The Swedish Agency for Agriculture's inventories and follow-up of ongoing cases of the root gall nematodes Meloidogyne chitwoodi and Meloidogyne fallax show that suspicions of root gall nematodes can be ruled out in some cases and two new cases are confirmed.
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Both of the new cases are in Skåne. Currently, 16 growers are affected.
Earlier this spring, the Swedish Agricultural Agency reported on suspicions that root gall nematodes affected a potato field on an experimental farm outside Kristianstad.
After a discovery of root gall nematodes in a sample taken by the experimental farm themselves, the Swedish Agency for Agriculture decided on plant protection measures for the field and continued to work with mapping and more sampling.
The results show no occurrence of root gall nematodes, which means that the Swedish Agency for Agriculture has canceled all measures.
"The experimental farm acted in an exemplary manner with an early notification," says Carin Bunnvik, head of unit at the Swedish Agricultural Agency's plant regulation unit.
"The measures are burdensome, but it can be absolutely decisive for effective control and reduced risk of spread that we can put in place early measures. Therefore, in some cases, it is also justified to act on suspicion, even if we later have to cancel the measures."
The measures to control root gall nematodes are extensive and mostly consist of excluding root gall nematode host plants, such as potatoes and carrots, to starve out the nematodes.
The strongest measures are taken in the first year with intensive weed control and by setting the entire fields fallow, that is, no crops may be grown.
In the following years, the measures are adapted based on the results that follow-up sampling shows. In most cases, this means gradual relief for affected growers.
Other reported suspicions have concerned already harvested potatoes. There, too, temporary measures have been taken which could then be lifted when the suspicions were written off.
In 2023, the Swedish Agency for Agriculture will also take close to 200 soil samples and examine close to 300 samples of potato tubers to inventory for root gall nematodes.
The samples are taken in connection with potato cultivation that will become food potatoes, starch or seed potatoes. In the 2023 inventory, a new case in Skåne has so far been discovered.
The root gall nematodes have previously been found in a few places in Skåne and Blekinge and in isolated places in Halland and Västra Götaland.
The Swedish Agency for Agriculture has previously reported that the follow-up of the cases shows good results from the strategy, but that it is both demanding and takes time. For one of the first fields to be attacked by root gall nematodes in 2017, all restrictions have been lifted.
In the follow-up of one of the latter cases, a wider tracing work has been carried out. There, the results so far show that one more company in Skåne has been affected.
The root gall nematodes are very small roundworms that are listed as quarantine pests in the EU and must be handled according to the Plant Protection Act.
This means that they must be fought with the goal of extinction.
They are spread, among other things, by soil and seed. For potato growers, it is important to use healthy seed, to reduce the risk of being affected. This applies to both growers with commercial activities and recreational growers.
To reduce the risks of multiplication and spread of root gall nematodes, growers should think risk-aware when sharing machinery and planning their crop rotation.
In order for the measures not to discourage anyone from reporting suspicions of quarantine pests, there is a compensation system.
"We often encounter a great deal of commitment to fight the quarantine pests, but we can only give compensation based on the measures decided by the Swedish Board of Agriculture. Therefore, it is important that we have a good dialogue with the companies and a consensus on the best measures," says Bunnvik. ■