This bed is encircled by a tightly clipped boxwood hedge as an extra special border for the hybrid teas. It unfortunately prevents much of the natural air movement at the base of the plants. This, combined with the generous applications of compost every spring and fall created a steam bath. I've removed the irises and replaced them with nine new roses. I now understand that roses don't like company and they want all the attention.
Pest problems tend to occur when plants are under stress.
Changing the habitat or breaking the life cycle of the pest will alter its future success. This sounds simple enough but can be rather difficult to execute when everything is happening so fast. I have thinned out my beds and pruned trees and shrubs more aggressively than usual in order to cope with the increase in moisture. Thinning will promote air movement through the plants and discourage diseases which tend to like humid, dark conditions. I personally dislike those conditions and don't blame many plants for sharing this opinion.