Is there fungus among us?

In the southeast United States, due to high humidity, the most important plant protectant that you can use for roses is a fungicide.  Fungicides come in many different forms, formulations, and modes of action.  Every company suggests that theirs is the best, so what do you use?

1.       Systemic fungicides – systemic fungicides work from within the plant to make the plant itself fight the onset of blackspot, powdery mildew, or downey mildew.  These fungicides can be applied foliarly (sprayed) or in a soil drench or granular application.  There are fertilizer products that include systemic fungicides as well.

2.       Contact fungicides – contact fungicides stay on leaves of the plants to destroy mold spores that are found there.  They are always applied foliarly and they come in many different forms.  Most of the “natural” fungicides on the market are contact fungicides.

3.       Application – whatever foliar spray you are using has to be applied correctly to be effective.  When spraying, the chemical has to be applied to the bottom of the leaf.  The bottom o f the leaf is porous and that is where the systemic fungicide can be absorbed into the plant and where the blackspot spores will attach and cause problems.  Apply the fungicide to the entire rose bush to the point of a light drip, paying special attention to the bottom of the leaves.

We have found that the best way to protect roses from the onset of fungal diseases is to combine a contact fungicide with a systemic fungicide.  This can be done with both items in the same spray application, if blackspot is causing major headaches, or it can be done by spraying a contact fungicide one week followed by a systemic the next week.  As always, carefully read the label of any chemical that you use and apply it per label instructions.  The Witherspoon Special Spray Recipe Set includes Captan and Thiomyl which are contact and systemic sprays respectively.  Preventive fungicide application is extremely important to have beautiful and healthy rose bushes with leaves from the ground up.