Articles
RISKS AND OPPORTUNITIES FOR BIOCONTROL AGENTS FOR THE CONTROL OF PLANT PESTS IN EUROPEAN HORTICULTURE
Depending on the crop intensification, there are variable degrees of the following features: modified abiotic environment (e. g., in greenhouse and soil – less production), high unitary value, fresh consumption and frequent exportation.
Some consequences for herbivore insects and their control:- high increase rates in insect populations, low economic thresholds, high risks of presence of insecticide residues, development of insecticide-resistance, invasion of new herbivores thorough international trading.
Only a true integrated approach to insect pest control methods may respond to that challenging situation.
Under the double pressure of decreasing insecticide availability and of the increasing demand for environmentally friendly, sustainable and safe methods to control insect pests, R&D&TT is paying more attention to non-chemical methods.
Modern integrated pest management systems include methods like biological and microbial control, host plant resistance, semiochemicals (pheromones and others) for mating disruption and mass trapping, specific cultural practices among others.
Biological control is, sensu stricto, the intentional use of arthropod predators and parasitoids to lower pest populations.
This can be achieved by manipulating predator or parasitoid populations of by managing crop and environment to enhance those.
Biological control techniques have been classically divided into three groups: inoculation, inundation, and conservation; (i) in the inoculation techniques a relatively low numbers of exotic natural enemies are released in the expectations they became established in the area and maintain their effectiveness along the time; (ii) inundation techniques use a high amount of natural enemies (e.g., hundreds of thousands per hectare) to quickly reduce pest numbers, and (iii) conservation biological control aims to conserve and enhance natural enemies already established in the area.
Biological control by inoculation of exotic natural enemies has been practised for more than one hundred years in the modern agriculture since the lady beetle Rodolia cardinalis was imported into California in the 19th century and successfully controlled the cottony cushion scale in citrus orchards.
Since then hundreds of successes of inoculation biological control are well documented in the literature.
There is HOWEVER, increasing criticism about the practice of importing and releasing exotic natural enemies to control insect pests.
Some data show the potential of exotic predators and parasitoids to impact on native insect fauna, both non target herbivores and other natural enemies.
The lady beetle Harmonia axyridis may be an example.
Introduced into Europe and the USA from Asia to control some aphid and scale species has established fast in many areas.
Several of its characteristics have been signalled as intrinsically risky although more research is needed to link some specific traits of exotic natural enemies to risks for native fauna.
The curious reader is referred to the following sources for more information about risks of biological control by inoculation. (1) See the journal Biocontrol (2008) 53 (1) for a complete description of the Harmonia case. (2) Bigler, F., Babendreier, and D., Kuhlmann U. (eds) 2006. ‘Environmental Impact of invertebrates for biological control of arthropods: Methods and Risk Assessment’, CAB International, Wallingford, UK.