Botrytis can cost growers a lot of money through the loss of unmarketable plants and direct costs of disease control. The HortLINK project conducted in Great Britain provides useful guidelines. It is necessary to adopt an integrated approach involving plant hygiene, environmental control and chemical treatment. Incoming seeds and cuttings should be checked if they have been treated (Botrytis can be carried on seed and in cuttings taken from infected stock). Damaged, dead or infected leaves and trimmings should be removed and benches should be washed down between crops. Plants should not be planted too deeply and need to be handled carefully to avoid mechanical damage. High humidity must be avoided; at a R.H. of 95% or above, Botrytis spores will germinate in only 2-3 hours. A temperature boost and ventilation for short periods to avoid R.H rising above 80% (major risk start at over 90%) is beneficial. In the summer it is better to ventilate first and then to give the boost of heat, vice versa in the winter. No computer software is yet available to manage this but growers can establish a time period in the computer for periods of greatest risk. Without extra heat, Botrytis can still be managed through using appropriate structures, irrigation and ventilation practices. Taller greenhouses are better. Tunnels should be placed at lease 3m apart. Side ventilation is important to avoid the gathering of still air in the centre. Side ventilation combined with roof ventilation is best. Ventilation fans should be placed in parallel or serial arrangement where they face down the bay in the same direction or face each other. Sub-irrigation is more appropriate. If overhead irrigation is used it should be applied early in the day. Alternating different plant chemicals gives better control, for example (active ingredients): pyrimethanil or mepanipyrim with dichorofluanid or chlorothalonil.  Botrytis is partially resistant to many traditionally used products. Chemicals should be sprayed with a high volume of water to ensure full coverage and penetration into the centre of the plants. Two preventative treatments should be given after striking the cuttings or potting. Claire Shaddick, "Commercial Greenhouse Grower", HDC Workshop.  green@actpub.co.uk  www.hdc.org.uk