Several synthetic floral lures have been described for the cetoniin scarabs Cetonia aurata aurata L. and Potosia cuprea Fabr. (Coleoptera, Scarabaeidae), exploiting their olfaction-guided behavioural preference for a wide range of flower volatiles.
A ternary mixture of 3-methyl eugenol, 1-phenylethanol and (E)-anethol has previously been described as a powerful synthetic floral attractant for both C. a. aurata and P. cuprea. The first objective of the present research was to test whether isoeugenol and eugenol, with a very similar molecular structure to 3-methyl eugenol, can substitute 3-methyl eugenol in the ternary blend. All baited traps caught significantly more of both species than unbaited control traps, however, traps containing 3-methyl eugenol caught significantly more than those with either isoeugenol or eugenol. This indicates a fine tuning in behavioural response to 3-methyl eugenol.
The second objective was to devise simpler attractant combinations for C. a. aurata and P. cuprea, based on previous field studies with synthetic floral compounds. Both C. a. aurata and P. cuprea showed strong attraction to the combination of 2-phenylethanol and 4-methoxyphenethyl alcohol, while the combination of 2-phenylethanol and 1,2,4-trimethoxybenzene resulted in medium-size catches, however, mostly catching P. cuprea. This level of selectivity may lead to the development of more selective lures for P. cuprea, and provide a better understanding of the feeding-related olfactory ecology of the two important pest chafer species.
A binary combination of the synthetic floral compounds (E)-anethol and (E)-cinnamaldehyde has been optimized as a female-targeted lure for adults of the click beetle, Agriotes ustulatus Schwarz (Coleoptera, Elateridae). This bait when placed in traps attracted significant numbers of beetles and a high percentage of the captured specimens was female. Painting the trap in white (a colour to which attraction of A. ustulatus was reported in the literature) had no significant effect on the performance of the floral attractant. To our knowledge this is the first synthetic attractant discovered for female click beetles. Application perspectives for female-targeted lures is shortly discussed.
The KLP+ (“hat”) trap baited with pheromone or floral lures is a highly efficient non-sticky trap for the western corn rootworm, Diabrotica v. virgifera. We tested the suitability of this trap design for the related species, D. speciosa and D. barberi, baited with their respective lures. Both species are exotic to Europe: the former inhabits South America, and the latter occurs in some parts of North America.In screening tests performed in Brazil, several synthetic floral compounds and their combinations were found to be attractive to D. speciosa. However, the greatest effect was recorded for the previously described attractant 1,4-dimethoxybenzene. When the most active compounds in the preliminary test, 2-phenylethanol, methyl anthranilate, eugenol or benzaldehyde were added to 1,4-dimethoxybenzene, no synergistic effects were observed. When 1,4-dimethoxybenzene was formulated in three types of polyethylene (PE) dispensers in KLP+ traps, PE bag dispensers were superior to two types of PE vial dispenser, and caught hundreds of D. speciosa. Unbaited traps caught only negligible numbers. There was an interesting non-target effect. KLP+ traps with 1,4-dimethoxybenzene caught large numbers of the cornsilk fly, Euxesta eluta, which is known as a maize pest.For D. barberi, both a pheromone and a potent floral lure are already known. In tests with KLP+ traps, we found that the pheromone and floral lures can be applied together in the same trap to maximize both male and female catches.In conclusion, for early detection programs in Europe, the application of KLP+ traps baited with 1,4-dimethoxybenzene in PE bag dispensers could be recommended for D. speciosa, and KLP+ traps with dual (pheromone and floral) lures for D. barberi. In the case of D. barberi, one should note that the lures also show some attraction for D. v. virgifera, and the ratio of D. barberi vs. D. v. virgifera in the catch will be predominantly determined by the relative population densities at the given site.
When applied in funnel traps, the known three-component floral lure of Cetonia a. aurata and Potosia cuprea attracts large numbers of beetles. Further increasing the attractive power of these traps offers the opportunity to develop a more potent mass-trapping tool that directly reduces local scarab populations and, hence, fruit damage. The current study was initiated by the observation of adult beetles aggregating and feeding in large numbers on ripening fruit, accompanied by the presence of fermentation volatiles detectable by the human nose. Addition of apple pieces to the ternary C. aurata aurata / P. cuprea lure resulted in increased catches, but only in traps where the apple fermented as a result of beetle feeding. Volatile extracts collected from fermenting apple were subjected to GC-EAG, and bioactive peaks were identified as 1-hexanol, acetic acid, n-butyric acid, isovaleric acid, hexanoic acid and 3-methylphenol by GC-MS and GC peak enhancement. In preliminary field trials, a synthetic mixture of all identified compounds reduced activity of the ternary lure, indicating that some were inhibitory. As certain individual compounds or their particular combinations enhanced activity of the ternary lure only numerically, further experiments are discussed to optimize a synergistic blend of fruit fermentation and/or beetle-derived volatiles.
There was no significant difference in the mean catch of
Scop. (Coleoptera: Scarabaeidae, Cetoniinae) in white or blue traps with the floral bait consisting of (
)-cinnamyl alcohol plus (
)-anethol (which is the previously optimized floral bait for the closely related scarab
Poda). Therefore we concluded that both scarabs can be trapped efficiently with the same trap, which could be advantageous from the practical point of view. In seasonal monitoring trials conducted at 8 sites in Europe using blue traps with the floral bait, adult beetles of both
were successfully detected and their flight pattern was clearly established. At the site in Sicily (Italy) only
was present, while in Bulgaria, Croatia and Hungary only
was captured. At a site near Rome (Italy) both scarabs were caught.