An outbreak of Desert Locusts (Schistocerca gregaria) swept through northern and eastern regions of Guinea-Bissau last week. The swarms of insects then moved into the southern areas of the country where they now threaten to decimate cashew crops that support the livelihoods of over sixty percent of the nation's farmers.

Experts fear this outbreak might foreshadow the coming of a full-blown locust plague. Previous locust plagues have occurred at unpredictable intervals. The most recent locust plague lasted from 1986-1989. Other plagues during the past century occurred in 1926-1934, 1940-1948, 1949-1963, and 1967-1969 (Source: Handwerk).

Concerns of a possible plague started in February 2004, when scientists observed unusually high locust breeding rates in Morocco and Algeria. Several months later, in the summer of 2004, swarms of locusts invaded Maritania, Mali, and Senegal. The UN Food and Agricultural Organisation (FAO) described the locust outbreaks in those countries as the worst seen in 15 years (Black).

This latest outbreak in Guinea-Bissau raises concerns. Locust plagues result in widespread food shortages for human populations. The Mauritanian government has predicted that hundreds of thousands of people in the region may suffer food shortages due to this year's outbreaks alone (Handwerk).

Farmers and governments often resort to harmful pesticides such as organophosphates to combat the outbreaks. But when locust numbers explode and cover millions of square miles, even this chemical treatment becomes ineffective in protecting crops.

Insects respond quickly to the application of insecticides, either developing resistance, spreading into untreated areas, or both. And insecticides carry heavy health and environmental price tags.

Find out more:

• UN Issues Locust Plague Warning (BBC News)
• Africa Fights Locust Plagues (National Geographic)

Photo © Global Photographers / iStockphoto.