• Control measures

Lutte intégrée

An IPM approach to control the pest is of prime importance. Different control options exist for the pest namely: physical/ silvicultural, chemical, genetic and biological methods.

Lutte prophylactique

Thinning significantly reduces the density of trees and shady conditions which are favourable for development of the aphid.

Lutte chimique

Treatment with insecticides of low toxicity to humans and other insects can be effected. Nevertheless, chemical control is not practical on huge trees and involves handling and regular spraying of toxic substances. In addition, this may lead to problems associated with environmental contamination, health safety and the possibility of resistance development in the pest.

Lutte biologique

Since cypress aphid is an exotic pest, classical biological control is the most suitable option for controlling it. Natural enemy groups of this pest include Aphidiinine parasitoids (Hymenoptera:Braconidae:Aphidiinae); coccinellid beetles (Coleoptera: Coccinellidae); syrphid flies (Diptera: Syrphidae) and chrysopids (Neuroptera: Chrysopidae).

 

Pauesia juniperorum (Hymenoptera: Braconidae) was selected locally as a potential agent for the biological control programme. This parasitoid was introduced in Africa in the 1990’s from United Kingdom and France and released in several countries. It has a narrow host range restricted to Cinara spp. and will not attack other parasitoid species. In Mauritius, the biological control programme was initiated in 2000. The parasitoids were imported from the Kenya Forestry Research Institute (KEFRI) with the objective of rearing it and carrying host specificity tests before release. Release was done in sleeve cages and directly on aphid colonies on cypress trees. Several consignments of parasitoids have been imported since 2001 for release.

 

Biology of P. juniperorum

The larvae feed on the internal organ of the host and eventually only the cuticle remains. The parasitoid pupa remains inside the host cuticle which stretches, darkens and becomes hard and gets attached to the twigs. At this stage, the parasitized aphid is referred to as a mummy. The pupal period lasts for about six days. After full development, the adult parasitoid emerges through an incomplete circular hole at the posterior end of the mummy. The total development time from egg to adult is about 14 days at 22°C. Adults can live up to 7 days.

 

Establishment of parasitoids

The parasitoids are adapting to our local conditions. Mummies and adults from the first generation have been observed in regions of the upper lands awhere parasitoids were released after several months. So far, since 2003, about 1500 parasitoids were released. However, no mummies are observed during the summer months as the aphid population is low in most surveyed areas due to a rapid rise in temperature. It is expected that successful establishment of this parasiotoid will be attained after several releases. New consignments will be imported during the months of July this year.

Auxiliaire de lutte biologique

Pauesia juniperorum parasitoid

Commentaires

Resistant varieties of cypresses and junipers can be planted to replace dead and infested trees. Genetic resistance to C. cuppressivora in Cupressus lusitanica has been found and investigated in Kenya.

For more information:

Alleck M. and Seewooruthun S.I. (2002): Cinara cuppressivora, a pest of cypress: some aspects of its biology and the assessment of its damage. In: Revue Agricole et Sucrière de l' Ile Maurice. Vol. 81, Nos. 1,2 and 3. MSIRI. Réduit. Mauritius: pp. 17-28.

Alleck M., Seewooruthun S.I. and Ramlagun D. (2005): Cypress aphid status in Mauritius and trial releass of Pauesia juniperorum, a promising biocontrol agent. Paper presented at the 7th Meeting of Agricultural Scientists, Réduit, Mauritius, 4 - 6 May 2005. Food and Agricultural Research Council.