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

Fig. 7. Fluorescein diacetate is a stain that helps visualize esterase activity. Erysiphe necator colonies that were subjected to an acute cold exposure have gaps of fluorescence in the hyphal strands, indicating damage.
(A) Control colonies do not have noticeable damage.
(B) Cold treated colonies (8 h at 2°C) have a greatly reduced fluorescent area and noticeable gaps in fluorescence in hyphal strands.



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