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Root rot disease of teak (Tectona grandis Linn. f.) is widely distributed in Nigeria where it is present in about 70% of teak plantations. The disease is caused by Rigidoporus lignosus (Klotzsch) Imazeki, sporocarps of which have been found in about 64% of the infected plantations. Disease incidence is more serious in shallow lateritic soils and sites with impeded drainage. The disease can be controlled using 2% Tillex chemical spray on infected trees. It can also be largely reduced in proposed plantations by careful site selection and pre-treatment of stumps left behind after land clearing.

SUMMARY Mycorrhiza was synthesized using Pinus oocarpa and Rhizopogon luteolus. After one year's successful growth in the laboratory, the seedlings raised were planted out in the field where the inoculated plants continued to grow normally. The uninoculated plants died after planting out. The results are believed to be significant in that a field establishment of mycorrhiza synthesized in controlled conditions is possible. The experiment also demonstrates the absence of suitable mycorrhizal fungi for pine establishment in Nigerian soils.

Sodium pentachlorophenol, which was previously found to be the most effective of eight different chemicals tested against blue-stain of timber and recommended at 1 and 2% levels for dipping, has now been further tested in the field. The results show that the chemical effectively controlled the blue-stain infection even at lower concentrations of 0.5 and 0.7%. Botryodiplodia theobromae was the chief causal agent of infection, although a Ceratocystis sp. was also present. The chemical at the concentrations used had a repelling action for 4-6 days after application on insect borers (Platypus hintzi and Xyleborus performa).