Factors affecting flower and immature fruit loss in pincherry and chokecherry
Date
1997
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ORCID
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Degree Level
Masters
Abstract
The objectives of this study were to quantitatively define the timing, extent and
causes of flower and immature fruit loss for pincherry (Prunus pensylvanica L.) and
chokecherry (Prunus virginiana L.). An estimated 75% of flower and immature fruit
loss in both pincherry and chokecherry occurred just after full bloom and was attributed
to inadequate pollen transfer. The remainder of the flowers and fruit lost was attributed
to insect damage. In 1995, insect damage to reproductive structures accounted for 14%
of flower and immature fruit loss in pincherry and 8% in chokecherry. The major insect
pest of pincherry fruit was a sawfly (Hoplocampa sp.) which accounted for 11% of total
fruit loss. The major insect pest in chokecherry was the leaf-roller (Archips argyrospila),
which was responsible for 7% of the total amount of flower and fruit loss. Diseases were
not a factor in flower or immature fruit loss in either pincherry or chokecherry.
Pincherry in this study was found to have a growing degree day requirement
(GDD5°C) of 144±8 for full bloom and 780±8 for fruit ripening. Chokecherry in this
study had a GDD5°C requirement of 224±20 for full bloom and 1099±23 for fruit
ripening. Pincherry required an average of 59±6 days from full bloom to harvest while
chokecherry required 76±3 days.
Yields of mature fruit in pincherry calculated from non-destructive sampling were
4.3% of potential yield (the total number of flowers at full bloom) in 1994 and 32.6% of
potential yield in 1995. Based on destructive sampling, yields were 38% and 48% of
potential yield in 1994 and 1995. The yields of mature fruit in chokecherry calculated
from non-destructive sampling were 7.5% of potential yield in 1994. In 1995 yields from two separate sites were 8.6% and 5% of potential yield and in 1996, 3.7% of potential
yield. From destructive sampling yields for chokecherry were 19% of potential yield in
1994 and 17% of potential yield in 1995.
Studies on the role of pollen source and the effect of supplemental cross
pollination of pincherry and chokecherry suggest that the majority of abscissions result
from a lack of adequate pollen transfer. Pincherry was found to be self-incompatible,
requiring cross-pollination to ensure maximum fruit-set. In 1996, flowers that were
cross-pollinated by hand produced a yield increase of 55.6% in comparison to yields from
flowers that were open-pollinated. Chokecherry was found to be partially self-compatible,
producing fruit yields of 7.1% of potential yield in 1995 and 18.8% of
potential yield in 1996 in flowers that were self-pollinated by hand. Flowers that were
cross-pollinated by hand resulted in a significant (p=0.05) 42.9% and 16.3% increase in
yield in 1995 and 1996 respectively, as compared to flowers that were open-pollinated. Pincherry flower buds were susceptible to freezing temperatures ranging from -4
to -12°C during the first stage of flower bud development designated as green bud.
Chokecherry flower buds in the green bud stage were susceptible to freezing in the range
of -8 to -20°C. Flower buds and flowers were susceptible to freezing temperatures in the
range of -2 to -4°C for pincherry from the first-white stage until post bloom and for
chokecherry from the open cluster to post bloom stages.
Orchard cultivation of both pincherry and chokecherry seems plausible but
pollination management strategies and insect pest control will be required to maximize
yields.
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Degree
Master of Science (M.Sc.)
Department
Horticulture
Program
Horticulture