Obert Chifamba, Agri — Every season, farmers in regions prone to African and Fall Armyworm attacks have grown accustomed to the pests' relentless presence in their fields with the once sporadic outbreaks becoming alarmingly regular -- almost anticipated occurrences on the agriculture calendar.
This has become a cycle that recurs year after year to the extent that farmers have to be on the edge every season, as they brace themselves for the inevitable damage these voracious insects can cause.
Essentially, they now constitute a clear and present danger to crops every season.
They also destroy pastures, so their presence even off the field is always unwelcome to the farmer.
It is, however, the catastrophic nature of the pest's attacks on crops that has become the major rallying point for stakeholders concerned with food security matters both on the household and national levels.
Government is going all out to make sure the pest is eradicated with teams currently on the ground in those areas that have recorded outbreaks and need urgent action to save crops from this armyworm holocaust.
The African armyworm (Spodoptera exempta) in particular, can leave a field in utter ruins, if not controlled in time.
It feeds on leaves causing 'windowing' or skeletisation, leaving only the structural veins or framework of the plant, giving it a skeletal appearance, which affects the plant's ability to photosynthesise thereby impacting its growth and overall health.
Skeletisation is, therefore, a common symptom of infestation by the pest and is a visual indicator of its presence and feeding activity in the field.
Armyworms feed on leaf tips and along leaf margins. When they eat whole leaves, they can remove them completely or leave only the midribs. Armyworm damage can be mistaken for cutworm feeding. The characteristic form of armyworm damage is leaf removal.
The African armyworm's counterpart, the Fall armyworm (Spodoptera frugiperda) is a moth native to the Americas that can cause significant damage to various crops, particularly maize, by feeding on leaves and stems in its caterpillar stage. It is considered a major global pest due to its ability to rapidly reproduce, migrate long distances, and feed on a wide variety of plants, including sorghum, rice, cotton, and sugarcane, leading to substantial crop losses if not properly managed.
The name "armyworm" comes from the behaviour of large groups of caterpillars moving across fields to find food.
The pest's larvae (caterpillars) feed on a wide range of plants, primarily maize, but also includes other crops like sorghum, millet, sugarcane, cotton, and various vegetables.
However, to be able to effectively control both brands of the pest in the event of an outbreak, farmers must be able to distinguish the differences between them. This will enable them to take targeted action based on the distinctions between the fall armyworm and other armyworm species. It is important for the farmers to accurately identify the fall and African armyworm pests if they are to administer the correct control measures, lest they use wrong chemicals, which only delays corrective action or even promotes pesticide resistance.
The African armyworm is a moth larva that is a major pest to crops and pastures in Africa. It is black with white stripes and a white V on their head. The adult is highly migratory. In Zimbabwe the pest is usually a problem from December to April. Its life cycle includes the egg, caterpillar, pupa and moth stages with a single female moth capable of laying between 400 and 1 300 eggs.
The larvae can grow and reproduce quickly, with pupation occurring within 10 days of hatching. An African armyworm outbreak is known to cause significant economic damage to crops and pastures with the pest credited with destroying entire crops in a matter of weeks. The pest is widely distributed across sub-Saharan Africa, especially in Central, Eastern, and Southern Africa. It has also been reported in Arabia, Southeast Asia, and Australia
Other distinguishing features of the pest include the fact that adult moths have a wingspan of 32-40mm with greyish-brown forewings and white hindwings, while the larvae have a distinctive white inverted "Y" marking on their face and four raised spots arranged in a square on their last abdominal segment. Adult moths are known to fly long distances, allowing them to rapidly spread to new areas. This makes it crucial for farmers to quickly act once they spot and identify them lest they spread to other areas within a short space of time making it difficult to control them thereafter.
In the event that farmers cannot correctly identify them, it is crucial to enlist the services of extension officers for advice and assistance. If they are resource-constrained, they should quickly indicate so that teams from Government can move in and arrest the situation before it spirals out of control.
Fall armyworm infestations on the one hand can cause significant yield losses in affected crops, particularly in developing countries where farmers may lack effective control methods. The pest's adult male moth has forewings of a shaded grey and brown colour with triangular white spots at the tip. It is an insect native to tropical and subtropical regions of the Americas reputed for its ability to feed on more than 350 plant species, including economically important crops such as maize, rice, sorghum, sugarcane, cotton, soya beans, potatoes, tobacco, onions, tomatoes and pepper to name some of them.
Fall armyworm is a highly invasive and destructive caterpillar, which if left unchecked, can increase in numbers increase rapidly due to the abundance of suitable host plants, its fast reproductive cycle and ability to disperse long distances. It is identifiable through its white "Y" on their forehead and four raised bumps in a square near the end of their abdomen. It is light green to dark brown with thin white lines on the back.
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The pest has small black spots on the body, which are shaped like a trapezium on each body segment and feeds on young leaves, whorl, tassels, silk and cobs. It causes defoliation and sometimes leaves just the main stem behind. It completes pupation and has a faster life cycle in warmer climates. It is sensitive to cold and is most active during late summer and early autumn.
Its dispersal is facilitated by wind, as it can be blown from field to field effortlessly.
In general, armyworms, especially the fall genre, can cause significant damage to crops, with reports of yield losses ranging from 11 to 58 percent in maize across Sub-Saharan Africa, potentially impacting millions of smallholder farmers and leading to substantial economic losses, particularly in staple crops like maize. This is so because they feed on leaves, stems, and reproductive parts of the plant. Severe infestations can leave crops completely destroyed resulting in food insecurity and income loss for farmers.
