Hybridizers: It can be fun to breed your own zinnias - Part 2, 1 by Zen_Man

Zen_Man wrote:
Incidentally, that last picture was not taken to document the white dots. It was taken to document disease-like symptoms on zinnias that are caused by insects. That picture shows a lot of cosmetic flaws on the white zinnia petals that were very likely caused by the Japanese Beetle in the picture. Its feet have sharp claws and, in just walking around, the beetle can leave claw marks on the petals. And it stops every now and then to take a taste.

It is good to understand this situation, because it doesn't do any good to spray a plant for disease prevention when the actual cause is cosmetic damage by insects. Japanese Beetles were a problem in Maine, but I just hand-picked them rather than spray insecticides.

The attached picture shows a plant bug on a zinnia and a "freckle" on the petal nearby. I didn't see the plant bug do it, but I strongly suspect the freckle was caused by the plant bug and not by a foliage disease starting on the zinnia petals. Spraying that zinnia to treat a non-existent foliage disease wouldn't be a good idea, unless it was part of an ongoing preventive program.

Incidentally, zinnia petals are relatively delicate compared to zinnia leaves and any spray that will get on the petals should be one-half-strength or one-quarter-strength as compared to what you might use on the foliage or in foliar feeding. Otherwise, you could damage the petals. I have inadvertently been guilty of that on more than one occasion, and now I try to be more careful in my foliar feeding and disease prevention spraying.

ZM

This message was edited Jan 13, 2009 3:30 PM