As temperatures drop and the soil gets cold, it is possible that slug activity could increase to cause damage to winter crops. Slugs have already caused some serious problems this winter and they can do so again. Growers will be aware that metaldehyde is now the main chemical active in the market, but have you ever wondered how old that active is or where it originates from?
Its history is interesting and associated with a country that most Europeans would not associate with chemicals, given its environment and agricultural systems. It is produced in Switzerland by a company called Lonza in the town of Visp, which is located to the east of Lake Geneva in a valley of the Rhone river. Indeed, the Rhone is important to the plant because its cold glacial waters are used to cool many of the processes ongoing in the plant.
Lonza is not exactly a small single product company. It has approximately 10,000 employees, 111 facilities and sells 265 different products. Its 90ha site in Visp is at the core of its manufacturing operation as it has a small chemical cracker located there, which provides the base chemicals for so many of its specialised products. This manufacturing site might appear to be out of character with a typical quaint Swiss mountain valley but it looks like it belongs there and that’s probably because it has been growing at this site for about a century.
The Visp site has close to 2,800 employees and it produces everything from rocket science technology to fertiliser, with some pharma in there now also and it is the biggest producer of vitamin B3 in the world. The company began as an electricity generator on a different site back in 1897 and moved to Visp in 1907 to help widen its portfolio of activity.
Metaldehyde, the main active ingredient in all remaining slug pellets today in Europe, was discovered as far back as 1923. In its pure state, it is a white powder with a very distinctive smell but its molluscicide properties were not discovered until the mid-1930s. Its initial use was quite different. It was used as an energy source, a type of energy block or fire lighter used to reheat food and frequently used by soldiers.
Since the mid-1980s, the company has been involved in producing intermediary products for the main chemical companies. And the sophisticated nature of its activities now see it involved in new antibody technology to help treat cancer. So it is not your typical chemical company producing commodity industrial chemicals.
It’s the cracker
A major unique characteristic of this Lonza plant at Visp is its high temperature chemical cracker. This is, if I remember correctly, one of only two high temperature crackers in the world.
It uses raw materials such as liquid petroleum gas and light liquid naphtha as its basic raw materials and the high temperature cracker gives very different and higher-value end products compared with the more common and much higher output capacity low temperature crackers.
The unique chemical output stream from the cracker means that the Lonza complex can engage in an integrated production network. And the policy is to move more to higher value products. While certainly not among the high-value products produced, metaldehyde is one of the many end products and it has acetaldehyde as its precursor, which is one of the products produced by the cracker.
It is interesting to know that acetaldehyde is found in nature in things such as wood ash, beers, apples, pineapples, grapefruit, bananas, peaches, pears, wine and strawberries. It is also found as a by-product of plant metabolism and decaying organic matter. So the raw material can hardly be described as unnatural or artificial. However, it is widely believed to be one of the major causes of alcohol-derived hangovers.
The conversion of acetaldehyde to metaldehyde is a relatively inefficient process, resulting in the production of nearly 90% paraldehyde with only 10% plus of metaldehyde. This is fine when there is a good market for paraldehyde, but when this is not the case the paraldehyde can be converted back into acetaldehyde to begin the process all over again.
Metaldehyde
Metaldehyde itself is an interesting compound. It does not accumulate in the tissues of organisms and can be metabolised by all organisms. There appears to be no risk of resistance development in slugs or snails and it is easily degraded in nature to carbon dioxide and water. The other important characteristic is that it is highly specific to molluscs in that it only attacks mucous producing cells.
It is easy to degrade in the soil, a process which takes about 30 days. However, it is mobile in water and so care is needed to keep it away from water sources. It is regarded as being harmless to earthworms because they have no mucous cells. In the slug, the product targets the mucous cells, which have a number of functions. The slug needs mucous for mobility and for digestion and it will die when mucous production ceases.
Lothar Ott is one of the main technical people on metaldehyde at Lonza. He says that slugs are normally killed within one day of feeding and that feeding stops immediately following ingestion.
Slugs are not a simple target, Lothar says. It is widely believed that only about 10% of the slug population feeds at any one time and that it is mainly the juveniles that cause the most serious damage. This makes control very difficult as one cubic metre of soil can have up to 200 slugs present. And when climatic conditions are not favourable, they can migrate down into the soil to a depth of about one metre for protection against either dryness or frost.
Having produced metaldehyde for almost 100 years, Lonza moved to produce slug pellets for the first time a few years ago. This product is called Axcela and Lonza claims that it is made using an optimised bait formulation. Standard low protein wheat flour is mixed with the active and then it is steam-pressed and extruded as little mini pellets.
This is a relatively standard process for most modern pellets but the Lonza pellet is also gelatinised and the company claims that this gelatinisation makes Axcela a unique product. The gelatinisation process is unique to Lonza and a new extrusion technique is also being used (patent pending).
