For more than a year, the ban on dimethoate, a pesticide used against various pests on many crops, has been approved. The ban in Europe comes into force this July 2020 having to look for alternatives to pests such as the olive fly in Spain, which is one of the main agricultural products of the country.
BRIEF INTRODUCTORY REFLECTION
The so-called “modern” agriculture cannot survive without the use of phytosanitary products. The tight margins that farmers achieve due to market and government pressure , fuel costs, labor and hundreds of other factors, mean that the yields per hectare of each crop must be optimized more and more . And feeding so many people is a difficult farming model to manage if not with these agricultural practices.
As we always say in Gardenprue, an individual garden (who may have it) cannot be extrapolated to intensive cultivation. A garden does not give us toooooooo every day fresh products in abundance in supermarkets and stores at any time we want. The success of the current food chain . That is a fact, not an opinion and we must face it as such or return to the individual subsistence model (who can, of course).
Although society is making an effort to alleviate the effects of phytosanitary products (which are a few), we are taking steps little by little to control their use, limit doses, and prohibit those that are shown to be harmful to biodiversity, human health. and rest of animals, contamination of aquifers and a long etcetera.
SOME PESTICIDES AND POLLINATORS
The fight against certain pests using phytosanitary products is something that we cannot ignore in modern agriculture. But it is true that for years the damage that some of these products can do to some ecosystems has been demonstrated.
For this reason, many organizations and governments are calling for the elimination of some of these products , including, as we will now see, dimethoate. We must look for alternatives because pollinators, being the bees the banner of this group of insects, have been diminished as a result of the use of these products.
In addition, it is good to ban certain products and give way to others so that pests do not become resistant by abuse of one or a few products.
WHAT IS DIMETHOATE?
Dimethoate is an organophosphate compound that acts systemically or by contact against grasshoppers, thrips, aphids and especially whiteflies of many crops, including the olive tree, but also: apple, corn, orange, melon, pear, walnut, soybean, tomato, wheat, watermelon, alfalfa, grape, tobacco….
THE DIMETHOATE PROBLEM AND BEES
The danger of some chemical synthesis phytosanitary products to the world population of bees has been known for a few years . The toxicity of many of them destroys them, depletes their populations and they are not able to survive as a group. But the most dangerous thing is that the same bees that are destroyed by pesticides are the same ones that pollinate many of the crops we plant. So the damage is twofold .
Dimethoate is one of those really toxic products for bees and the unfortunate thing is that it is not something that has been known recently. There are already studies like this one from 1984 in which its mortality rate and the residue that remains in lemon blossoms are studied days after the application of the treatment.
We have been using this phytosanitary for a long time and the alarm of the decrease in the population of bees has led us to greatly control its use and finally ban it.
IT IS IMPORTANT TO DIFFERENTIATE THE HONEY BEE FROM THE WILD ONE
Whenever the impact of pesticides on bees comes to mind, we only remember the honey bee . But the truth is that in these cases we have to remember more about the wild ones. And you will think that there are not many but the truth is that the ratio of wild bees vs honey bees is 1000 to 1.
Apis melifera. Photo by: gbohne
For this reason, the imbalance of ecosystems and the loss of biodiversity can be very pronounced if these small pollinators are ruined by one or the combination of several products to combat pests.
In any case, it is also more than studied that dimethoate affects bees in general, honey and non-honey bees.
DIMETHOATE FOR THE OLIVE FLY.
In Spain, the olive grove is one of the main agricultural crops, which has made us so famous for the exquisite oil we produce. In the article on the cultivation of the olive tree as well as its pruning you will learn more about this tree, maker of our liquid gold: extra virgin olive oil.
The olive fly is one of the main pests that attack the olive tree. Mainly, the egg deposited in the olive hatches during the months of September and October, a period in which the olive is developing its final maturation. The larvae feed on the olive and the olive stem, falling to the ground and getting lost.
The fact that the olive is chopped causes indirect damage such as the attack of bacteria and fungi multiplying the devastating effects on the crop.
In addition, the oil inside it becomes rancid, not achieving the expected quality in the final oil. It will not be an olive suitable for the production of the oil that we know.
Olive fly ( Bactrocera oleae). Photo de: Katja Schulz
ALTERNATIVES TO DIMETHOATE IN THE FIGHT AGAINST THE OLIVE FLY
Oil producers, both in Spain and Europe, have been looking for alternatives to this phytosanitary for some time. In fact, many already saw the ban coming. There are producers concerned about protecting their crops against this dreaded pest.
