How to Manage Pests
UC Pest Management Guidelines
Initial infections of Rhizopus fruit rot appear as discolored, water-soaked spots on fruit. These lesions enlarge rapidly, releasing enzymes that leave the berry limp, brown, and leaky. Under conditions of high relative humidity, the berry rapidly becomes covered with a coat of white mycelium and sporangiophores. The sporangiophores develop black, spherical sporangia, each containing thousands of spores. When disrupted, these sporulating berries release a cloud containing millions of spores. Rhizopus and mucor fruit rots closely resemble each other and may be difficult to differentiate in the field.
The fungus is an excellent saprophyte that lives on and helps break down decaying organic matter. It invades strawberries through wounds and secretes enzymes that degrade and kill the tissue ahead of the actual fungal growth. The fungus is active most of the year in California and survives cold periods as mycelium or spores on organic debris. Spores are airborne. The pathogen has a large host range and is prevalent worldwide.
Rhizopus stops growing at temperatures below 46° to 50°F (8° to 10°C), so rapid postharvest cooling of fruit is essential for disease control. Field sanitation also is extremely important: do not leave discarded plant refuse or berries in the furrows, and be sure to remove all ripe fruit from the field. There are some benefits to the use of protective fungicides, but unless the disease is widespread throughout the field, this pathogen should not cause excessive damage.
Organically Acceptable Methods
UC IPM Pest Management Guidelines: Strawberry