Bottom‐up and top‐down effects in a tritrophic system: the population dynamics of Plutella xylostella (L.)–Cotesia plutellae (Kurdjumov) on different host plants

Abstract

1. The effects of host-plant resistance on the population dynamics of the Diamondback moth, Plutella xylostella L., and its solitary parasitoid, Cotesia plutellae (Kurdjumov), were studied in replicated time-series experiments.2. Host-plant resistance did not affect the equilibrial abundance of the Diamondback moth, but it affected the dynamics of Diamondback moth populations.3. The mean population size of Diamondback moth showed no significant difference between Brassica rapa (a susceptible host plant) and Brassica napus (a partially resistant host plant) either in the presence or absence of the parasitoid.4. Time-series analysis suggests that the dynamics of Diamondback moth on B. rapa were underpinned by delayed density-dependent processes. In contrast, the dynamics of the moth on B. napus were influenced by a direct density-dependent process.5. Although measures of short-term parasitism showed a significantly higher rate of parasitism by C. plutellae on Diamondback moth feeding on B. napus compared with B. rapa, this individual performance does not translate into differences in the population dynamics. Analysis shows no significant difference in the persistence time of the population-level interaction between the host and parasitoid on the two different host plants.

Seletividade de atrazine e nicosulfuron a Podisus nigrispinus (Heteroptera: Pentatomidae)

“…Em trabalhos com inseticidas, verificou-se alta toxicidade a ninfas de P. nigrispinus expostas ao neonicotinoide imidaclopride, em manejo de pragas na cultura do algodão (Torres & Ruberson, 2004). Insetos de segundo e terceiro estádios de P. nigrispinus apresentaram alta mortalidade devido à exposição dos inseticidas imidaclopride e ao piretroide (betaciflutrina), o que pode ser atribuído ao contato do predador com os resíduos (Karimzadeh et al, 2004;Sarfraz et al, 2008). Assim, podem-se associar os resultados encontrados à menor tolerância da cutícula dos insetos nessa fase inicial de desenvolvimento.…”

Plant-mediated effects in the Brassicaceae on the performance and behaviour of parasitoids

“…In addition, individual foraging decisions do not necessarily translate directly into differences in population dynamics. For example, parasitism rates by C. plutellae differed when the parasitoids were reared on two different host plants in short-term experiments, but in long-term experiments the population dynamics were similar on both host plant species (Karimzadeh et al 2004). Field studies are thus necessary to reveal the relative importance of HIPV on plant/parasitoid fitness in both managed agricultural and unmanaged natural ecosystems (Geervliet et al 2000).…”

Relative influences of plant type and parasitoid initial density on host–parasitoid relationships in a tritrophic system

“…Similarly, the cultures of C. plutellae, in turn, were maintained on P. xylostella larvae in oviposition cages (40 × 40 × 40 cm). Both cultures were reared in a standard constant environment (25 ± 2°C; 70 ± 5% RH; and L:D 16:8 h) (Karimzadeh et al 2004;Karimzadeh & Sayyed 2011).…”

“…There is much interest in tritrophic interactions between plants, herbivores and natural enemies, driven by the need to integrate both host plant resistance and biological control in the management of arthropod pests in ecological population and communities (Price et al 1980;Gange & Brown 1997;Tscharntke & Hawkins 2002;Karimzadeh et al 2004;Walker et al 2008). …”

“…The role of bottom-up effects and, in particular, food limitation in regulating insect populations is of prime importance (Bonsall & Eber 2001) as the population dynamics of both herbivore and herbivore-natural enemy interactions may be influenced by variation in host plant characteristics (Hunter & Price 1992;Karimzadeh et al 2004). For instance, variation in host plant quality may affect the body size of herbivorous insects, which, in turn, can determine life history parameters, such as fecundity, longevity and survival, all directly relevant to population dynamics (Karimzadeh et al 2004;Karimzadeh & Wright 2008;Soufbaf et al 2010aSoufbaf et al , 2010bSoufbaf et al , 2013Kianpour et al 2014). Furthermore, plants can indirectly influence the performance of natural enemies (Price et al 1980;Soufbaf et al 2012;Karimzadeh et al 2013).…”