DIY Worm Control

Silence of the Pears

This blog post is for people with backyard fruit trees, fruit trees where you have problems with worms eating your fruit before you can.   But first, a joke:

  • What’s grosser than gross?
  • Biting into a pear and finding a worm.
  • What’s grosser than that?
  • Biting into a pear and finding half a worm.

When I was a kid in fourth grade this joke was the height of sophisticated humor.  Now that I am a grown-up pear farmer, this isn’t a joke - it’s a horror story.  Worms can silently destroy all of the fruit on a tree.  In this joke/horror story, the gross worm is most likely a codling moth larva.  My goal is to provide you with a homeowner scale way to prevent codling moth damage, without chemical pesticides or an unreasonable amount of effort.

Another horror story is the movie Silence of the Lambs.

 Silence: from Lambs to Pears

Silence: from Lambs to Pears

This is the IMDB summary of Silence of the Lambs:  “A young FBI cadet (Agent Starling) must receive the help of an incarcerated and manipulative cannibal killer (Dr. Lecter) to help catch a madman (Wild Bill) who skins his victims.”  You are Agent Starling; let me be your Dr. Lecter.  Together we will bring the worm, Wild Bill, to justice.

The Silencer

Convention dictates that these pest control write-ups contain a bit of natural history of the pest in question.  I don’t know why this convention exists and frankly, question its utility.  But, if Dr. Lecter had told Agent Starling Wild Bill’s pertinent details clearly and concisely from the beginning – the movie would not have been as good. Dr. Lecter also commanded Agent Starling to follow first principles – to know her problems.  Out of respect (for tradition, movie craft, and Dr. Lecter), I’ll half-heartedly follow the convention.

Long ago, codling moths evolved in western Asia/southwest Siberia, a climate as bleak and punishing as the bottom of Wild Bill’s cistern.  This miserable climate forged a creature maddeningly difficult to control - a worthy opponent.  Thankfully, I have yet to see a codling moth do this dance.

 Life cycle of the codling moth

Life cycle of the codling moth

The codling moth life cycle goes moth -> egg -> worm then back to moth.  It’s the worm stage of the codling moth life cycle causes us the problems - adult moths eat nothing.

Worms eat fruit from the inside (hidden from ourselves and other predators), you can’t get rid of the worms without destroying the fruit.  The eggs are laid very close to, if not on, the fruit itself, so it’s impractical to try to go after codling moth eggs.  Homeowners could spray insecticides for other life stages, but that’s very labor intensive and unpalatable for lots of people.

 Speaking of unpalatable, a worm in an apple.

Speaking of unpalatable, a worm in an apple.

End of Silence

Wild Bill said, “It rubs the lotion on its skin or else it gets the hose again.”  These are not the words of a man you can reason with.  You can’t reason with a codling moth either.  However, you can show them the light of justice.  Our light of justice just happens to shine out of a bug zapper.    

Bug zappers use lights to draw adult codling moths to them.  Electrified metal grates then sizzle and fry up the moths like the liver that Dr. Lecter ate with some fava beans and a nice Chianti.  Used consistently, during the right times of the year, a bug zapper will kill the adult moths before they can lay the eggs from whence their vile worms hatch.  Bug zappers will protect your fruit from a silent and ancient evil.

Here is what to get:  

  1.  A bug zapper - $65 from Amazon
  2.  Extension cord - $17 from Amazon
  3.  Timer - $10 from Amazon

Hang the bug zapper in your yard between May 1 and August 31, when adult moths are out and flying around.  Use the timer so that the bug zapper runs for 2 hours a day, one hour before and one after sunset, to save power.  To know when sunset happens at your house, you can:

  1. Google “sunset time” for where you live
  2. Use the formula
  3. Make a guess based off this chart
 Sunset times

Sunset times


Mated female codling moths don’t fly very far, therefore hang the bug zapper within 25 feet of and at the height of the top third of the tree you are trying to protect.  

Many bug zappers make claims like “1 - acre coverage”.  Based off insect flight patterns, I can’t see how the manufacturers can support these claims.  There is no way one bug zapper will protect an acre of fruit trees; you would need 20-25 bug zappers to protect a full acre.

 An artistic representation of what a bug zapper in a tree looks like.  Because taking pictures is hard.

An artistic representation of what a bug zapper in a tree looks like.  Because taking pictures is hard.

The bug zapper operates on 40 watts of electricity.  From May 1 through August 31 is 123 days.  At 2 hours per day run time, the bug zapper will run for 246 hours per year.  40 watts for 246 hours is 9,840-watt hours, or 9.84-kilo watt-hours (kWh).  Using an electric cost of $.14 per kWh, it will cost about $1.38 to run the bug zapper for a full season.  This bug zapper based pest control system will cost about $93 to run the first year, or less if you spread the initial costs over a few years of cost.

Bug zappers don’t just provide pest control: they also provide entertainment.  Watching bugs sizzle out of existence while sitting in a lawn chair and drinking some delicious cider (there’s really no such thing as a nice Chianti) isn’t highbrow entertainment, but it is entertaining.