Apple pest report

Flyspeck

In orchards that received renewed fungicide protection after the rain on August 20, flyspeck infections are not expected to accumulate enough wet hours to be a threat for fruit harvested before October 2 for storage, and at least a week later than that for fresh pick harvest. With no extended rainy periods in the current forecast, there should be low risk general risk of flyspeck in those orchards well into October.

The story is different for orchards where the final fungicide application was made prior to August 20, and where protection was largely depleted by the heavy rain on August 20. In those blocks, fruit harvested after September 14 and put into cold storage have some potential risk of further flyspeck development until fruit become cool and dry resulting in visible colonies. Apples on the tree could start to show visible flyspeck infections starting around September 22. Risk of visible flyspeck colonies increases for dates beyond September 22. Trees with thick canopies and in low spots where morning fog and dew persists are most at risk.

Scab

Spending about 20 minutes per block to inspect 100 shoots for scab-infected leaves gives you valuable management information for next spring. Finding fewer than 5 scabby leaves per 100 shoots indicates that the orchard will have a low scab inoculum level next spring, and that fungicide protection can be begin as late as late Tight cluster instead of at Green tip. Finding 18 or more scabby leaves per 100 shoots is strong indication that scab prevention sprays should begin as soon as green tissue is present next spring (Green tip).

Apple leaves lose natural resistance to quiescent scab infections starting around mid-September. Prior to that, inactive scab infections may be present but not visible. After mid-September, you can get an accurate assessment of next spring's scab spore potential. Waiting too long brings on a variety of other leaf spots as leaves senesce, making it impossible to quickly and accurately gauge the scab level. The date when these 'old age' leaf spots start appearing varies by year, orchard, and cultivar. The period for all-green apple leaves and efficient scab scouting in southern Maine usually lasts until around October 10.

McIntosh Maturity

Starch index values provided by Dr. Renae Moran. No ethylene detected as of September 5.

Excerpt from the September 1 Orchard Newsletter by Dr. Moran:

"When starch index is in the range of 5.0 to 6.0, it is ok to harvest for short term CA storage, but fruit may be too ripe for long term. This is usually about the time when McIntosh ethylene levels cause fruit to ripen and drop. When starch index is past 6.0, McIntosh are ripe and should not be stored longer than two months. \

Starch index of 5 to 6 does not always coincide with the beginning of ethylene production. Internal ethylene is a better indicator of when it is too late to harvest for long term storage. When picking fruit for immediate sale, it is not necessary to measure ethylene or starch index."

Happy Harvest!

- Glen

Glen Koehler
Pest Management Office
491 College Avenue
Orono, ME 04473
Voice: 207-581-3882
Email: gkoehler@umext.maine.edu
Web: PRONewEngland.org
Fax: 207-581-3881

TDD 1-800-287-8957

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