Assessing the Potential of Inoculative Field Releases of Telenomus remus to Control Spodoptera frugiperda in Ghana

Abstract

In response to the threat caused by the fall armyworm to African maize farmers, we conducted a series of field release studies with the egg parasitoid Telenomus remus in Ghana. Three releases of ≈15,000 individuals each were conducted in maize plots of 0.5 ha each in the major and minor rainy seasons of 2020, and compared to no-release control plots as well as to farmer-managed plots with chemical pest control. No egg mass parasitism was observed directly before the first field release. Egg mass parasitism reached 33% in the T. remus release plot in the major rainy season, while 72–100% of egg masses were parasitized in the minor rainy season, during which pest densities were much lower. However, no significant difference in egg mass parasitism was found among the T. remus release plots, the no-release control plots and the farmer-managed plots. Similarly, no significant decrease in larval numbers or plant damage was found in the T. remus release fields compared to the no-release plots, while lower leaf and tassel damage was observed in farmer-managed plots. Larval parasitism due to other parasitoids reached 18–42% in the major rainy season but was significantly lower in the minor rainy season, with no significant differences among treatments. We did not observe significant differences in cob damage or yield among the three treatments. However, the lack of any significant differences between the release and no-release plots, which may be attributed to parasitoid dispersal during the five weeks of observation, would require further studies to confirm. Interestingly, a single application of Emamectin benzoate did not significantly affect the parasitism rates of T. remus and, thus, merits further investigation in the context of developing IPM strategies against FAW.

The use of Telenomus remus (Nixon, 1937) (Hymenoptera: Scelionidae) in the management of Spodoptera spp.: potential, challenges and major benefits

“…A major point of concern is to what extent releases at one site can also have an effect on larger areas during the season. Recent findings from Ghana (Agboyi et al 2021) are in line with studies from the Americas (Hernández et al 1989) indicating that dispersal of T. remus throughout the season is high, and that a small number of release points per ha (< 5) may be sufficient. These studies further suggest that releases for individual smallholder farmers owning little land may be inefficient, but on the other hand that regional approaches could work very well.…”

“…Africa, Asia and Australia (e.g. Kenis et al 2019;Agboyi et al 2021). We here thus review the available literature on T. remus, with a focus on the substantial practical experiences gained in Latin America on the management of FAW and other species of the genus Spodoptera, aiming to provide better guidance for improved and potentially global application of T. remus in integrated pest management programs against FAW.…”

“…Combined results for the two seasons, showed that 64% eggs were parasitized under these conditions while < 10% were observed in control fields. In field release studies in Ghana, three releases of 30,000 T. remus per ha were conducted in maize plots of 0.5 ha in the major and minor rainy season respectively (Agboyi et al 2021). Egg mass parasitism reached 33% in the T. remus release plot in the major rainy season while 72-100% of egg masses were parasitized in the minor rainy season during which pest densities were much lower.…”

Abundance, diversity and richness of natural enemies of the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), in Zambia

“…Regression analysis was used to test the influence of rainfall on the number of natural enemies across study areas. Relative abundance (RA) of the parasitoids and predators was determined by counting the number of individuals of a given parasitoid or predator species (Ni) divided by the total number of all individuals of all parasitoid or predator species (N) and converted to percent values ( 23 ). Parasitoid and predator diversity was determined by applying the Shannon–Weiner diversity index (H) ( 40 ).…”

“…Control strategies, such as push–pull ( 20 ), maize-legume intercropping ( 21 ), microbial control ( 22 ), and augmentative biological control strategies ( 23 ), are being developed and implemented for the management of FAW. These strategies enhance crop performance and ecosystem services, such as the regulation of pest populations by natural enemies ( 24 ).…”