Development of an Advisory System for Grapevine Powdery Mildew in Eastern North America: A Reassessment of Epidemic Progress

Fig. 6. Erysiphe necator colonies developing on field tissue in the early part of the growing season are typified by diffuse growth, low fecundity, and host-cell necrosis at the site of appressorium formation.



Image from Plant Health Progress article:
Development of an Advisory System for Grapevine Powdery Mildew in Eastern North America: A Reassessment of Epidemic Progress