|What are the small balls of sap on my grapes and what funtion do they do for the plant? They look like aphid damage, but there are no insects present.|
|What you describe is perfectly normal and even has a name. It is called guttation. Vines growing vigorously in the spring can exhibit guttation under high moisture conditions. Guttation occurs when diffusion pressure builds inside plant because of high soil moisture and a low rate of transpiration due to high humidity. Pressure is released by exuding water and minerals from specialized leaf-tip cells called hydathodes. Sap pearls will form on the end of the serrated leaf tips often leaving a dry salt mark after drying up during the day. As mentioned before, it is perfectly normal and nothing to worry about.