Influence of plant sulphur nutrition on oviposition and larval performance of the diamondback moth

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Abstract
We measured adult oviposition preference, larval growth, and feeding behaviour of the crucifer specialist Plutella xylostella (L.) (Lepidoptera: Plutellidae) on plants of Brassica napus (L.) cv. Express (Brassicaceae), grown under three different sulphur regimes. The nutrient solutions used were the following: one sulphur‐free (S0), one normal sulphur (Sn, normal field concentration), and one sulphur‐rich (S+, double concentration of Sn). Females laid more eggs on Sn than on S0 plants, while only a slight, non‐significant difference was observed between Sn and S+ plants. Moreover, the development time from hatching to emergence was significantly shorter, and adults were heavier on Sn than on S0 plants. Comparing these same two parameters from Sn and S+ plants, we found a shorter development time on plants rich in sulphur, although this trend was not statistically significant. Larval feeding preferences were tested in a dual choice assay using leaf discs. A significantly higher number of larvae preferred leaf discs of Sn plants than those of S0 plants. Furthermore, the larvae preferred S+ to Sn discs. An optimal supply of sulphur to oilseed rape is necessary for a good seed harvest, and it also plays an important role in acceptance by P. xylostella of the host plant. Maintaining higher levels of sulphur in the plant nutrient solution benefits insect performance, both at the adult and larval stage.