Integrated control of Sclerotinia in carrots by foliage clipping

Carrots become most vulnerable to Sclerotinia infection when fallen foliage creates dead stem tissue in the lower canopy, allowing germinating soil borne sclerotia to infect foliage. Clipping carrot foliage from the side of beds or ridges is a technique that opens air flow through the crop in order to reduce the conditions that favour Sclerotinia infection. The technique was developed in Canada. Trials were carried from 2009-13 in the UK in commercial crops, using discs to cut foliage either side of the beds. The optimum time to clip is when the foliage has begun to fall over, typically in August, but before any Sclerotinia infection is seen. Over the 5 years of trials the average increase in control of clipping was 60%. The effect was best seen in the susceptible 'Nairobi', although proportionately a similar level of control was seen in other cultivars. The majority of infection occurred on the windward side of the bed, and clipping had most effect on this side. As part of an integrated control strategy foliage clipping will potentially allow for fungicide inputs to be reduced and offer a control option in organic crops.