If your trees display evidence of anthracnose (see this page on the signs to look for) then you will need to take quick action in stopping and reversing its effects. Anthracnose is a problem which an increasing number of growers are experiencing and although it appears to affect mainly deciduous trees one should familiarize oneself with the symptoms so that if detected you can take the necessary measures.
One of the tested active ingredients is Mancozeb. The available consumer product is Unizeb. This product is being used by many bonsai growers including myself with good results and a clear improvement. As it does not have a wetting agent I have included SK Eco Oil which will increase the contact of the fungicide. SK Eco Oil is itself a fungicide also and is also very effective against red spider mites.
You can also purchase Unizeb and SK Eco Oil separately. I would also strongly suggest you consider occasionally spraying with Sporekill which can be used as a surface disinfectant and combined with other sprays as an effective fungicidal spore killer.
Choose from an assortment of sprayer solutions here and be sure to wear protection when treating with any pesticide.