Effect of Bemisia tabaci SSA1 host density and cassava genotype on host feeding capacity and parasitism by two Hymenoptera parasitoid species

ABSTRACT

Encarsia sophia Girault and Dodd and Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) are important biological control agents of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) because of their outstanding parasitic and destructive host-feeding ability. This study evaluated their parasitism and host-feeding capacity at five B. tabaci SSA1 host densities (10, 40, 60, 100 and 140) on three cassava genotypes (Alado alado, NAROCASS 1 and NASE 14) in the screenhouse. The results revealed that host density and parasitoid species had significant effects (P < 0.001) on host feeding and parasitism of B. tabaci SSA1, while cassava genotype had no effect (P > 0.05). Both E. mundus and E. sophia females killed more hosts by parasitism and host feeding with increased host density; E. mundus parasitised 1.5 and 40.2 nymphs at host density of 10 and 140 nymphs, respectively. At all host densities, E. sophia killed more hosts by feeding while E. mundus parasitised more hosts. However, E. mundus caused more total nymph death than E. sophia at all host densities. At a host density of 100 nymphs, E. mundus killed 38.9 nymphs compared to the 22.4 nymphs killed by E. sophia. In conclusion, the two parasitoids had a density-dependent relationship with the host, irrespective of species which bodes well for biological control programs. Thus, the deployment of these hymenopteran parasitoids in areas with high B. tabaci SSA1 populations through augmentative release would offer commendable pest population suppression. The interaction of cassava genotype with parasitoid species improved biocontrol efficiency, hence as long as a glabrous cassava genotype is planted, efficacy is enhanced.

KEYWORDS:

• Whitefly
• prey density
• Encarsia sophia
• Eretmocerus mundus
• biological control

Acknowledgments

We acknowledge the technical and logistical support from the Root Crops Research Programme at the National Crops Resources Research Institute and Makerere University. Special thanks to Emma Kayiwa for the technical support. KK, SM, CAO, JK and MHO conceived and designed the research. KK, JK and MHO conducted experiments. KK, SM, JK and MHO analysed data. KK, SM, JK and MHO wrote the manuscript. SM, CAO, JC, JK and MHO offered supervision. SM, CAO, JC project administration and funding acquisition. All authors read and approved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data presented in this study are available on request from the corresponding author.

Additional information

Funding

This work was supported by the African Cassava Whitefly Project funded by Bill and Melinda Gates Foundation. Funding granted through Natural Resources Institute, University of Greenwich [Grant Agreement OPP1058938].