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Trapping Plum Curculio

Plum curculio (PC) were a growing pest problem again in 2002 in many stone and pome fruit orchards. Plum curculio are a small, warty, grey - brown weevil (a type of beetle) with a long snout. The adult weevils create a characteristic crescent-shaped feeding scar on fruit. The larvae are white, plump, legless grubs that cause damage to fruit that is similar to oriental fruit moth damage.

When I last wrote about plum curculio in the Tender Fruit Grapevine Sept./Oct. 2001 issue, I briefly mentioned 'Circle traps', designed by Kansas pecan grower, Edmund Circle, that can be used to monitor this pest. Several people have asked me about the traps and where they can get them. These traps (see pictures) are not a substitute for monitoring fruit for PC damage, but they can be useful for timing control options.

Pros:

These traps are useful in areas with high curculio pressure and early in the year around the time of first PC emergence. So, if you had problems with curculio damage (and you are sure that the damage is PC) make a note on your field maps so that pest scouts next spring can focus their attention on the problem areas of your orchard. This is most often an orchard edge along a ravine or bush where the weevils overwinter. These problem edges are the best place for the Circle traps.

At a problem site in 2001, a series of three traps caught 9 weevils in two days, accurately indicating the first emergence of adults that year. In 2002, one trap at a different problem site caught 19 plum curculio adults in two days indicating the need for control measures.

These traps are relatively cheap and easy to make (see website below), and unlike some other PC trap designs, Circle traps are off the orchard floor and out of the way for ground cover management.

Cons:

These traps will not give accurate timing of curculio emergence if the weevils are in locally low numbers. Traps may catch no weevils at all, yet damage will be found in the orchard.

The traps will also not catch enough weevils to provide any control of this pest. They are a monitoring tool like sticky traps - good for knowing when the insects are active, but not for providing information on population levels or control of the pest.

Again, these traps are definitely not a substitute for good pest scouting of fruit to check for curculio damage.

Hows:
Tie the traps securely on a tree with relatively smooth bark - otherwise weevils walking up the tree will go under the mesh and not be trapped. Check the trap frequently when conditions are good for plum curculio emergence (above 16 C following rain around shuck fall) and for at least 4 weeks after. Make sure you know what this pest looks like - other weevils, especially pale green weevils, will be caught.

Where:

So far the only catalogue where I've seen the Circle traps is Great Lakes IPM, 10220 Church Road, Vestaburg, Michigan 48891. (989-268-5693) at a cost of $9.50 US each. Complete details on making Circle traps along with additional information on PC and other PC traps can be found on the Oklahoma State University website.

'Circle trunk trap' tied securely to trunk.

Correct placement of Circle trap.
Face opening toward likely area of infestation

Simple construction of mesh with spacer slats.
Weevils walk up the tree and are directed into mesh funnel and trapped

Pale green weevils in top of open trap.
These are NOT the target pest - many different small insects will be caught

Plum curculio, 4-6mm long. Rough, warty, grey-brown weevil.

Learn more

• Plum Curculio on Peaches - OMAFRA Infosheet
• Great Lakes IPM
• OSU Extra - the Extension, Research, and Teaching Archive of Oklahoma State University

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