Biological Control Agents for Control of Pests in Greenhouses

First we describe the different types of biocontrol used in greenhouses and present examples of each type. Next we summarize the history of greenhouse biocontrol, which started in 1926, showed a problematic period when synthetic chemical pesticides became available after 1945, and flourished again since the 1970s. After 1970, the number of natural enemies becoming available for commercial augmentative biocontrol in greenhouses grew very fast, as well as the industry producting these control agents. Biocontrol of the most important clusters of greenhouse pests is summarized, as well as the taxonomic groups of natural enemies that play a main role in greenhouses. More than 90% of natural enemy species used in greenhouses belong to the Arthropoda and less than 10%, many belonging to the Nematoda, are non-arthropods. This is followed by sections on finding and evaluation of potential biocontrol agents, and on mass production, storage, release and quality control of natural enemies. Since the 1970s, production of biocontrol agents has moved from a cottage industry to professional research and production facilities. Many efficient agents have been identified, quality control protocols, mass-production, shipment and release methods matured, and adequate guidance for farmers has been developed. Most natural enemy species (75%) are produced in low or medium numbers per week (hundreds to a hundred thousand), and are applied in situations where only low numbers are needed, such as private gardens, hospitals, banks, and shopping malls. The other 25% of the species are produced in numbers of 100,000 to up to millions per week and regularly released in many of the greenhouse crops. Microbial pesticides are predominantly used as corrective treatments in greenhouse crops where natural enemies are providing insufficient control. Europe is still the largest commercial market for arthropod greenhouse biocontrol agents, and North America is the largest market for microbial control agents. We then continue with a discussion on the pros and cons of use of polyphagous predators, and the use of semiochemicals. Finally, we summarize factors that indicate a positive future for greenhouse biocontrol, as well as developments frustrating its implementation.