Mint companion plants enhance the attraction of the generalist predator Nesidiocoris tenuis according to its experiences of conspecific mint volatiles.

Mint plants enable improvement of pest management by attracting herbivore enemies to constitutively released mint volatiles. The generalist predator Nesidiocoris tenuis is used worldwide to control agricultural pests, but little is known about whether mint can serve as a companion plant that attracts this predator. To examine this, olfactory responses of N. tenuis were assessed using apple mint, candy mint, and spearmint as odor sources. Of the volatiles released by these mint species, candy mint volatiles alone were more attractive than those from undamaged eggplant, and were as attractive as volatiles from eggplant damaged with Spodoptera litura larvae. However, no prominent preference for particular volatile(s) among the mint volatiles was shown by O. strigicollis. When N. tenuis had been previously exposed to candy mint, the predator showed a stronger preference for candy mint volatiles than damaged eggplant volatiles. It was, however, irrelevant whether the predator received benefit or not by predating animal prey during the mint-experience period. In contrast, spearmint-experience increased the preference for spearmint volatiles only when the predator acquired prey during the mint-experience period. These findings suggest that previous exposure of N. tenuis to some particular mint species can increase its preference for volatiles from the conspecific mints.

Mint companion plants attract the predatory mite Phytoseiulus persimilis.

Mint plants could theoretically serve as companion plants (CPs) that attract enemies of herbivores in tritrophic interactions. In order to explore the traits of mint volatiles as attractant cues for enemies of two-spotted spider mites, we performed Y-tube olfactometer assays of predatory mites, Phytoseiulus persimilis and Neoseiulus californicus, towards three mint species, apple mint, candy mint, and spearmint, as odor source. Clean candy mint and spearmint were attractive to P. persimilis, when compared with clean air and undamaged Phaseolus vulgaris plants serving as the target crop. Moreover, clean candy mint plants were even more attractive than volatiles from P. vulgaris plants damaged by spider mites. These predator responses were induced additively by candy mint volatiles plus volatiles from damaged P. vulgaris plants, as shown using both Y-tube olfactometer and open-space assay systems. However, the number of spider mite eggs consumed by P. persimilis on P. vulgaris plants did not differ in the presence compared to the absence of mint volatiles, indicating that mint volatiles affect the attraction but not the appetite of P. persimilis. Together, these findings suggest that the use of candy mint and spearmint as CPs is an ideal platform for spider mite pest management via the attraction of predatory mites.

Field survey of Glycyrrhiza plants in Central Asia (3). Chemical characterization of G. glabra collected in Uzbekistan.

The chemical characteristics of Glycyrrhiza glabra L. were investigated at a habitat in Uzbekistan. HPLC analysis of the underground parts indicated that glycyrrhizin contents varied from 3.3 to 6.1% of dry weight, and that glabridin, a species-specific flavonoid for G. glabra, was detected in all underground samples (0.08-0.35% of dry weight). HPLC analysis of the leaves indicated that G. glabra plants collected in the present study could be divided into two types, RT-type and IQ-type, according to their major flavonol glycosides, rutin or isoquercitrin, respectively.

Field survey of Glycyrrhiza plants in Central Asia (1). Characterization of G. uralensis, G. glabra and the putative intermediate collected in Kazakhstan.

The characteristics of Glycyrrhiza plants from 12 collection sites in southeastern Kazakhstan were investigated. G. uralensis was observed at 9 of the sites from Almaty to Shu, and G. glabra was observed at 8 sites. At 4 sites near Shu, and 1 site near Almaty, G. glabra and G. uralensis grew together forming a mixed population, and intermediate-type plants between them were also observed at 3 sites. Although two nucleotide substitutions of the chloroplast rbcL gene were observed between G. uralensis and G. glabra, rbcL sequences of the intermediate-types were divided into G. uralensis-type (G-A type) and G. glabra-type (A-T type). HPLC analysis of the roots indicated that species-specific flavonoids, glabridin and glycycoumarin, were detected in the roots of G. glabra and G. uralensis, respectively, but neither flavonoid was detected in underground parts of the intermediate-types. HPLC analysis of their leaves indicated a significant difference among G. uralensis, G. glabra and the intermediate-type plants. Both G. glabra-specific and G. uralensis-specific compounds were detected in the leaves of the intermediate-type, thus suggesting that the intermediate plants are hybrids of G. glabra and G. uralensis.