Written by Donata Kizza and Aime E. Ndayisenga
In early 2017, army worms were reported to have invaded Rwanda destroying maize, sweetpotato, among other crops. This was the first time the country had experienced an army worm attack which caused damages on a large sweetpotato seed multiplication site at the Rwanda Agriculture Board in Karama.
According to the Ministry of Agriculture, the outbreak led to the destruction of 15,699 hectares of maize. However, with support from the national government, farmers received training on how to manage the army worms through spraying and hand picking.
Unfortunately, towards the end of December 2017 there was another army worm attack in Bugesera district. Among the affected field farms was a 3 hectare orange-fleshed sweetpotato rapid multiplication field that belongs to International Potato Centre (CIP).
On spotting the arms worms, Leonidas Nzaramba a field supervisor quickly acted on the issue and prevented further damage. “With the continuous spraying and hand-picking of the pests, the vines were not affected,” said Nzaramba.
“Farmers need to adopt the habit of checking on their crops more often, because early identification of the worms can prevent extensive damages,” Nzaramba added.
Army worms are a serious threat to sweetpotato as they have a short period of 3 to 4 days for the eggs to hatch into a larva. The eggs hatch into armyworm caterpillars that feed on the crop leaves and then turn into butterflies in 24-25 days cycle.
It is also known that one large larva can destroy a plant on its own while a large population of older larvae can destroy a field overnight.
If their lifecycle takes 22-29 days and the adult female moth lays to about 1000 eggs in the soil, army worms might remain a threat to crops like sweetpotato since there is a possibility of repeated attacks.
Nshimiyimana Jean Claude, an agronomist at International Potato Centre, said farmers should be well-equipped and knowledgeable about how to control the pest to minimise attacks and damage.
“Although pesticides, such as Rocket, are reliable, farmers must have more options, including biological control methods, where a farmer may use palm oil to attract ants which attack the army worms,” he added.
The agronomist further explained that farmers must also use clean planting materials as well as avoid planting on plots previously attacked by the army worm
“Isolating the sweetpotato fields far from the pest attack is equally important,” Nshimiyimana concluded.