Cultivated crops are affected with various fungal, bacterial and viral diseases as well as a number of insect pests. Many cultivation technical, chemical and biological control methods have been developed in order to control these. The purpose of such methods is to prevent the qualitative and quantitative crop losses caused by plant diseases and other pests.
In general the term biological control of plant diseases means the control of plant pathogens by another organism, which is then called a biological control organism of plant diseases, and the preparation made thereof a biological control agent or a biopesticide. The mechanisms of the biological control of plant diseases do vary, and the effect is often based on the cooperative action of many different mechanisms. The control effect may be based on inhibitory chemical agents produced by the organism, sometimes the control organism parasitizes the pathogen or competes with it for growth space and/or the nutrients available.
The need of discovering new biological control agents has been increased by the fact that many of the traditional chemical pesticides have turned out to be deleterious to the environment and human beings. A disadvantage of the chemicals is also the fact that many pests have become resistant to one or even a number of pesticides. The development of resistance to biopesticides is instead improbable because the effect thereof is based on a number of mechanisms of different types. The chemicals usually affect faster and more effectively than biopesticides. Biopesticides for their part are often longer-acting than chemicals as their effect is based on a viable and reproducible microorganism.
The most important group of biopesticides are bacterial products targeted against insects. Bioinsecticides based on the bacterium Bacillus thuringiensis may be the most commonly used. A biofungicide based on the actinomycete Streptomyces being effective against a number of soil-borne and seed-borne fungal diseases of plants is produced in Finland. Fungi of the genus Trichoderma have also fungicidal activity.
Bacteria of the genus Pseudomonas, especially of the species Pseudomonas fluorescens have been studied a lot and nowadays a great amount of P. fluorescens strains are known which have fungicidal activity. See e.g. published patent applications WO 92/18613, FI 92 1722 and WO 90/01327, as well as EP-patent 228 457.
It is known that fungi of the genus Gliocladium have fungicidal activity. Gliocladium virens strains, especially the G. virens strain G1-3, have been described in patent literature. A problem in the use of this species has been, however, that nobody has been able to produce a formulation of this fungus, in which the viability of the fungus would keep on a satisfactory level during the storage of the formulation. In U.S. Pat. Nos. 4,668,512, 4,724,147 and 4,818,530 besides other fungal strains the use of Gliocladium virens strains is described in the preparation of biofungicidal formulations. Also in U.S. Pat. Nos. 5,165,928, 5,194,258 and 5,268,173 the use of Gliocladium virens strains as biofungicides has been described.