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Electron and Confocal Microscopy Unit

These flower mites may avoid pesticides by hiding out in a rose’s internal organs

While stopping and smelling the roses, keep an eye out for signs of the tiny mites that may be living inside them. The rose bud mite (Phyllocoptes fructiphilus) is half as big as a grain of salt, and it spreads a virus that has been devastating roses across the United States since the 1940s. So far, this virus has been deemed incurable. Now, scientists may have figured out why these mites are so hard to find and control: They take up residence deep within the flower’s internal organs.

Rose bud mites transfer the rose rosette virus while feeding on the flower. This virus then transforms the once-beautiful plant into one with excessive thorns, deformed flowers, and tight clusters of flower buds called rosettes. Since the mite was discovered in California, this disease has spread to 30 states.

To gain a clearer picture of how these mites wreak such havoc, scientists studied the stems, leaves, and flowers of both diseased and healthy roses from 10 states and Washington, D.C. The team reports in the Journal of Environmental Horticulture that high-resolution images revealed that the mites hide deep within the flowers.

The mites embed themselves in the tiny hairs on a flower’s sepals, the leaflike appendages located at its base. This placement may protect the mites from insecticides and sprays, the scientists suggest.

For rose producers, breeders, and enthusiasts, these findings could help find ways to stop the mite from spreading.