After two weeks of waiting and checking on tiny mice it would appear that my attempt to initiate a bio control program using harlequin ladybirds has been a failure. The aphids are still high in numbers and happily feeding. Also there is no sign of the ladybirds around the plant each time that I have checked.
On the plus side I have noticed an increased number of mummified aphids, containing a larval parasitoid with in, on Cuphea ‘tiny mice’ . I have come to the conclusion that I should spray the plant with SB plant invigorator spray soon. This is because, although the parasitoids are helping to reduce the aphid levels, the plant is still highly infested so I feel I should actively remove them. The spray should have no effect on any larval parasitoids within the the mummified aphids, therefore any future parasitoids that will help protect the greenhouse will be unaffected.
I have seen ants on the Cuphea. I suspect they have chased away the ladybirds. If you can get rid of the ants – which farm the aphids – then you might have luck with ladybirds.