Mmaize farmers in the Rhine Valley have known about crow and fritfly infestation for years. For a long time, they were able to protect their stocks from this with the tried-and-tested seed dressing Mesurol (active ingredient: methiocarb).
But since the discontinuation of this highly effective dressing in April 2020 and at the same time the fungicidal dressing TMTD (active ingredient Thiram), which had a side effect against bird damage, the damage has increased significantly. “In the Ortenau district alone, we recorded damage from crows and frit flies on around 1,000 hectares last year. In some cases there was a total failure," reports crop cultivation consultant Volker Heitz from the agricultural office in the district of Ortenau.
According to Dr. Hubert Sprich from ZG Raiffeisen especially the early sowing until mid-April. "I estimate the loss of earnings as a result to be around 10%," says Sprich. In Bavaria, according to Prof. Michael Zellner from the LfL Bayern, damage up to and including total loss occurred above all where there were larger colonies of rookers and pigeons. According to the German Maize Committee (DMK), around 16% of the area under cultivation in Germany was affected by feeding damage, mainly caused by crows. The area infested with frit flies is estimated at around 13%.
APPROVAL FOR KORIT EXPIRES
This situation will probably get worse in the future. Because the only alternative that is currently effective against crows, the product Korit 420 FS with the active ingredient Ziram, has already been counted. Admission ends on April 30, 2021. It is currently unclear how long the use-by period will last.
Practical experience with Korit 420 FS is good. Even if the product, according to Dr. Hubert Sprich shows a lesser effect than Mesurol and varies depending on the bird pressure. Because this dressing is only approved in the EU and not in Germany, some seed suppliers imported seed treated with Korit 420 FS from Austria and France to Germany as early as 2020. Demand for it will probably continue to rise this year.
KWS also imports Korit-treated seeds from neighboring countries, but uses the active ingredient in a special mixture with zinc, manganese, humic acid and a microorganism. The product "Initio Bird Protect" should therefore make the corn plant more stress-tolerant and vital, especially at low temperatures when growth has come to a standstill.
ARE ALTERNATIVES IN SIGHT?
So far, the prospects for effective alternatives to Korit 420 FS have been poor. Dressing tests with biological preparations based on plant extracts were carried out at the Julius Kühn Institute in Münster.
Dr. Alexandra Esther reports on the first results: "In aviaries, they definitely acted as a repellent for crows. In the field, on the other hand, these treatments did not protect the seed from being eaten by crows.” Further research is needed.
Only the first experiences of organic farmerswith a new plant strengthener based on hops from the company Arvalus give hope. The biological dressing "Promos" is intended to protect seed from bird damage and to support the even growth of the young maize plants, especially in wet and cold weather.
Promos is applied like a normal dressing, but preferably several weeks before sowing. "The corn row with untreated seed was gone, the ones with Promos-treated seed left the crows standing," reports farmer Leonhard Birle from Dinkelscherben. He grows organic corn on 5 to 10 ha every year.
His colleague Reinhold Mang from Fischach confirms: "In the neighboring field there was a total loss of half a hectare in 2020, but my corn remained undamaged." He has been using Promos for two years. In the first year, however, the result was sobering: "After a rainy period with 100 ml of rain, the stain was washed off." Mang has also experimented with chili powder, without success. In the meantime, Arvalus has changed the formulation so that the stain adheres better. And there are limits to the effectiveness even when it is cold: "Because these are natural substances, the agent can then become inactive and no longer work as well," explains Managing Director Christian Matthesius on request.
The companies want to stick with it, even if the price of promos is decent at €30.90 per unit of 50,000 grains. "For me it's more expensive not to pickle because the problem with crow feeding is increasing," says organic farmer Stefan Wild from Hurlach. He has been using the dressing for three years on 10 to 15 hectares and before that he often had total failures due to crows. "It doesn't get that far anymore."
NO STAIN AGAINST FRITTIES
On the other hand, there is already no longer any effective dressing against fritfly infestation. "In 2021, practitioners will therefore probably have no choice but to apply an insecticide with the herbicide treatment in the spring in the event of an infestation that is worth combating," Sprich suspects. The three insecticides Karate Zeon, Kaiso Sorbie and Hunter, all with the active ingredient lambda-cyhalothrin, are approved for this purpose. “We urgently need Fritfly monitoring and more tests on this problem. Because the topic is burning,” says Sprich.
Silvia Lehnert - Top Agrar