Effect of narrow-leaved plantain cultivar on development of two geometrid pests, Scopula rubraria and Epyaxa rosearia

Narrow-leaved plantain Plantago lanceolata has become common as a forage crop in New Zealand and has led to the emergence of two native moths, Scopula rubraria and Epyaxa rosearia, as significant pests, particularly in the North Island. Plantain is known to contain defensive compounds against insects and a laboratory study was undertaken to compare the growth and development of both moth species on four plantain cultivars and one breeding line. It was found that larval feeding and development varied with plant line and leaf age, with Ceres Tonic and especially SF Boston being most favourable plantain lines for both pests. No E. rosearia larvae survived on mature foliage from Luisetti Tuatara or the breeding line JC Upright. While the differences between plant lines appeared to be related to foliar digestibility and metabolisable energy indices, rather than aucubin and catalpol levels, the results indicate that narrow-leaved plantain has attributes that could be exploited to achieve better resistance against these pests.