Performance of an oligophagous insect in relation to the age of the host plant

Abstract

Performance de um Inseto Oligófago em Relação à Idade da Planta Hospedeira RESUMO -A performance de insetos folívoros monófagos e oligófagos deveria ser afetada negativamente pelo envelhecimento das suas plantas hospedeiras. Plutella xylostella L. (Lepidoptera: Yponomeutidae), uma especialista em Cruciferae, foi criada em laboratório com folhas destacadas de repolho (Brassica oleraceae var. capitata). Foram utilizadas a quarta folha expandida de plantas de diferentes idades mais as folhas dos três estratos da planta madura. O envelhecimento da planta aumentou a mortalidade preimaginal e reduziu a taxa de desenvolvimento das larvas, o peso das pupas e a fecundidade dos adultos. A taxa reprodutiva líquida (Ro) e a taxa intrínseca de crescimento populacional (r) diminuíram com o envelhecimento da planta. Nenhuma das categorias de folhas da planta madura mostrou-se qualitativamente superior às folhas de plantas mais jovens. Se em condições de campo existir uma correlação positiva entre preferencia de oviposição e performance da prole, espera-se uma tendência temporal decrescente na intensidade de ataque de larvas ao longo do desenvolvimento da planta. PALAVRAS-CHAVE: Desenvolvimento larval, sucesso reprodutivo, fenologia da planta, Plutella xylostella, LepidopteraABSTRACT -The performance of monophagous and oligophagous herbivore insects should be negatively influenced by the ageing of their host plants. Plutella xylostella L. (Lepidoptera: Yponomeutidae), a specialist in Cruciferae, was reared in the laboratory on detached cabbage leaves (Brassica oleraceae var. capitata). We used fourth expanded leaves from differently aged plants, and leaves from three strata of the mature plant. Plant ageing increased pre-imaginal mortality and reduced larval developing rate, pupae weight, and fecundity. The insect net reproductive rate (Ro) and intrinsic rate of population growth (r) decreased as plant aged. No leaf category of mature plants was qualitatively superior to leaves from younger plants. If there exist a positive correlation between oviposition preference and offspring performance, in field conditions, a decreasing temporal trend in the intensity of attack along the host plant development can be expected.

Choice of feeding sites, growth and survival by Crocidolomia pavonana (F.)

“…Between plant age, the oldest leaf (leaf 1) from younger plant have a greater mining sites than on oldest leaf from older plant, which support the assertion that younger leaves are more acceptable for feeding. Previous studies have demonstrated that P. xylostella prefer and perform better on younger leaves which contains high level of nitrogen and proteins (Campos et al, 2003;Campos et al, 2004;Silva & Furlong, 2012;Moreira et al, 2016). Some inactive mining sites by P. xylostella were observed on older leaves (leaf 1 and 2) suggesting that larvae were test feeding or have pre-feeding movement before moving on to a more suitable leaf for mining, as suggested by Silva & Furlong (2012).…”

“…This result is consistent with previous findings where female moths of P. xylostella preferred to lay eggs on younger plants where there was a greater chance of larval survival and development Zhang et al, 2012). Younger plants are considered nutritionally superior over older plants and suitable for offspring performance (Campos et al, 2003;Campos et al, 2004Campos et al, , 2016Coley et al, 2006). Similarly, the intra-plant distribution and the excised leaf experiment showed significant preference for feeding on younger leaves.…”

“…As leaves age the nutritional value decreases (Mattson, 1980;Teixeira et al, 2013;Moreira et al, 2016) and this should encourage movement of neonates to a more suitable site for feeding (Zalucki et al, 2002). So in addition to chemical cues or phagostimulants, larval preference for younger leaves is likely to be driven by nutritional quality (as discussed by Campos et al, 2003;Moreira et al, 2016). Access to these leaves would provide tissue containing higher levels of nitrogen (Mattson, 1980) and proteins that are essential for larval development (Campos et al, 2003;Moreira et al, 2016).…”

“…So in addition to chemical cues or phagostimulants, larval preference for younger leaves is likely to be driven by nutritional quality (as discussed by Campos et al, 2003;Moreira et al, 2016). Access to these leaves would provide tissue containing higher levels of nitrogen (Mattson, 1980) and proteins that are essential for larval development (Campos et al, 2003;Moreira et al, 2016).…”

“…original leaf 1) regardless of where they were positioned . Leaf choice by P. xylostella neonates can be attributed to different factors such as nutritional quality (Campos et al, 2003;Teixeira et al, 2013;Moreira et al, 2015), plant compounds (Nikoeei et al, 2015) and morphological traits, such as leaf wax (Eigenbrode et al, 1990;Eigenbrode et al, 1991).…”