South Perth, Western Australia
July 8, 2003

Managing broadleaf weeds in pulse crops is difficult, but field pea growers have some good options according to Western Australia Department of Agriculture pulse agronomist Mark Seymour.

Mr Seymour said while grass weed control was relatively easy in grain legume crops, care was needed to safely control broadleaf weeds with post-emergent herbicides.

“Fortunately there are a number of products registered for use in field peas. Combined with peas' good early vigour and competitive ability, it is possible to clean up paddocks,” Mr Seymour said. “In addition, crop topping close to harvest can reduce the seed set of many weeds.”

Mr Seymour said the Department offered some basic guidelines to prevent crop damage and poor weed control. He said post-emergent herbicides should only be applied to a healthy pulse crop and not to stressed plants, either waterlogged or affected by drought.

“Pulse growers should also avoid spraying too soon after any physical damage such as sand blasting, rolling or frost,” Mr Seymour said. “Most post emergent herbicides should be applied from the three node stage onwards.  Spraying too early compromises crop safety and spraying past the five to six node stage usually compromises weed control, as the weeds have grown too big. 

“And lastly, growers need to take care adding oil to any herbicide applied to grain legumes.  Similarly tank mixes of grass herbicides that require the addition of oil should be avoided.”

Mr Seymour said the post-emergent herbicide options for broadleaf weed control included Brodal® and metribuzin mixes to manage radish, turnip and mustard.  Increasing the rates particularly of metribuzin assists in managing doublegee but crop safety may become compromised.

Raptor®, with the addition of BS1000, can be used from emergence up to four-node stage.  Raptor® provided good control of wild radish and was registered to control wild turnip, mustard, lupin, barley, brome grass and volunteer cereal.  It suppresses the growth of doublegee, wireweed and silver grass.

MCPA 250®, present as sodium salt, is a low cost method to clean up paddocks of late germinating radish, turnip and mustard.  It can be applied when peas are 10-15 cm high.  It does set back the crop, and should only be used where good growing conditions are expected following application.

Further information on recommended application rates is detailed in the June issue of ‘On The Pulse’ available on the Department's website at www.agric.wa.gov.au/agency/pubns/otp/index.htm