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Stapel O.,Technical Institute for Horticulture | Guerrand J.,Laboratory of Phytopathology
Acta Horticulturae | Year: 2012

Results from experiments conducted in 2008 and 2009 under production situations show significantly fewer symptoms of white rust (Puccinia horiana Henn.) after acibenzolar-s-methyl (ASM, Bion WG50) treatment in potted chrysanthemums (Dendranthema × grandiflorum). Plants were treated 4 times at a 10 day interval and infested plants were placed in the experiment plots 4 days after the first treatments. Rust symptoms were quantified at 4 (2009) and 5 (2008) observation dates. Under high parasitic pressure, plants treated with ASM rarely showed symptoms of chrysanthemum white rust whereas the water treated control received severe damage. Also treatments with 2 natural products (PrevB2, Dipper) resulted in lower symptom development. Laboratory tests revealed low spore germination rates after application of PrevB2 and Dipper but high spore germination with ASM. This finding suggests that ASM has an elicitor effect on chrysanthemum plants against white rust while PrevB2 and Dipper act mainly as a fungicide. A more effective and durable control programme against white rust in chrysanthemum productions is expected when a possible plant elicitor ASM is alternated with directly acting fungicides.

Stapel J.O.,Technical Institute for Horticulture | Maugin E.,Technical Institute for Horticulture | Trihan S.,Technical Institute for Horticulture | Ferre A.,Technical Institute for Horticulture
Acta Horticulturae | Year: 2011

The application of chemical growth regulators in ornamental plant production (ex. daminozide, paclobutrazol, etephon) is a common practice in obtaining compact plants, but their use poses health and environmental risks. Reduction of regulator treatment may also significantly reduce production costs in terms of labour and products. In this evaluation of 5 light filters, significantly compact ornamental and vegetable young plants were obtained using filters that increase the R/FR ratio. A filter that allows maximum UV transmission had less impact on growth in ornamental plants. These evaluations were performed under production situations in different regions in France. The light filter Solatrol appears to have the most impact on the 60 cultures tested, followed by pigments such as ReduHeat and TransPAR. An UV transparent film proved effective in growth reduction in vegetable young plant production. A correlation is found between importance of the growth regulator effect of a light filter and the somrad received during a given culture, indicating a potentially higher efficacy of R/FR filters in regions with higher light intensities. Results obtained in southern France support this finding. However, an initially high R/FR ratio obtained with a light filter declines in time as is found in Solatrol samples collected during a 3 year period. In certain growth regulator intensive cultures such as potted chrysanthemums, the return of investment of light filters may be accomplished within one year.

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