What was it all about?

Grey mould disease in strawberries is caused by the fungus Botrytis cinereal, which establishes latent infections in developing flowers which appear as decays as the fruit ripen.

This project sought to develop a biological control agent for grey mould in strawberries that growers can use to protect their yield.

The team began by collecting a variety of microorganisms from different strawberry growing environments around Australia and tested the ability of each to attack grey mould, both in culture and on strawberry leaves. From 34 candidates collected, the most promising nine were selected and developed into prototype spore powder for field trials.

Field trials revealed that other species of fungus, known as Trichoderma, were best at combatting grey mould. They were able to colonise the ovary of strawberry flowers and reduce latent grey mould infection – a necessary first step in reducing the impact of the disease.

The best four varieties were identified and trialled further. The new agents were found to be very effective in controlling grey mould, even in heavily infected strawberries.

The researchers trialled different rates of application and also investigated the effectiveness of the Trichoderma agents when used in conjunction with in other chemicals typically used in strawberry growing.  

They found no inhibition of Trichoderma from being oversprayed with sulphur, copper oxychloride, copper hydroxide, or potassium bicarbonate, which provide some powdery mildew control options. Myclobutanil and trifloxystrobin inhibited the Trichoderma population by about one third.

As a result of this research, a prototype spore formulation (Strawbotizer) was prepared, ready for commercial trials.

Results suggest the formulation will reduce losses to grey mould by around 65 per cent if used at 100g/Ha on a weekly basis with compatible chemicals.