Slug Invasion in Crops Would Be Stopped by Plow

“This year’s rainy summer was a veritable paradise for pests – aphids spread uncontrollably, invasive slugs ate vegetables and berries, and the harvest was reduced by rot and diseases. Winter crops sown in the fall, especially rapeseed, did not hold up either – slugs ate some of them so much this year that they are unlikely to recover in the spring.

 

I liked the new technologies

 

Recently, no-till agriculture has become popular in Lithuania. This means that when sowing in the fields, the soil is not plowed, and the seeds are placed directly in the ground, only loosened, to a depth of no more than 10 cm. State support is provided for these sustainable technologies under the provisions of the “Strategic Plan for the Development of Lithuania for 2023–2027” as a way to reduce CO2 emissions and improve soil quality. This method of farming is also beneficial for farmers because it saves time and money: work is done faster, fuel is saved, and less fertilizer is used, because the organic matter remaining after harvesting fertilizes the soil itself.

 

Considering that the soil in Lithuania is extremely depleted, this technology looks attractive because it is preserved, and most importantly, as experts say, it creates favorable conditions for the development of biodiversity in the soil, ensuring the availability of moisture for crops. According to those engaged in sustainable farming, the yield can be obtained by several dozen percent higher thanks to these technologies.

 

In a word, modern, attractive, which is why many farmers throughout Lithuania have started to apply no-till technologies. However, slugs began to breed in the uncultivated soil.

 

The stick hit with the other end

 

Zigmantas Aleksandravičius, vice-chairman of the Lithuanian Farmers' Union (LŪS), chairman of the Kupiškis branch, when asked what happened that Lithuania was attacked by invasive slugs, did not think long before answering: "It's all because of direct sowing. Now, many farmers in Lithuania are using sustainable, no-till technologies in crop production, so when the soil is not plowed, the remaining stubble creates good conditions for slugs to breed."

 

According to Z. Aleksandravičius, about five or six years ago, new seeders without any tillage appeared on the agricultural machinery market. This is really good technology, but sellers need to sell it. “That’s how the promotion of no-till agriculture began, luring farmers to engage in this new technology primarily in order to buy out the equipment,” explains the vice-chairman of LŪS. “It was even loudly suggested that the plow be cut up as obsolete and given to scrap metal. Farmers were misled about this, and then even better – they themselves began to convince each other of the benefits of such technologies, to mislead each other about how good it would be not to till the land, what the overall benefits would be. But these technologies were not invented by the farmers themselves, but by the developers of the technologies. That’s how we made a mess of ourselves.”

 

Z. Aleksandravičius often has to participate in gatherings of farmers all over Europe and he notices that in most countries people are no longer enthusiastic about these modern technologies. Why? We have given up plowing the soil, chemical plant protection products have become ineffective, because most of them use the same active ingredient. So we have nothing to fight against slugs. “Now we have made one not very wise decision – we have started sowing catch crops,” Z. Aleksandravičius is indignant, “and these are mainly cruciferous plants, in short, cousins ​​of rapeseed, so slugs are happy to gnaw on them too. And they are breeding.”

 

They are already gnawing wheat too

 

The vice-chairman of the Lithuanian Agricultural Farmers’ Union says that some of the rapeseed that was completely gnawed or simply gnawed will definitely not recover in the spring. An even bigger problem is that they have already spread to wheat. What is the solution? “It is time to say goodbye to the plow,” says a farmer from the Kupiškis district. “This is the only medicine that can save us from the slug invasion. The climate is changing, there are new pests that have never been seen before, new grasses that no amount of chemistry can eradicate. No one is saying that we need to completely abandon no-till farming, but at least every few years the soil needs to be plowed.”

 

Z. Aleksandravičius regrets that such reckless agitation to engage in direct sowing affects many farmers, especially young ones. Many have their own interests in such agitation, and there are few competent agricultural scientists in Lithuania who could boldly and reasonedly express a different opinion.

 

The interlocutor does not think that the predicted cold winter would help either - even if the forecasts are confirmed, invasive (Spanish or large) slugs will not disappear due to the cold. Especially since every farm has straw and grass residues where they can successfully overwinter.

