The caterpillars of both have similar characteristics and habit feeding on leaves and growing points. Control with insecticides has proved difficult because the caterpillars hide inside rolled up leaves and are protected from spray deposits.
With no biological control organisms recommended, HDC commissioned project HNS 170 in 2008. It showed that the egg parasitoid wasp Trichogramma brassicae could successfully parasitise egg masses of carnation tortrix moth in cage tests.
The next aim in a new project, HNS 177, was to evaluate Trichogramma parasitoids on a commercial scale by introducing them at weekly intervals to a polythene tunnel with a natural infestation of moths. The inexpensive commercial product is supplied as black parasitised eggs stuck on card.
Trichogramma parasitoids were introduced at the rate of 20/sq m onto a liner crop of Chaenomoles naturally infested with light brown moth and where carnation tortrix had been present in previous years.
Successfully parasitised egg masses turned black and were easy to recognise. Although slow to start, after four introductions 90 per cent of the egg masses were parasitised and Trichogramma parasitoids gave good control of light brown moth. Two supplementary sprays of integrated pest management-compatible insecticide Dipel DF were needed to gain complete control.
- For details on all HDC activities, visit www.hdc.org.uk.