Kotze C., Van Niekerk J., Mostert L., Halleen F., Fourie P.
Department of Plant Pathology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; Plant Protection Division, ARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa; Citrus Research International, P.O. Box 2201, Stellenbosch 7602, South Africa
Kotze, C., Department of Plant Pathology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; Van Niekerk, J., Department of Plant Pathology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; Mostert, L., Department of Plant Pathology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; Halleen, F., Department of Plant Pathology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa, Plant Protection Division, ARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa; Fourie, P., Department of Plant Pathology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa, Citrus Research International, P.O. Box 2201, Stellenbosch 7602, South Africa
Trunk diseases of grapevine are caused by numerous pathogens, including Eutypa lata, Phaeomoniella chlamydospora, and species of Botryosphaeriaceae (incl. Botryosphaeria and aggregate genera), Phomopsis and Phaeoacremonium. Since infections occur mainly through pruning wounds, that have been shown by previous research to stay susceptible for up to 16 weeks after pruning, long-term pruning wound protection is required for prevention of infection. This study evaluated several biocontrol agents against a range of trunk disease pathogens in dual plate laboratory trials to determine macroscopic and microscopic interactions. The biocontrol agents had a substantial effect on all the pathogens, with a wide range of macroscopic and microscopic interactions observed. The best performing biocontrol agents were tested in two field trials. Fresh pruning wounds were treated with benomyl, Trichoderma products (Biotricho®, Vinevax® and ECO 77®) and isolates (USPP-T1 and -T2, identified as T. atroviride) and Bacillus subtilis. Seven days after treatment the pruning wounds were inoculated by spraying with spore suspensions of Neofusicoccum australe, N. parvum, Diplodia seriata, Lasiodiplodia theobromae, Eutypa lata, Phaeomoniella chlamydospora or Phomopsis viticola. Eight months after inoculation, the treatments were evaluated by isolation onto potato dextrose agar. The efficacy of the biocontrol agents was in most cases similar or superior to that observed for benomyl. Isolate USPP-T1, in particular, was very effective, reducing incidence of Ph. viticola, E. lata, Pa. chlamydospora, N. australe, N. parvum, D. seriata and L. theobromae by 69, 76, 77, 78, 80, 85 and 92%, respectively. This is the first report of biological protection of grapevine pruning wounds against this group of grapevine trunk disease pathogens.