Attractiveness of some novel crops for flower- visiting hoverflies (Diptera: Syrphidae): comparisons from two continents.

Abstract

Due to their design and cultivation practices, agricultural habitats are often hostile environments to beneficial arthropods. The continuous presence of these arthropods is, however, generally regarded as useful and desirable, as they provide the most acceptable form of pest control. Manipulating agricultural fields in order to enhance their suitability as habitat for natural enemies is an age-old practice increasing in sophistication and effectiveness. Such manipulation techniques involve creating habitat refuges such as headlands, hedgerows or grass banks (Thomas et al., 1991) which serve as recolonisation foci, or providing key resources like alternative food or nectar (Powell, 1986) which keep or attract natural enemies near the required site of action.
Several species of beneficial arthropods, for example parasitoid wasps and hoverflies, require nectar and or pollen for maturation feeding (Schnieder, 1948; Jervis & Kidd, 1986). Increasing the flower availability in or near crop stands can increase natural enemy effectiveness (Powell, 1986; Russell, 1989). This can be achieved either by increasing within-field diversity, or by maintaining grassy or weedy edges. The species utilised by beneficial arthropods in such patches are often pernicious weeds.
To test whether crop species can be used to this end, we evaluated several novel and potential crop plants for their attractiveness to natural enemies. A suitable candidate plant would have triple benefits, namely it would serve as a habitat refuge for ground-active beneficial arthropods, provide pollen and nectar for natural enemies such as hoverflies and parasitoid wasps, and provide a useful product for the farmer.