Plum Curculio Expected This Weekend!

Adult Plum Curculio Ovipositing Egg

With the approach of petal fall upon us, and the temperatures predicted to be in the high 60's to low 70's this weekend, it is prime time for our ugly little friend, plum curculio (PC)! As soon as the temperatures hit 70, that is their signal to move into the apple trees.  Adult plum curculio beetles, pictured to the left, emerge in the spring, right around or just after petal fall, to feed on apple buds, flowers, leaves and young fruit.

Plum Curculio "stings" leave large "corked" spot on mature apples.

Female beetles cut holes in the young fruit and deposit one egg in each cavity.  These oviposition sites are easily identified by their crescent shaped cuts. Unlike codling moth, the larvae of plum curculio rarely cause damage to the fruit. The fruit is primarily damaged superficially by the egg-laying and feeding by the adults. These "stings" will cork over and cause an indentation in the fruit as it matures making it look deformed and unsightly.  The question then becomes, how do we control them??  Pesticide application at this time is very important for plum curculio control. But, to prevent fruit drop, and due to toxicity to bees if there are still blooms on the trees, do not use carbaryl (Sevin®) or any pyrethrin based spray as these are highly toxic to honey bees and other pollinators. 

So, for home growers, an acetamiprid spray such as Ortho® Flower, Fruit &  Vegetable Insect Killer Ready-Spray is a deterrent.  If no blooms are present  on any trees, a pyrethrin based spray can be used, but remember, pyrethrin will harm any beneficial insects as  well as bees.  Acetamiprid, in the cyano class of neonicotinoids, has been deemed safe to use when bees are not active, usually early in the evening before dusk.  Cultural practices include picking up and disposing of any fallen fruit which will reduce problems with plum curculio, other insects, and many plant diseases. For conventional growers, Avaunt or Assail are two choices you might use, based on your codling moth protocol and your apple maggot protocol.  For a pure organic spray, the two most frequently used insecticides are Surround® and Pyganic®, both certified organic. The organic products may need to be sprayed multiple times for complete control at 7 to 10 day intervals or after any rain. And, as always, follow all label directions on any spray product.

For a complete Fact Sheet on Plum Curculio, consult the Cornell University Plum Curculio Fact Sheet and for an indepth look at plum curculio management in stone and pome fruits from Michigan State University.