An Annotated Checklist of Clearwing Borer Pests of Ornamental Plants Trapped using Commercially available Pheromone Lures

Materials and Methods

Lures were obtained from two major pheromone producers, Scentry ™ and Trece ™. Trece Pherocon 1C wing traps were used, as this trap type is in common use in commercial nurseries, landscapes, and orchards. The lures used were Trece greater peachtree borer, lesser peachtree borer, and lilac/ash borer, and Scentry dogwood borer and clearwing borer. Traps were baited and placed in several locations, including managed and unmanaged landscapes and commercial nurseries, in Maryland and Washington D.C, and were monitored approximately twice each week. Lures were replaced at regular intervals according to the recommendations of the manufacturer or supplier.

Results and Discussion

Lures marketed for specific target species did not consistently trap those targets to the exclusion of other species. The range of species trapped by different lures used are shown in Table 1.

The attraction to all lures appeared to be fairly general, with all lures attracting at least some individuals in addition to the target species, and in addition to the target genus. Lures that attracted the greatest number of species were the Trece lilac/ash borer and the Scentry clearwing borer lures. Both captured 7 species in 3 genera. The Scentry dogwood borer lure also attracted a broad range of species. The lure with the most specific activity was the Trece lesser peachtree borer lure. This lure captured only 4 species in 3 genera. Furthermore, the total number of individuals of other species was low. The relative specificity of the lesser peachtree borer lure is not surprising. The compound (E,Z)3,13-octadecadien-1-o1 acetate (EZA), which is known to attract the lesser peachtree borer, is less attractive to the other common species captured in this study (9).

Identification of species was problematic in many instances. The overlap in size ranges of the two peachtree borers often made it impossible to distinguish between them. No practical solution to this problem was found, hence there were several uncertain reports of lesser peachtree borers in all traps (Table 1). Taft et al. (9) present characteristics useful for differentiating between peachtree borer and lesser peachtree borer. However, characteristics used in identification, such as wing coloration, are often obscured or rendered useless after insects have been caught in the trap. Also several individuals were captured that had distinct features, but which could not be identified using the commonly available guides. Without complete identification aids, the identity of these individuals remains unknown.

The number of individuals of a species caught over the season at a given location may be influenced by many factors, such as proximity of host plant to trap, weather, or natural enemies. However, our data suggest that lures marketed for a particular species may be less effective at attracting the target species than other lures at the same location. At the University of Maryland site, the Trece lilac/ash borer lure consistently trapped fewer lilac/ash borers than did the Scentry dogwood borer lure. Conversely, the Trece lilac/ash borer lure appeared to attract more dogwood borers than did the Scentry dogwood borer lure. Because the traps were approximately 50 yds. apart, it seems unlikely that difference in proximity to host plants of target species was a major factor.

At the University of Maryland site, the first flight of dogwood borers was not detected. However, individuals of the second flight were captured effectively with the Trece lilac/ash borer and dogwood borer lures, both of which were in use during the first flight period at Maryland. At the Smithsonian Institution site, the early dogwood borer flight was detected with the Scentry dogwood borer lure, and the second flight individuals were caught using the Trece lilac/ash borerand dogwood borer lures. Although there is only 1 generation of dogwood borer reported in this area (2,3), Potter and Timmons (5) suggested that there are two distinct flight periods that may correspond to two different populations in Kentucky. Further study is needed to determine the status of this highly polyphagous (3) species which has a history of unreliable trapping in Maryland (2).

An unexpected result was the general attractiveness of the Trece lilac/ash borer and Scentry dogwood borer lures, which are marketed for single species. Both lures caught several species of clearwing borers.