Controlling Apple Maggot Fly in Apple Trees

The apple maggot fly is here and it’s destroying beautiful apples.

From this…

beautiful apples

To this…

apple fly maggot

We’re no experts on the subject, but we do love our fruit and thought we’d share some of the strategies we’ve learned about to combat these pesky apple pests.

What’s the Problem?

Apples that are dimpled on the outside and looked bruised, rotten or covered in tiny brown vein-like lines on the inside.  Warning, the following photos and descriptions may be disturbing!

apple fly maggot
Notice the dimples on the outside. That’s from the female apple maggot fly laying her eggs.
apple fly maggot
Some apples look okay on the outside, some are misshapen, but the little dots and dimples indicate a problem.
apple fly maggot
On the inside, bruising, rotting and tunneling occur when the larvae start to feed and move through the apple.

 

apple fly maggot
No one wants to take a bite of that! Technically, safe for making juice or applesauce.

 

What Causes the Problem?

These particular symptoms are caused by the apple maggot fly – Rhagoletis pomonella.

apple maggot fly
Apple Maggot Fly Photo Source: City of Edmonton

Slightly smaller than a housefly, adult apple maggots​ ​are 1/5 inch long and have black bands — resembling a W — running across their transparent wings.

apple maggot flies
Smaller than house fly, distinct black and white markings on transparent wings. Photo Source: Nova Scotia Fruit Growers Assoc.

The larvae (1/4 inch long) are white, tapered maggots that tunnel throughout the flesh of fruit.​ ​Sometimes called railroad worm​s. They are only found in the flesh, not the core (those are coddling moth maggots).

The Apple Maggot Fly Lifecycle

In order to stop them, you need to understand their lifecycle:

Adult flies come out of the ground around late June early July and can be active until early fall. They feed then mate and then lay eggs by piercing the skin of the apple (making the dimples). The eggs are deposited just under the skin.  The eggs hatch into maggots (after about a week) which feed and tunnel inside the flesh of the apple, leaving the apple bruised and tunneled on the inside. The maggots then leave the apple, usually once the apple falls to the ground, but sometimes before then. They enter the soil where they pupate and hang out for the winter (sometimes for up to two years) to emerge and start the cycle again the following spring.

Apple maggot flies are tough and will travel. Even if you manage your property very well, they can come from surrounding areas to find your apples, so be vigilant.

How to Control Them

Here are some steps to control them based on ideas and excerpts from these articles: University of Minnesota Extension on Apple Maggot FliesCityFruit.orgGrainnews. Ideally, use a combination of techniques.

  1. Break Their Lifecycle.  
  • pick up any fallen apples IMMEDIATELY to prevent the maggots from moving from the apple to the soil
  • throw infested apples in the garbage, not your compost bin
  • if possible, lay a tarp under the tree while apples are falling as a barrier to prevent them from burrowing into the soil

2. Put Up Traps

Traps will help reduce the number of flies that reach your apples and they are a good indicator of when and if the apple maggot fly is a threat. However, the traps will likely not get all of the flies. Still, they’re a good bet. If you get a lot of apple maggot flies you may want to consider spraying an insecticide like spinosad, a natural bacterium insecticide.

When: Put up traps when flies emerge from the ground and keep up until apples are harvested.  Aim for June 1.

Re-apply: Remove anything stuck to the traps and re-apply tanglefoot every 4 weeks or as needed to ensure they’re still sticky

How Many: Hang 1-2 traps per dwarf tree, 4 to 8 for large trees (one trap per 100 apples)

Where: Hang head height towards the outside of the tree so it can easily be seen. Hang close to fruit, not on its own, but far enough so wind won’t cause fruit or leaves to touch the trap.

Types of Traps: Use one or a combination of these traps.
Yellow panel traps: These look and smell like the fly’s food; insect honeydew and bird droppings. 
Red ball traps: These resemble apples and attract mature mating insects.
Ladd traps: These use a bright yellow plastic panel with red hemispheres attached to the center.
Real apple traps: Delicious or Gala apples coated with Tangle-Trap attract and capture apple maggot flies.

Laura chose the reuseable red ball traps from a kit purchased at a greenhouse like T&T Seeds, (~$39 for 2 round traps with all necessary equipment). 

I chose to make red ball traps by painting a 3 inch sphere with red paint, sealing it and covering it with tanglefoot. (~ $20 for supplies for 4 traps). Not sure how reusable these will be.

For more on making your own trap or cleaning reusable traps read Making Homemade Apple Maggot Fly Traps.

3. Wrap The Fruit 

Wrapping each apple in a stocking is guaranteed to keep the apple maggot fly from your fruit, but it is a ton of work. When fruit is young, each apple is covered with a protective sock.

apple socks
Protecting each apple with a sock. Photo Source: Philadelphia Orchard Project

Let’s hope we can conquer this little beast!

Good luck out there.

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