- How dangerous are snails to rapeseed?
- How to combat these pests?
Snails are no less dangerous than the flea or the snail
In fact, it is not only this year that snails will pose a big problem in rapeseed. In fact, they pose a huge threat every year. However, in many locations, their exceptional intensity is noticeable. And soon they will pose a significant threat to young rapeseed plantations.
Often, in the context of rapeseed pests in the initial stages of its development, we talk about the leafhopper, flea beetles, etc. Meanwhile, we sometimes forget about snails, and they are one of the most dangerous pests. In some situations, they are capable of consuming an entire, not insignificant, plantation very quickly.
The most dangerous for rapeseed is the spotted slug. It can lay about 600 eggs per year. Its peak presence is in late summer and early autumn, which is also the period of rapeseed emergence. Also dangerous are the slugs (including the common and the great).
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The most dangerous on the edges of fields
While snails are not only dangerous right after emergence, it is then that the damage they cause can be the greatest. Then, entire plants are eaten, while as the leaf mass develops, they are still damaged, but it is often the case that a part of the plant is essentially destroyed, i.e. we will notice the gnawed leaves.
The greatest damage will always occur on the edges of fields, especially near ditches, bushes, and woodlots. These places are a natural base for snails. During the day, when the sun appears, they return to their hiding places. It sometimes happens that, as mentioned above, the edges of fields are significantly damaged. Snails feed on them because they are close to their hiding places and feel relatively safe in these places. Importantly, at night they are able to "drive" even deep into the field.
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How to combat snails?
The threshold of damage assumed for snail feeding is 2-3 snails per square meter or 5% of damaged plants. This is how it looks at the emergence stage, later the threshold was set at 10% of damaged plants or 4 snails per square meter (in the BBCH 13 – 14 phase).
When it comes to chemical methods, we can combat snails with molluscicides. These, depending on the product, act by contact or stomach. They are usually available in granulate form. Most often, protection against snails is carried out in such a way that around the plantation, especially near ditches and woodlots, a molluscicide is scattered, with the help of which we create a buffer strip.
Iron phosphate-based preparations will work through the stomach. After consuming the granulate, the snails are not immediately neutralized. They return to their hiding places and die there.
In turn, solutions based on metaldehyde and iron phosphate are available that work both on contact and in the stomach. After the snail comes into contact with the granule (or consumes it), the cells responsible for the secretion of mucus are destroyed. As a result of excessive secretion of mucus, the snails quickly become numb.
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Snails are dangerous even later
Especially at the beginning, i.e. at the stage of emergence, you need to pay attention to feeding by snails. Although they will pose a threat throughout the autumn, with the increase in biomass the percentage of damage will be lower – snails will satisfy their nutritional requirements with a small amount of rapeseed, while after emergence they must consume even whole plants. However, this does not mean that then, in the later stages, the harmfulness will be negligible. It is rarely said that snails can transmit fungal diseases. That is, by leaving mucus, contact with many plants, there is also a chance that they will transfer pathogens from infected plants to healthy organisms.
