| It is common practice within greenhouse operations to monitor insect populations with yellow
or blue sticky cards placed throughout the crop. This is an effective strategy to time insecticide treatments when they are most needed, thus reducing direct insect damage to the crops. However, this system by itself provides little or no value in monitoring the presence of virus carrying (viruliferous) insects in the crop. Years ago it was found that certain petunia cultivars could be excellent indicator plants for tospoviruses. A healthy thrips feeding on the plant creates typical cleared areas. The feeding scars left by a viruliferous thrips are distinctly different, leaving a black lesion wherever the thrips have fed.
By placing petunia plants within the crop, and checking them weekly, a grower could immediately spot a virus threat and react accordingly.
Read about in: "Using petunia indicator plants to monitor tospoviruses in
ornamental plants" by Karen Robb, Christine Casey, Anna Whitfield, Leslie
Campbell, Julie Newman and Diane Ullman.
http://commserv.ucdavis.edu/CESanDiego/petunia.pdf
Read more at: University of Minnesota, Extension Bulletin
http://www.extension.umn.edu/distribution/horticulture/DG7375.html
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