Ingestion and excretion of nitrogen by larvae of a cabbage armyworm: the effects of fertilizer application

Abstract

1 Insect frass has significant impacts on decomposition and soil nitrogen dynamics. Although the frass contains various forms of nitrogen that may differently influence nitrogen dynamics in the decomposition process, how the nitrogen form in the insect frass is influenced by host plant quality remains poorly understood. 2 The present study examined the effects of application of fertilizer on leaf quality of Brassica rapa L. var. perviridis Bailey (Brassicaceae), and on the consumption, frass excretion and frass quality of its insect pest Mamestra brassicae (L.) (Lepidoptera: Noctuidae), with a particular focus on the dynamics of inorganic nitrogen. 3 Brassica rapa increased total nitrogen concentration, and accumulated inorganic nitrogen [i.e. leaf nitrate-nitrogen (NO 3 − -N) and ammonium-nitrogen (NH 4 + -N)] in the leaves in response to the application of fertilizer. 4 Although leaf consumption and frass excreted by M. brassicae was not affected by fertilizer treatment, frass quality was influenced by host plant quality as altered by fertilizer applications. Frass contained high concentrations of total nitrogen, NO 3 − -N, and NH 4 + -N under high fertilizer treatment. In particular, the larvae excreted much more NH 4 + -N than ingested. The relationship between host plant quality and insect frass quality, as well as the potential implications for decomposition and nutrient dynamics, are discussed.

Positive and negative impacts of insect frass quality on soil nitrogen availability and plant growth

“…-N. The frass with high NH 4 ? -N clearly resulted from feeding on host plants with a high level of N (Kagata and Ohgushi 2011). Thus, the present study demonstrated that insect frass quality can both positively and negatively influence decomposition and nutrient dynamics in soil.…”

“…perviridis Bailey (Brassicaceae), at various fertilization levels (Kagata and Ohgushi 2011). We showed that the frass quality of M. brassicae larvae was strongly affected by the quality of host plant leaves, and that the larval frass had high levels of total N, nitrate-N (NO 3 --N), and ammonium-N (NH 4 ?…”

“…On the other hand, effects of frass quality on decomposition process have been paid less attention than effects of frass quantity, despite the fact that the quality of herbivorous insect frass differs depending on host plant quality and insect species identity (Madritch et al 2007;Kagata and Ohgushi 2011). It is well known that the process of decomposition of plant litter is strongly affected by litter chemicals (Enríquez et al 1993).…”

Carbon to nitrogen excretion ratio in lepidopteran larvae: relative importance of ecological stoichiometry and metabolic scaling

“…For example, N enrichment due to N deposition increases N in plants (Fenn et al 1996, Throop and Lerdau 2004). If the plant C:N ratio is less than 14, insect herbivores that feed on those plants may excrete relatively N‐biased frass (Kagata and Ohgushi 2011). In contrast, elevated atmospheric CO 2 level decreases N in plants (Cotrufo et al 1998, Lindroth 2010), and therefore insect herbivores may excrete more C‐biased frass in such an environmental condition (but see Knepp et al 2007).…”

Ecosystem consequences of selective feeding of an insect herbivore: palatability-decomposability relationship revisited

“…Insect frass contains larger amounts of N and labile carbon (C) than leaf litter (Lovett & Ruesink, 1995;Madritch et al, 2007). In addition, insect frass quality is strongly influenced by host leaf quality, such as nitrogen and tannins (Madritch et al, 2007;Kagata & Ohgushi, 2011) which are chemicals known to determine the decomposition efficiency of leaf litter (Enríquez et al, 1993;Kraus et al, 2003). In addition, insect frass quality is strongly influenced by host leaf quality, such as nitrogen and tannins (Madritch et al, 2007;Kagata & Ohgushi, 2011) which are chemicals known to determine the decomposition efficiency of leaf litter (Enríquez et al, 1993;Kraus et al, 2003).…”