Ultimately, the mindset is being forced to change. It no longer consists of “throwing some magic powder” and disengaging . Now, the integrated fight, with mixed solutions is going to be the common treatment.
All this leads to rethinking the form of struggle with various control methods, cultural practices, precision agriculture for diagnosis and forecasting, biological struggle, in short, being much more aware of the crop and its controllable variables to predict the less controllable ones.
And this, without a doubt, will inexorably affect prices, whether we want to or not. Extreme vigilance, investment in variable control, diversification of methods requires more cost for the producer.
It is a complicated situation but the final conclusion is that we cannot run out of bees, pollinators are the most necessary even for our own crops.
THE “SNIFF” TRAPS. IT IS NOT A METHOD IN ITSELF, BUT IT HELPS TO IDENTIFY THE STATUS OF THE PEST.
This type of olive fly traps has been used for a long time . They are quite homemade but effective. The name is due to a technician from the Cooperativa Olivarera los Pedroches whose idea it was.
It simply consists of a typically 1.5 liter bottle of water in which 4 holes of about 4 mm are drilled in the upper middle part and inside 4% diammonium phosphate water is placed . This is a nitrogen-based attractant that attracts the fly by falling into the water and drowning.
Trampa olipe. Photo the Wikimedia commons
A yellow band is usually added as it is an attractive color for the fly, increasing the effectiveness of the trap. In addition, the traps should be placed on the south face of the tree, which is where the fly attacks the most (more mature olives).
In addition to eliminating a few flies, it serves mainly as a counting trap every 10-15 days to see the status of the pest and to be able to anticipate complementary treatments.
FROM HERE WE MUST RESORT TO:
If the incidence of the pest is no longer controllable because the count indicates that it is spreading, because there is already more than 1% of the chopped fruit, etc. then we must resort to treatments according to their nature: chemical treatments, cultural practices, biological fight, ecological treatments, etc. but no longer able to use dimethoate in any way.
Cultural practices such as choice of varieties tolerant or resistant (Picual, Manzanillda, Hojiblanca among the best known), varieties of early harvesting or destruction of pupae in late winter left on the floor or remove all olive tree that can attract in the spring following the fly.
Many times these practices cannot be carried out because the variety we have is what it is.
The treatment by patching or also called bait treatment corresponds to the treatments encompassed in the so-called conventional agriculture .
This method consists of a partial treatment application, without covering 100% of the tree or trees. This is achieved by:
- Application by alternate bands in which the solution is applied and others in which it is not. The normal thing is to treat one band and not another, or even treat one band and not two, depending on whether the cultivation is more or less intensive.
- Alternating bait trees that are given a full application and others that are not treated.
- By patching, applying only to a part of the tree, about one or two square meters of the crown.
With this method we only apply with insecticide + attractant in 25% of the farm with the global advantages that this entails such as less water consumption and treatment, less residue on the fruit, less environmental impact, savings in all senses (time, costs , labor), less exposure, greater security etc. etc.
When the olive bitten by the olive fly is greater than 7%, then a total spraying is needed . This application has been carried out with dimethoate, which has been permanently banned as of July of this year.
As we can see, within integrated pest management, there are very marked steps from preventive measures to an inescapable total spraying only in the last resort.
In organic it is possible to combat the olive fly by applying a bacterium that attacks the olive fly. The use of bacteria that parasitize the digestive tract of pest larvae is already well known, studied and contrasted. Do you remember the use of Bacillus Thuringiensis ?, perhaps this is one of the most famous.
For the olive fly, the bacterium Saccharopolyspora spinosa , a bacterium discovered in a soil sample from the Virgin Islands in the 1980s, can be used. This bacterium proved its effectiveness in one of the most feared pests by tomato growers, Tuta Absolute.
The advantage of this treatment is that its low rate of environmental and toxicological impact has been demonstrated, being admitted as an ecological insecticide . Its trade name is Spintor. It is also effective against fruit flies.
This method, together with a massive trapping with olipe traps, can control the olive fly without having to use chemical alternatives to dimethoate.
It is also advisable to undergo preventive treatments with repellants such as those based on copper such as Bordeaux mixture .
There are still no natural predators of the olive fly that have shown true efficacy. Naturally there are, of that there is no doubt, every insect has its natural predator, but they are not voracious enough to consider them an option on their own. They are species such as Psyttalia concolor or Lasiptera berlesiana .
We are faced with a complicated but not impossible challenge. It will be necessary to make sacrifices at the human level, R&D, economic but surely that in the end we will be able to move forward with our appreciated oil without eliminating pollinators.