Armyworms are the caterpillar stage of moths. The name armyworm comes from their way of ravaging a crop; they match along the ground like a vast army of worms in search of more food. The appearance started being reported in Africa in early January; mostly in South Africa and earlier in West Africa. It might have reached Africa through imported plants. Another school of thought suggests its migration across the Atlantic on favourable winds over multiple generations; it is a strong migrant. Also read: Tuta absoluta menace series
Their affinity for most staple foods like maize, wheat, rice, sorghum, and millet, among other crops makes armyworms a great threat to food security. In addition to this, the armyworm eat pasture grasses hence negatively impacting livestock production.
At times the attacks have been reported as a combination of the native African armyworm and a new invasive species called Fall armyworm.
The armyworm is about 3cm in length. There can be around 1000 caterpillars per square metre. On maize the insect strip the leaves of mature maize plants bare. It also feeds on the reproductive parts of the crop. This damage may lead to at least 40% crop loss.
The situation needs to be arrested early, the best way being the use of pesticides; both chemical and biological. In Kenya there are two well known chemicals developed specifically to deal with the whole family of caterpillar. These are developed by DuPont De Nemours and sold in Kenya by Elgon Kenya ltd. The chemicals are Coragen 20SC with an active ingredient Rynaxpyr/Chlorantraniliprole and Avaunt 150 EC with active ingredient Indoxacarb.
The best way is to remain vigilant after establishing crop in the field. Regular scouting activities should be carried out in the field.