Rot pathogens can limit marketable product by affecting the growth, quality and storability of the fruit. Grey mould, caused by Botrytis cinerea is considered the most important post-harvest strawberry fruit rot pathogen. Botrytis cinerea infects over 200 plant species and worldwide, it causes annual losses of $10 billion to $100 billion. Botrytis is able to counteract a broad range of plant defence chemicals.
Botrytis cinerea is highly adaptive and versatile crop pathogen developing resistance to almost every mode of action chemistry, including pyraclostrabin/boscalid, fenhexamid, and iprodione. Globally, on-farm strawberry production generally relies on pre and post-harvest fungicide applications. These are not only costly in terms of prophylactic fungicide usage, man hours to apply but increases risk of treatment resistance and impacts on the environment.
A DEFRA report identified strawberries on average received 13 fungicides with only 0.2% of strawberries not treated. Two other rot pathogens which growers face are Mucor and Rhizopus. Like Botrytis, they are not limited to soft fruit and have a wide host range to include melon, peach, sweet potato and head-rot of sunflower. Unlike Botrytis both Mucor and Rhizopus can cause human infection.
Mucormycosis is an increasingly common fungal infection (caused by Rhizopus and Mucor species) with a high mortality rate in immunocompromised patients reported. For example, the mortality rate was 46% among people with sinus infections, 76% for pulmonary infections, and 96% for disseminated mucormycosis. In soft fruit production, Botrytis, Mucor and Rhizopus are the silent rots hiding behind the mask of latent infection, risking consignment rejection by retailers at point of sale. If they can evade this, which they often do, will lurk and later appear on fruit in your fridge or fruit bowl.