Biopesticides - pros and cons
Biopesticides have a range of attractive properties for IPM. We list the main benefits here, and we also look at some of the challenges of working with biopesticides.
- In addition to their ability to control pests and diseases, biopesticides produce little or no toxic residue, and partly for this reason they are usually considered to be minimal risk products for human health. Many biopesticides are residue-exempt and are not required to be routinely monitored by regulatory authorities or retailers.
- Re-entry and handling intervals are becoming more important considerations when selecting a plant protection product for use, especially in protected crop and many biopesticides have a zero or low re-entry and handling interval.
- Biopesticides can often be applied with existing spray equipment, and some microbial biopesticides can reproduce on or near to the target pest / disease, giving a degree of self-perpetuating control.
- As alternatives to conventional chemical pesticides, they can help reduce the selection pressure for the evolution of pesticide resistance in pest populations, and there is good evidence that some microbial biopesticides can stop the expression of resistance once it has evolved.
- The risk of pests and disease developing resistance to biopesticides is often considered to be low, certainly for those agents that have multiple modes of action. However, in principle there is always a potential for a target pest / disease to develop resistance or tolerance, dependent upon the size of the selection pressure, and hence we think it is good practice to adopt an anti-resistance strategy when using biopesticides.
- Biopesticides often have good compatibility both with biological pest control agents (natural enemies) and with conventional chemical pesticides, so they can be readily incorporated into IPM programmes.
- Bioinsecticides can also be useful as a second line of defence or supplementary treatment. In pest management, there are often times in the season when the invertebrate pest population starts to run away from the ability of a predator or parasitoid to control it. In such situations, a bioinsecticide can be used to hold back the population development of the invertebrate pest and allow the predator or parasitoid to “catch up”. Having this back-up often makes the difference between success and failure of IPM in protected crops.
- The costs of developing a biopesticide are significantly lower than those of a conventional chemical pesticide, which should encourage companies to develop a wide range of products.
The downsides to using biopesticides include the following:
- A slower rate of control and often a lower efficacy and shorter persistence compared to conventional pesticides.
- Greater susceptibility to adverse environmental conditions.
- Because biopesticides are not as “robust” as conventional pesticides, they require a greater level of knowledge on behalf of the grower to use them effectively.