Sustainable farming - pests of pasture

grass grubIn a nutshell...

There is a wide range of pests in New Zealand that damage pasture.

  • The main ones are
    • Argentine stem weevil
    • Army worm
    • Australian soldier fly
    • Black beetle
    • Black field cricket
    • Bluegreen lucerne aphid
    • Clover flea
    • Clover weevil
    • Grass grub
    • Greasy cutworm
    • Lucerne flea
    • Porina
    • Sitona weevil
    • Slugs
    • Sod web worm
    • Tasmanian grass grub
    • Whitefringed weevil
  • Insect pests seem to come in cycles.  This is because there is a build up of diseases that kill them or reduce their population, and this takes time.
  • Insect pests that have arrived from overseas (eg clover weevil, bee varroa mite, painted apple moth) are a major hazard as they have no natural predators in New Zealand.
  • Chemicals inevitably have to be used to eliminate and control insect pests, and these are having an increasing negative effect on our clean green image.  This is despite evidence that the levels of chemical in export and home-consumed produce are well below approved limits.
  • A major attraction of organic farming is the use of non-chemical methods of pest control.

How can you tell if you have a problem?

  • Low pasture production caused by pasture pests that damage the roots and leaves of grasses and clover.
  • Damage is visible as dead, dying or yellowing patches of grass.
  • Damage may be in certain seasons because of the lifecycle of the pest.  It's mainly the larvae that do most damage by eating plant roots.
  • Also seen as clover with pale green, withering leaves, where the clover flea has rasped off the soft under-leaf tissue, or the clover weevil has eaten circular patches around the leaf edge.
  • Grass plants that have been pulled up by the grazing stock.  Here pasture pests such as grass grub larvae have eaten the roots.
  • Insect pests on weeds that could spread to pasture plants.

How can you tell if you're doing well?

  • Healthy grass and clover that grows well.
  • No seasonal damage to the pasture plants.
  • No patches of dead, dying or pale green pasture.
  • No damaged leaves on the grass or particularly the clover.

What can you do to improve things?

  • Investigate the problem thoroughly and get an accurate diagnosis of the pest.
  • Don't dive in immediately with chemicals until you have checked the correct chemical and the correct dose to be applied.
  • Chemicals are very expensive, so it pays to read all literature about them and instructions for use.
  • Look at possible non-chemical management cures and prevention.
  • Realise that pests occur in cycles and may disappear on their own.
  • Don't be panicked by sellers of product to control or eliminate the pest.  Ask to see evidence.
  • Consider biological control methods.
  • Consider "integrated pest control" where a range of methods are used together.

Where can you go for help?

  • Regional Councils
  • County Councils
  • Federated Farmers of NZ
  • Ministry of Agriculture and Forestry
  • Department of Conservation
  • Lucas, R. (1994).  What's that pest?  Identify and control New Zealand garden pests and disease.  The Open Polytech.  ISBN 0-473-02153-6.
  • Helson, G, A.(1974).  Insect pests.  NZ Ministry of Agriculture and Fisheries, Bulletin No.413.  Government Printer.
  • Scott, R.R (Editor) (1984). New Zealand pest and beneficial insects.  Lincoln University College of Agriculture.  ISBN 0-86476-000-0
     

 

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