The breeding ground for fungi in the world of trees and plants is one of cool and wet conditions. This year we have had record amounts of rain fall which persisted well into the summer and through the time that is typically our dry period. As a consulting Arborist My office was inundated with calls for “sick trees” and falling leaves starting around the end of July. Most time the question arises ” what can we do?
There are a couple of things to consider when combating tree fungi which result in leaf drop and leaf spot fungi. The primary thing to consider is that the weather conditions which bring about a high fungal spore counts do not normally come in consecutive years and often times those symptoms will go away on there in the subsequent year. A strong strategy for managing fungi is what My Prof always said, “good sanitation!” Good sanitation is the cleaning up of downed leaf and twig litter as well as keeping low limbs pruned up off of the ground. In addition to this keeping the tree thinned out for air movement is another great tool , allowing the tree to dry quickly after rain fall. The spores that inoculate the trees hide in the leaf litter and in the ground often “splashing up ” onto low branches reinfecting the tree ,That is why sanitation is important. Most people assume that a spray is the best approach. Although fungicides do exist and are used on fruit tree farms this method is often not practical in residential settings. When farmers use fungicides the timing and frequency of treatment is critical. For example when Apple trees are treated for scab or rust they must be sprayed at bud burst and then every 7 to 10 days until full leaf expansion . As you can well imagine the timing of such a program over a large client base although doable is a large undertaking. Again, the simplest and best approach tends to be sound arboricultural practices .
If one of your trees or plants has been struck by a fungal out break I would suggest a couple of things in closing. One, trees are getting ready to enter their dormant period and will likely push out a new and good set of leaves in the Spring wait and see what happens. Second, If you are really concerned a good root treatment although certainly not a cure is great for helping the trees cope with stress. Lastly if you simply are not sure what to do set up a consultation with a a certified tree expert or and ISA certified arborist.