Eric Gussin of Lonza told us that the gelatinisation process alters the structure of the flour starch during manufacture. This allows for faster absorption of water to soften the pellet to make it more palatable to a passing slug. But dry pellets are essential to provide uniform spreadability.
The production process requires very good mixing for uniform distribution of the metaldehyde in the flour mix before extrusion.
The pellets are regarded as small at 2.4 x 2.4mm in size, on average. These smaller pellets provide about 85,000 pellets per kilo of pellets, which supply more baiting points per square metre for a given application rate per hectare. A 7kg application rate per hectare will result in about 60 bait points per square metre in the field.
For spreadability purposes, the pellets need to be hard and dense – hard to withstand the impact of being hit by the veins on the spreading disc and dense to absorb enough energy to travel the wide spreading distances. But being hard generates another problem as the slugs can only feed on soft palatable material.
Absorbing moisture
Once the pellets are spread on the soil, they are capable of absorbing moisture. This allows the pellet to soften and it also changes to a paler shade of blue.
To decrease the risk of crop damage, you should have more pellets than plants in a square metre, so that a moving slug has a higher chance of encountering a pellet than a plant. And the higher the pellet density, the quicker a slug will encounter the bait and be killed. Slugs do not seem to have good sensory ability so whether they encounter a plant or a pellet is a matter of chance and relative numbers.
The formulation on an ideal slug pellet is a fine balance, Lothar said. It needs palatability to be consumed but you do not want it taken by other organisms. To be efficient, you need to be sure that a slug will consume a sufficient amount of the poison at the first encounter to take in a lethal dose. Good control is heavily influenced by having an adequate number of baiting points, but the pellets still need to be big enough to travel the necessary spread distance.
The pellets need to be rainfast and the active should not leach into soil water. And pellets should not be prone to moulding as slugs will not consume mounted bait.
Research
There has been a lot of research conducted, which shows that Axcela pellets have high breaking resistance for spreading, swell and soften as they take in moisture, are quickly found by the slugs post-application and that slugs feed for longer and consume more on their first meal.
Ultimately, they are killed more quickly than with other good formulations. And all of these characteristics mean more surviving plants in the field.
Metaldehyde is manufactured for all of Europe in a beautiful valley in the town of Visp in Switzerland.It was originally manufactured as an energy source back in 1923.Lonza only recently began to make and sell actual slug pellets under the Axcela brand.The molluscicide is said to not affect any species other and molluscs. Making the ideal slug pellet is a balance between many different objectives.
As temperatures drop and the soil gets cold, it is possible that slug activity could increase to cause damage to winter crops. Slugs have already caused some serious problems this winter and they can do so again. Growers will be aware that metaldehyde is now the main chemical active in the market, but have you ever wondered how old that active is or where it originates from?
Its history is interesting and associated with a country that most Europeans would not associate with chemicals, given its environment and agricultural systems. It is produced in Switzerland by a company called Lonza in the town of Visp, which is located to the east of Lake Geneva in a valley of the Rhone river. Indeed, the Rhone is important to the plant because its cold glacial waters are used to cool many of the processes ongoing in the plant.
Lonza is not exactly a small single product company. It has approximately 10,000 employees, 111 facilities and sells 265 different products. Its 90ha site in Visp is at the core of its manufacturing operation as it has a small chemical cracker located there, which provides the base chemicals for so many of its specialised products. This manufacturing site might appear to be out of character with a typical quaint Swiss mountain valley but it looks like it belongs there and that’s probably because it has been growing at this site for about a century.
The Visp site has close to 2,800 employees and it produces everything from rocket science technology to fertiliser, with some pharma in there now also and it is the biggest producer of vitamin B3 in the world. The company began as an electricity generator on a different site back in 1897 and moved to Visp in 1907 to help widen its portfolio of activity.
Metaldehyde, the main active ingredient in all remaining slug pellets today in Europe, was discovered as far back as 1923. In its pure state, it is a white powder with a very distinctive smell but its molluscicide properties were not discovered until the mid-1930s. Its initial use was quite different. It was used as an energy source, a type of energy block or fire lighter used to reheat food and frequently used by soldiers.
Since the mid-1980s, the company has been involved in producing intermediary products for the main chemical companies. And the sophisticated nature of its activities now see it involved in new antibody technology to help treat cancer. So it is not your typical chemical company producing commodity industrial chemicals.
It’s the cracker
A major unique characteristic of this Lonza plant at Visp is its high temperature chemical cracker. This is, if I remember correctly, one of only two high temperature crackers in the world.
It uses raw materials such as liquid petroleum gas and light liquid naphtha as its basic raw materials and the high temperature cracker gives very different and higher-value end products compared with the more common and much higher output capacity low temperature crackers.
The unique chemical output stream from the cracker means that the Lonza complex can engage in an integrated production network. And the policy is to move more to higher value products. While certainly not among the high-value products produced, metaldehyde is one of the many end products and it has acetaldehyde as its precursor, which is one of the products produced by the cracker.
