Our First Major Insect of the Growing Season

Plum Curculio Ovipositing Egg

With apple scab season in our midst, and petal fall ending, it is time to turn our attention to several insect pests.  I have had the first sighting of plum curculio activity in the orchard today.   Plum curculio (PC) is one of the most difficult insect pests to contain.  They enter the orchard from the perimeter after the adults pass the winter hidden under leaves, along fence rows, in brush piles, rock walls and in other protected places. In spring when the weather warms up (mean temperature 60°F. or maximum temperature above 75°F.), about the same time apples are blooming, the adults become active. The adult plum curculio beetles, pictured to the left, emerge right around or just after petal fall, to feed on apple buds, flowers, leaves and young fruit.  The duration of full bloom to petal fall is usually about 5 to 10 days.  From petal fall to fruit set is generally another 5 to 10 days, depending on temperatures.  Once the fruit sets, female beetles cut holes in the young fruit and deposit one egg in each cavity. 

 

 

These sites, called oviposition stings, 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. 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 as well as any beneficial insects. 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 as a deterrent, even though there may be no fruit.  Picking up and disposing of any fallen fruit 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 in depth look at 

 Reference in this publication to any specific commercial product, process, or service, or the use

of any trade, firm, or corporation name is for general informational purposes only and does not

constitute an endorsement or certification of any kind by Royal Oak Farm.

People using spray products assume responsibility for their use

in accordance with current label directions of the manufacturer.