Everett
Without question Northwest Ohio including Wood County has been suffering droughty conditions. Hold onto your hats. Some of the early leaf drop on our flowering trees and shrubs is not from lack of rainfall.
Did you know that Ornamental Crab Apples and Ornamental Cherries are in the same family as Roses? Did you also know that this family also includes pears, hawthorns, strawberries, blackberries, and raspberries?
These plants all belong to the Rosaceae family. What is also common to this family is forms of leaf spotting fungi. There is a plethora bunch of names depending on the plant that these leaf spotting fungi are called. Examples include black spot on roses, scab on apples and pears, and common leaf spot of strawberries and cherries.
The leaf spotting fungi all have three things in common. The first one is they are a member of the Rosaceae family. The second is the leaf spotting fungi needs to be present. Finally, the third is the right climatic conditions for the fungi to grow and spread.
These leaf spotting fungi proliferated in the spring when the new leaves were forming. The weather conditions that favor leaf spot development is cool wet weather from nine to 17 days. Not only did we have 17 days of this, the entire months of March, April, and early to mid-May we had these climatic conditions.
The leaf spotting fungi feeds on the chlorophyl of the developing leaves creating the spots on the leaves. Some of the spots merged in a term called coalescing. The coalescing gives the appearance of a sheet of spot lesions. Once the environment changes to drier hotter weather the fungus goes dormant and leaves the damaged yellow leaves behind. Leaves with many lesions may develop holes in the leaves from the damaged areas allowing the dead tissue to drop out giving the appearance of insect damage. This is commonly seen on cherries. On apples and pears coalescing tissue causes the leaves to crinkle. With roses the leaves develop black spots across the leaves.
After all this occurs leaves start dropping early some as early as August. The good news is normally this does not cause long term damage to most of the trees and shrubs in the Rosaceae family.
The best way to prevent leaf spotting fungi is to plant disease resistant plants; however, this is not always practical in an established landscape. Cultural controls include raking and composting fallen leaves. Fungicides may be applied to the leaves to protect the plants from fungus attack. Fungicides are applied in the spring during cool wet weather or when conditions favor leaf spotting disease development.
Fungicides work differently from insecticides and some herbicides. Fungicides are applied before and when climatic conditions are right to protect plants from fungi attack. Once a plant is infected applying fungicides will only prevent fungi growth on new developing tissue, and not control any damaged tissue already present. In nutshell fungicides are preventive use only.
Fungicides are classified as pesticides. therefore, applying fungicides after your plants are already infected not only does not control the disease, but it adds another pesticide to our outdoor environment.
There is one more caution in preventing other types of fungal disease that may occur on our maturing vegetable and flower gardens. When applying supplemental water to your gardens, water in the morning preferably before 10 am. This allows leaves to dry out before night fall. During the night, the dew point goes up, and the temperatures drop. If the leaves are wet, going into the evening the climatic conditions are ripe for other disease development. Applying preventative measures not only reduces pesticides in our environment, but it also creates happy plants.