It is interesting to know that acetaldehyde is found in nature in things such as wood ash, beers, apples, pineapples, grapefruit, bananas, peaches, pears, wine and strawberries. It is also found as a by-product of plant metabolism and decaying organic matter. So the raw material can hardly be described as unnatural or artificial. However, it is widely believed to be one of the major causes of alcohol-derived hangovers.
The conversion of acetaldehyde to metaldehyde is a relatively inefficient process, resulting in the production of nearly 90% paraldehyde with only 10% plus of metaldehyde. This is fine when there is a good market for paraldehyde, but when this is not the case the paraldehyde can be converted back into acetaldehyde to begin the process all over again.
Metaldehyde
Metaldehyde itself is an interesting compound. It does not accumulate in the tissues of organisms and can be metabolised by all organisms. There appears to be no risk of resistance development in slugs or snails and it is easily degraded in nature to carbon dioxide and water. The other important characteristic is that it is highly specific to molluscs in that it only attacks mucous producing cells.
It is easy to degrade in the soil, a process which takes about 30 days. However, it is mobile in water and so care is needed to keep it away from water sources. It is regarded as being harmless to earthworms because they have no mucous cells. In the slug, the product targets the mucous cells, which have a number of functions. The slug needs mucous for mobility and for digestion and it will die when mucous production ceases.
Lothar Ott is one of the main technical people on metaldehyde at Lonza. He says that slugs are normally killed within one day of feeding and that feeding stops immediately following ingestion.
Slugs are not a simple target, Lothar says. It is widely believed that only about 10% of the slug population feeds at any one time and that it is mainly the juveniles that cause the most serious damage. This makes control very difficult as one cubic metre of soil can have up to 200 slugs present. And when climatic conditions are not favourable, they can migrate down into the soil to a depth of about one metre for protection against either dryness or frost.
Having produced metaldehyde for almost 100 years, Lonza moved to produce slug pellets for the first time a few years ago. This product is called Axcela and Lonza claims that it is made using an optimised bait formulation. Standard low protein wheat flour is mixed with the active and then it is steam-pressed and extruded as little mini pellets.
This is a relatively standard process for most modern pellets but the Lonza pellet is also gelatinised and the company claims that this gelatinisation makes Axcela a unique product. The gelatinisation process is unique to Lonza and a new extrusion technique is also being used (patent pending).
Eric Gussin of Lonza told us that the gelatinisation process alters the structure of the flour starch during manufacture. This allows for faster absorption of water to soften the pellet to make it more palatable to a passing slug. But dry pellets are essential to provide uniform spreadability.
The production process requires very good mixing for uniform distribution of the metaldehyde in the flour mix before extrusion.
The pellets are regarded as small at 2.4 x 2.4mm in size, on average. These smaller pellets provide about 85,000 pellets per kilo of pellets, which supply more baiting points per square metre for a given application rate per hectare. A 7kg application rate per hectare will result in about 60 bait points per square metre in the field.
For spreadability purposes, the pellets need to be hard and dense – hard to withstand the impact of being hit by the veins on the spreading disc and dense to absorb enough energy to travel the wide spreading distances. But being hard generates another problem as the slugs can only feed on soft palatable material.
Absorbing moisture
Once the pellets are spread on the soil, they are capable of absorbing moisture. This allows the pellet to soften and it also changes to a paler shade of blue.
To decrease the risk of crop damage, you should have more pellets than plants in a square metre, so that a moving slug has a higher chance of encountering a pellet than a plant. And the higher the pellet density, the quicker a slug will encounter the bait and be killed. Slugs do not seem to have good sensory ability so whether they encounter a plant or a pellet is a matter of chance and relative numbers.
The formulation on an ideal slug pellet is a fine balance, Lothar said. It needs palatability to be consumed but you do not want it taken by other organisms. To be efficient, you need to be sure that a slug will consume a sufficient amount of the poison at the first encounter to take in a lethal dose. Good control is heavily influenced by having an adequate number of baiting points, but the pellets still need to be big enough to travel the necessary spread distance.
The pellets need to be rainfast and the active should not leach into soil water. And pellets should not be prone to moulding as slugs will not consume mounted bait.
Research
There has been a lot of research conducted, which shows that Axcela pellets have high breaking resistance for spreading, swell and soften as they take in moisture, are quickly found by the slugs post-application and that slugs feed for longer and consume more on their first meal.
Ultimately, they are killed more quickly than with other good formulations. And all of these characteristics mean more surviving plants in the field.
Metaldehyde is manufactured for all of Europe in a beautiful valley in the town of Visp in Switzerland.It was originally manufactured as an energy source back in 1923.Lonza only recently began to make and sell actual slug pellets under the Axcela brand.The molluscicide is said to not affect any species other and molluscs. Making the ideal slug pellet is a balance between many different objectives. 
This is a subscriber-only article
SHARING OPTIONS: