A trial was carried out in unimproved tussock grassland on the East Otago Plateau of the South Island of New Zealand to investigate the impact of native broad-nosed weevils (Coleoptera: Curculionidae) feeding on survival, establishment, and yield of oversown white clover. The trial consisted of 20 sites 1 km apart where two plots were established in each of 5 consecutive years. At each of the sites in each year, one of the plots was sprayed with parathion at 2-weekly intervals from September to December to allow seedlings to establish in #x201C;insect-free#x201D; conditions. The other plot was left untreated. The plots were sown in October and, by late December, seedlings suffered on average 40 and 6 mortality in the untreated and sprayed plots respectively. Sublethal insect feeding reduced nodulation on average by 46 and final established plant density by 39 in the unsprayed plots. Despite identical treatment of the two plots after the initial 3 months, white clover yields were significantly higher in the plots initially protected from insects where on average 58 more clover dry matter (an increase from 87 to 137 kg/ha per year) was produced over 5 years of harvesting the plots.
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