Occurrence of Viroids in Commercial Hop (<i>Humulus lupulus</i> L.) Production Areas of Washington State

Fig. 4. Aerial photograph of a ‘Glacier’ hop garden reveals distinct differences in canopy development. The hop garden was photographed with a false color infra-red camera 1 week before commercial harvest. Red is indicative of vegetation while turquoise indicates no vegetative cover. The canopy of rows 1 to 7 is extensive with very little soil exposure; these are rows of ‘Glacier’ in which Hop stunt viroid (HSVd) was not detected. Rows 8 to 34 reveal reduced red intensity that indicates weak and sparse canopy development relative to that of rows 1 to 7. These rows were planted with rhizomes of ‘Glacier’ from a different source and the plants that developed were infected with HSVd. Both portions of the hop garden were planted at the same time and grown using the same practices. The only consistent difference in virus or viroid content between the plantings is the presence or absence of HSVd. (Photo courtesy of Washington State University Center for Precision Agricultural Systems).

Image from Plant Health Progress article:
Occurrence of Viroids in Commercial Hop (Humulus lupulus L.) Production Areas of Washington State