A Look Back at the Season....
Disease Situation:
Apple Scab: Since 1999 was a very dry season, we started the 2000 growing
season with many orchards having lower amounts of overwintering inoculum than
"normal" because the dry weather last year was not favorable for scab
development. However, Vermont saw one of the wettest springs on record, making for a very
challenging primary scab season. It appears that in some orchards scab lesions showed up
on the very earliest leaves (perhaps infected during the wet conditions that were present
in some parts of the state on April 22-23) and after that it was a battle all throughout
the remainder of the scab season. In other orchards, it appears the period from May
5-12 was critical because of all the rain and the washing off of fungicide residue,
allowing infection to occur before the next fungicide application. In visits to
orchards around the state, it was not difficult to find scab. With
potentially high PADs heading into next season, we will need to be on the alert for
the 2001 season.
On a brighter note, delayed-spray trials conducted by UVM grad student Jess Reardon have
shown promising results even in a challenging year for apple scab.
Fire Blight: Luckily, no orchards in the state reported fire blight
infection although the Maryblyt program predicted that conditions were favorable for
infection during Bloom in two of the orchards we where monitoring.
Powdery Mildew: Powdery mildew was severe on Cortlands in a few orchards we visited
which did not use any SI or Stroby fungicides. The disease had a noticeable impact
on canopy leaf density. It is a reminder that even in Vermont where cold
winter temperatures can reduce overwintering inoculum, powdery mildew can build up and be
severe on susceptible cultivars.
Cedar Apple Rust: The potential for infection was high because of the wet
weather we had but, we observed only a few foliar lesions in some commercial
orchards around the state. For the most part, the fungicides such as the EBDC and
the SI fungicides that were applied from Tight Cluster through Petal Fall were
effective in preventing infection.
Quince Rust: Given the wet spring, it was not surprising to
see quince rust lesions
Phytophora Crown and Root Rot: Typical symptoms of Phytophora
crown and root rot were observed -- both in orchard blocks that were considered
well-drained and in blocks whose soil tends to stay wet. Again, the rain we had last
autumn associated with the hurricane plus the rains this spring provided conditions
favorable for infection.
Sooty Blotch/Fly Speck: We are not aware
of high incidences of sooty blotch and fly speck this year. Two reasons may explain this:
1) many growers maintained a full protectant fungicide schedule throughout the growing
season to control scab, thereby also controlling these summer diseases; and 2) our
relatively cool summer may have provided temperatures not conducive to disease
development.
|
