Question
I planted Marigolds and Silvia and they were doing great.  Now I have noticed a white poder on the leaves and hundreds of little white bugs that fly out of them when watering the plants.  The Marigold buds are dying before they even bloom.  What do I do?

Answer
Bonnie, it sounds like your marigolds have contracted powdery mildew, a fungus disease that infects several annuals, including marigolds and zinnia. There are disease resistant hybrid varieties on the market, but they must be grown from seed which can be purchased through a bonafide seed company.

To combat this disease, you must use a copper based fungicide. I use a product called Soap Shield, and it works great. But it is best to start spraying in early summer to prevent the disease, because once the plant is infected, powdery mildew is extremely difficult to cure. Attached is a link to this product if you are interested.

http://www.gardensalive.com/product.asp?pn=8066&ss=Soap%20Shield

In regard to the insects, these are most likely white flies. They are minute in size, but do a tremendous amount of damage because of their large quantities. They tend to attack plants that have been weakened by disease, which certainly fits your description.

There are combination products sold at most garden centers that will control both insects and disease. These are sold primarily for fruit trees, but will also work well on flowering plants.

I hope this answered your question. Good luck, and please write again if I can ever be of assistance.

Regards,

Mike