 

The forecasts are poor

 

The farmer from the Kupiškis district is also supported by Saulius Stirna, who works on hundreds of hectares in the territories of the Elektrėnai and Kaišiadorys districts. “This problem came to Lithuania and to the whole of Europe with no-till agriculture. When it appeared, slugs also appeared,” says the chairman of the Elektrėnai and Kaišiadorys branch of the Lithuanian Agricultural Society. “In traditional agriculture, when plowing, using a plow, there are definitely fewer of them. Science should offer more effective means to destroy these pests. Now the means are very expensive, and their efficiency is very low.”

 

S. Stirna says that slugs have been attacking crops for several years, but their number is increasing every year. There are regions where they have been breeding in crops for several years. “Our farm has also suffered, but we are trying to apply mixed tillage, so there are fewer slugs. We only sow on at least minimally cultivated land. And those who only use stubble sowing face problems.”

 

The interlocutor says that slugs have already reached cereals, so in order to avoid such a full-scale influx, there will be nothing left but close proximity. "When you plow, you cover the ground with both mice and slugs. That way they die. Otherwise, they breed under the straw. They need a moist environment, and this year the climate is favorable, the season is humid. A cold winter will not help," S. Stirna is convinced. "They adapt, like, for example, earthworms and mice, which burrow into the ground in winter. I don't believe that the cold will exterminate them. Maybe, but if there are severe frosts and there is no snow, the number of slugs will decrease, but the crops will also freeze, and if there is snow, the crops will survive the winter well, but the slugs will not disappear either." According to the farmer, the crops will hardly recover after the slug invasion. After all, the very youngest first leaves were gnawed.

 

When products with the same active ingredient are constantly used, they cease to be effective.

 

The climate is constantly warming

 

The head of the Plant Pathology and Protection Department of the Institute of Agriculture of the Lithuanian Agricultural and Forestry Sciences Centre (LAMMC ŽI), a senior researcher, Dr. Roma Semaškienė says that the climate that has been warming in recent decades and longer autumn periods have had a significant impact on agriculture, which is especially affecting agricultural plants.

 

“Indeed, this year there are more slugs in rapeseed crops than ever before, as well as aphids that transmit diseases,” says the scientist. “Not only farmers, but also owners of private gardens and orchards are noticing the problems,” shares Dr. R. Semaškienė. “How to solve them? There is a tendency to use chemical plant protection products as little as possible, but we cannot manage only with biological ones, which are very few or not available on the market at all. Inevitably, we have to use chemicals, but we need to do this very rationally, following the recommendations of manufacturers and specialists so that there is not too much.”

 

According to the specialist, invasive slugs are a cause for concern because they are already everywhere – in crops, parks, and private estates. They are difficult to eradicate. “The impact of the cold winter might have been there if the cold had been like it used to be in Lithuania, and such cold winters were constant. I think there would be fewer slugs and aphids,” Dr. R. Semaškienė is convinced. “The climate is warming, and there is usually more humidity at the end of summer, which is good for plants, but also good for pests.”

 

True, the interviewee says that not only were the winters colder in the past, but also the chemicals were stronger. It wasn’t necessarily right, maybe it was too strong, but farmers used it. Now, fortunately, the requirements for chemical protection measures are very strict, so we need to look for other ways to manage with the existing ones in order to achieve a good result. Unfortunately, there is a lack of diversity in active ingredients.

 

Outlook: Some of the damaged rapeseed crops may not even survive the spring.

 

Plowing would help

 

Farmers are now joking that they should only pick slugs by hand, as this is the most reliable way to protect crops, because chemicals don't really work, and how much of it would be needed for hundreds of hectares? However, representatives of traditional agriculture face this slug problem less. Is it true that, according to the scientist, sustainable agriculture creates the conditions for such an uncontrolled influx of pests?

 

“I recently had to participate in a discussion about whether no-till agriculture creates favorable conditions for pests. Ploughing, tillage, and other technologies would help solve the problem,” says Dr. R. Semaškienė. “The worst thing is that a lot of things are done in our country without thinking carefully, and if no-till is already in fashion, we give in to it. But everything needs to be decided very carefully. After all, you can’t pick slugs by hand if you have not one, but tens or hundreds of hectares. The saddest thing is that sometimes even the recommendations for pest control in no-till agriculture include, for example, that you can use lactic acid to kill them. But is this rational on hundreds of hectares?”

