Effect of black beetle, in association with nitrogen and summer spelling, on pasture production on sandy soils

Abstract

Abstract Pasture production was measured on plots infested with black beetle, Heteronychus arator (F.) (Scarabaeidae: Coleoptera), and insecticide-treated plots from 1983 to 1986 on sandy soils near Kaitaia in Northland. Black beetle densities ranged from 11 to 27/m2 on ryegrass (Lolium perenne L.)—dominant and from 16 to 112/m2 on kikuyu grass (Pennisetum clandestinum Hochst.) —dominant pastures. Livestock pulling plants from the soil caused pasture damage on plots infested with black beetle. Insecticidal control of black beetle, however, resulted in relatively small transient increases in pasture production. In contrast, nitrogen (N) applications significantly boosted production, ranging from 35 and 25 kg dry matter (DM)/kg N in spring to 25 and 17 kg DM/kg in winter for ryegrass- and kikuyu grass-dommant pastures, respectively. Spelling kikuyu grass p~sture from grazing over the summer and autumn III 1985 and 1986 resulted in an increase in pasture production of from 470 to 960 kg DM/ha. The role of bl...