Host location and oviposition of lepidopteran herbivores in diversified broccoli cropping systems

Abstract

1 Host location and oviposition are crucial steps in the life cycles of insect herbivores. A diversified cropping system may interfere with these processes, ultimately reducing pest colonization of crops and the need for chemical interventions. 2 In the present study, nonhost vegetation was added to a broccoli ( Brassica oleracea var. italica ) cropping system to determine the effect of plant diversification on host location and colonization of broccoli by Lepidopteran pests. The two diversification strategies applied consisted of a broccoli/potato ( Solanum tuberosum ) strip crop, made up of 1.65 m (tractor width) replications of two rows of potatoes and two rows of broccoli, and a cereal rye ( Secale cereale ) cover crop, which formed a sacrificial planting that was killed and rolled flat to minimize weed competition and improve the agronomic performance of the subsequent broccoli crop. 3 Diamondback moth Plutella xylostella eggs, and subsequent larvae and pupae, were less abundant on broccoli with the cover crop, probably due to interference with host location and oviposition processes. The strip crop had no effect. 4 Numbers of cabbage white butterflies Pieris rapae eggs and larvae did not differ among treatments, probably due to the superior ability of these Lepidoptera to visually locate hosts and their active egg-dispersing behaviour. 5 These results of the present study indicate that the success of crop diversification strategies are contingent on the relative ability of the target herbivore to locate its host plant and the scale of diversity (e.g. the distance between the host and the nonhost plants), rather than diversity itself.

Effects of mixed cropping on population densities and parasitism rates of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

“…The results correspond with the results obtained in previous studies, which tested the pest-suppressive effect of the intercropping of the herb sage, Salvia officinalis L. (Lamiaceae) (Dover 1986), thyme, Thymus vulgaris L. (Lamiaceae) (Dover 1986 (Bukovinszky et al 2004). Conversely, there is an exception to this: strip cropping of potato, Solanum tuberosum L. (Solanaceae) had no influence on P. xylostella oviposition on broccoli (Broad et al 2008).…”

“…Several authors have suggested that olfactory and/or visual disruption of P. xylostella hostfinding is a feasible mechanism for the resource concentration effect in mixed cropping systems (Finch and Collier 2000;Bukovinszky et al 2005;Couty et al 2006;Broad et al 2008). In this study, the coriander intercrop could have ''masked'' (Tahvanainen and Root 1972) the presence of cabbage by interfering with its odor profile.…”

Plant Volatiles Influence Electrophysiological and Behavioral Responses of Lygus hesperus

“…In particular, plant odors help guide insects to food sources (Byers et al 1985;Blight et al 1995;Stensmyr et al 2001;Dobson 2006), oviposition sites (Showler 2001;Broad et al 2008), and often that work in concert with insect-derived odors to facilitate mate finding (Dickens 1989;Landolt and Phillips 1997;van Tol et al 2004;Frati et al 2009). Furthermore, herbivory usually alters the blend of volatiles emitted by plants (Dicke and van Loon 2003;Tumlinson and Engelberth 2008), thereby providing additional information to insects about the potential suitability of the plant for colonization (De Moraes et al 2001;Meiners et al 2005;Choh et al 2008).…”

Bottom‐up and top‐down effects of tree species diversity on leaf insect herbivory

“…Plant diversity is a key driver of insect herbivory in grassland, agricultural, and forest ecosystems (Allan et al, 2013;Broad, Schellhorn, Lisson, & Mendham, 2008;Castagneyrol et al, 2014), because heterospecific neighbors may either decrease (associational resistance) or increase (associational susceptibility) the likelihood of focal plants being attacked by insect herbivores (Barbosa et al, 2009;Root, 1973;Tahvanainen & Root, 1972;White & Whitham, 2000). Several reviews and meta-analyses suggest that associational resistance is the most common pattern (Andow, 1991;Barbosa et al, 2009), particularly in forest ecosystems (Castagneyrol et al, 2014;Jactel & Brockerhoff, 2007).…”