Grass grub tolerant pastures and fertiliser nitrogen as an alternative to white clover in pasture subject to grass grub attack

Abstract

The effect of replacing white clover with fertiliser nitrogen (N) on dry matter production and grass grub populations in 'Grasslands Roa' tell fescue (Festuca arundinacea Schreb.), 'Grasslands Mat-u' phalaris (Phalutis aquatica L.), 'Grasslands Kara' cocksfoot (Dactylis glomerata L.), 'Grasslands Mama' prairie grass (Bromus willdenowii Kunth) and 'old' (30 year plus) ryegrass was measured over a 2 year period. For all pastures the replacement of white clover with fertiliser N significantly reduced grass grub numbers. This was greatest in tall fescue, phalaris and cocksfoot, showing that pure swards of these species were resistant to grass grub. Decreases in grass grub numbers in ryegrass and prairie grass were less. There was overall a significant increase in pasture production by eliminating white clover and applying fertiliser N, with a differential response between species. Average annual production of prairie grass was unaffected, whereas the yield of cocksfoot increased by 9 % and old ryegrass, phalaris and tall fescue increased by 26 % . Most of this extra production for tall fescue and phalaris occurred in autumn. These results show that the use of tall fescue and phalaris and the replacement of white clover with fertiliser N has potential for increasing pasture production in districts subject to grass damage. Keywords old ryegrass, Roa tall fescue, Maru phalaris, Kara cocksfoot, Matua prairie grass, white clover, grass grub, nitrogen fertiliser