The worst pest ofis the Black-fly, which should be anticipated early in the summer. The best cure is to spray with nicotine wash or dust the tips with tobacco dust, using small bellows for the purpose. Spray as a prevention; do not wait until the pest has actually appeared. If it does show up, then prompt measures must be taken (and repeated as necessary), to stamp it out immediately.
Another obnoxious pest is the leaf miner. This is difficult to control because the fly lays its eggs and disappears, and the grubs which hatch out do the damage by eating their way through the leaf between the upper and under skins. They cause the well known silver-brown markings, and because they eat away the green of the leaves, the health of the plant is seriously affected. If plants are attacked, remove the affected leaves. It is better to prevent an appearance by early spraying with quassia extract and soap solution. Use this deterrent during May and June, when the fly is most active. Also look out for, such as groundsel, which harbour this pest, and be sure that all such are pulled up and burnt.
Another pest which sometimes appears is the red spider, which is best controlled by spraying with ordinary cold water. An occasional dose of soot water, made by immersing soot in a barrel of water, is useful as a stimulant, and helps the plants to resist all kinds of pests.
This is a fungus trouble which has been very prevalent of late years amongst Chrysanthemums. It can only be treated by the use of a fungicide, and as it is believed that the spores exist in theit is recommended that the soil should be treated with fungicide before it is used for potting. Special preparations are sold for the purpose but the use of Cheshunt Compound, as in the case of a soil prepared for tomatoes, should be effective.