Pestic. Sci. 1976, 7, 634-635

Towards Rational Design and Elevation of Pheromone Traps”

Trevor Lewis and Ewen D. M. Macaulay

Rothamsted Experimental Station, Harpenden, Hertfordshire AL5 2JQ

Many varied trap designs have been developed for monitoring insect populations using sex attract- ants, but design features that contribute to an effective trap have not been systematically investi- gated. This paper shows how the design, adhesive surface and elevation of trap in a crop affects the size of catches.

In an attempt to develop a monitoring system for pea moth, Cydiu nigricuna (Steph.) six models of trap were chosen largely on the basis of their cheapness, convenience of handling and servicing, and their durability in the field (Lewis et ul.).l Using 0.1 mg of (E,E)-dodeca-8,10-dienyl acetate as a lure in each trap (Wall et u I . ) , ~ and “Stickem special” as an adhesive, catches of male pea moths in the different models were compared over 13 days. Most moths were caught on an open “triangular” model orientated with the wind, and least on a “lantern” model incorporating solid baffles (Figure 1).

The probable patterns of pheromone plumes spreading from traps were simulated by releasing smoke from traps placed in pea crops and in a wind tunnel. The smoke plumes were photographed and measured. The “triangular” model produced the most elongated pattern and, generally, the more elongated the plume produced by a trap, the greater the catch of male moths. Thus, trap designs that generate a long thin plume are preferable as monitoring devices for pea moth, and probably for many other pest species. This is presumably because flying insects can more easily trace a narrow concentrated scent plume than a diffuse one to its source.

The type of adhesive used in a trap also greatly affected the catch. Of five commercial products used, “Bird Tanglefoot” provided the most effective retentive surface. There may be both physical and chemical reasons for these differences.

T L

Figure 1. The “triangular” (T) and “lantern” (L) designs that respectively caught the most and least moths of six models tested. The sex attractant was dispersed from rubber stoppers held in the centre of each trap.

a Summary of a contribution presented at a meeting Insect pheromones: aspects of their use in pest control, on 6 April 1976 organised jointly by the Physicochemical and Biophysical Panel (Pesticides Group) Society of Chemical Industry and the Association of Applied Biologists.

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Catches in pea crops differed depending on the elevation of the trap. When catches in traps placed on the ground, at mid-crop, crop level and twice crop height were compared, most moths were caught in the lower traps when winds (measured at crop level) exceeded 2 m/s, but in the higher ones when winds were less than 2 m/s. Thus, the best compromise position for siting moni- toring traps for pea moth is about three-quarter crop height where considerable numbers of moths are caught in both fast and slow winds.

Plume patterns generated by traps in a wind tunnel were compared with flight tracks traced from a film of moths flying to sources of sex attractant. The results suggested that the insects progress upwind along a scent trail in a series of reversing zig-zags made in response to changes in concentration of scent within or at the edges of the plume.

A more detailed account of this work is given by Lewis and Macaulay.3

References 1. Lewis, T.; Wall, C.; Macaulay, E. D. M.; Greenway, A. R. Ann. appl. Biof. 1975, 80, 257. 2. Wall, C.; Greenway, A. R.; Burt, P. E. Phys. Ent. 1976, 1, 151. 3. Lewis, T.; Macaulay, E. D. M. Ecol. Em. 1976, 1, 175.

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