A pheromone trap for population monitoring. Courtesy of Manfred Mielke, USDA Forest Service, Bugwood.org (#1399010)
The use of traps for insect detection is an important method in any IPM program. Traps can provide an accurate picture of pest presence on a farm and may also allow for proper timing of pesticide applications. This proper timing ensures that the pesticides used will be effective and may ultimately lead to a reduction in the amount of pesticides used. Below are descriptions of three insect traps that can be easily used in Christmas tree plantations.
White Pine Weevil Detection Traps
The Tedder’s trap, a baited, pyramid-shaped trap (Figure 1), is used for monitoring the spring emergence of adult white pine weevils. This insect feeds on the leaders of most conifer trees. The dark, pyramid-shaped base of the trap resembles the general shape of a conifer, the alcohol and turpentine baits mimic the odors emitted by wounded conifers, and the funnel top captures the weevils much like a minnow trap. Performance of these traps can be greatly enhanced by monitoring soil temperatures at the trap location. (For more details, see the White Pine Weevil fact sheet.)
Figure 1. Pyramidal Tedder’s trap. Courtesy of Brian Schildt, PDA
The Whalon Modified Tedder’s trap is sold by Great Lakes IPM. Each trap kit includes a 4-foot-tall base, a trap top, and 2 stakes. This trap is also advertised as a plum curculio and pecan weevil trap. The version sold as a white pine weevil trap includes 2 plastic vials to be used for the alcohol and turpentine bait. This product is listed as catalog # IPM-502 and sells for $16.50 in the 2010 catalog.
The top assembly, which consists of a plastic funnel and cylinder (Figure 2), can be purchased separately. It is listed as the Boll Weevil Top Assembly, catalog # IPM-1006T, and sells for $1.75 (2010 catalog).
Figure 2. Weevil trap top assembly. Courtesy of Cathy Thomas, PDA
Building a Trap Base
The trap base must be prepared if only the trap top is purchased or if a base has deteriorated with usage.
- The base consists of two triangles (see Figure 3 for dimensions) that may be constructed from any outdoor hearty material (ply-wood, corrugated plastic, etc.). A material with a rougher surface will provide a better climbing surface for the weevils. Since the base is intended to resemble a tree (to the weevils), the material should be dark in color—dark brown, dark green, or black. Paint with sand added would also provide a good gripping surface for the weevils.
- When cutting out the triangles, cut a slot 24 inches long in the bottom of one triangle, which will be vane A. A similar slot 24 inches long, vane B, must be cut in the top of the other triangle.
Figure 3. Building the trap. Courtesy of Rayanne D. Lehman, PDA
- Slide triangle A (slot in bottom) over the top of triangle B (slot on top). The bottom and top edges of both triangles should be even. When assembled properly, the base will stand freely with four vanes.
- Using fine-gauge wire, utilize the small holes along the top of vane A to attach two small bottles. These may be the vials provided with the trap kit or other small bottles (Figure 4). Inexpensive, small, glass salt and pepper shakers are a good option. The bottles should lie flat against the angle created by the vanes and have their tops as close as possible to the top of the base.
- Fill one bottle with 95 percent ethyl alcohol (available in stores selling wine and spirits) or denatured alcohol (avail-able in hardware stores); fill the other with gum turpentine (Figure 5). Unless the bottle lids have holes, do not put lids on the bottles.
- Fit the trap top over the base, covering the tops of the bottles containing the alcohol and turpentine. Use fine-gauge wire or plastic twist ties to secure the top to the holes at the top of the trap base (Figure 6).
- Twist the plastic vial over the funnel to screw into place. (The funnel and vial may come already assembled.) This is where the weevils will be trapped (Figure 7) after crawling up the vane and entering through the small opening in the screening.
Figure 4. Bait vials attached to upper portion of the trap. Courtesy of Brian Schildt, PDA
Figure 5. A kit containing baits, collection bags, and all other trap supplies. Courtesy of Cathy Thomas, PDA
Figure 6. Securely wire top to the base. Courtesy of Cathy Thomas, PDA
Figure 7. Weevils caught in trap (plastic vial has been removed). Courtesy of Sandy Gardosik, PDA
Using the Traps
- Weevils become active when air temperatures exceed 50°F and soil temperatures reach 50°F (Figure 8). Earliest emergence occurs in the warmest fields. For best results, the traps must be in place before the pests are active on a daily basis. Place the traps in the field to be monitored in late winter (February) or early spring (early March).
- Locate each trap in the tree row, prefer-ably next to a tree that has had weevil damage the previous season (Figure 9). Prevent the trap from blowing over by using tent stakes, wire (if necessary), and the holes in bottoms of trap base. Do not use string or twine, as small animals will chew this and may destroy the base in the process.
- Weevils overwintering at the bases of trees will be attracted by the scents given off by the evaporation of the alcohol and turpentine. When they become active, they will climb the base of the trap and enter the funnel portion at the top. Once inside the funnel, they will remain inside the large plastic vial until removed.
- Generally, two traps per block are sufficient. For extremely large blocks, increase the number of traps.
- Replenish the contents of the alcohol and turpentine bottles regularly. If rain has occurred, the bottles should be emptied and filled with fresh material. Comparison trials in Pennsylvania showed that unbaited traps did not capture weevils.
- Check the traps for weevils daily, if possible, during early spring. If any insects are in the trap, empty the contents into a container of soapy water or rubbing alcohol to kill the pests.
- Apply a registered pesticide to the terminals of susceptible trees as soon as possible after the first white pine weevil is captured. During cool springs, it may be necessary to repeat the application if weevils continue to appear in the traps 4–6 weeks after the first application. Follow all label directions for application of any pesticide.
- These traps are for detection of weevil activity and will not offer control.
Identifying the Weevils
Several weevil species, as well as spiders, flies, stoneflies, and other beetles, will be attracted to the traps (Figure 10). It is important for the grower to properly identify the weevils that are associated with Christmas tree production. Four such species exist in Pennsylvania: white pine weevil, eastern (formerly northern) pine weevil, pales weevil, and pine root collar weevil. Both white pine weevil and eastern pine weevil are very similar in appearance. They both are dark red brown and have large, white and gold patches on the back of their wing coverings. To the untrained and unaided eye, the main difference is their size. The target species, white pine weevil, is the smaller of the two. Pales weevil and pine root collar weevil will also be attracted to the traps. They can easily be separated from the previous two species by size and color but are difficult to separate from each other. These weevils are larger and dark brown to almost black with small, white patches on the top of their wing coverings. Pine root collar weevil is the larger of these two species.
Figure 10. Pales weevil (left), and white pine weevil (right). Courtesy of Gerald J. Lenhard, Louisiana State University, Bugwood.org (#0795087)
Adapted from Regulatory Horticulture article by Sandy Gardosik and Rayanne D. Lehman, PDA