Management experiments on aphids (Acyrthosiphon spp.) and beneficial insects in lucerne

Abstract

Stand management in lucerne (Medicago sativa) was used to conserve natural enemies and reduce overwintering aphid (Acyrthosiphon kondoi and A. pisum) numbers. Comparison of stem and sweep net counts allowed sweep counts of predators to be calibrated, and showed that the parasite, Aphidius eadyi, and the predator, Micromus tasmaniae, were best synchronised with lucerne aphid populations. Lucerne reservoirs created by strip-cutting or strip-grazing were associated with lower aphid populations and lower ratios of aphids:predators, except in spring. Laboratory-bred parasites were released to augment early spring populations, but slow dispersal reduced their impact. Winter grazing and herbicide treatment significantly reduced aphid populations in spring. Insecticide trials confirmed the place of pirimicarb as a selective aphicide in integrated programmes.

Keywords:

• lucerne
• aphid management
• Acyrthosiphon kondoi
• A. pisum
• sampling
• beneficial insects
• synchrony
• crop reservoirs
• parasite augmentation
• winter management
• selective insecticides