THE EFFECT OF SUPERPHOSPHATE APPLICATION, 2,4‐DB AND GRAZING ON BROOMRAPE (<i>OROBANCHE MINOR</i> SM.) IN A SUBTERRANEAN CLOVER PASTURE

Abstract

Summary Two 5‐year trials were conducted in New South Wales on the control of broomrape ( Orobanche minor Sm.), a plant parasite of subterranean clover ( Trifolium subterraneum L.) and skeleton weed ( Chondrilla juncea L.). Applications of superphosphate to two soils of low phosphorus status stimulated clover growth, which caused a reduction in the number of skeleton weed plants and a decrease in the broomrape population. Similar but less effective control was obtained when subterranean clover pasture was sprayed with 2,4‐DB for skeleton weed control as soon as the clover seedlings had developed trifoliate leaves. In spring, sheep readily grazed the broomrape stems before flowering, causing death of the plants. Autumn application of super phosphate, coupled with grazing of the pasture by sheep, significantly reduced broomrape density.