In the late 1980's, W. Louis Tedders, Bruce Wood and John Bligh of the USDA, ARS Southeastern Fruit and Tree Nut Laboratory at Byron, GA invented a pyramid-shaped trap for detecting and monitoring pecan weevils. I first tested the "Tedders" trap against the plum curculio in spring of 1993. This research stimulated a large number of other entomologists and growers to test the trap and to develop others as a result of new research findings.
The Tedders trap is a black pyramid that presents a silhouette which likely mimics the visual image presented by a tree trunk to a weevil walking on the ground. Using the trap, I have collected close to 100 different species of Curculionoidea (weevils and their relatives). The trap is being used in citrus to monitoring the citrus root weevil complex, in fruit crops for plum curculio and Pachneous spp., and also has potential for use in regeneration pine stands for monitoring the regeneration weevil species, Hylobius pales and Pachylobius picivorus. The trap usually captures both sexes, and therefore, may suppress weevil populations when used in crops.
The Tedders trap is placed on the ground under the dripline of the tree. Stimulated by research on the Tedders trap, a Mr. Circle, a resourceful Kansas pecan grower who also grazed cows in his orchards, invented another trap known as the "Circle" trap that is made of screen wire and attached to the tree trunk. See "Monitoring Adult Weevil Populations in Pecan and Fruit Trees in Oklahoma" for directions on making the Circle trap and another design for the Tedders trap. Both traps capture weevils as they emerge from the ground and walk to or on the tree trunk.
The following guidelines are suggested for building and using the Tedders to monitor plum curculio. Plum curculios overwinter as adults mostly outside the orchard in debris under hardwood trees. Some occasionally overwinter inside the orchard. Once temperature conditions are optimum (sustained warm temperatures day and night in the high 60's - low 70's ºF), plum curculio adults emerge and begin to feed. Emergence in north Florida and south Georgia low-chill peaches and nectarines coincides with the bloom to shuck split stages. Males emerge first followed a few days later by the females. Once mating takes place the female has a pre-oviposition period of a few days before she begins depositing eggs in fruit. Plum curculio adults feed on fruit and other plant parts, but most damage is done by the larvae which feed in the fruit. When the egg is deposited into the fruit, the female first cuts an oval slit on the fruit surface which leaves a detectable scare.
You can buy the complete Tedders trap or just the tops from Gempler's Supply (http://www.gemplers.com) or make them yourself out of 1/8-inch masonite, plywood or cloroplast sheeting. I prefer the masonite as it cost less and doesn't blow down in the wind as frequently with the design as below. Paint the traps flat black.
Plum curculio: Three to five traps per cultivar block should be placed in the orchard by mid bloom of the earliest cultivar or no later than 15 February in north Florida. Place traps on the border rows within the tree rows under the canopy about 1m from the tree. Use whitewash, white paint or white plastic wrapped around the tree trunk from the ground to the scaffold limbs to increase the trap catch of plum curculios. This removes the tree trunk as a natural competitor with the trap and increases trap catch about 35 percent.
Inspect traps every two to three days. The exact plum curculio emergence date and pattern will vary with weather from place to place and year to year. February 19 is the earliest date over the last 10 years that we have ever trapped plum curculio in north Florida. Record the trap catches to include the date, number of plum curculios caught in each trap and trap location.
Convert the number of plum curculios caught from all traps on each inspection date into number of plum curculios/trap/day. In other words the number of plum curculios from "X" number of traps after "Y" number of days. Example: 15 plum curculios from five traps during a two day period. Fifteen divided by 10 (5 traps x 2 days) = 1.5 plum curculios/trap/day. Save these records for comparisons of before and after treatments and collection numbers from year to year, etc. Begin control measures within five days of first collection of plum curculio in the trap. Be sure to clean the traps of other critters and spider webs as needed. Keep grass and other debris away from the traps. Bare soil (harrow or herbicide) under the traps and under the trap trees is recommended.
Pecan weevil: Select trees for monitoring based on which trees had pecan weevil larval infestations two seasons ago. These are the trees that will have pecan weevil adults emerging in the highest numbers in the current season as the pecan weevil has a two year and partial three year life cycle. Pecan weevil tend to aggregate on individual trees and reinfest them year after year. Use one to two traps per tree and three to five trees per orchard block. Pecan weevil emergence varies greatly from year to year sometimes beginning as early as 15 July or as late as mid-August. Pecan weevil emergence is greatly affected by soil moisture. Therefore, the initial emergence and peak population emergence can vary from orchard to orchard and tree to tree.
Treatment decisions: growers should determine whether and when to treat based on a number of factors that will not be discussed here. Pecan weevils are difficult to control and the most effective insecticide often negatively effects beneficials and leads to outbreaks of aphids and scorch mites. Consult the pecan management recommendations provided by the UF/IFAS Cooperative Extension Service for details.
Note to organic growers and backyard gardeners: We think that perhaps one to three traps placed around each fruit tree will reduce the damage from plum curculio in small plots. A white wrap or wash on the tree trunk is highly recommended.
Note to citrus growers: The Tedders trap can also be used to monitor the citrus root weevil complex. For citrus build a trap 2 feet high (top half of trap as shown) and place it under the drip line of the tree such that low hanging branches do not come in contact with the trap.
Plans for the base of the Tedders trap using a four right triangle vane design. This design offers some advantages over the original configuration in that all of the pieces are the same and interchangeable. However, it requires some cable ties or wire and a metal or plastic rod 1/4-1/2 inch x 4 feet long (an plastic electric fence rod will work). The trap top (boll weevil trap) can be purchased from Gemplers. The Tedders trap base is made of eighth-inch tempered masonite. Shown here constructed from four identical triangles held together by heavy plastic cable ties through the holes. When folded out in the correct position the four vanes will fit together perpendicular to each other leaving a square hole open in the center to fit over the support rod. Placement in the ground properly is important. Use a claw hammer to clear debris down to bare ground where the trap will be placed to a diameter of 2 to 3 feet. Use the claw to score a plus sign (+) in the soil about 2 inches deep. Place the central support rod into the soil at the center of the plus sign and push into the ground leaving about 3 feet above ground. Unfold the trap forming the center hole with the vanes and place the trap over the rod so that it fits into the soil. The cable ties fastening the vanes should be tight enough so that the rod is not visible and the vanes fit snugly together. Mound and tamp some dirt around the trap for support. Trap height does not appear critical, but in our tests, 4-foot traps have performed the best.
Mizell III RF. (November 2003). Insect Management in Pecans. EDIS. http://edis.ifas.ufl.edu/IG077 (5 December 2003).
Mudder PG, McCraw PD, Reid W, Grantham RA. (July 1997). Monitoring adult weevil populations in pecan and fruit trees in Oklahoma. OSU Extension Facts. (5 December 2003).