Applying the principles of integrated pest management to dock control
Are docks an issue in your grassland? Teagasc Advisor in Tralee, Eamonn Dempsey fills us in on why chemical control shouldn’t be your first port of call, but instead the principles of integrated pest management should be applied.
Perennial weeds are difficult to control, as the same plant continues to grow every year while still being able to flower and set seed. Docks, which have a deep and large root, are a good example of a perennial weed that competes with grass for light, nutrients and space.
As part of the Sustainable Use of Pesticides Directive, the principles of integrated pest management (IPM) should be applied when controlling weeds such as docks. In simple terms, this means to consider alternatives to pesticides e.g. liming, crop rotation, drainage and cultivation techniques.
How do we apply the principles of integrated pest management to a dock infestation?
Both the farmer and advisor should walk the field to discuss and evaluate the following information:
- The level of dock infestation and other weeds;
- Stocking rate;
- Fertiliser application and type;
- Soil sample analysis; Silage cutting;
- History of dock treatment and products used;
- Poaching and supplementary feeding;
- Slurry application;
- Grazing management;
- Drainage.
Once you have a clear picture of the condition and management of the field, you can discuss means of control which can be either IPM or chemical or a combination of both.
I will give you an example of information gathered from a field with dock infestation. The field is over eight years in permanent pasture with no clover, some poor unproductive grasses, no silage cut and a stocking rate of 130kg/N/ha. Soil sample analysis shows the field is high in phosphorus (P) and potassium (K), fertilised with CAN/Urea, slurry applied at a rate of 2,500 gallons/acre in spring and no lime spread in the last five years. Rotational grazing and supplementary feeding is also carried out on this good, dry field.
Controlling docks sustainably
One option would be to select a herbicide and blanket spray the docks at the correct stage of growth and time of year. However, to apply the principles of IPM, this is not the correct course of action. The best course of action is to use a combination of IPM and chemical control.
Considering the pasture is over eight years old, reseeding is recommended - spring as opposed to autumn, as grass seed establishment is supported with better weather. When reseeding spray, off the old sward with glyphosate, plough and take a soil sample on the ploughed field to identify the need for P, K and lime.
Post-sowing management is a critical part of IPM; if docks are not controlled at seeding stage; you will again have a heavy dock infestation in the field. Sward variety is also a very important part of IPM, so ensure the variety chosen can compete with docks in pasture establishment.
For chemical control, use herbicides to target weeds such as docks ideally before weeds reach 10cm in height, or 5- 6 weeks after reseeding. Additionally, apply good management practices such as: recommended fertiliser rates to match stocking rate; rotational grazing; rotate silage fields for cutting; and top fields when necessary. Manage the reseeded field in accordance with the principles of integrated pest management to avoid future use of pesticides to control docks and other weeds.