Coming Soon to your Home Fruit Trees: Plum Curculio
Paulette Greenberg, Anoka County Extension Master Gardener
It’s finally spring, and for those of us who are lucky enough to have stone fruit trees like peaches, plums, and cherries, we are seeing the first blossoms of the year. With them come the dreams of harvesting bushels of deliciously sweet and juicy fruit later this summer. Unfortunately, something darker and more sinister is also stirring beneath our trees, and it has plans to ruin those harvests. It’s time to start looking for signs of the plum curculio.
I learned about this pest of stone fruit (and apple) trees last year when I noticed dozens of immature plums and peaches dropping from my trees in late June. They all had puncture marks next to clear, tacky droplets. I scoured extension websites and finally identified the pest, but it was too late to save most of my peaches.
The plum curculio is a snout-nosed beetle that overwinters in the soil underneath and around fruit trees. They become active within the two weeks after the blossoms drop. The adults feed on developing fruit and mate; then females will pierce the fruit’s skin and lay an egg, which will hatch within a week or two. A female plum curculio can lay a few hundred eggs in her lifetime, which is why it is considered one of the most devastating pests of stone fruit. The grubs will tunnel further into the fruit, go through a few molting cycles, and then tunnel back out of the fruit to finish the pupal cycle on the ground. They will emerge as adults about a month later to feed and seek winter shelter, starting the cycle over again.
How to spot damage:
Crescent-shaped entry holes where an egg has been laid.
Premature fruit drop and misshapen fruit
Brown marks where adults have fed.
Appearance of adults on trees. If you see them after fruit has developed, chances are they’ve already laid some eggs.
Managing Plum Curculio:
Good horticultural sanitation practices are the first defense. Remove fallen fruit immediately and dispose of them in the garbage, not your compost heap or the woods, or you’ll be sorry next year!
“Shake it off.” Take an old sheet (lighter colors are better) and drape it on the ground under your tree early in the day, when adults are sluggish. Shake the tree gently to dislodge, and dispatch them in a pail of soapy water, along with any Japanese beetles you find.
Remove unmanaged or wild fruit trees from your property. This includes apple and crabapple trees.
I did manage to rescue a few peaches and plums last year. This year, I am going to experiment with using muslin drawstring bags on my developing peaches to see if a physical barrier will prevent the eggs from being laid in the first place.
For more information on Plum Curculio, visit these links: What insect is this? : Garden : University of Minnesota Extension or Plum Curculio | Extension | West Virginia University