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The study was conducted to evaluate in vitro and in vivo control of fungal antagonists on Rigidoporus lignosus (klotzsch) Imaz in Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg. in the rain forest zone of Nigeria. In vitro assessments of biological agents were carried out in dixenic cultures in Petri plates. In vivo tests were carried out in the nursery using Hypocrea virens and Hypocrea jecorina. Significant differences were observed with the dual inoculations of fungal antagonists and R. lignosus inoculated the same day, and the antagonists inoculated 24 h before inoculation of R. lignosus. Hypocrea jecorina was most effective in the control of R. lignosus with percentage inhibition of 86.83 %. Hypocrea virens, H. jecorina, Trichoderma spirale, Trichoderma sp., Trichoderma sp. Pers, and Hypocrea lixii were effective on R. lignosus. Fungal antagonists inoculated 24 h before inoculation of R. lignosus exhibited higher inhibitory efficacies than antagonists and R. lignosus inoculated the same day. In the in vivo evaluation of fungi antagonists on R. lignosus, seedlings in H. jecorina treatment at 60 d and H. virens treatment at 150 d after inoculations respectively had the highest plant heaths (highest length of stem and length of tap rot, lowest plant death, and least foliar symptom) compared to the control. Mortality rate was higher at 60 d after inoculation and decline from the third months onward. Significant differences were observed between the control and R. lignosus treatment in all the parameters evaluated.

Early detection of root diseases is a great problem in perennial crops, especially in rubber tree. Planters are continually confronted with the balance of efficiency/cost of the detection. Therefore, a trial was set up to compare three sampling densities and four exposure techniques for detection of white root rot in rubber plantings. A complete census of all trees is the only efficient method of detection in a control program. When reducing the sampling density, a lot of infected trees are not detected and they remain an inoculum source for the spread of the disease. Mulching for one month followed by root exposure is the best technique to reveal the presence of the fungus. The sampling density is of greater significance than the infection exposure method.

Laccase from Rigidoporus lignosus, a white-rot basidiomycete, has been isolated from culture filtrates. The enzyme was purified to homogeneity and some of its structural and kinetic parameters have been determined. The effects of pH, temperature, and organic solvents on the activity and stability of the enzyme, under different conditions, were also assayed. The results we have obtained, including the rather broad substrate specificity of enzyme, combined with their relatively easy production and purification, suggest that laccase may be efficiently employed in a variety of biotechnology applications.

Les trois principaux parasites des racines d'Hevea brasiliensis en Afrique sont Rigidoporus lignosus, Phellinus noxius et Armillaria sp.. Seul Rigidoporus lignosus, qui est responsable de la pourriture blanche des racines est présent dans les zones hévéicoles et reste la cause principale de mortalité des arbres en Afrique. De nouveaux fongicides ont été testés afin d'améliorer la lutte contre la pourriture blanche des racines causée par Rigidoporus lignosus. Certains composés à base de triazole se sont révélés être très efficaces in vitro et sur des expérimentations à petite échelle avec des seedlings ou des stumps placés en sols infestés artificiellement. Deux applications tous les 6 mois de fongicide sous forme liquide (Alto, Sandoz) et des applications de triadimenol sous forme granulaire (Bayfidan, Bayer) à raison de 0,5 g a.i. par arbre ont donné de bons résultats au champ. Leur utilisation est recommandée dans la pratique. (traduction du résumé d'auteur)