African Armyworms in Liberia, Destroy Crops

BBC reports that a type of caterpillar known as “African Armyworm” is destroying crops and vegetation in Liberia, increasing the threats of food crisis. It is known that fully adult, repaid spreading armyworms can destroy a crop field in a matter of days.

The menace known as the “African armyworm” is in fact a caterpillar.

During the rainy season, the insects emerge in sudden swarms and rapidly devour crops such as maize, sorghum, millet, rice and sugar cane.

The pest gets its moniker from its habit of “marching” in large numbers into crop fields.

Like locusts, armyworms appear in huge numbers, ravage farms, and then move on once fields are barren.

They also cause disease, as their faeces enters rivers and streams can contaminate drinking water supplies.

Where did they come from?

The armyworms are the larvae of nocturnal moths, of the species Spodoptera exempta.
Map

During the rainy seasons, the moths spread and begin laying eggs in grasses and food crops. Each female lays between 500 and 1,000 eggs in her 10-day lifetime.

The moths are capable of long-distance migration – more than 100km (60 miles) per night – allowing the swarms to spread rapidly.

Once hatched, the larvae migrate through grasslands in snake-like colonies. On reaching crop fields, they begin feasting.

At full size (5cm – 2in) the caterpillars can lay waste to whole farms within days. They then simply move on to the next available target.

How serious is the outbreak in Liberia?

The last time swarms attacked on this scale in Liberia was in the late 1970s.

The losses could cause serious food shortages. Liberia is already heavily dependent on imported rice to feed its 3.5 million citizens.

The government says it cannot cope with the scale of the outbreak and has called in the UN Food and Agriculture Organisation (FAO) to help.

To make matters worse, the worms are now spreading to neighbouring Guinea and towards Sierra Leone.

In recent years there have also been major outbreaks in Tanzania and Kenya.

Can anything be done to halt their march?

At present, the best weapon against the pest is to spray crops with chemical insecticides.
Armyworm (Liberia’s agriculture minister website)
The bugs are among the world’s most destructive agricultural pests

These are too expensive for most farmers, so the government is stepping in and calling for international assistance, to begin aerial crop spraying.

Forecasting systems do exist in some African countries, to warn farmers about possible outbreaks in time to spray crops, where they can afford to.

But these warnings do not always work because attacks often affect isolated communities that are difficult to contact.

A more radical approach to prevention – a virus known as NPV – is being investigated by researchers from the UK, Canada and Tanzania.

The naturally occurring virus is specifically lethal to army worms, but it appears too late in most years to prevent them causing serious crop damage.

Scientists hope to study and harness the virus, to create an effective pest control technique.

Their goal is to create a pesticide which will be harmless to humans and other wildlife, but will destroy army worms and thus keep Africa’s staple food crops intact.

Infopediass