Moreno Greatti explains how pneumatic sowing machines produce a fine dust by causing abrasions on the coating of rougher, uneven maize seeds, with allegedly disastrous effects on bees. (May '09)
Dr. Moreno Greatti, from the Department of Plant Biology and Protection at the University of Udine in Italy, is the author of a pivotal study on the dispersion of seed coating particles containing neonicotinoids into the air and along field borders during maize sowing. He has shown that pneumatic sowing machines produce a fine dust by causing abrasions on the coating of rougher, uneven maize seeds, with allegedly disastrous effects on bees.
Do you think your research may have steered the Italian government towards the ban?
My research may well have weighed in with the decision, however it was taken on board quite late, since I carried it out back in 2001-2002. Bees are exceptional monitor insects, and signal anything that is going wrong in the environment immediately. We first realized that something was wrong with maize sowing, precisely because bees were dying, back in 1999. It took Germany a much shorter time to introduce their ban since they noticed a big collapse in bee numbers.
What are the effects of neonicotinoid dispersion during maize sowing?
This dust has a fallout on vegetation along the field borders. Bees fly on to grass and flowers to gather nectar, pollen and morning dew and become poisoned. These active substances are extremely deceptive because they are neurotoxic and do not cause mass mortality outside apiaries. Bees basically go mad and become lost; or, if they manage to find their way back home, do not communicate with the other bees any more.
How do neonicotinoids work?
They are systemic products, in that they are absorbed by the plant and leaves, or by the roots, as in the case of sowing, and remain inside the plant, in the lymph. They are highly soluble in water. In maize plants, according to our studies, they last up to 85 days since sowing time.
There is a big argument according to which it is mainly the fault of pesticides in general if bees die.
Bee collapse has several causes, and agriculture is one of them, although probably a disease such as varroa takes an even higher toll. Then there are these new viruses, which have arrived from the Far East and are damaging our honey bees. Bees have, in this sense, become globalized, too. Their immune system might be weakened by diseases, but also by sublethal doses of pesticides. It is very difficult to tell how big the impact of pesticides is, because it varies according to the area.
What is the human safety record of neonicotinoids?
The point is, these neonicotinoids are extremely persistent. In the soil, they last half a year at least; in certain cases, some of them may even last over a year. They last long in the plant, too. But treatment is done several months before harvest, so there shouldn’t be any residue problems. Besides, in Italy any treatment during blossoming is forbidden by law. However, nobody seems to have given second thought about farmers’ overexposure to neonicotinoid dust during sowing with coated maize seeds.
Do you think seed coating with neonicotinoids should be banned altogether?
Nothing justifies coating maize seeds, really. It makes no sense. Some researchers from the University of Padua in Italy have carried out a five-year study showing that coating maize seeds have no positive effect on plants. This appears to be the case in a typical single crop system, for instance, where certain insects cannot develop as they would within a crop rotation system. On the contrary, coating beetroot and potato seeds can be very useful and causes no harm to bees.
What about bees sucking dew contaminated with neonicotinoids?
Professor Vincenzo Girolami from the University of Padua carried out a yet unpublished, wonderful study about the devastating effects on bees of neonicotinoids being exuded by maize leaves. It shows that a bee sucking this poisoned dew drops dead on the spot within 20 seconds flat. Long-leaved plants exude tiny droplets of water in the morning. Well, Professor Girolami grew plants from neonicotinoid-coated maize seeds and observed that the concentration of these active substances in the dew is comparable with the pesticide solutions that are used to treat orchards. Bees are basically sucking concentrated poison. This effect would obviously persist even if the industry found a way of enclosing maize seeds within a smooth, biodegradable plastic coating, which would at least eliminate dispersion during sowing, though.
Should honeybees become a protected species?
I would just like to remark that, were it not for beekeepers, bees would have already been extinct by now.
(1 June 2009)