Cover spraying

Cover spraying is the application of an agricultural chemical across an entire crop. While these can be applied in a variety of ways, commonly it is through some form of machinery that blows fine droplets throughout a tree’s canopy, or through an overhead boom spray for low crops. There is a wide range of chemicals that can be applied in this way.

Historically, systemic insecticides such as dimethoate and fenthion (trade names Rogor and Lebaycid) were used in this way and were able to kill fruit flies present in the orchard and also had a residual effect that would kill any eggs or larvae either in fruit, or laid into fruit after the treatment. However, many previously permitted uses of these sprays have since been withdrawn.

There is a range of other chemical products that can be applied via cover spray, such as clothianidin, trichlorfon, and chlorpyrifos, with other chemcials being trialled by researchers and state departments of agriculture. For the latest information on chemicals that are registered for fruit fly control you should consult the Public Chemical Registration Information System (PubCRIS) or your local chemical supply company or garden store.

Benefits

  • Cover sprays can provide quick control and responsive control of adult fruit flies in the orchard and in some cases eggs or larvae
  • Fruit fly cover sprays can be applied with equipment that is already available
  • It may be possible to quickly evaluate the effect of the cover spray against target pests
  • There will be a high level of confidence in the effect of the cover spray.

Drawbacks

  • Cover sprays usually have an indiscriminate effect and may kill beneficial insects and disrupt Integrated Pest Management (IPM) programs
  • Not all cover sprays have a residual effect – they do not necessarily have a lasting effect against fruit flies that enter your orchard after the chemical has been sprayed, or the effect may only last a number of days
  • They may have a substantial withholding period, meaning fruit cannot be sold or consumed for a certain period of time after the spray has been applied
  • Cover sprays may have a damaging (phytotoxic) effect on certain fruits or foliage
  • Some chemicals may also be toxic to fish, birds or other wildlife

Are cover sprays right for your situation?

Cover spraying may be right for you if you live in an area prone to fruit fly attack and you are able to diligently apply the sprays. However, there are mixed reports about the effectiveness of some cover sprays so applying local knowledge and obtaining advice is vital.

Factors affecting success

  • Effectiveness of the cover spray product you use
  • Usage in combination with other control methods such as sanitation and baiting
  • Timing of the spray application (best before fruit fly have attacked)
  • Adequacy of spray coverage on to plant parts

Further information

Video: Control of Mediterranean fruit fly in WA backyards
Department of Agriculture and Food WA

Mediterranean fruit fly
Department of Agriculture and Food WA

 

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