Feeding preference of Altica deserticola for leaves of Glycyrrhiza glabra and G. uralensis and its mechanism.

Altica deserticola (Coleoptera: Chrysomelidae) is a monophagous insect that feeds on, and is thus a harmful pest of, liquorice. Both adults and larvae feed on leaves, causing serious damage to leaf blades. It will even lead to the extinction of liquorice, resulting in significant economic losses. Leaf-disc tests were used to determine the feeding preference of A. deserticola on leaves of Glycyrrhiza uralensis and G. glabra and explore the underlying mechanism of liquorice feeding resistance to A. deserticola by comparing leaf hardness and thickness, cuticle thickness, and nitrogen and tannin content in the two plants. The results showed that larvae and adults have the same feeding preferences, i.e., both preferably fed on G. uralensis, indicating a higher resistance in this species. The hardness, thickness, and the thickness of the stratum corneum of the leaves of G. glabra were significantly greater than those of G. uralensis. Nitrogen content was higher in G. uralensis, while total tannin, tannic acid, and catechin content were higher in G. glabra. The thick cuticle and hard texture of G. glabra leaves may be an important physical trait for effectively resisting A. deserticola feeding, while high tannin and low nitrogen content may also be important.

Volatiles released by Chinese liquorice roots mediate host location behaviour by neonate Porphyrophora sophorae (Hemiptera: Margarodidae).

BACKGROUND: The cochineal scale, Porphyrophora sophorae (Hemiptera: Coccoidea, Margarodidae), is one of the most serious arthropod pests of Chinese liquorice, Glycyrrhiza uralensis (Fabaceae), an important medicinal herb. The adult females tend to deposit the ovisacs in soil relatively far away from liquorice plants. After hatching, neonates move out of the soil and may use chemical cues to search for new hosts. RESULTS: We collected and analysed the volatiles from soils with and without liquorice roots, and chromatographic profiles revealed hexanal, ß-pinene and hexanol as potential host-finding cues for P. sphorae. The attractiveness of these compounds to neonates was studied in the laboratory using four-arm olfactometer bioassays. The larvae showed a clear preference for ß-pinene over hexanal and hexanol, as well as all possible combinations of the three compounds. In addition, a field experiment confirmed that ß-pinene was significantly more attractive than hexanal and hexanol. CONCLUSION: Newly eclosed larvae of P. sphorae exploit root volatiles as chemical cues to locate their host plant. ß-Pinene proved to be the major chemical cue used by P. sphorae neonates searching for roots of their host plant. © 2016 Society of Chemical Industry.