Effects of insects, seeding rate, and insecticide seed dressing on white clover and Maku lotus in tussock grassland

Abstract

Abstract Native insects, especially broad-nosed weevils (Curculionidae; Leptopiinae), living in tussock grassland, feed on oversown white clover (Trifolium repens L. ‘Grasslands Huia’) seedlings, causing damage and loss of plants. The maintenance of relatively ‘insect-free’ conditions by using regular parathion spray treatment reduced seedling losses 8 weeks after sowing from 19 to 1%. Seed dressing with oxamyl decreased seedling loss by about 65% during the first 4–5 weeks after germination, improved plant establishment by 20%, and increased plant yield by 28% in the second season. Neither omethoate seed dressing nor doubling seeding rate gave significant improvement in plant establishment or yield, although omethoate gave newly germinated seedlings some protection from insects. Lotus pedunculatus Cav. ‘Grasslands Maku’ was not severely damaged as a result of insect feeding activity because of suspected repellent and toxic properties of the plant.