Prescription screening and field evaluation of broad spectrum attractants of scarab beetles from Ricinus communis

To screen plant-derived attractants for ecological management of three scarab beetles (Holotrichia oblita, H. parallela and Anomala corpulenta), 10 binary blends (labeled as 1, 2, …, 10, see below) with 5 main volatiles from the leaves of Ricinus communis were selected. Then the electrophysiological activity and attractiveness of the selected R. communis volatiles blends were evaluated by electroantennogram (EAG) and field trapping experiments. The EAG bioassay showed that blends containing green leaf volatile of cis-3-hexen-1-ol usually exhibited strong EAG activities. Blend 1 (cis-3-hexen-1-ol plus dibutyl phthalate) and blend 6 (cis-3-hexen-1-ol plus benzyl alcohol) showed stronger EAG response to both sexes of the three scarab beetle species. Blend 7 (cis-3-hexen-1-ol plus 2-phenylethanol) exhibited a fairly strong EAG activity toward H. oblita sexes. Also blend 8 (cinnamaldehyde plus benzyl alcohol) effectively stimulated response to male A. corpulenta antennae. The preliminary trapping experiment indicated that among the ten candidate binary blends, blends 6, 8 and 1 performed the best regarding the target species at occurrence peak with respectively 110.30, 101.73 and 74.97 catches per trap in 30 days. Most interestingly, the blends also attracted a certain number of A. exoleta. Further mass-trapping experiments conducted in Luoyang and Kaifeng regions were used to compare the attractiveness of the mentioned 3 blends. The results showed that blends 6 and 1 caught significantly more scarab beetles than blend 8. A significantly great number of H. parallela and a few A. corpulenta and Popillia quadriguttata were among the species caught in the trapping experiment conducted in Luoyang. In the Kaifeng trapping experiment, Maladera orientalis was the most abundant species caught, followed by H. parallela and P. quadriguttata. The different natural distributions of the scarab species in different regions possibly explained the differences in trapped species. Altogether, blends 6 and 1 were possibly the two promising ecological control attractants that were generically targeted to several scarab beetle species in the region.