Abstract :
Prunus necrotic ringspoi virus (PNRSV) is borne in
stonefruit pollen. Previous work has shown that virus
particles can enter cucumber seedlings when virus-bearing
pollen grains contact puncture holes made in plant
cells by thrips feeding. Stonefrtiit plant parts on which
pollen is deposited and thrips spend considerable time
feeding, are likely sites of PNRSV inoculation. The principal
agents of pollen deposition may therefore play a
key role in PNRSV epidemiology. We determined the
principal sites of pollen deposition on Japanese plum
trees and the major pollen depositing agents in a PNRSVinfected
orchard in southeastern Queensland. Plum pollen
was deposited mostly onto flowers, with few grains
being found on leaves or stems. Within the flowers, pollen
grains were distributed mostly on the petals, but some
were found on the sepals, filaments and carpels. Honey
bees were the most frequent visitors to plum flowers and
they deposited more than any other insects. Flies ʹvisited
flowers at low frequencies and also deposited pollen. Significant
amounts of pollen were deposited onto flowers by
unidentified nocturnal agents. Thrips were not observed
during the study period, although they were present in
the orchard. Previous studies have assumed that thrips
carry virus-bearing pollen as well as bring it into proximity
of feeding wounds. Our results suggest that,
although thrips carriage of pollen may occur, it is not
necessary for PNRSV spread in stonefruit orchards
