[NAFEX] Plastic bags over apples vs. spraying

Nathan Torgerson nathantorgerson at yahoo.com
Mon Apr 19 14:02:16 EDT 2004

As the temperature hit 90 and windy in Minnesota yesterday and the apple trees are about to bloom, it's hard not to think ahead about the coming apple season!

To get summer topics started, I wanted to share my experience I had last year with covering apples with sandwich bags.  I would sure like to hear if others have tried this and what kind of results were obtained.


In year 2003 I experimented with covering apples with sandwich bags (with twist ties) over the apples on one of my trees (The Univiersity on Minnesota has been trialing this technique).  I was trying this to increase the quality of the apples without the need for spraying.  The Zestar apple tree I used has had apples for three years and the apples were beginning to be deformed last year with brown spots (cedar-apple rust?) and apple maggots, as well as being attacked by catbirds.


On June 1st, I thinned the apple tree to 80 apples (4-6" spacing). 20 apples I left alone as controls, 30 of the apples were covered with sandwich bags with twist ties with small cuts in the corners of the bags, and 30 bags without the corners cut out (The corners cut-outs are to allow water to escape if water gets inside, but I got lazy and wanted to figure out if it was necessary).  June 1st is a little early to be thinning, but that is the recommended time to put the bags on the apples to keep the apple maggots off of them. The apples ranged in size from a dime to a quarter).  I also figured that the earlier I got the bags on that it might also help keep some of the later generations of other pests out, such as coddling moths, if I tied the bags on relatively tight, but not too tight to choke the apple. It took a little over an hour to thin and bag the apples.

When the tree thinned itself in June, I lost about 20 of the bagged apples and 5-10 of the control apples.  The rest made it to harvest.


The color of the apples, the size, the ripening time, and the flavor of the apples in the bags seemed identical to the control apples.

The catbirds that routinely attacked my apples the year before didn't touch any of the bagged apples, and may have pecked at a couple controls, which opened the skin for bees and ants to eat out of them. (Note: a couple of the apples on antoher tree I had on until October, and the squirrels carried those two away, bags and all.  They didn't bother  teh Zesar tree, which ripens in late August/early September in MN).

Of the 40 bagged apples harvested: 

36 of the apples were free of blemishes...no apple maggots, no coddling moths, and no brown spots on the skin (cedar-apple rust spots?). I didnt' notice any difference between the bags with teh corners cut out and the ones that did not.  A small amount of water were in a couple of the non-cut bags, but not enought to worry about.  

2 apples had some pest...I am guessing coddling moth.  

2 apples had a split in the skin about an inch long. I don't know what it was from, the bag didn't have a hole in it that would suggest damage from a bird.  Could the apples have overheated in theie bags and split open a little?  The apples tasted fine.

Every one if the 10 control apples had blemishes on it, either from brids, apple maggots, bees, and/or brown spots (cedar-apple rust?).  The U of MN hasn't claimed that plastic bags prevent cedar rust damage, but could it?

I'll take pictures of the fruit to document it better this year.  Since as least one generation of coddling moth attacks the blossoms and not the fruit, I don't think bagging will completely control them if you have a serious problem, but it still might help. I don't have a major issue yet, but my trees are young.  Anyway, if all the apples are bagged, I fugure at least the coddling larvae will be trapped in the bags an not escpape to get me next year.


 Andover, MN, Zone 4


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