Honeycrisp apples look perfect but have brown patches inside

Asked September 27, 2019, 10:50 AM EDT

A Houghton County Michigan resident has a small honeycrisp orchard and is finding that although the apples appear just about perfect on the outside there are small brown spots/patches on the inside with no insect/larva "tracks". There is absolutely no indication from the outer appearance that there is anything wrong with the apples but so far 100% of apples picked and sliced/opened have these little brown patches inside. The apple trees show no indication of disease or insect infestation. What are these brown spots? What causes them and how can they be prevented in the future?

Houghton County Michigan

1 Response

I am guessing this is apple maggot. It is a fly that emerges in late summer after rains and lays its egg in the apples. It is also called railroad worm because of the brown trails the insects leave as they tunnel through the fruit. I think I can see some trails.
Apple maggot is a major pest in New England. Here in SW Michigan we need to be aware of it from July on. I am not sure when you would need to start to worry about it up there but I would suspect you might be able to wait until August. Sprays are timed to follow rains. the fly emerges and flies around for about a week and then begins to lay eggs in the fruit. Generally a quarter inch of rain is necessary for the flies to emerge but they are not that well timed if the ground is already wet.
Growers and scouts use yellow sticky traps to monitor for the pest and then spray after they catch the fly on the sticky trap. They also use baited red balls to monitor when the flies begin to lay their eggs.