RAPID EPIPHYTIC COLONIZATION OF APPLE FLOWERS AND THE ROLE OF INSECTS AND RAIN

The stigma imprint technique was shown to be more sensitive than flower washing for detecting the presence of Erwinia amylovora on the stigmas of inoculated flowers.
The technique is rapid and simple enabling daily sampling of large numbers of flowers.
Imprints were taken daily in a Jonathan apple orchard in West Mountain, Utah in 1996 and 1997 and a mixed apple orchard in Spanish Fork, Utah in 1998. E. amylovora was not detected in the flower samples in early bloom.
The incidence increased to nearly 100% colonization in 2–3 days during periods without rain. E. amylovora was first detected on washes of bulked insects caught daily in a Malaise trap on the same day that the bacterium was first detected on the flowers.
Flowers on branches covered with nets to exclude insects did not become colonized.
There was a large increase in the number of muscoid flies on yellow sticky traps adjacent to oozing cankers but not on traps on nearby healthy trees.

VIII International Workshop on Fire Blight

S.V. Thomson, A.C. Wagner, S.C. Gouk

Erwinia amylovora, insect vector, muscidae

https://doi.org/10.17660/ActaHortic.1999.489.78