By Naomi Uzor
FOOD and Agricultural Organisation of the United Nation has estated that some $95 billion worth of food production at global level is lost annually to weed, compared with $85 billion for pathogens, $46 billion for insects and $2.4 billion for vertebrates (excluding humans).
This figure, according to FAO clearly show that weeds should be regarded as farmersâ€™ natural enemy No. 1.
At todayâ€™s prices, $95 billion translates into some 380 million tonnes of wheat, or more than half of world production expected in 2009. And of those $95 billion, $70 billion are estimated to be lost in poor countries.
Economic losses may be even greater considering that more than half of the time farmers spend in the fields is devoted to weed control, said weed expert Ricardo Labrada-Romero.Â It follows that if farms are to increase their productivity one of the first things they must do is improve weed management.
Nowhere is this more important than in Africa, where weeds are a major cause of stagnating yields and production.
â€œWith only manual labour available, African smallholders need to weed every day and that means a family physically canâ€™t handle more than 1-1.5 hectares,â€ Labrada-Romero explains. â€œBut proper management would allow them to farm more land and grow more food.â€
Modern integrated weed management involves much more than spraying herbicides. Crop rotation is one effective technique because weeds are often biologically adapted to a given food crop so that changing the crop can reduce weeds too.
Also important, says Labrada-Romero, is the use of certified, quality seeds. Many of the seeds produced and used by farmers are contaminated by weed seeds. If smallholders produce their own seeds, they should be taught to clean them so as to avoid planting weeds in their fields at sowing time.
Soil solarization, a simple non-chemical technique, can be used to control weed seeds and seedlings as well as many soil-borne pathogens and pests. Transparent polyethylene plastic placed on moist soil during the hot summer months increases soil temperatures to levels that are lethal to weeds.
And as for water weeds – a separate but very menacing threat in many parts of the world – biological control methods can be used.Â Introduction of specific insects native to the Amazon has, for instance, proved successful in keeping disastrous water hyacinths infestations in check.
The damage caused by one weed alone, BroomrapeÂ (OrobancheÂ spp), an aggressive root weed which attacks legumes and vegetables and can not only lead to complete crop failure but also make fields infertile for many years.