Fall Armyworm, Spodoptera frugiperda Infestations in East Africa: Assessment of Damage and Parasitism

Abstract

The fall armyworm (FAW), Spodoptera frugiperda, threatens maize production in Africa. A survey was conducted to determine the distribution of FAW and its natural enemies and damage severity in Ethiopia, Kenya and Tanzania in 2017 and 2018. A total of 287 smallholder maize farms (holding smaller than 2 hectares of land) were randomly selected and surveyed. FAW is widely distributed in the three countries and the percent of infested maize fields ranged from 33% to 100% in Ethiopia, 93% to 100% in Tanzania and 100% in Kenya in 2017, whereas they ranged from 80% to 100% and 82.2% to 100% in Ethiopia and Kenya, respectively, in 2018. The percent of FAW infestation of plants in the surveyed fields ranged from 5% to 100%. In 2017, the leaf damage score of the average of the fields ranged from 1.8 to 7 (9 = highest level of damage), while 2018, it ranged from 1.9 to 6.8. In 2017, five different species of parasitoids were recovered from FAW eggs and larvae. Cotesia icipe (Hymenoptera: Braconidae) was the main parasitoid recorded in Ethiopia, with a percent parasitism rate of 37.6%. Chelonus curvimaculatus Cameron (Hymenoptera: Braconidae) was the only egg-larval parasitoid recorded in Kenya and had a 4.8% parasitism rate. In 2018, six species of egg and larval parasitoids were recovered with C. icipe being the dominant larval parasitoid, with percentage parasitism ranging from 16% to 42% in the three surveyed countries. In Kenya, Telenomus remus (Hymenoptera: Scelionidae) was the dominant egg parasitoid, causing up to 69.3% egg parasitism as compared to only 4% by C. curvimaculatus. Although FAW has rapidly spread throughout these three countries, we were encouraged to see a reasonable level of biological control in place. Augmentative biological control can be implemented to suppress FAW in East Africa.

Parasitoid Complex of Fall Armyworm, Spodoptera frugiperda, in Ghana and Benin

“…Ten parasitoid species attacking the eggs and larvae of S. frugiperda were found in Ghana and Benin. In similar surveys carried out in Ethiopia, Kenya and Tanzania, seven parasitoid species were collected [18,19]. The two main parasitoids of S. frugiperda in Ghana and Benin are two braconids, the larval parasitoid C. luteum and the egg-larval parasitoid Ch.…”

“…and Chelonus sp., respectively. Coccygidium luteum was also found to attack fall armyworms in Ethiopia, Kenya and Tanzania [18,19]. In contrast, two different Chelonus species were found in West and East Africa.…”

“…In contrast, two different Chelonus species were found in West and East Africa. Chelonus curvimaculatus Cameron was obtained in Kenya [18,19] whereas Ch. bifoveolatus, a comparatively larger species, is prevalent in Ghana and Benin.…”

“…The microgasterid Cotesia icipe was recorded in very low numbers in Ghana and Benin. By contrast, in Ethiopia, Kenya and Tanzania, it has become the most abundant larval parasitoid of S. frugiperda [18,19] following its recent description from specimens obtained from S. exigua and Spodoptera littoralis (Boisduval) [33]. Since these two latter moth species are widely spread throughout sub-Saharan Africa (SSA), the reason for the sporadic occurrence of C. icipe on S. frugiperda in West Africa calls for further research.…”

“…However, there is presently limited available information on the natural enemies of S. frugiperda in Africa. Some authors studied the parasitoid complex of the pest in Ethiopia, Kenya, Tanzania [18,19] and Senegal [20]. In addition, the platygasterid egg parasitoid Telenomus remus Dixon was recorded in Côte d'Ivoire, Benin and Niger [21] and the biology of the braconid larval parasitoid (Coccygidium luteum Brullé) has recently been studied in Ghana [22].…”