If you're looking to completely eliminate a pest, biological control isn't the right choice. While inexpensive in the long run, the process of establishing a biological control system is a costly task. Biological control can be less or more expensive than pesticides. You can incur significant expenses studying, choosing, testing and breeding a bioagent.
However, in cases where bioagents are applied to low-level pest populations, pest control can be long-term and economical. Some fungi attack insects and kill them. A fungal spore penetrates the insect and grows all over it. It takes about a week for the insect to die.
Fungi are cost-effective, unless a high application rate is needed for severe insect infestations. A major disadvantage of biological pest control may be that it takes a long time to actually control the pest population. The disadvantages of biological control are that natural enemies can move away. In greenhouses this problem can be managed, but not in the open field.
Extending on a larger plot also takes time. Secondly, pests are never completely destroyed because the natural enemy needs to stay alive and therefore they will never destroy the entire population. Finally, it is not possible to use them before the pest has occurred and this means that some damage will be caused to the crops. Classic biological control or import involves introducing a pest's natural enemies to a new location where they don't occur naturally.
The first cases were often unofficial and not based on research, and some introduced species became serious pests. Landscape composition could moderate the effects of augmentative biocontrol through two different mechanisms. Once potential biological control agents have been identified, they are tested abroad to ensure that they are host-specific, that is, they will not attack any plant other than the herb to be controlled and, therefore, will not become a pest if introduced into Australia. Rapae populations, their control levels varied significantly throughout the growing season and between landscapes.
It has been suggested that the introduction of a biological control scheme against a pest, and the resulting removal of broad-spectrum pesticides, may lead to new pest problems, but there is no evidence of this in several well-studied agroecosystems, including greenhouse systems. Biological control or biocontrol is a method of controlling pests such as insects, mites, weeds and plant diseases using other organisms. The United States Department of Agriculture (USDA) initiated research into classical biological control after the establishment of the Division of Entomology in 1881, with C. Pest Control and Pollination Cost-Benefit Analysis of Hedge Restoration in a Simplified Agricultural Landscape.
More recently, guidance on procedures and methods for environmental risk assessment (ERA) of non-native invertebrate biological control agents has been proposed (van Lenteren et al. Control is greater if the agent has temporary persistence so that it can maintain its population even in the temporary absence of the target species, and if it is an opportunistic forager, allowing it to quickly exploit a pest population. As a generalization, the view that biological control contributes to a reduction in pesticide use with corresponding environmental benefits can be strongly argued. However, as a starting point, it might be more efficient to focus first on changes within crop systems that could increase natural pest control.
The favorable economics of biological control in relation to the use of pesticides also applies to the commercial application of the technique. Simple landscapes, defined as landscapes with high proportions of farmland, were positively correlated with the abundance of foliar and terrestrial predators (depending on the control plots). Examples include control of whiteflies, leafminers, thrips, aphids and mites by parasitoids and predators in greenhouses (van Lenteren 2000a). .