Farm Bureau Newsletter
Rain on Strawberry Crops
With these late rains we are having, what are the effects on the local strawberry crop?
Thank you for your concern about the strawberries. Some of us are regretting that we hoped for so much water, because yes indeed it is now setting the growers back.
While frequent rains do not damage strawberry plants themselves that are being grown in properly drained fields – and as a matter of fact can be beneficial since they help in leaching away accumulated and harmful salts- they do cause harm to fruit in two ways.
Rain damage: Damage from rain becomes apparent in strawberry very soon after the rain has passed. One might observe outright damage from the rain droplets striking the surface of the soft fruit, or cracking usually at the stem end and water soaking, where the plant or the fruit simply has taken up an excess of water. While close observers of strawberry note that some varieties seem to exhibit some tolerance to rain, any precipitation over ½” will result in a lot of damaged fruit, no matter what the variety.
Fungal Infection: The real concern for growers during these rains is infection by the fungus Botrytis cinerea, which causes gray mold of the fruit. It is important to point out that this fungus mainly infects floral parts first, but the resulting immature fruit immediately after flowering shows no symptoms of disease. It is only after the fruit reaches maturity, in other words is red and ripe, that we see the symptoms, the gray masses of mold and spores which are thriving on the increased soluble solids within. These spores and fungal parts are then spread around even more to other flowers by continuing rains and splashing water.
With this in mind, it is important that growers of strawberries realize that it is the flower which needs to be protected by the use of fungicides, not the fruit. If one has a lot of flowers open and a rainstorm is in the forecast, it is judicious to apply a fungicide to protect those flowers. Applying to fruit already infected serves very little purpose at all.
The above has been a brief clarification of rain damage in strawberries. Please contact Mark Bolda at UCCE Santa Cruz if you have more questions on this topic or any other topics concerning blackberry, raspberry or strawberry production.