of squash powdery mildew was assessed at least once each week in each plot. Variation in severity with both overall plant density and relative density of squash will be
characterized mathematically.
Impacts
This project will improve understanding of the potential role of polyculture in managing foliar diseases of vegetables.
Publications
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Progress 10/01/01 to 09/30/02
Outputs
Combined effects of (a) overall density of plants and (b) the relative density of the two constituent crop species on the productivity of a biculture of summer squash and cucumber were evaluated. A field experiment was established at Lane, Oklahoma. An experimental unit consisted of a plot (5.5 m wide x 8.2 m long) containing three rows of plants. The 20 possible combinations of four levels of overall density (0.6, 1.2, 2.4, and 4.8 plants/m2) and five levels of relative density (0, 44, 55, 66, and 100% cucumber plants) were randomized to plots in each of four replicate blocks. All seeds were sown on June 7, 2002 and marketable fruits were harvested on four dates from July 17 to July 31. Combined yield of cucumber and squash was optimized when the percentage of cucumber plants in the biculture was 62% and with an overall plant density of 3.2 plants/m2.
Impacts
The results of this project will provide site-specific information regarding an alternative to fungicides for the control of a foliar disease in a vegetable crop. This information will lead to improved strategies pest management that minimize pesticide applications to vegetables.
Publications
- No publications reported this period
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Progress 10/01/00 to 09/30/01
Outputs
To evaluate effects of Auxigro(tm) (Auxein Corp., Lansing, MI) on powdery mildew of squash (cv Goldbar), a field experiment was established in Lane, Oklahoma on Sept. 14, 2001. The experiment comprised 10 plots. Each plot (2 m wide x 50 m long) contained one row of plants. On Oct. 25, the recommended rate of Auxigro was applied to five, randomly-selected plots. In each plot, the mean number of colonies per leaf (on average over 20 arbitrarily-selected plants) measured I. Colonies were counted on the fifth oldest leaf on the primary stem of each plant using a 9-point, visual rating scale. Auxigro reduced I by approximately 40%. On Oct. 29, Nov. 1, and Nov. 8, respectively mean I (on average over all plots) was 21, 31, and 31 colonies per leaf in untreated plots whereas in treated plots, mean I was 8, 12, and 14 colonies per leaf.
Impacts
The results of this project will provide site-specific information regarding an alternative to fungicides for the control of a foliar disease in a vegetable crop. This information will lead to improved strategies pest management that minimize pesticide applications to vegetables.
Publications
- Edelson, J.V., Duthie, J.A., 2002 (in press). Toxicity of biorational insecticides: activity against the green peach aphid. xx:xxxx-xxxx Pest Management Science.
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Progress 10/01/99 to 09/30/00
Outputs
Effects on incidence of watermelon anthracnose (w) of the total dose of chlorothalonil applied during a cropping season (d) and the number of applications of chlorothalonil (n) were distinguished. Levels of w were measured once each week from the time of appearance of symptoms until harvest in replicated field plots treated with various combinations of d and n. A logistic equation of the form w = A.exp[-(B.d+C.d..n)]/{1+exp[-D.(E-t)]} characterized the combined effects of d and n on variation in w over time (t). In the absence of chlorothalonil, w increased with t at an intrinsic rate of D to an upper limit of A. The value of t was E when w was 50% of A, and B and C gave intrinsic rates of decrease of w with respect to d and the product d.n, respectively. Thus, as n was increased at any given level of d, w decreased.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 10/01/98 to 09/30/99
Outputs
To compare the effectiveness of fungicides in the control of powdery mildew of pumpkin, a field experiment was established at the Wes Watkins Agricultural Research and Extension Center in Lane Oklahoma on June 25, 1999. In untreated plots, the fraction of leaves with one or more colonies (I) was 88% at harvest. Disease incidence was least when Quadris was applied alone (I=25%) or when a total of five applications of Quadris were alternated with a total of two applications of Bravo (I=27%). Incidence also was reduced when Bravo was applied alone (I=39%) or when a total of five applications of Bravo were alternated with a total of two applications of Quadris (I=45%).
Impacts
(N/A)
Publications
- Wu, L., Damicone, J.P., Duthie, J.A., and Melouk, H.A.. 1999. Effects of temperature and duration of high relative humidity on infection of peanut cultivars by Cercospora arachidicola. Phytopathology 89:653-659.
- Roberts, B.W., Duthie, J.A., Edelson, J.V., Cartwright, B.O., Shrefler, J.W., and Roe, N. 1999. Limitations and possibilities for some conservation tillage systems with vegetable crops in the southern plains of the United States. HortTechnology 9:359-365.
