MIRlDS IN 'GRASSLANDS MAKU' LOTUS SEED CROPS: FRIENDS OR FOES?

Abstract

The need for mirid (Calocoris norvegicus Gmel.) control to improve seed yields of 'Grasslands Maku' lotus seed crops was studied over two seasons on a crop near Lincoln, Canterbury. In 1980 seed yields were increased by 40% to 850 kg/ha by the application of bromophos (500 g a.i./ha) in mid-December to remove a population of 30 mirids/20 net sweeps. In 1981, demetonb-methyl (200 g a.i./haj was applied along with a water only control in mid-November, followed by a blanket spray of bromophos in mid-December. There were two separate effects resulting from the use of metasystox. Although demetondmethyl protection gave a higher seed yield/stem for early-formed flowerheads the pattern was reversed for the later-formed flowerheads because early mirid attack increased flowerhead numbers/stem. Laterformed umbels gave a more concentrated span of flowering, which enhanced better timing of harvest of this crop which is prone to pod shattering. The recommendation is to control mirids only in mid-December using bromophos. an insecticide that is relatively bee safe. Key Words: Seed production, Lotus pedunculatus, mirids, Calocoris norvegicus, insecticide control