 

The farmer has to decide

 

“The problem of crop protection needs to be addressed in a comprehensive manner,” the LAMMC ŽI specialist is convinced. “If it is not possible to work the land, plow it, we have to use chemical means. It seems that there are quite a few of them, but the active substances are still the same. When products with the same active substance are constantly used, they cease to be effective. Here we could compare it to antibiotics for humans: specialists warn that they should not be used unnecessarily, because over time they will cease to be effective. This happened with pesticides containing the same active substance. I had to look into it – there are about twelve plant protection products with the same active substance, which means we are greatly increasing the risk of resistance.”

 

We have promoted non-agricultural agriculture as extremely beneficial for the soil, nature, plants, and food, but if we fail to eradicate pests, if they will destroy crops even more in the long run, what next? The scientist says that there is no one recipe for everyone. Farmers, having gone to their fields, must feel whether the time for harvesting is approaching, or whether it is still possible to use conservation technologies. Nothing can be predicted in advance, decisions must be made here and now. A valuable provision for biodiversity, but it is necessary to check whether harmful organisms are also preserved in the soil. They can overwinter in plants. And some harmful organisms die during plowing, for example, ergot.

 

Do not choose the same tools

 

Dr. R. Semaškienė says that rapeseed tends to recover, but if more negative factors appear, poor wintering of crops also contributes to the devastation of slugs, they may not recover. Slugs thin out crops.

 

Unconditional no-till agriculture can lead to another end, so at least occasionally it is necessary to move the soil. After all, even in a small plot, we try to at least move it with a shovel to stir up organisms, especially pests.

 

We asked the specialist what the prospects are for protection products with a wider range of active ingredients? “The requirements for the registration of protection products have become much stricter, and as a result, the number of active ingredients has also decreased. Registrants often do not register them due to their negative impact on the environment and people,” says Dr. R. Semaškienė. “Lithuania is among those countries where stricter requirements apply. Therefore, I would advise farmers not to constantly choose products with the same active ingredient when buying, then the benefits will be greater.”

 

A problem throughout Lithuania

 

The problem in sliuzai crops was also recorded by the crop consultants of the Lithuanian Agricultural Advisory Service (LŽŪKT), who monitored the situation throughout Lithuania. For example, LŽŪKT crop production consultant Asta Kiminienė, after observing crops in the Akmenė district, stated: “Although it is often stated that the slug problem is typical of direct-seeded fields, this year the situation is different – ​​due to the rainy and cool season, slugs have created extremely favorable conditions for reproduction and spread. They have severely damaged rapeseed crops on surrounding farms as well.”

 

Kaišiadorys district consultant Snieguolė Sarapinienė also noticed the abundance of slugs in the fields: “As soon as you enter the rapeseed crop under observation, you immediately see the slug problem. The most damage is on the edges of the field, where the leaves of the plants are severely gnawed in places. Upon inspection, slugs of various sizes were found, and as you move towards the middle of the field, the damage decreases. The farmer tried to control them – he scattered granules on the edges, but this was not enough. Slugs are extremely resistant – they feed at temperatures of just 1–2 °C and can withstand frosts of up to 8 °C. The most dangerous period is up to the 4-leaf stage, when these pests can completely destroy the plants.”

 

Jurbarkas district consultant Jurgita Ališauskienė wrote in her report: “This year, farmers in Jurbarkas district faced several challenges – excess soil moisture and an abundance of pests: slugs, mealybugs, hidden beetles and other pests. Damages were also recorded in the monitored crop: aphids – 5 percent, mealybugs – 55 percent, root hidden beetles – 10 percent, cabbage moth – 10 percent.”

 

So, not only slugs, but also other pests and diseases plagued the crops. It is obvious that, as the climate warms, specialists and representatives of responsible institutions will have to rewrite the lists of protective measures and increase their diversity. After all, it is better to use a variety of measures, and not the same, but stronger or larger amounts.”