When the Honeycrisp apple was introduced by the University of Minnesota, I had to get a tree. As usual, enthusiasm overruled reason, and when I planted the tree I didn't even think about how to prevent wormy apples.
A few years passed, and the tree finally bore the long-awaited fruit: knobby little pocked apples crawling with apple maggot.
I knew about apple pests — apple maggot is probably the worst here — but I didn't want to spray the tree with chemicals. To get perfect apples, you have to spray several times during the summer and in rainy years like this one, you have to reapply the chemicals, too.
In my tight urban yard, the idea of using chemicals was unappealing, especially with my neighbor's side door a few feet away. I started investigating other options, and found out that in Japan, they bag apples to prevent pests. They literally put bags around apples when the fruit is small and let the apples mature all sealed off from bugs and the elements.
I ordered some Japanese apple bags on the internet. Each tissue bag was double-layered, with a soft gray bag hidden inside a bright red one. Both bags were supposed to be slipped over the apples and secured with a wire twist.
It was easier said than done. The bags flew off during storms, ripped and just fell off. I had a grand total of one good apple left at harvest, and hungered for more.
Then I participated in an informal U of M trial on bagging apples in plastic sandwich bags, and I've been doing that ever since.
I bag my apples when they're the size of a big grape. Timing is critical, since apple maggots usually show up around the first of July. Since apples grow in clusters, I thin the branch so that two or three of the biggest and cleanest apples remain. Using regular sandwich-size Baggies, I slip the bag over the fruit and press the seal shut from either side of the fruit, stapling the bag on both sides for good measure. It's best of cut the bottom corners of the bags to release water and moisture.
And that's all there is to it.
While the work sounds picky, it's worth it. I can bag 80 to 100 apples in a couple of hours. I thought the fruit would cook or spoil in the bag, but they don't. Some of my Honeycrisp get russetting in the bag — raised rust-colored lines on the fruit skin — but that's only a cosmetic problem. A few apples drop during the summer and sometimes earwigs and lady beetles get into the bags when the fruit is nearly ripe and eat around the stem. But I get about 95 percent very good tennis-ball sized fruit, and none of it is wormy.
Last year I gave some of my apples to friends, who could not believe how good a Honeycrisp fresh off the tree tastes. They're amazing.
You can read about bagging apples here: www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Feb0102.html

And you can read all about growing apples in Minnesota here: www.extension.umn.edu/distribution/horticulture/M1235.html

Here's what those branches looked like once the fruit had been thinned and two apples were bagged.