Exploring best tactics to combat fall armyworm

To combat the voracious pest and prevent the huge losses, policymakers, extension agencies and growers could learn from the experiences of farmers in the Americas and adapt the same to suit the smallholder African production system.

CEREAL farmers across Sub-Saharan Africa are experiencing heavy losses due to the devastation by an invasive pest: the fall armyworm - Spodoptera frugiperda. In Africa, it has caused huge losses to staple cereals, especially maize and sorghum, affecting food security and trade. Damage to maize alone is estimated to be between US$ 2,5- US6,2 billion per year.

The fall armyworm’s lifespan, from egg to larva to moth, lasts between one to three months.

It’s during the larva stage that it does the most crop damage. Controlling them is a challenge because they reproduce fast and in large numbers, can migrate great distances, hide within growing leaves and have been reported to resist several pesticides.

Emergency responses by the affected countries have been based on the use of pesticides, but in most cases this has proven costly and not very effective. Various tactics - both old and new - are being tested to try and control the fall armyworm in Africa.

These include the use of inter-cropping technology, natural enemies, early warning systems and use of biopesticides.

To combat the voracious pest and prevent the huge losses, policymakers, extension agencies and growers could learn from the experiences of farmers in the Americas and adapt the same to suit the smallholder African production system.

This knowledge must be shared with farmers and agricultural officers. And any policy developed must involve local and international stakeholders before being rolled out.

The pest, an alien from the Americas, was first reported in Africa in 2016.

Starting in the São Tomé and Príncipe islands and Nigeria, in just two years it spread to over 38 African countries.

The speed with which they spread could be due to a few factors. Firstly, female armyworms produce a huge number of eggs (between 50-200 eggs per batch) and can have up to 10 batches within her lifespan. Secondly, the moths are carried by the wind across vast distances. Some have been known to travel up to 1 000km.

Thirdly, numbers aren’t being reduced by their natural enemies, which means they can multiply uninhibited. All these factors are crucial to keep in mind when managing an outbreak.

Pesticides: In Sub-Saharan Africa, most food is produced by smallholder farmers. When they try to control an outbreak, they will often use pesticides as these are believed to instantly suppress the pest. The use of chemical pesticides seems to be most common practice that is currently heavily supported by government.

But pesticides can be harmful, particularly to the environment as they affect non-targeted organisms, like bees.

Though often overlooked, there are other more natural approaches which have proven effective.

Push-pull and other intercropping technology: In this approach, crops are grown alongside one another. Some act as a deterrent to insect pests and weeds. The system has reduced pest infestation drastically. This technology has the additional benefit of providing high quality fodder for livestock and improving yields and soil fertility.

For example, when a “trap” crop (such as napier grass) is planted around maize rows, it attracts stemborer moths to lay eggs on it. But, because the grass isn’t nutritious, very few stem borer larvae will survive.

In the case of fall armyworm, this has proven effective when maize is inter-cropped with drought-tolerant greenleaf desmodium and planting Brachiaria as a border crop around this inter crop. When compared to mono crop areas, data collected from over 250 farmers, who adopted this technology in drier areas of Kenya, Uganda and Tanzania showed a reduction of 82,7 percent in the average number of larvae per plant and 86,7 percent in plant damage per plot.

Inter cropping maize with edible legumes can also result in up to 40 percent reduction in armyworm incidence and damage.

On the basis of these multiple benefits, the International Centre of Insect Physiology and Ecology and partners are rolling out the approach in sub-Saharan Africa.

Early warning ,surveillance and monitoring systems: Surveillance and monitoring are crucial to managing an outbreak. They ensure that identification happens very early, before a full outbreak and allows for proper response management.

Pheromone traps, which use the smell of a female armyworm to attract a male, can be a very useful surveillance tool. - The Conversation. ◆ Read full article on www . herald.co. zw