This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Generally speaking thrips and aphides are the worst enemies of Ferns, but they can be kept in check by the use of nicotine, soft-soap, and quassia solutions being freely applied when necessary; or by vaporizing the houses. A pest known as the "mite" has, however, practically defied all remedies, and thousands of market Ferns - chiefly Pteris cretica and its varieties, and the Aspleniums of the bulbiferum section - have been destroyed by its attacks. Vaporizing, syringing, and fumigating have proved useless, and there was nothing left but to burn infected stock, clear out and sterilize the soil by burning, and cleanse the houses by thoroughly washing with hot limewash and paraffin emulsions - operations that meant a considerable reduction in the profits of the grower for market. In some cases where none of these proceedings were carried out, and were even despised, the loss was suffered as an "act of God", and allowed to wear itself out. This it did in two or three years, apparently the result of over-production and suffocation on the part of the Fern mite. With this disease, as most others, it will pay the grower to keep his soil sweet and pure by exposure to the weather before use, by attention to proper ventilation and keeping up a "buoyant" atmosphere, and by attention to careful watering.