Prepare for apple maggots

While early July means different things to different people, if you are an apple grower, it reminds you that this is the beginning of apple maggot season in Minnesota. This pest spends the winter as pupae in the soil and begins to emerge as adults starting about July 1.

Why are they are pests?
Apple maggot is the most important apple pest
in the state and damages apples in a couple of ways. First, the adult females injure apples as they lay their eggs. Their sharp ovipositor punctures the skin, giving apples a less attractive, dimpled look.

The most serious damage occurs when the larvae tunnel through the apples. Their feeding injures the  flesh, causing brown streaks. These damaged areas become soft and rot, causing apples to become lumpy and misshapen.

Can you protect your apples without insecticides?
A great method to protect your apples nonchemically is to bag them. Use sandwich bags or similar plastic bags. Once you put the bags over the apples, zip it up, tie it, or staple it to close them. Cut the bottom corners off each bag so there is a small opening for water to run out. Leave the bags on the apples during the growing season and remove them when you are ready to harvest your apples.

Bagging apples is a great nonchemical method to fight apple maggots.  Photo: Jeff Hahn, UMN Extension

This method is labor intensive and takes time but each bagged apple is protected from apple maggots for the entire season. This is easier to do if your trees are small or medium sized; bag as many apples as you can from the ground or from a short ladder.

Trap them out
Another non-chemical method is to hang sticky traps in your trees. These traps are round, a little larger than an actual apple and colored red or black, making them (hopefully) more attractive than real apples. When apple maggots land on these spheres, which are coated with a sticky glue, they become stuck and die.

Hang about five traps in an average sized tree. You can buy traps from a garden store or online or make your own. Make sure to periodically clean these traps as they do fill up with all kinds of insects. Trapping as the sole management method is less effective than bagging or insecticides.

* Bag your apples or hang your traps by July 1. *

What insecticide options are there?
There are a couple of methods for treating your trees.  The first is to monitor for apple maggots and spray when they are detected.

To know when apple maggots are present in your orchard, hang a single sticky trap in the tree by July 1. Check the trap regularly for apple maggots. Make sure you can correctly identify an apple maggot as other flies can be stuck on the trap. Apple maggots have distinctive black banding on the wings and a white spot on its abdomen near the thorax.

You can use traps to tell you when apple maggots are present.  Photo:  Jeff Hahn, UMN Extension

Once you have a confirmed one apple maggot on the trap (without a lure), spray your trees. If you are using a lure, then wait until you have caught five apple maggots. Continue to monitor and treat when apple maggots are present (Note: be sure not to treat any more frequently than directed by the pesticide label).

Another option is to treat apple maggots on a regular schedule, once every 10 - 14 days starting July 1. This method is the most effective, but it also uses more insecticide.

Effective insecticides include spinosad, permethrin, lambda cyhalothrin, and carbaryl. Make sure the product you wish to use is labeled for apples.

For more information, see Apple maggots in home orchards.