Multiple Fungicide Resistance in Botrytis: A Growing Problem in German Soft-Fruit Production

In the mild and humid climate of northwestern Europe, fungal pre-harvest rots are a major factor limiting the production of soft-fruits such as strawberries and raspberries. By far the most important fungal disease is grey mould caused by Botrytis cinerea Pers.:Fr., now known to be an aggregate of at least two distinct species (Fournier et al., 2005; Giraud et al., 1999). Primary infections are initiated at flowering, resulting in a quiescent colonisation of floral organs (Bristow et al., 1986; Puhl & Treutter, 2008). Upon ripening of the infected fruit, a brown rot becomes apparent (Fig. 1A) which rapidly engulfs the entire fruit, culminating in the production of conidiophores (Fig. 1B). If mild and humid conditions prevail at harvest time, conidia released from fruits with primary infections may infect healthy fruits, causing a catastrophic grey mould epidemic (Fig. 1C). Repeated fungicide applications during flowering are therefore essential to control B. cinerea in soft-fruit production.