Apparent competition or apparent mutualism? An analysis of the influence of rose bush strip management on aphid population in wheat field

Abstract

Apparent competition, mediated by a shared predator, plays a key role in conservation biological control. Appropriate agroecosystems management may favour this type of indirect interaction. In that context, our aim was to test the effect of rose bush [Rosa rugosa (Thunb.)] strips on the building up of aphid populations and of their natural enemies in adjacent cereal habitats. Several aphid species are currently found on Rosa sp. including Metopolophium dirhodum (Walker) for which it is a primary host. Aphid predators and parasitoids may build their populations on the aphid population present on Rosa sp. and later on migrate to wheat field during the cereal aphid infestation. Moreover, the flowers of the rose bushes may provide a source of nectar and pollen to these natural enemies.Our experiment was conducted in three rose margin wheat plots with a strip of rose bushes of R. rugosa and three control plots. Plots were compared during 2 years (2003 and 2004). Aphid, parasitoid and predator densities were recorded from May to the harvest of wheat on rose bushes and in wheat. In 2003, the aphid densities were moderate but in 2004, the population of aphid was very high.Even if predator and parasitoids arrived earlier in rose margin field than in control ones, the presence of rose bushes did not influence the aphid population within the field. Metopolophium dirhodum did not seem to migrate from the rose bushes to wheat. The level of parasitism was weak in rose bushes and the natural enemy population was not different in rose margin wheat and in control plots. The causes of the lack of efficiency of this type of management are discussed as well as the high aphid population in wheat in 2004.

Regional Tritrophic Relationship Patterns of Five Aphid Parasitoid Species (Hymenoptera: Braconidae: Aphidiinae) in Agroecosystem-Dominated Landscapes of Southeastern Europe

“…Movement of some speciÞc parasitoids from noncrop habitats to crop Þelds depends on many factors, ranging from intrinsic biological [e.g., dispersal rate, Weisser and Vö lkl (1997) pointed out low dispersal rate for Lysiphlebus species; host preference, Cameron (1984) showed that A. ervi reared from Acyrthosiphon pisum (Harris) are not so much effective against Sitobion avenae (F.)] to different environmental factors such as presence of alternative food or shelter resources, or suitable aphid hosts in the crop Þelds in comparison with noncrop habitats (Rand et al 2006, Frere et al 2007. Population genetic studies on parasitoid species sourcing from two different hosts together with their habitat stability were undertaken by Antolin et al (2006).…”

Coccinellids in Biological Control

“…The work of Grez et al (2010) in Chile illustrates just how speciesspecifi c coccinellid responses can be to various types vegetation bordering agricultural fi elds. However, border vegetation planted to provide supplementary food resources or alternative prey for coccinellids may sometimes impede their timely dispersal into adjacent crops, a phenomenon often referred to as ' apparent competition ' (Frere et al 2007 ). For example, stinging nettle, Urtica dioica , has long been recognized as a reservoir plant for coccinellids (Perrin 1975 ), but such reservoirs cannot benefi t biological control unless beetles leave them and enter crop fi elds.…”

Multitrophic interactions among plants, aphids, alternate prey and shared natural enemies - a review

“…In other instances, however, aggregation of mobile generalist predators in response to high densities of herbivores in one habitat may lessen predation pressure on other herbivores in other habitats. Frere et al (2007) report, for example, that cereal aphid populations were especially high in wheat plots that were close to strips of rose bush, perhaps because predators and parasitoids aggregated instead to attack aphid populations infesting the roses.…”