Feeding preference of Altica deserticola on Glycyrrhiza glabra leaves provided with different water and nitrogen levels

Abstract

We explored the resistance of Glycyrrhiza glabra (licorice) to Altica deserticola and formulated a water-fertilizer management regime to improve the insect resistance in licorice crops. Four treatments (combinations of low and high soil moisture content with low and high nitrogen (N) fertilizer content) were performed. The resistance mechanism was studied by comparing the leaf hardness; leaf thickness; cuticle thickness; and water, N, and tannin content of G. glabra, as well as the feeding preference of A. deserticola for G. glabra leavesusing leaf-disc tests under the four treatments. The results showed that A. deserticola preferred to feed on leaves under the low soil moisture level and high N fertilizer (LWHN) level treatment and least preferred leaves under the low soil moisture level and low N fertilizer (LWLN) level treatment. Soil moisture and N had a significant interaction on the leaf and cuticle thickness and the water, N, and tannin contents. Glycyrrhiza glabra leaves were the thickest and had the thickest cuticle under LWLN; the water and N contents of the leaves and the tannin contents were also the highest. Under the LWHN treatment, G. glabra had thin leaves, the thinnest cuticle, the highest N content, and the lowest tannin content. In conclusion, a reasonable water and N regime may effectively reduce the feeding damage by A. deserticola to G. glabra leaves.