Biological control agents for soil-based diseases have little benefit when used on column stocks, Horticultural Development Company research carried out by the National Cut Flower Centre (NCFC) has shown.
Grower-based trials were carried out on a variety of biological treatments for Pythium and Fusarium as part of project PO 005 and pot trials focusing on chemical solutions were done at Stockbridge Technology Centre.
NCFC project manager Lyndon Mason said: "Growers came to us saying they have had increased variability of flowering over the past few years, unexplained disease problems and increases in plant losses, and as a result they had lost confidence in the crop."
He added that the results show that nothing seems to fully control Fusarium and said varietal selection is very important. Steaming proved to be significant, with most treatments in the unsteamed area of the Fusarium trial not producing a single marketable stem, so it is not possible to move away from the use of steam, said Mason.
"From what we've seen in these trials, biological agents have very little effect," he added. "Some growers have had results and some haven't, but these scientific trials haven't shown results. Nothing seems to control Fusarium so we're stuck with it for the time being. Soil structure improvement has come out as the most important thing."
Mushroom compost produced outstanding results in the Pythium trial, while bark produced the best stems in the Fusarium trial.
Mason added that the weather in 2012 has meant that outdoor trials have not produced the hoped-for results, but it has not affected protected trials at the cut flower centre.
Plants being trialled in 2012 have included Trumpet antirrhinum, Lisianthus, phlox, sedum, eryngium, Aster ericoides, sunflowers, annual asters, hardy foliage and column stocks.
Also being trialled are the Breanthus range of annual dianthus and the Solomio and Star Spray carnations from Hilverda Kooij.
Industry research Latest projects detailed
The Horticulture Development Company is funding cut flower industry research through its studentships and fellowships, growers attending the National Cut Flower Centre open day earlier this month were told.
The projects include thermal and visual image analysis for crop disease monitoring, the use of sterile insect technique to increase integrated pest management success and weed control in ornamentals.