Powdery mildew

摘要

Accurate identification of the species in an outbreak is vital to choose the correct chemical treatment. Powdery mildews are among the most serious of all plant diseases, attacking both protected and outdoor ornamental crops. Lonicera, Clematis, Spiraea, maple, oak, Rhododendron, roses and thorns are among the main nursery stock hosts. The most susceptible bedding and pot plants include pansies, trailing Petunia, Verbena and Myosotis, while powdery mildew is a particular problem for poinsettia growers. One form, Mediterranean powdery mildew, Leveillula taurica, can also occur on other crops. Whatever your crop, regular inspection and accurate identification of the powdery mildew species involved in any outbreak is vital, not only because you may have a notifiable disease but because effective chemical control depends on using the right material for the type of powdery mildew you have— not all chemicals are equally effective against all genera. There is a risk of disease resistance, so use alternate products from different chemical groups to reduce it.