Question
Hi Dr Vann,
I'm a newbie gardener - in that - I've inherited a backyard full of trees from the previous owners of my house.
Last summer I noticed - the weeping willows, the maples and another tree - had big black spots on the leaves. The Home Depot next door identified it as some sort of plant disease - and suggested I spray a product called Dormant - early spring the following year.
So this year - very faithfully - I sprayed Dormant (which is a 1:2 mixture of horticulture oil and Lime Sulphur) before the newbie leaves sprouted.
My question is - have I done the right thing? If yes, how many times am i supposed to apply this spray. The smaller trees I managed to cover every stem with the spray - but the 11 feet maples I just about managed the bottom 6 feet. Is this adequate? What else can I do?

please help

thanks

farah

Answer
Hi Farah:

Spraying early for leaf diseases is good.  Most of the products work best as preventatives, that is, they need to go on just as the buds are breaking.  Multiple applications are usually necessary.  This is based on the information on the bottle label.  The label gives you information on what pests are controlled, mixing proportions, frequency of application.  Good idea to read the label before you make your first application.  Multiple applications are necessary to protect all of that new growth that is forming.  Ideally, you don't want to leave any new tissues unprotected.

As far as coverage goes, to work the best, these materials need to cover the entire plant.  Many of us just don't have the necessary equipment to cover those tall plants.  You may end up covering what you can, unless you wish to hire a professional to do the job.

One helpful thing to do for trees and shrubs is to rake up, collect, and destroy those leaves and twigs that fall from the tree over the winter.  Just go in BEFORE the buds swell in the spring and do this cleanup.  This is helpful since many diseases and insect pests can spend the winter on this dead plant debris under the plant.  By doing a cleanup, this can help to minimize the insect/disease problem the following growing season.

Also, keep in mind that some leaf diseases on our shrubs and trees are significant and some are not.  Always good idea to find out what disease you have and what impact it may have.  Many trees and shrubs can "tolerate" lots of diseases if they are cared for with good husbandry.

Good luck and welcome to gardening!  Contact your local county Agricultural Extension office for good gardening advise.  If you need help locating this office in your county, let me know what state and county you live in and I can send you a telephone number to contact them.

Regards
Steve