Nitrogen fertilization rate affects feeding, larval performance, and oviposition preference of the beet armyworm, Spodoptera exigua, on cotton

Abstract

Nitrogen (N) is one of the most critical chemical elements for plant and animal growth, exerting a variety of bottom‐up effects. Development and oviposition of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), were studied in relation to varying N fertilization levels (42, 112, 196, and 280 p.p.m.) in cotton [Gossypium hirsutum L. (Malvaceae)]. Low N fertilization of cotton plants led to reduced plant biomass and a lower percentage of N in leaf blades and in leaf petioles. Development of S. exigua larvae fed with plants with reduced N applications (42 and 112 p.p.m.) was prolonged relative to treatments receiving higher N fertilization. Almost all larvae reared on artificial diets underwent only five instars before pupation. However, most larvae reared on cotton plants, irrespective of N levels, experienced a supernumerary sixth larval instar. Furthermore, significantly more larvae reared on lower N cotton plants underwent supernumerary development compared to larvae reared on higher N cotton plants. Life‐time feeding damage per larva ranged from 55 to 65 cm2, depending on the nutritional quality of the food plant, although the differences were not statistically significant. Larvae distinguished between cotton plants with various nutritional qualities and fed preferentially on higher N plants. Female moth oviposition choice was also affected by host plant nutritional quality: cotton plants with higher N levels were preferentially chosen by S. exigua females for oviposition. The mechanisms of these effects are unclear, but they can have important implications for population dynamics and pest status of beet armyworms in the field.

Nitrogen Deficiency Affects Bottom-Up Cascade Without Disrupting Indirect Plant Defense

“…1). This contrasts with findings reported by Chen et al(2008b) and Merkx-Jacques et al(2008) who found that S. exigua larvae opted for leaves of high N content or a protein-biased diet, respectively. The incongruent feeding behavior of the two species may reflect their different feeding preferences.…”

“…Caterpillars fed with -N leaves gained less weight during their development and had reduced pupal and adult weights compared to larvae reared on +N leaves (Table 2). Similar results were reported from Spodoptera exigua developing on N deficient cotton (Chen et al 2008b) or larvae of other Lepidoptera feeding on several host plants (Coley et al 2006). However, studies exist where the correlation between food N content and herbivore growth is less consistent, implying that N is a limiting nutrient for larval development, but not the only one (Tabashnik 1982).…”

Effects of chlorantraniliprole on development and reproduction of beet armyworm, Spodoptera exigua (Hübner)

“…Secondly, chlorantraniliprole perhaps induced the generation of the supernumerary instars larvae of S. exigua. There are normally five instars and sometimes six instars in larval period, the percentage of 6th-instars of S. exigua may be increased under stress (Chen et al 2008). Spruce budworms are able to recover from exposure to Bt variety kurstaki without suffering reduction in pupal weight, in the terms of pupal weight the ability of spruce budworm to compensate for sublethal Bt effects was directly related to whether it produced supernumerary instars (Moreau and Bauce 2003).…”

Interactive Influence of Leaf Age, Light Intensity, and Girdling on Green Ash Foliar Chemistry and Emerald Ash Borer Development

“…For example, herbivores that feed upon plants with higher nutritional quality generally grow faster and perform better (i.e., have greater reproductive potential and longevity) than those reared on lower quality plants (Mattson 1980;Chen et al 2008a. In addition, many plant allelochemicals adversely affect herbivore colonization and life histories (Ryan 1990).…”