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item Kousik, Chandrasekar - Shaker

Submitted to: Fungicide and Nematocide Tests
Publication Type: Research Notes
Publication Acceptance Date: 1/4/2006
Publication Date: 2/26/2006
Citation: Kousik, C.S. 2006. Evaluation of Ranman 400SC for management of phytophthora blight of bell pepper, 2004-05. Fungicide and Nematicide Tests. 61:V009.

Interpretive Summary:

Technical Abstract: The objectives of this experiment were to determine if a banded application of Ranman 400SC at transplanting followed by subsequent sprays would aid in management of root and foliar phase of Phytophthora blight. The experiments were conducted in a commercial pepper field at Boynton Beach, Fl, where P. capsici infections have been observed for several years. Metalaxyl tolerant and sensitive strains of P. capsici have been isolated from this farm. The soil was Myakka fine sand. Ten-week-old seedlings of a susceptible pepper hybrid grown in 98 cell jiffy trays were planted in a commercial growers field (22 Oct 04) on raised silver plastic mulched beds on 38-in centers with drip irrigation. There were 4 replications per treatment with two rows of 14 plants (7/row) per replication. Plants were spaced 14 in apart. The plots were arranged in a randomized complete block design. The fertilization and insect management schedules were those routinely followed by the grower. The first treatment on 22 Oct was a banded application (drench) of the chemicals at 50 gal/A about 2 hr after transplanting. Plants were drenched such that there was a runoff from the plants down to the soil. All Subsequent applications were sprays and applied on 29 Oct, 12, 26 Nov, 10, 23 Dec using a hand held pressurized sprayer. Silwett L-77 (2 fl oz/A) was added to all the Ranman 400SC treatments. Disease development in the plots was relatively slow during the initial growth stages of the plants. Disease was first observed in the check plots 42 days after transplanting. Disease in check plots then progressed rapidly and by 73 days after transplanting, most of the untreated plants were dead. Both foliar and root infections were observed. All chemical treatments significantly slowed the disease development compared to the untreated check. Combinations of Ranman 400SC plus Aliette 80WG or Ranman 400SC plus Ridomil Gold Copper 65 WP, significantly decreased disease, however, these treatments were not significantly more effective than treatments of Ranman alone. Ranman treated plots had significantly lower disease compared to Ridomil treated plots. Fruit yield was significantly greater in the treated plots compared to the untreated check. Significant correlation (R2= -0.79, P=0.0001) between levels of disease (AUDPC) and plot yield was observed. Combination of Ranman plus Ridomil had significantly greater yield compared to Ridomil treatments alone. Based on these results, band application of Ranman soon after transplanting followed by subsequent sprays can aid in managing Phytophthora blight of peppers.