The world’s population has doubled since 1970 to 7.7 billion. The UN has projected that the figure will reach 9.8 billion in 2050 and 11.2 billion in 2100. Nepal’s population today is 29.94 million. The pressure lies on agriculture to meet the demands of the ever-increasing number of bellies. Yet, agriculture has been constantly facing the adversities of climate change leading to food insecurity. Considering this fact, the Ministry of Agriculture and Livestock Development has accorded the highest priority to respond to the negative consequences of climate change by formulating policies, programmes and activities.

Because of increasing temperatures, erratic rainfall and humidity stresses, pests and diseases which were never seen in the past have been affecting crops. We have also witnessed the problem of no or poor grain formation in maize and rice. Abnormalities like these are increasing, which will ultimately have an impact on human beings. Recent threats created by the fall armyworm, a devastating insect, in Nepal is a case of climate change and shifting agricultural patterns.

The pest in question

Armyworms are caterpillar pests of pastures and cereal crops. They mostly feed on leaves at night, but under certain circumstances, will feed on the seed stem, resulting in head loss. They overwinter as pupae or as mature larvae which pupate in the spring. Moths emerge in the spring, mate, and lay eggs in masses on the host plant. The larvae feed for about four weeks but do most of their damage during the last 10 days of this period. It is not a fastidious pest and enjoys eating all kinds of weed species to varieties of crops. It is native to tropical and subtropical regions of the Americas.

The fall armyworm was first detected in Central and Western Africa in early 2016 and quickly spread across virtually all of Sub-Saharan Africa. In July 2018, it was confirmed in India and Yemen. Because of trade and the moths’ strong flying ability, it has the potential to spread further. This pest travelled all the way from America to Africa and finally invaded Asia and has been recently attempting to enter Nepal. The Nepal Agriculture Research Council reported its occurrence in a maize field in Gaindakot, Nawalparasi only a month ago. This has to be officially confirmed by Plant Quarantine and Pesticide Management through the ministry. Its occurrence has also been reported in a maize field in eastern Chitwan. The fall armyworm has a large host plant range that spans nearly 100 plant species in 27 families. In the absence of natural control or effective management, it can cause significant damage to crops. Economic losses may be huge if timely control measures are not adopted.

A number of characteristics make them particularly hard to control. This includes the fact that the moths are strong flyers, breed at an astonishingly high rate and their larvae can feed on a wide range of host plants. Apart from being a strong flyer, adult females are highly fertile, laying in excess of 1,000 eggs during their lifetime. It has the ability to feed on many plant species, but the preferred hosts are grass-based plants such as maize, sorghum, millet, rice and sugarcane. The most damaging reports from its native range are for maize.

Another reason the fall armyworm is difficult to manage is its tendency to build up resistance to pesticides, because of which they are untouched by common chemicals. There have been efforts to curb its devastating effect by planting BT-maize in developed countries like the US and Brazil. The fall armyworm has been reported to cause annual losses of $600 million in Brazil alone. The caterpillars also feed on other important crops, such as cowpea, potato and soybean which may result in direct losses. At this stage, we know little about the potential impact on crops in Nepal, but there is widespread fear that it could be devastating and may lead to severe food insecurity. It can be assumed that huge economic losses may incur in case of sporadic occurrences in Nepal.

How it got here

There are many theories about how the fall armyworm arrived in Nepal. The name comes from the habit of mass movement of the caterpillars in autumn. One assumption is that it arrived on foodstuffs imported through the open and porous border. This is probable, as insects can easily cross borders with infested plant material. There are also some arguments that the fall armyworm arrived in Nepal riding on wind currents. This is because wind-borne adult insects can move over vast distances. Another guess is the indirect killing of natural enemies of the fall armyworm. This could have led to pest resurgence and resistance. Whichever way the fall armyworm arrived in Nepal, its spread has to be stopped by any means.

Late planted fields and later maturing varieties are more likely to become infested. Given the severe economic threat that the fall armyworm poses, governments and international bodies should initiate and put in place emergency plans that span control methods across borders. They include monitoring with pheromone traps to determine the spread of the fall armyworm, road shows to increase public awareness and emergency registration of appropriate pesticides. The eradication of this pest at this stage is unlikely. Control of the pest will be best achieved if managed on an international scale with India and other Asian countries in a coordinated effort. Proper use of biopesticides and botanicals along with the enhanced implementation of integrated pest management assisted with the application of Spinosad—a chemical insecticide naturally made by certain bacteria—may help its sustainable management. A National Working Group Team has been formed, and the Ministry of Agriculture and Livestock Development is on high alert.

- GC is a secretary at the Ministry of Agriculture and Livestock Development.