Overview
- What are granuloviruses?
- Use of granuloviruses
- Mode of action and application of granulovirus-based biopesticides
- Benefits of granulovirus-based biopesticides
- Considerations
Granuloviruses are naturally occurring viruses capable of infecting and killing certain insect pests, mostly those in the Lepidoptera order. With their high host specificity, they are a powerful solution for sustainable pest control.
What are granuloviruses?
Granuloviruses, also called GVs, are a genus of viruses that infect insects. They belong to the Baculoviridae family and are closely related to another group of viruses attacking insects, the nucleopolyhedroviruses (NPVs). All these viruses are highly specific to one or several closely related insect species.
Use of granuloviruses
Granuloviruses are a popular active ingredient in microbial biopesticides and have already been used for several decades. They are particularly appreciated as they are specific and can effectively control a pest without harming beneficial insects.
Granulovirus-based biopesticides are primarily used against Lepidopteran pests in their larval stages, notably the codling moth (Cydia pomonella) and the Diamondback moth (Plutella xylostella).
Some examples of partner products from Andermatt Canada that can be found on the CABI BioProtection Portal include:
- Plutex®: registered in Canada, this product controls the diamondback moth on Brassica crops.
- Madex HP®: also registered in Canada, this product targets the codling moth and has been successfully used for more than 20 years.
Mode of action and application of granulovirus-based biopesticides
Mode of action
Like all viruses, granuloviruses can only become active and replicate once inside a living host cell. Specifically, granuloviruses work on insect larvae by ingestion, meaning that the pest needs to ‘eat’ the virus. For instance, larvae can ingest the virus off leaves previously treated with the granulovirus-based biopesticide.
Once ingested, the infection starts, and the virus enters the larva’s gut where it releases viral particles. These particles help the virus multiply and also degrade specific proteins from the larva, leading to its liquefaction and ultimately death.
A late-stage infection is easily recognizable as the larva appears to stop feeding and is less mobile. It also starts to change colour and turn brownish. When the larva dies, it bursts open and releases even more viral particles into the environment, which are free to infect more larvae.
Application
Since the targeted pest needs to ingest the virus through plant tissues, it is essential to apply granulovirus-based biopesticides where the pest usually eats the crop. For example, if the larvae eat the leaves, the product needs to be applied to the leaves.
In general, the application of granulovirus-based biopesticides is similar to that of chemical pesticides. They are more frequently produced in liquid formulations and can be applied with most conventional spray equipment. They can also be found in a dust or powder formulation.
Benefits of granulovirus-based biopesticides
Granuloviruses in pest management have many benefits, such as:
- Compatibility with other products: due to their mode of action, granuloviruses can be used in combination with other biological and chemical pesticides. This means they are also compatible with Integrated Pest Management (IPM) programmes.
- Non-toxic and no residues: granulovirus products leave no residues on produce, making them safe for the consumers and allowing growers to access various market opportunities.
- Specificity: granuloviruses are specific to a single or several closely related species, making them safe for surrounding beneficial organisms.
- Extended shelf life: these products usually have a long shelf-life with proper storage conditions, similar to those of chemical pesticides.
Considerations
While granuloviruses offer numerous benefits, certain factors should be considered to maximize their effectiveness:
- Application timing: Granuloviruses are most effective when applied early in the pest’s lifecycle, as they primarily target larvae. Younger larvae also require a lower application rate, which is more cost-effective.
- Environmental conditions: UV radiation and high temperatures can rapidly degrade viral particles, reducing efficacy. It is preferable to adjust the application timing to avoid direct UV rays, for example, by applying later in the afternoon. However, a recent finding showed that new formulation technologies can protect the virus from UV rays. This holds a significant potential for future applications.
- Combination with other products: with repeated use, a pest could eventually build resistance against a granulovirus strain. To avoid this happening and for optimal results, granulovirus-based products should be used as part of an IPM programme that includes other control methods and products.
Overall, granulovirus-based products are a good alternative to chemicals as they have no unwanted effects on the environment and human health. Growers can effectively manage some problematic Lepidopteran pest populations while protecting ecosystems and reducing reliance on harmful chemicals.
