Have you noticed that there are few rowan berries this year? At least the rowanberry mill has done that. So the little insect goes for its plan B: Apple trees. – It seems that there is a large attack of rowan berry moth this year. Whether it will be as big as two years ago is too early to say, but it looks scary. Apple growers who operate organically can risk one hundred percent damage. So says researcher at the Norwegian Institute for Bioeconomy (Nibio) Gunnhild Jaastad. Nibio has developed a national warning system for moth attacks, based on information from around 50 stations around the country. In addition, they are working on developing traps with artificial roe smell to combat the pest. Photo: Erling Fløistad / Bioforsk A little tempting table fruit. For more than a hundred years, the blackberry moth has been the most serious insect damage to apples in the Nordic region. They prefer to develop their larvae in roe, but when there is little of it, they turn their eyes to the apples. – The larvae gnaw light brown times inside the apple criss-cross, and in some varieties they can go all the way to the core and eat the seeds, write Geir K. Knudsen and Sverre Kobro in plantevernlexikonet.no. The fruit juice that comes out of the holes dries into a white powder. The result is apples few will find tempting to eat. But they can still be used to make mash or mash. Facts about the blackberry moth The blackberry moth, Argyresthia conjugella, has been the most serious apple pest in the Nordic region since the late 1890s. The only effective measure has been the use of pesticides. Spraying agents are constantly being evaluated when it comes to negative impacts on the environment and users. This creates a great need for new plant control methods, and thus new knowledge about the pests so that new methods for control can be developed. The host plant in Norway is rowan, Sorbus aucuparia, but it is also found in a number of other Sorbus species. Roe can be found in most habitats from fjords to mountains and from south to north. The roe is variable with us, which means that the number of berries will vary from year to year in a fixed pattern. There are usually good berry years at the same time throughout Norway, and probably also in Sweden and Finland. Only when there are few rowan berries does the rowan mill go to work on apples. Infested apples develop a small hole in the skin where the larvae burrowed into. The area around the hole becomes almost black. A little fruit juice trickles out of the hole and dries to a fine powder. In case of strong attacks, there can be many such holes in each apple. The larvae gnaw their way into the apple criss-cross, and in some cases, they can go all the way to the core and feed on the seed. Infested apples can be used for must or sides, but are not very appetizing to eat fresh. In some years rowan berry moth can cause total damage to the crop, but in years with enough berries on the rowan, the apple goes completely free. Source: Nibio The larvae become adults after approximately 2 months. Then they are 7 millimeters long. Photo: Sverre Kobro / Nibio May use pesticides Private individuals are not allowed to use chemical agents against the moth in their garden. Nor is it free for the fruit growers. According to Nibio, it was previously sprayed with arsenic and nicotine, later DDT and finally Gusathion, which is now banned. – Those who do not farm organically have been granted a dispensation to use a pesticide this year. It worked well two years ago, but we won’t know for sure until the apples are harvested, says researcher Jaastad. Those who farm organically do not have much to do against the moth attack. They can use rapeseed oil mixed with soap, but this only works on the eggs. They therefore have to get the timing right and perhaps spray several times, because the eggs are laid over a long period. When the roe in the background has few berries, the roe berry moths resort to the apple tree next door. Photo: Eivind Aabakken / news Also two years ago there were few rowan berries, and thus a ruined apple harvest in several places. Not since 1994 had there been such large-scale attacks – in several fields up to 100 per cent of the crops were damaged. Gunnhild Jaastad says climate change may be a factor. – Higher temperatures have a positive effect on insects; they become more active. And now it looks as if the rowan moth flies – and can thus lay eggs – over a longer period. It can be very problematic for the producers. General manager at Nibio Ullensvang, Gunnhild Jaastad, says we won’t see the full extent of the moth attacks until the harvest. Photo: Privat Also includes private gardens At Inderøy Mosteri in Trøndelag, we get to join general manager Yngve Henriksen on an inspection of the apple orchard. The traces of the rowan berry mill are clear, but not dramatic. – It’s not bad for us, because we can press the apples as long as there are no more than nine to ten holes in them. But there will be some sorting out. Henriksen says he has been contacted by several concerned private garden owners who have been heavily attacked by the moth this summer. – They are primarily wondering what this is. But it is not dangerous in any other way than that this year’s crop is lost. It is not something that “sits down” in your garden. Next year you start from scratch again. – Don’t cut down the rowanberry trees! warns apple grower Yngve Henriksen. It is better that the moth chooses the roe than the apples. Photo: Eivind Aabakken / news – It is not dangerous to drink the juice But it is not only the mill that is to blame if the fruit harvest is bad. A cold summer and thus little pollination is an important factor this year. – During flowering, the bees lay in the hives and slept. With us, four of the apple varieties were not pollinated, and thus there were no apples either, says Yngve Henriksen in Inderøy Mosteri. However, researcher Gunnhild Jaastad has a small consolation: – Even if the apples have holes from larvae, it is fine to make sides and juice. People won’t notice anything about the taste. But I can imagine that this year’s apple juice will be somewhat more protein-rich than usual, she laughs.
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The rognebærmøllen creates trouble for this year’s apple harvest – news Trøndelag
