Weeds can very quickly become established especially under warm and humid conditions. Although some farmers believe that they help to stabilise the soil surface they have several disadvantages when growing among a cultivated crop. They can compete with the crop plants for nutrients, water, oxygen in the soil and light. They may also be alternative hosts for some pests and diseases. This is of special importance for weeds which are related to the pepper crop. The same can be said for the occasional 'volunteer' plants which have survived in the soil from a previous crop. If the 'volunteer' plant is related to the pepper crop (for example tobacco or tomato) then it would be a likely source of virus infection.
On small scale crops weeds are usually removed either by hand or by some method of cultivation such as hoeing, this may often be the most efficient way to weed within the rows. Cultivators are also used, but whatever the method it is important to control the weeds before they flower and set seed. Care must also be taken not to disturb or damage roots of the pepper crop which are near the surface.
Chemical weed killers are sometimes used for weed control in large scale areas of pepper crops. Trade preparations of contact herbicides such as Paraquat and/or soil-acting herbicides such as Trifluralin may be used in the right circumstances. Care must be taken to ensure that the weed killer chosen is suitable for the crop and local conditions. The persistence of a weed killer must be taken into account especially if a cover crop is planned or the present crop is nearing the end of its economic life. In the case of contact weed killers it is important that the chemical being used does not drift onto other crops, gardens and reserves, or splash on the foliage or stems of the pepper plants otherwise they will also be damaged or killed. Residual weed killers are not suitable for ridge and furrow irrigation systems. It is strongly recommended that advice should be obtained from the extension service (see also the end section on 'Organic crops and environmental issues, page 49).