Spring and autumn nitrogen effects on susceptibility of low-endophyte ‘Grasslands Nui’ ryegrass to damage by Argentine stem weevil larvae

Abstract

The probability of a low-endophyte perennialryegrass tiller being damaged by Argentine stem weevil (ASW) (Listronotus bonariensis (Kuschel)) larvae was investigated for different insecticide and nitrogen (N) fertiliser treatments. Damage of tagged tillers by ASW was recorded every 3 – 4 days from October to May in 1984/85 and 1985/86 from combinations of treatments with and without insecticide, and with and without N fertiliser applied in spring and autumn. Damage by ASW was reduced by a third but not eliminated with insecticide treatment. N applied in spring resulted in increased damage to tagged tillers by ASW and reduced ryegrass content of the sward. N applied in autumn had no effect on damage by ASW but increased the ryegrass content of the sward. It is recommended that N be applied to low-endophyte ryegrass swards in autumn to enhance recovery from damage by ASW, but that N be withheld during spring.

Keywords:

• Argentine stem weevil
• Listronotus bonariensis
• Coleoptera
• Curculionidae
• insect pests
• pasture pests
• pasture
• ryegrasses
• Lolium perenne
• ‘Grasslands Nui’
• Trifolium repens
• nitrogen
• insecticides
• susceptibility
• low endophyte