Short and long term efficacy and prevalence of Cryphonectria parasitica hypovirulent strains released as biocontrol agents of chestnut blight

Chestnut blight, Cryphonectria parasitica (Murrill) Barr, was reported in Portugal 1989. The disease rapidly spread within the chestnut region of Trás-os-Montes (the Northeast Portugal). Eradication and mechanical/burning exclusion failed to control natural hypovirulence is still absent or very low incidence. introduction human-assisted therapeutic therefore required disease. We presente here efficacy field applications (short long term) a locally characterized hypovirulent strain (CHV1-RBB111), by punch method two orchards (Valpaços Vinhais). Valpaços incidence 68% (65 out 96 trees) Vinhais it 46% (78 169 trees). In both locations, diversity vegetative incompatibility (vc type) largely dominated (> 85%) single vc type (EU11). Valpaços, all cankers orchard were treated (63 cankers) 31 trees (cankers) treated. One year after application, high with 93.8% healed 90.3% Vinhais, these values increased 100% 93.5% (respectively) four years. persistence introduced CHV1-RBB 111 present almost dominant inwards on application site revealing an endophytic behavior. non-C. microfungi abundant 14 different species. Biscogniauxia mediterranea (De Not.) Kuntze most orchards. Treatment (CHV1-RBB111) found be effective controlling blight regeneration cortical tissues recovery trees.