Age-dependent efficacy of putative dead-end trap crops Barbarea verna and Lepidium sativum on diamondback moth, Plutella xylostella

Abstract

Dead-end trap crops are plants used in pest management that are highly attractive to egg-laying adults but do not support the survival of the developing offspring. For the diamondback moth (DBM; Plutella xylostella), Barbarea vulgaris and B. verna (upland cress) are proven dead-end trap crops but the evidence for Lepidium sativum has been contradictory with one study claiming dead-end effects but others showing that it is a suitable host. Since glucosinolate and saponin levels, which, respectively, stimulate oviposition and act as deterrents, vary with plant age in Barbarea spp., the goal of the present study was to investigate the effects of plant age on the attractiveness and dead-end properties of upland cress and two cultivars of L. sativum (garden cress and broadleaf cress). When given the opportunity to lay eggs on the putative dead-end trap crops or cabbage (Brassica oleracea), DBM did not preferentially lay eggs on garden cress and upland cress until the plants were 5 weeks or older, while broadleaf cress was attractive at all ages. Egg-to-adult survival and growth rate on garden cress and broadleaf cress was as high or higher as on cabbage, regardless of plant age. Upland cress did not reduce survival of DBM at 2 and 5 weeks old but did at 10 weeks old. We confirm that plant age is critical to the effectiveness of upland cress as a dead-end trap crop and conclude that garden cress and broadleaf cress can be suitable trap crops but exhibit no dead-end properties.