Abstract
Simple SummaryThe dark black chafer, Holotrichia parallela, which is widely distributed all over the world, is an economically important pest in agriculture and forestry. In the north part of China, this beetle causes serious damage to the peanut plant. Much attention has been paid to olfactory perception of volatile compounds from supplemental nutrition hosts by H. parallela prior to sexual maturation. However, volatile compounds attractive to this beetle from the peanut plant have not been identified yet. In this study, we collected the volatile compounds from peanut seedlings by dynamic headspace adsorption and identified twelve electrophysiologically active compounds responsible for the attraction of H. parallela to the peanut. Among the eight chemically identified compounds, β-caryophyllene and hexanal significantly attracted both sexes of H. parallela when tested individually in the field. A blend of β-caryophyllene and hexanal at a ratio of 2:1 was most attractive to the beetles. The addition of the remaining compounds to the binary mixture did not increase the attractiveness. The findings of this study reveal that β-caryophyllene and hexanal can be potentially used for development of effective attractants for management of H. parallela.Holotrichia parallela (Coleoptera: Scarabaeidae: Melolonthinae) is a notorious pest of many crops, especially peanuts. In this study, volatiles from peanut plants were analyzed using both gas chromatographic-electroantennographic detection (GC-EAD) and gas chromatography/mass spectrometry (GC/MS) techniques, and tested for adult attraction with field trapping bioassays in Hebei Province, China. GC-EAD analyses indicated that H. parallela antennae strongly responded to twelve GC peaks, including eight identified compounds, (Z)-β-ocimene, hexanal, 6-methyl-5-hepten-2-one, nonanal, dihydromyrcenol, linalool, β-caryophyllene, methyl salicylate, and four unidentified compounds. When tested individually in field conditions from 24 to 31 July, 2020, β-caryophyllene and hexanal significantly attracted both sexes of H. parallela, whereas all other compounds were unattractive. A blend of β-caryophyllene and hexanal at a ratio of 2:1, close to the natural ratio of these two compounds from the intact peanut plant, was most attractive to the beetles. The remaining identified compounds, (Z)-β-ocimene, 6-methyl-5-hepten-2-one, nonanal, dihydromyrcenol, linalool, and methyl salicylate had no synergistic effects on H. parallela attraction when tested in combination with the blend of β-caryophyllene and hexanal. These results demonstrated that β-caryophyllene and hexanal in the volatiles from peanut plants have strong attraction to H. parallela. These two compounds have the potential to be used for monitoring H. parallela and its management programs.
Highlights
The dark black chafer, Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae: Melolonthinae), is one of the most economically important pest species in agriculture and forestry in China, Japan, Korea, and the Russian Far East region [1]
Our gas chromatographic-electroantennographic detection (GC-EAD) and gas chromatography/mass spectrometry (GC/MS) analyses found twelve peanut volatile compounds, (Z)-β-ocimene, hexanal, 6-methyl-5-hepten-2-one, nonanal, dihydromyrcenol, linalool, β-caryophyllene, methyl salicylate, and four unidentified compounds (Figure 1), which are consistently detected by the antenna of H. parallela adults
The present study showed that β-caryophyllene and hexanal were the most attractive compounds among the electrophysiologically active compounds from peanuts, and the binary blend of β-caryophyllene and hexanal was more attractive than all ternary blends
Summary
The dark black chafer, Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae: Melolonthinae), is one of the most economically important pest species in agriculture and forestry in China, Japan, Korea, and the Russian Far East region [1]. The scarab larvae live underground and feed on a large amount of plant roots, while the adults feed on the aerial parts of various plant species, such as corn, soybean, and other crops and trees. The larvae (so-called “grubs”) feed on peanut roots and pods, resulting in 10–20% losses annually [2]. Spraying synthetic insecticides in the evening, while adults are actively feeding, could be an effective method. Repeated applications of highly toxic insecticides to target grubs and adults can lead to environmentally detrimental consequences, i.e., the “3R” problems: residue, resistance, and resurgence [3]. It is necessary to adopt an environmentally friendly solution for the management of H. parallela
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