01 May 2016

Will Apple Maggot be the End of Apple Trees?

City of Edmonton
Native to North America, apple maggot Rhagoletis pomonella was first identified as a pest in the Edmonton Alberta region in 2005.  They affect mainly apple trees but have been known to be a problem with hawthorne, cherry, plum, peach, pear, wild rose hips, and cotoneaster.  

Missouri Botanical Garden

The apple maggot has a 500 metre range.  You can tell you may have apple maggot if you see black spots on your fruit, pitting or dimpling.  If you suspect apple maggot, you can verify their existence by cutting open an apple. Tunnelling through the white flesh indicates their presence.  If the fruit is picked early enough and sliced open, placing it immediately in an airtight jar for a day or so will draw the 6.5 to 8 mm maggot out and you will see a small white grub/maggot.  There is no discernible head nor legs.

There is a danger that apple maggot population is on the upwards trend.  So what can you do to prevent or treat the problem?  Apple maggot traps are a non-toxic method of prevention.  It's not 100% effective but it works very well.  The apple maggot trap is essentially a red ball coated with a sticky substance (pheromones) that you hang on your tree.  Some say it works best on the south side of your tree but if in doubt, hang a few, one or more on each side.  It works by drawing the fly to the fruit which they then stick to.  The traps may be cleaned in water and reused by applying tanglefoot as a coating.

At the puncture site on the fruit, the female fly lays her egg.  The maggot then hatches and eats its way through the fruit, creating a tunnel.  When the apples fall from the tree in late summer, early autumn, it is necessary to clean every last one up and dispose of them because at this time the maggot will emerge from the apple to overwinter in the soil around the tree.  Use a tarp or something similar under the apple tree to catch falling apples to interrupt the maggots burrowing in the ground to overwinter.   

The maggots then emerge again from the pupae stage in late June to early July as adult flies, easily distinguished from the house fly as their wings are striped in black and white.  Then after mating, the cycle begins again. 

Last year, at the end of May, apple maggot traps could not be found anywhere in the city.  Some greenhouses were able to get a second shipment in but in case not, substitute a fake apple coated with tanglefoot and hang in your apple tree.

I wish we could make a public service announcement so every homeowner with an apple tree would be made aware of the necessity of prevention and treatment. In the meantime, it is up to you, the apple growers, to spread the word with your neighbours.  The best way to control or even eliminate the problem is by interrupting the life cycle.  Remember, the fly has a 500 metre range, so if one neighbour doesn't take appropriate measures, the problem will continue.  

Not to be a bearer of doom and gloom but here it is:  the city of Edmonton pest control department predicts within five years, there will be no apple trees unaffected in our region.  We must all do our part.



1 comment:

joo said...

Very interesting post!


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