Ornamental plants are highly vulnerable to disease and pest attacks, especially in greenhouses, where the conditions are very favorable for their occurrence. Since the cost of growing ornamental plants is large, damage caused by diseases and pests greatly reduces production income, so all methods of combating them should be used. The most important of these is to provide the plants with the best growth conditions, decontamination of premises, the ground, hardware etc.. and direct control by the use of chemicals.
No less important than disease and pest control is the prevention of their occurrence. Plants grown according to their requirements are more resistant to attacks by diseases and pests, therefore, the recommendations for the correct choice of land should be followed carefully, fertilizing, maintaining the right temperature and humidity in greenhouses and frames. Using only healthy seeds for reproduction is also of great importance, seedlings, bulbs etc..
Inappropriate cultivation may or indirectly cause disease symptoms, e.g. lack of light - plants stretch and fade, or create favorable conditions for the development of pathogenic organisms, e.g. excessive humidity at too high temperature favors the development of powdery mildew.
Decontamination of soil with high temperature. In floriculture, we will most often deal with decontamination of the soil by means of high temperature. The most practical method of this type of decontamination is evaporation of the soil with the use of appropriate devices supplying steam to the soil inside the greenhouse or heaps of soil.. Steam harrows are used for this purpose, steam forks, perforated pipes or drains, etc..
Steam harrows consist of a tubular frame, similar to a harrow, with many tubular teeth 15-30 cm long., provided with holes approx 3 mm. The tines of a harrow connected to the steam source are hammered into the ground and open the steam supply pipe. The soil should be loosened beforehand, and during evaporation, it is tightly covered with a tarpaulin or foil. The temperature of the top layer of the steamed earth should be 90-96 °, decontamination time - 1-1.5 hours. Because the tines of the steam harrow are quite short, we usually use it to evaporate soil in frames, while for decontamination of deeper layers of soil in a greenhouse or on piles, we use a steam fork. They work in the same way as a steam harrow, i.e.. steam passes through the holes in the teeth of the pipes, but the teeth are longer - 60-75 cm, and larger holes - 4-5 mm. The forks are 1.5-2.5 m wide, the teeth are set every 25-35 cm. When disinfecting with a pitchfork, a deep ditch is first dug in the greenhouse 35 cm and a width approximately equal to that of the forks. The soil from the ditch is shifted to the other end of the site. The bottom of the ditch becomes loosened and 2-3 pairs of forks are placed on it. On one side of the ditch (from the side, in which the forks are to be moved) planks are arranged, to prevent landslides. Right behind this wall is a second ditch, covering the forks in the first ditch with the selected soil. Steam is then supplied and held through 20 minutes, then the forks are moved to the second ditch, a third trench is dug, etc..
It is very practical to decontaminate the soil in the greenhouse with the use of drains. The drainage device is fixed, so the procedure can be performed at any time, in addition, it is used for deep irrigation. It can be used for 10-15 years, so it is profitable. Systems for the construction of drainage devices may be different; here we present the system used in the Chróścina Nyska floriculture plant. Drainage pipes are placed butted together and connected with clay and cement mortar. Wires are inserted in the places of joining, which, after the mortar has hardened, are removed, thus obtaining holes, steam will come out from there.
Less land, intended e.g.. for sowing plants in boxes, it evaporates in various types of boilers; you can use for this purpose, for example. linen boilers, potato steamers etc.. At the bottom of such a vessel placed on the firebox, water is poured, which, when heated, will generate steam. The second bottom is placed in the pan, punched, basing them e.g.. on bricks, yes, so that it is above the water. The sieved and dried earth is poured onto this bottom in a layer of about 50 cm. Pairing should take 30-60 minutes, at a temperature of 100 °. Even more convenient for this purpose are special metal boxes with a double bottom and a side opening for introducing steam from the device used for its production.
Whether, what devices we use for pairing, follow these rules:
1. The soil to be steamed must be loosened and not too moist, and also not too cold, let alone not frozen.
2. The ground should be tightly covered with a tarpaulin during steaming and for several hours afterwards, foil, etc., so high temperature operation lasts longer.
3. After evaporation, the soil must be left lying down for 2-3 weeks, that the beneficial microbes start working in it again. V / if necessary, the steamed soil can be stored for one year, but then before use, remove a layer a few centimeters thick from the outside.
4. Steamed soil must not be mixed with soil that is not decontaminated or added to it with organic fertilizers, as it could cause a new infection.
Soil decontamination by evaporation is preferable to chemical decontamination, as it destroys more pathogenic organisms and pests, it does not kill most of the beneficial bacteria and does not leave any poisonous substances in the soil, and at the same time destroys the seed weeds.