Premature apple drop
I have a haralson apple tree that is approximately 15 years old. It starts dropping its apples in early summer and continues throughout the growing season. By the end of the season, there are no apples on the tree while I have picked up 3-4 grocery bags of small, dimpled, misshaped apples throughout the summer. Over the years, I have sprayed with Liquid Sevin or Bonide, with no noticeable improvement. I have, also, hung red sphere traps which did not trap many bugs. Would dormant oil help or Is it possible that I just have a "bad" tree?
Hennepin County Minnesota
Thank you for the question. I'm guessing that you have two questions; one about premature fruit drop and one about apple pests causing light brown streaks in apple flesh. Apples drop fruit starting with petal fall. This is normal as those fruits that were incompletely fertilized are shed from the tree. The second noticeable fruit drop occurs in June when the tree drops those fruits that are in excess of its ability to nourish to maturity. There are many things that factor in to fruit drop; nutrient availability, climatic conditions, summer pruning and insect infestations. Low soil fertility can also cause premature drop of apples. Soils low in magnesium or high in potassium can contribute to drop. We suggest a soil test to determine if this is an issue. The University of Minnesota Soil Testing laboratory can do this for you. Here is their website: http://soiltest.cfans.umn.edu/
Read more here to learn about fruit drop: http://msue.anr.msu.edu/news/why_does_apple_fruit_drop_prematurely
The tan lines you describe inside your apples may be from apple maggots. Apple maggots burrow throughout the apple flesh making brownish trails, sometimes destroying all the edible parts. Adult apple maggots are flies, just slightly smaller than house flies, their wings marked with dark bands. Read here to learn about their life cycle and control measures: http://www.extension.umn.edu/garden/yard-garden/fruit/apple-pest-management/maggot/ Be sure to read and follow exactly the directions on the container of any chemical you use.
Learn about apple tree care in the home garden here: http://www.extension.umn.edu/garden/yard-garden/fruit/apples-and-pears-in-minnesota-home-gardens/ Pay special attention to the part on how to prune your tree because that is an important part of managing your tree for fruit production.