Evaluation of Foliar Fungicide Sprays for the Control of Boxwood Blight, Caused by the Fungus Cylindrocladium buxicola

Abstract

Cylindrocladium buxicola causes a damaging blight disease on boxwood which has spread rapidly throughout Europe since introduction of the pathogen in England in the mid 1990s. The pathogen has also been recently identified in the USA and British Columbia. The disease is difficult to control using cultural methods and information about chemical control is lacking. To address this, preventative and curative foliar fungicide sprays previously shown in laboratory tests to have efficacy were evaluated over two autumn/winter seasons in the UK. Results from the first autumn/winter season showed that the premix product Opponent (epoxiconazole + kresoxim-methyl + pyraclostrobin) was the best treatment when applied preventatively 3 days before inoculation. In the second autumn/winter season, curative treatment of diseased plants was best achieved with a weekly program of fungicides starting 3 days before inoculation and alternating with two or three products including Bravo (chlorothalonil), Signum (boscalid + pyraclostrobin), and Octave (prochloraz). The only fungicide tested and available to amateur growers in the UK, Fungus Clear (penconazole), was found to give moderate control of boxwood blight. Accepted for publication 7 August 2012. Published 24 October 2013.