How host-specific is diamondback moth? A study on performance with brassicaceous and non-brassicaceous species

摘要

Diamondback moth, Plutella xylostella ( L.) ( Lepidoptera: Plutellidae) is oligophagous on Brassicaceae, but is known to have occasionally switched to also feed upon hosts of other plant families. The spider flower, Cleome hassleriana Chodat ( Capparaceae) and garden nasturtium Tropaeolum majus L. ( Tropaeolaceae) are taxonomically distinct but chemically related to Brassicaceae by containing glucosinolates. Both of these plant species can occur sympatrically with wild crucifers, and so could potentially harbor P. xylostella populations, perhaps providing bridge hosts until crop plants are available. But these non-brassicaceous plants have never been reported to be infested with P. xylostella in the region. In this extensive laboratory and greenhouse study, we tested ovipositional preferences of P. xylostella in a free-choice situation using two Brassicaceae viz. conventional canola, Brassica napus L. , flixweed, Descurainia sophia ( L. ) Webb ex Prantl, and two non-Brassicaceae viz. C. hasslerianaand T. majus. No-choice tests were conducted to investigate key life history parameters i. e. , survival, developmental time, herbivory, pupal weight, silk weight, adult weight, forewing wing area, and longevity ( without food) for both female and malespecimens when reared on all four plant species. Although several P. xylostella developmental parameters were similar on C. hassleriana and T. majus as on more preferred Brassicaceae, non-hosts lacked the ability to compensate as well for P. xylostella herbivory. Host shifting by P. xylostella is evidently a strategy for population survival when preferred hosts are not available, and is a strategy that may predispose new generation offspring for enhanced migratory capability.