SUMMARY AND CONCLUSION.Fern mite (Tarsonemus tepidariorum, Warburton) is of distinct economic importance. It attacks the younger parts only of the fern (Asplenium bulbiferumand its varieties), causing the fronds to become. distorted and the plant to be dwarfed so that it is unsaleable. The disease spreads rapidly in a greenhouse due to the rapid multiplication of the mite and the very short life‐cycle of 17 days on the average. All stages of the pest may be found during the summer, and the winter is passed mainly as an adult female, although a few eggs may also be found at that time. The mites spread from one nursery to another by the introduction of infested plants; from one plant to another by crawling from leaf to leaf where these touch, and probably by walking along the surface. of the moist earth; and by the planting of young “pips” taken from infested parents. The disease is difficult to control.Preventive measures offer more chance of success than do remedial. The young “pips” should be planted clean, and then kept free from the pest by means of deterrent sprays. The “pips” are treated with some insecticide before planting.Badly infested plants should be burnt and the soil and houses should be sterilised.It is essential to produce healthy plants. To obtain this, certain factors are important, such as proper ventilation, adequate drainage and the correct degree of temperature and humidity.Potash manures and lime are good. Nitrogenous manures should be sparingly.Rotation of the greenhouse crops is advisable.Plants would be produced clean, if they could be propagate