Further increases in the effectiveness of RNAi strategies
might be achieved by utilizing multiple targets. The feasibility
of pyramiding multiple targets by RNAi has been
demonstrated in Drosophila [51] but has yet to be applied
to crop-protection strategies. The development of an understanding
of the specificity of RNAi gene knockdown in
insects should allow crops to be produced that express a
cocktail of dsRNAs that are highly effective against target
insect pest species. The sequence specificity of dsRNAs can
bemaximised by a careful bioinformatic approach, although
multiple gene knockdown events might be achieved with a
single dsRNA by targeting genes belonging to large families
with high sequence similarity. However, care must be taken
to avoid the possibility that loss of function is compensated
for by another untargeted gene.