Pre-emergent herbicides are a useful tool for combating weeds. They are generally applied before the spring break—before the new weeds germinate.
Pre-emergent herbicides are useful for newly worked ground or areas where weed pressure is high.
Selecting the appropriate pre-emergent herbicide to control the weed spectrum present in the orchard can reduce the need to apply multiple herbicide applications during the season.
Application
Pre-emergent herbicides need to be applied to bare ground with little or no organic matter.
Pre-emergent herbicides are only effective on germinating seeds within the soil profile, and can be applied with a knockdown herbicide if there are pre-existing weeds.
For hard to control weeds, tank mixing more than one pre-emergent herbicide can help increase the weed spectrum of control.
Incorporation
Rain or irrigation is needed to incorporate the herbicide into the soil.
This helps avoid the adverse impact of UV light breaking down the herbicide and thereby reducing its efficacy.
Incorporating the herbicide into the soil also ensures it comes into contact with any newly germinating seeds.
Products
Sinbar and Zoliar are the products of choice for providing good residual control of the common weeds in southern Victorian orchards.
There are a number of pre-emergent herbicides available (see Table 1) and they all have strengths and weaknesses with respect to the weed spectrum they control.
Remember to rotate herbicides and use products from different chemical groups to reduce the risk of resistance and selection for problem weeds in the orchard.
For more information on addressing your weed control requirements consult your technical expert.
See the table of products in Tree Fruit August 2013
