I expected a bumper crop last year but almost all my apples fell before they...

Asked May 25, 2015, 12:39 PM EDT

I expected a bumper crop last year but almost all my apples fell before they matured. Many had light brown hair line colors inside. What kind of blight is this? I sprayed with dormant oil before leaf out and after blossom drop, I used a fruit spray and later I used Seven to get rid of Japanese beetles. I have used this spray method for several years. I didn't get a chance to use oil spray this year. Here's a photo of my tree taken 2 weeks ago. The apples have set, and pea sized apples have started to drop.

Ramsey County Minnesota apple insects apple trees fruit drop

3 Responses

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.

Thank you for contacting Extension.

Thanks for the quick reply. YES, it is Apple Maggot judging from the photo in the link you sent. I suspected that judging from one of your people said on WCCO last Saturday.That's exactly what my apples looked like inside. I do pick up the apples from the ground and have done so for years, but it is hard on mt 80 year old body. I just crawl on the ground with a basket. I looked at my bottle of SEVIN and it lists Apple Maggot as a controlled pest. I also discovered that I was using it at half strength, 1 1/2 ounces not 3 ounces per gal. Can I start spraying now that the flowers have set fruit? or wait longer.

Do not use your Sevin now. I have copied information here for you from chapter 7 of Integrated Pest Management Manual for Minnesota Apple Growers, a Minnesota Department of Agriculture publication: Apply insecticides for control of apple maggot and other summer pests starting July 15 and continuing on a 14-day schedule into late August. A last insecticide application in September for late-maturing apples would offer protection from late-season pests. This information is intended for apple tree growers who are used to conventional pest control practices and are unprepared or unable to implement significant changes in their apple production practices. If you wish to use fewer pesticides, there are sections in chapter 7 that outline scouting procedures to identify a certain threshold of insect presence before resorting to chemicals. This concept is broadly called "Integrated Pest Management" and focuses on ways of controlling pests, tolerating some, and using as few chemicals as possible since they have adverse effects on pollinators and other wildlife.

Here is the full publication: https://www.mda.state.mn.us/news/publications/pestsplants/pestmanagement/ipm/ipmapplemanual.pdf