Weed Control

Weeds pose a serious problem in the South African sugar industry and, in extreme cases, can lead to complete crop failure. Weeds are normally grouped into the three categories, namely, Broadleaf Weeds, Grasses and Sedges. The effect that these weeds have on cane yield will depend on the rate of growth of the crop and the type of weed. Weeds are less of a problem in a fast growing crop.

SASRI advocates an integrated pest management (IPM) approach to weed control, i.e. a sustainable approach which combines biological, cultural, physical and chemical tools in a way that minimises economic, health and environmental risks.

Whole-Farm Weed Management Plan

There is an economic benefit to preventing weeds in a field from developing into a ‘crisis management’ situation. If fields are allowed to be overrun with tall weeds, they will reduce crop yield and become expensive to control. This often calls for expensive herbicides which may also be harmful to cane.

It is therefore best to develop a Whole-Farm Weed Management Plan, using the following steps:

Step One

These details should be plotted on map of the farm. GIS software would be useful for this exercise.

Compile a list of field, crop and weed attributes:

  • Field details: soil type, field topography
  • Crop details: variety, age, height, harvest date, yields (actual and potential)
  • Weed details: grass type, percentage coverage

Step Two
Compile a list of resources available:

  • Equipment
  • Labour

Step Three
Assign control methods to each field based on:

  • Field, crop and weed attributes
  • Resources available

Step Four
Conduct a cost/ benefit evaluation for each control method:

  • Cost: chemical, labour, water, tractor, equipment, treatment damage to crop
  • Benefit: from increased yield

Step Five
Prioritise fields for treatment, taking into account:

  • Field, crop and weed attributes
  • Cost/ benefit ratios (focus on fields where the expected return on investmentis highest)
  • High priority fields typically have low-density infestations, or are due forreplant
  • Medium priority fields have relatively low grass cover or have high potential yields but with dense grass cover
  • Low priority fields have dense infestation on marginal soils or are fallow fields

Step Six
Plan follow-up control methods:

  • Based on expected amount of surviving regenerated vegetative material
  • Annual maintenance control involves treatment of low levels of infestation (high priority) and appropriate treatment of other weeds

Contact Person

Dr Peta Campbell
Weed Scientist
Tel: 031 508 7400 (Switchboard)
Tel: 031 508 7438 (Direct)
Email: peta.campbell@sugar.org.za

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