Herbivore response to habitat manipulation with floral resources: a study of the cabbage root fly

Abstract

Biological control of pest insects can be improved by providing natural enemies with additional food resources such as floral nectar within the production field. However, herbivores may also benefit from this practice. The aim of this 3‐year field study was to investigate if dill and buckwheat, aimed as food resources for natural enemies, could increase the densities of the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae), a severe pest on crucifers. Differences in egg density, numbers of pupae and sex ratio were compared between cabbage plots with or without flowers. Habitat manipulation by intercropping flowering plants with cabbage did not increase the overall D. radicum egg density in our 3‐year study, and there were no significant differences in egg numbers between treatments in any year. No effect on the fecundity of D. radicum was observed, most likely because of the high mobility and feeding behaviour of the female flies, combined with high abundance and diversity of other food sources around the fields during this period. Despite equal egg numbers, fewer pupae were found in plots with flowers than without in one of three studied years. This finding suggests that natural enemies attacking larvae and pupae of D. radicum were either more abundant or efficient in cabbage plots with flowers.

Development of an Insectary Plant Mixture for New Mexico and its Effect on Pests and Beneficial Insects Associated with Pumpkins

“…However, as has been reported in other cropping systems, parasitic Hymenoptera were consistently attracted by the presence of floral resources (Frank and Shrewsbury 2004, Begum et al 2006, Mark et al 2012. The beneficial effects of plant nectar on the longevity and fecundity of parasitoids have been demonstrated for a number of species (Baggen and Gurr 1998, Begum et al 2006, Lavendero et al 2006, Nafziger and Fadamiro 2011, Nilsson et al 2012, and the addition of flowering plants to cropping systems has resulted in increased parasitism of pests in some (but not all) similar studies of this type (Grossman and Quarles 1993, Thies and Tscharntke 1999, Keller and Baker 2002, Irvin et al 2006, Mark et al 2012. The use of sticky traps for monitoring beneficial insects had the drawback of precluding species-level determination of parasitoid taxa, and most of the species attracted were probably associated with hosts other than the target pests.…”

“…Ideally, such 'insectary' plantings should be comprised of a mixture of different species that vary in flower structure, size, color, and flowering period so as to benefit the maximum number of beneficial insects while not stimulating increases in pest species (Baggen and Gurr 1998;Baggen et al 1999;Begum et al 2006;Lavendero et al 2006;Kehrli and Bachera 2008;Winkler et al 2009;Nilsson et al 2011Nilsson et al , 2012. Commercial seed mixtures of insectary flowers are available, but do not perform consistently well under different conditions (Carreck and Williams 1997).…”

Hedgerows surrounding organic apple orchards in north‐west Spain: potential to conserve beneficial insects

“…Consequently, there is evident interest in identifying the flowering species that colonize and establish themselves in fruit orchards, as well as in understanding the role that these plants may play in conserving beneficial insect groups, such as those involved in pollination or in biological control of pests. (Ambrosino et al, 2006;Irvin et al, 2006;Hogg et al, 2011;Markó et al, 2012;Nilsson et al, 2012), although plants already growing in an area may be as attractive as the usually recommended non-native plants (Fiedler & Landis, 2007). Many studies with sown floral strips have been conducted with a small group of annual flowering plants non-native to the management areas, such as Borago officinalis L., Coriandrum sativum L., Fagopyrum esculentum Moench, Lobularia maritima L. Desv.…”

“…or Phacelia tanacetifolia Benth. (Ambrosino et al, 2006;Irvin et al, 2006;Hogg et al, 2011;Markó et al, 2012;Nilsson et al, 2012), although plants already growing in an area may be as attractive as the usually recommended non-native plants (Fiedler & Landis, 2007). Moreover, native plants may have several advantages: these species are adapted to the local environment, form part of the native biodiversity and are less likely to be invasive (Fiedler & Landis, 2007).…”

Weeds within willow short-rotation coppices alter the arthropod community and improve biological control of the blue willow beetle

“…The resource concentration hypothesis predicts that herbivores, especially specialists with a narrow host range, will more easily find concentrated host plants and remain within these monocultures. One prominent strategy for increasing biological control is to allow non-crop plants to grow in a field as a form of intercropping (Nilsson et al 2012;Winkler et al 2010). Andow 1991), and this will tend to suppress the herbivores in polycultures.…”