Crop Topping Pulse Crops
Often higher rates are used to control other broadleaf weeds that may be present. Note that glyphosate can affect germination percentages so it is best not to retain seed from paddocks that have been crop topped using glyphosate. Paraquat products on the other hand such as Gramoxone can be used successfully right up until the milky dough stage of the ryegrass. At 800ml/ha it is a slightly cheaper alternative to glyphosate at $2.80/ha, and provides more flexibility with timing. Gramoxone is registered for crop topping in beans, peas, lentils, lupins, chickpeas, and vetch, with a harvest withholding period of 7 days. Again the late maturity of lentils and chickpeas makes the use of Gramoxone impractical. The label provides rates of 400800ml of a 250g/L strength product such as Gramoxone for crop topping. Research has found that there is a rate response to paraquat when developing resistance, so using the higher rate of 800ml/ha is recommended. If you have grass weeds which have escaped selective grass herbicides, crop topping will provide another “arrow in the quiver” to avoid seed set and seedbank replenishment.
Grass weeds are maturing rather quickly with the continued dry conditions and warmer weather. This means that getting the timing right to crop top them and prevent seed from entering the seed bank is critical. Crop topping is an important part of managing group A herbicide resistant ryegrass, and pulse crops provide an ideal time to hit any escapees from selective grass herbicide applications with a non-selective crop top. For crop topping pulses you can use either glyphosate or paraquat based products, depending on the growth stage of the crop and target grasses Ideally glyphosate needs to be used slightly earlier than paraquat to target the ryegrass, and will have the best result prior to the ryegrass getting through flowering. However, the crop needs to be physiologically mature and in ‘dry down’ mode before...
Please join StudyMode to read the full document