![Elizabeth Bush This image provided by Bugwood.org shows powdery mildew symptoms on zinnia foliage. (Elizabeth Bush/Virginia Polytechnic Institute and State University/Bugwood.org via AP)](https://mapi.associatedpress.com/v2/items/417b8be72ff2423faa3f4420a7dc866e/preview/preview.jpg?s=680x)
This image provided by Bugwood.org shows powdery mildew symptoms on zinnia foliage. (Elizabeth Bush/Virginia Polytechnic Institute and State University/Bugwood.org via AP)
![Elizabeth Bush This image provided by Bugwood.org shows powdery mildew symptoms on zinnia plants. (Elizabeth Bush/Virginia Polytechnic Institute and State University/Bugwood.org via AP)](https://mapi.associatedpress.com/v2/items/27da978eaba1412e8a76a0488e7981fe/preview/preview.jpg?s=680x)
This image provided by Bugwood.org shows powdery mildew symptoms on zinnia plants. (Elizabeth Bush/Virginia Polytechnic Institute and State University/Bugwood.org via AP)
![Elizabeth Bush This image provided by Bugwood.org shows powdery mildew symptoms on a zinnia plant. (Elizabeth Bush/Virginia Polytechnic Institute and State University/Bugwood.org via AP)](https://mapi.associatedpress.com/v2/items/617432330582401c997708887f4d1e1d/preview/preview.jpg?s=680x)
This image provided by Bugwood.org shows powdery mildew symptoms on a zinnia plant. (Elizabeth Bush/Virginia Polytechnic Institute and State University/Bugwood.org via AP)