This
article comes to you from the January 2011 edition of “The Latest
Dirt” – the newsletter of the Cooperative Extension Service of the
University of Kentucky. It is authored by John Hartman, the Extension
Plant Pathology Specialist
How
will fruit crop diseases respond to the Drought of 2010?
John
Hartman, Extension Plant Pathology Specialist
During
this past growing season, Kentucky crops suffered from hot weather
and varying degrees of drought,
depending on location. In most of Western Kentucky, the drought began
in June, whereas in central
regions the drought began in August.
For
perennial crops such as apples and peaches, the drought likely
affected the health and productivity of Kentucky orchards. This past
summer, leaves of drought-stressed plants closed their stomata which
reduced their rate of photosynthesis. Photosynthesis reduction may
not kill a tree or shrub, but it means fewer carbohydrates are made
and stored for future use. Recently transplanted fruit trees posed
the greatest risk because they had not yet developed extensive root
systems.
After
experiencing a drought, some fungal fruit diseases do not show
symptoms until the following season
after the drought has passed causing diseases such as Botryosphaeria
canker of apple or blueberry,
peach Cytospora canker, or Armillaria root rot of most tree fruits is
not clear.
The
stress condition may have interfered with the plants’ defenses
against such pathogens, or possibly, the
reduced carbohydrate reserves provided the plant less energy to fight
pathogen invasions. Some
apples and peaches, in their search for water, could have sacrificed
surface roots to the drought while
relying more heavily on deeper roots.
If
we have excessive rains in root rot diseases. This could leave fruit
trees with few functional roots so you
may expect additional orchard decline. A benefit of drought is a
possible reduction in foliar diseases in the next year. There could
be less carry-over inoculum from foliar and fruit diseases such as
apple scab, cherry leaf spot, powdery mildew, or fruit rot diseases,
for example. However, if we
have a wet spring, this could be a short-lived benefit.
Looking
ahead even farther, the rust infections of cedar that should have
occurred, but didn’t during the dry
2010 summer, might result in fewer cedar galls in the spring of 2012
plus less rust on apples that same
summer. Kentucky fruit growers should be aware that even after the
2010 drought ends, their fruit trees will still carry scars and
memories of it. If you want to improve tree health, you should reduce
competition from weeds, provide good drainage during wet periods plus
adequate water during
dry periods and thin fruits to avoid excessive fruit load.
—
Contact
information for the local Cooperative Extension Service is included
below. Be sure to reach out to them – they are a great resource and
we thank them for allowing us to share this article on our blog!
Cooperative
Extension Service
Jefferson
County
810
Barret Ave.
Louisville,
KY 40204-1782
(502)
569-2344
Fax:
(502) 569-3958
http://ces.ca.uky.edu/jefferson/
You
can also find them on facebook by searching for “Jefferson County
Cooperative Extension Service”