The Fall armyworm, which has the scientific name of Spodoptera frugiperda, is a major pest of staple crops. The larvae prefer feeding on young maize plants, but also feed on a range of other crops, including millet, sorghum, rice, wheat, sugar cane, and vegetables. The pest originates from the tropical and sub-tropical regions of North and South America.
Feeding on maize can result in up to 100% crop loss if pest populations are high and no control measures are taken. Larger caterpillars can cause extensive destruction of seedlings and young plants by cutting the stem. Feeding on grain also makes the plant susceptible to fungal attack. Destruction of the silk results in reduced pollination and formation of grain.
Fall armyworm was first reported in Africa in 2016 and has caused significant damage to maize and other crops, and has great potential for further spread and damage. As of May 2017, it had been reported in 26 African countries.
Researchers have estimated that 13.5 million tonnes of maize could be lost to Fall armyworm in just 14 African countries, which is over 20% of total production. Losses in rice, sugar cane, and sorghum will also be serious. The overall cost of losses in maize, sorghum, rice, and sugar cane in Africa in 2017-2018 is predicted to be more than $13 billion US.
The Fall armyworm is actually a caterpillar rather than a worm, and the adult stage of the pest is a moth. The caterpillar attacks the growing point (the top) of the plant and burrows into the cobs.
There are a number of species of armyworms, including the African armyworm, but the “fall” variety causes the most widespread damage.
What are some key facts?
- Fall armyworm caterpillars don’t just attack maize; they can feed on a wide range of crop plants.
- The adult moths lay eggs at night on the lower leaves in tight clusters of 150-200 eggs.
- The caterpillars that cause the damage on plants are most active in the early morning and evening. This is therefore the best time to spray pesticides.
- The Fall armyworm has four life cycle stages: eggs, caterpillar (larvae), pupae, and moths.
- The adult moths are strong fliers and capable of dispersing long distances.
What are the big challenges of Fall armyworm?
- Because Fall Armyworm is a new pest, very little is currently known about its adaptation to conditions in Africa. More research is needed and more awareness as well. National activities and a regional FAO-led plan are being developed to support these activities.
- In the tropics, FAW has the potential to breed continuously throughout the year. This potentially means bigger populations of Fall armyworm and more damage.
- Fall armyworm caterpillars can be difficult to identify as they look similar to other caterpillars.
- The older caterpillars crawl deep into the whorl or burrow into the maize ears/cobs, making it difficult to reach them with insecticides or biopesticides.
- There are reports that FAW has developed resistance to some chemical pesticides in the countries where it originates.
Predicted impact of climate change on production
- Fall armyworm is a tropical species adapted to the warmer parts of South America. The optimum temperature for caterpillar development is reported to be 28°C. Therefore, in the tropics, there is a potential for continuous breeding, resulting in four to six generations per year. Whether this will occur in Africa has yet to be confirmed.
The above article was adapted from @Farm Radio International resource pack @CABI. All rights reserved