In Hungary hotbed, plastic and glass greenhouse areas increased in recent years.
As a result of this the science of protection of vegetable crops grown in these structures is constantly being confronted with new problems, one of the most important of them being soil sterilization.
Up to 1960 the fungus Rhizoctonia solani was one of the frequently met diseases in Hungary.
It was destructive to crops, caused damping off of seedlings and root rot in the more adult plants.
The following preparations were extensively used in the control of this pathogenic fungus: Fuklasin F, Berzema Ferbam 20, Berzema Ferbam 50, which contain active substance iron (III/-dimethyldithiocarbamate) and are produced in the German Democratic Republic.
The preparations TMTD (tetra-methyl-thiuramdisulfide), made in Germany, Holland and Poland, appeared after 1962 and proved to be especially effective against damping off of seedlings.
These preparations are thoroughly mixed with the covering earth one or two weeks prior to or immediately before sowing the seed, which is covered by this disinfected earth.
The TMTD preparations have the advantage of being easily handled, demand no special appliances and devices, are cheap, practical, not poisonous to man or warm-blooded animals, require no period of waiting between treatment and use of soil, offer effective control of damping off of seedlings.
On the other hand they have the disadvantage, inherent to their specific action, to kill only pathogens of fungus origin, in the first place Rhizoctonia solani and species of Sklerotinia.
For several years tobacco mosaic virus has been steadily increasing in greenhouse grown peppers and tomatoes.
It attacks not only the leaves but also the fruits and causes great losses in yield.
In addition to this pathogen in hotbed and greenhouse soil, ever more often are encountered damages by the root gall Nematoda of the Meloidogyne species.
This necessitates the use of such ways and means of control that ensure higher and allround effectiveness.
With a view to disinfecting the soil we tested and compared in 1968 some gassing means as for instance Ditrapex and Basamid of comprehensive action - fungicidal, nematocidal, and insecticidal effect on the one hand, and various methods of soil sterilization based on thermal action on the other hand.
The experiments were carried out in NDK and Venlo types of greenhouses of the Scientific Research Institute of Plant Protection and the Institute of Plant Growing in Budapest.
The soil was disinfected on the spot and in heaps, covered with polyethylene film, using Ditrapex and Basamid.
The steaming of the soil was performed in a closed steam chest.
Furthermore we tested the Swiss machine Terra-Force for soil disinfection, operated with direct heat or dry heat.
The soil to be disinfected is fed through an aperture, supplied with a sieve,