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Progress 10/01/97 to 09/30/98
Outputs
Experiments designed to evaluate economic benefits of application of a mixture of mancozeb and benlate for control of anthracnose of watermelon were repeated in 1998. In each experiment, varying the number of applications of fungicide varied the total dose of fungicide applied to the experimental plots during a cropping season. Results confirmed that benefits of fungicide varied considerably among experiments and appeared to depend on weather. For each additional application of fungicide, marketable yield increased by 0 to 2.5 Mg/ha. If the cost of an application was 65 $/ha and the value of watermelon fruits is 0.25 $/kg, then the net benefit of fungicide varied from -65 to 690 $/ha per application.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 10/01/96 to 09/30/97
Outputs
Benefits of application of a mixture of mancozeb and benlate, for anthracnose control were evaluated in each of three experiments. Benefits varied considerably among experiments and appeared to depend on weather. In Expt. 1, weather was not conducive to the development of the disease and there was no evidence levels of disease were reduced or that yield was increased by fungicide application. Yield of marketable fruits was greater in Expts. 2 and 3 than in Expt. 1. Weather favored rapid increase of anthracnose in Expts. 2 and 3. As the number of fungicide applications during a growing season was increased from zero to six, the intensity of anthracnose declined linearly and marketable yield increased linearly. For each application, yield was increased by 2.0 Mg/ha for the cultivar Sangria in Expt. 2 and by 2.7 Mg/ha and 0.6 Mg/ha for the cultivars Sangria and Black Diamond, respectively, in Expt. 3.
Impacts
(N/A)
Publications
- Duthie, J.A. 1997. Models of the response of foliar parasites to combined effects of temperature and duration of wetness.
- Damicone, J.P., and Duthie, J.A. 1997. Managing watermelon anthracnose. Pp 243-246 In: Proc. 16th Ann. Ok. Hort. Ind. Show. B.D. McCraw (ed.). Dept. Hort. and L.A., Oklahoma State University,
- Rowland, S.J., Duthie, J.A., Roberts, B.W., and Edelson, J.V. 1997. Evaluation of fungicides for control of anthracnose of watermelon. Fungicide and Nematicide Tests 52:198.
- Roberts, B.W., Shrefler, J., Duthie, J.A., and Edelson, J.V. 1997 Watermelon weed control: current and future possibilities. (Abstr.)
- Roberts, B.W., Roe, N., Duthie, J.A., Edelson, J.V., Shrefler, J., Cornforth, G., Enis, J., Smith, S. 1997. Integrating watermelon and forage crops. (Abstr.) HortScience 32:539.
- Roberts, B.W., Shrefler, J., Duthie, J.A., and Edelson, J.V. (in press) Mechanical and chemical alternatives for weed control in watermelon. (Abstr.) Hortscience 00:0000.
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Progress 10/01/95 to 09/30/96
Outputs
Effects of antracnose (Colletotrichum orbiculare) on yield of watermelon (Citrullus lunatus) were evaluated. An effect of anthracnose on yield was detected in two of three experiments. In one experiment, size of marketable fruit was reduced but there was no evidence of an effect on the abundance of marketable fruit. Conversely, in a second experiment, disease affected abundance of marketable fruit but there was no evidence of an effect ont he size of marketable fruit. Effects of cultivar resistance on fungicidal control of anthracnose were evaluated. Intensity of anthracnose declined with increased frequency of fungicide (benomyl) application but there was no evidence that the effect differed between the cultivars Black Diamond and Sangria.
Impacts
(N/A)
Publications
- Driever, G., Duthie, J.A., & von Broembsen, S.L. 1996. Fungicide application thresholds for pecan scab derived from epidemiological & weather data. Phytopath. 86:S86
- Duthie, J.A. & Damicone, J.P. 1996. A mechanistic model of combined effects of temperature & duration of wetness on intensity of foliar disease. Phytopath. 86:S4.
- Motes, J.E., Roberts, B.W., Edelson, J.V., Damicone, J.P., & Duthie, J. A. 1996. Cantalope production. OSU Fact Sheet F-6237.
- Motes, J.E., Roberts, B.W., Edelson, J.V., Damicone, J.P., & Duthie, J.A. 1996. Slicing cucumber production. OSU Fact Sheet F-6023.
- Bruton, B.D. & Duthie, J.A. 1996. Fusarium rot. pp. 50-51. In: Compendium of Cucurbit Diseases. Zitter, T.A., Hopkins, D.L., & Thomas, C.E. (eds.) APS Press, St. Paul, MN.
- Bruton, B.D. & Duthie, J.A. 1996. Pink root. pp. 20-21. In: Compendium of Curcurbit Diseases. Zitter, T.A., Hopkins, D.L., & Thomas, C.E. (eds.) APS Press, St. Paul, MN.
- Bruton, B.D. & Duthie, J. A. 1996. Red rot. pp. 54-55. In: Compendium of Curcurbit Diseases. Zitter, T.A., Hopkins, D. L., & Thomas, C.E. (eds.) APS Press, St. Paul, MN.
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