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Reducing crop loss by keeping out alien pests and boosting plant health knowledge is crucial to food security, says CABI's Dennis Rangi.

Global food security is now in sharp focus because of rising food prices and a growing world population. It is estimated that there will be a 50 per cent rise in demand for food by 2030 — how this will be met has become a key question for countries in both the developed and developing worlds.

There are about 525 million farms worldwide — most less than two hectares in size — that provide a livelihood to about 40 per cent of the global population.Improving the productivity of small farms, in particular, is critical to ensuring food security.

But this does not just mean helping farmers to increase yields. Equally important is supporting farmers to lose less of what they grow.

This is particularly true in Africa, wherepoor plant health is a major factor in low productivity. In many countries, nearly half of crops are lost to pests and diseases — the maize weevil is a common nativepest in most African countries that can wipe out up to 40 per cent of stored crop.

These losses waste energy, water, inputs and labour. In Uganda alone, the International Institute of Tropical Agriculture estimates that the cost of crop diseases is a staggering US$200 million.

Keeping out alien species

One quick win for Africa is to use current technology to improve quarantine to keep out invasive alien species.

Increased travel and trade increases the risk that imports will contain unwelcome stowaways that can devastate local natural resources. In Africa, the larger grain borer, an insect imported from Central Americain grain donations in the late 1970s and early 1980s, is steadily eating its way through the continent's maize stores and is now more destructive than the maize weevil.

The pest costs Tanzania US$91 million each year in lost maize. It can also destroy up to 70 per cent of dried cassava stores, and is costing West Africa up to US$800 million annually.

Besides the physical losses, significant resources are used to contain the larger grain borer. In 2006, the cost of chemicals to control it in East Africa was estimated to be US$18.7 per hectare, which is prohibitive for most small farmers.

There are other examples of devastating invasive pests and diseases. Wheat rust, for example, has cut yields by as much as 80 per cent in Kenya and Uganda.

African countries must improve quarantine — by enforcement and systematic evaluation of scientific, technical and economic data to make informed decisions.

Countries also need to improve storage. One study by my organisation, CABI, found that pests that attack stored crops cost Kenya, Malawi and Tanzania US$150–300 million every year. Some of these losses could be prevented through simple solutions such as growing less susceptible varieties or implementing drying methods.

The local knowledge challenge

Reducing agricultural losses in Africa is not just about deploying technologies — farmers also need more knowledge about managing plant health. This includes helping them to rapidly identify, diagnose and manage pests and diseases in their crops.

But finding relevant and affordable solutions will be a massive challenge given the increasing risk of unintentional introductions of pests, and changing weather patterns that can rapidly encourage new pests and diseases to emerge.

One result of decades of declining support for agriculture is that weak extension services often fail to deliver what the farmer needs. We need mechanisms that can identify and address problems when and where they arise, making the most of local capacity.

The Global Plant Clinic (GPC) — a CABI initiative — is one example of a knowledge-based approach that can improve plant health and food security.

It is a network of mobile plant health clinics at which local agronomists and extension agents help diagnose plant health problems and detect emerging pests on the spot, and recommend safe, suitable and affordable management methods to farmers (see A new vision of plant health services for world's poor).

Over the past decade, the GPC has built up a network of more than 80 independent clinics — and trained more than 500 plant doctors — across Africa, Asia and Latin America. In Butembo, Democratic Republic of Congo, hundreds of farmers attend the clinics each week.

The GPC, by increasing farmers' knowledge, is helping them treat their crops more effectively, and is improving food security by boosting productivity and increasing incomes.

Helping farmers lose less from pests and diseases — be it through rigorous quarantine, improved storage or better plant health management — is as vital to improving food security as measures such as crop breeding and developing new seeds that help farmers grow more.

Dennis Rangi is executive director for international development at CABI, the agriculture and environment organisation.

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