A Retrospective Study of Cinara cupressivora Damage on Cupressus lusitanica Clonal Seed Orchard in Malawi between 1997 and 2003

Abstract

A retrospective study covering a period of seven years (1997-2003) was conducted to assess the extent of damage of Cinara cupressivora on Cupressus lusitanica Orchard and determine any correlation with climatic factors in Dedza, Malawi. Furthermore, the study was also aimed at determining the efficacy of Pauesia juniperorum as a biological control. The data was extracted from monthly reports of the Forestry Research Institute of Malawi (Centre), where a total of 319 trees were assessed. A statistically significant (X2=13.97, P<0.001) association was found between the damage of the trees and increased number of C. cupressivora. The damage was found to be eighteen times (Odds Ratio=18.1) more likely to occur on trees attacked by C. cupressivora than those not attacked. The hot-dry season was found to be significantly (X2=8.6, P<0.001) associated with the increased number of C. cupressivora, and the damage was found to be three times (Odds Ratio=3.4) more likely to occur in this season compared to cold-wet and warm-wet seasons. Consequently, the results further show a significant (X2=26.37, P<0.001) association between the survival of trees and the presence of P. juniperorum. The trees attacked by C. cupressivora were found to be twenty-nine times (Odds Ratio=29.1) more likely to survive with the presence of P. juniperorum than those where the parasitic wasp were absent. It is, therefore, recommended that classical biological control is the most suitable and permanent solution for control. Hence, P. juniperorum is a potential agent for the biological control of C. cupressivora.