[NAFEX] Plastic bags over apples vs. spraying

Nathan Torgerson nathantorgerson at yahoo.com
Tue Apr 20 14:36:56 EDT 2004


The article (2001, http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Jan0101.html#apples) also talks about another study that used a clay spray that had similar results to the plastice bags.  This might be a good alternative for orchards, just another type of mechanical barrier to keep pests away.  
I'm pretty sure I bagged my tree in an hour (60 apples), but the article mentions fifty in several hours, so either my memory is bad or the article had some really slow baggers!
(It's probably a little of both).
    
If bagging really does work for a wide area of the country, I would expect that someone will make devices that will allow you to bag an apple in a few seconds. (Elastic band opening on a plastic bag with a dispencer, for example).  I thought I read somewhere that they already have a machine to put paper bags over fruit. The pain with paper bags is that you need to remove them late in the season in order for the fruit to ripen properly.
 
Article clipping:
>>>>>>>>
I've been following work done by the Agricultural Research Service, part of the USDA. Researchers there have sprayed apples, among other plants, with a special clay (kaolin) coating. They've found the coating is highly effective in minimizing insect damage and disease. The apples that were coated weighed an average of 17% more than the uncoated! While this will be great for commercial growers who would have the sprayers needed to coat a tree, home orchardists will benefit from a bagging method. (The article, "Whitewashing Agriculture", was published in the November 2000 issue of Agricultural Research magazine. Read it on-line at: http://www.ars.usda.gov/is/AR/archive/nov00/white1100.htm
>>>>>>>>>>>>>>
 
Nate

Tom Olenio <tolenio at sentex.net> wrote:
Hello, 
I have not read the article on bagging, but the first thought that jumps to mind is that it is a self limiting practice. 
It is fine for a hobbyist who has just a few trees in their backyard.  However, if you have a number of trees, the practice becomes impractical. 
In my own mind, any more than 4 trees would be a large chore.  Any more than 10 trees and you would need a crew. 
You would still need to spray fungicide at "green tip" and fungicide and pesticide at "petal drop", while waiting for the apple to form, prior to bagging. 
I will give the article a read though. 
Later, 
Tom 
Nathan Torgerson wrote: Results from a study about bagging apples done in Minnesota from year 2000 to 2002 can be found at: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Feb0102.html They started several different types of bags in year 2000, but by last year they went exclusively to plastic bags because of the high success rate.  What I like about the process is that, even though it takes a little while in the Spring to bag them, you can forget about them teh rest of the year!  You can go on vacation and not worry about spraying schedules, weather, or the dangers of chemical applications on fruit.  Antoher intersting part of their findings was that the apples were at least 15% larger..which is interesting.  I didn't weigh mine, but they were pretty good size.  They left two apples per cluster, while I only left one per cluster when thinning, becuase it was a lot easier to bag the apples with only one left per cluster.  They also found that certain green apples didn't do as
 well. Would there be any interest in having a NAFEX study on bagging apples?  The results shown in Minnesota only are from Zone 4...I'd be interested to know if the method works in warmer zones, in more/less humid areas, or areas with more/less sunshine. Also, it would be interesting for people to try it that have high coddling moth problems and disease issues to see if the plastic barrier helps. Nate  
Mark Lee <markl at nytec.com> wrote: Thanks Nate!  This is really good information.  I have heard of bagging apples before, but not using ordinary sandwich bags.  I am surprised that you did not have to cut ventilation holes in the bag.  We have a big problem with scab in the Seattle area.  I wonder if this would be a problem in the plastic bags.  My biggest problem as far as fruit quality goes is with coddling moths.  I think I will bag some apples this year with your method and see how it works for me.

-Mark Lee, Seattle, zone 7B/8A 

-----Original Message----- 
From: nafex-bounces at lists.ibiblio.org [mailto:nafex-bounces at lists.ibiblio.org] On Behalf Of Nathan Torgerson 
Sent: Monday, April 19, 2004 11:02 AM 
To: North American Fruit Explorers 
Subject: [NAFEX] Plastic bags over apples vs. spraying 

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. 
Test: 
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. 
Technique: 
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. 
Results: 
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. 
Nate 
Andover, MN, Zone 4 

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