Manage curculio nucum in hazelnut orchards

Nötviveln (weevils nuts) is generally considered to be the worst pest in commercial nötodlingar and is the main reason for the use of pesticides in nötodlingar worldwide. Also in southern Sweden seems to be a bit of a nuisance and many farmers I have been in contact with the south complain of major attacks on their bushes. To understand what we can do about nötviveln it is good to know about its ecology [1, 7].

year garden book 2018!

Nötvivelns ecology

Nötviveln overwinter as mature larvae in the soil under the hazel bushes. In the spring the larvae pupate and develop into adult beetles. These are the right sluggish and needs at least 16 degree air temperature for hurricane move, which can be an advantage for us northern hazelnut growers. Nötvivelns inertia may be why nötviveln so far does not seem to occur north of Upland. Only when it's over around 20 degrees can fly nötviveln. Det verkar som de vuxna skalbaggarna sällan kommer igång förrän i juni. Early in the season eating weevil hazel flowers, if temperatures allow the. Then it starts eating the young nuts. The nuts as the weevil eats the early season will be stunted and brown. A little later in the season leading vivelns feasting to almost black and hollow nuts. Both fall to the ground before they normally developed the nuts are ripe och dessa behöver man inte samla in.

Nötvivel, weevils nuts
This is what the adult nötviveln out. Photo: @entomart, Wikimedia Commons.

after mating, which usually takes place in July in our climate, begins the females lay eggs in the nuts. Females creates small holes with their long munverktyg and lays an egg in each beef. Det karakteristiska hålet i skalet uppstår när den fullt utvecklade larven tuggar sig igenom nötens skal ungefär 4-5 weeks later. When it comes out of its hole releases the go and burrow into the ground, built a hard cocoon, waiting out the long winter of the cycle will continue. Most nötvivlarna dig down to a depth of 20-30 cm, some even down to 40 cm, and only 5 percent fall in the top 10 cm of soil. To be able to dig down larvae need moist and loose soil [5].

fight curculio nucum

Based nötvivelns ecology, it seems reasonable to give the larvae in the soil, immobile for much of the year and next, and under the bushes. In conventional commercial plantations, it is still common to spray in the spring and early summer with pesticides to kill the mature beetles. As a more environmentally friendly alternative to fighting is used both nematodes and fungi. A kind of nematode that has proven to work well, Heterorhabditis bacteriophora which significantly reduces the number of caterpillars that develop in spring [5]. Also, the soil-dwelling fungus Beauveria bassiana seems to be very effective against nötvivellarverna. For it to have the desired effect needs to Earth where the larvae can be expected to be thoroughly watered with a preparation of this fungus. 99,5 percent of the larvae died after treatment with Beauveria bassiana in a scientific experiment conducted in Italy [4].

Personally, I have a little hard for such preparations, even if they are biological and harmless. In permakulturkretsar often talks about chickens would help to keep in check nötvivlar by placing them among nötbuskarna in August-September, when the larvae crawl out of the nuts. It could be very possible that it works, but it is no variation in the biological control of nötviveln as humanly appears to be explored in the literature. Given that the larvae dig down so deep that they do is also the question of how many larvae hens can get before they disappear into the ground deep as the hens can not reach. However, it can not hurt to let out the hens among the hazel bushes in the spring when the beetles just being hatched [3]. Although various soil beetles may have nötvivellarver as food [9]. To create good conditions for the populations of beneficial insects is always a good idea in the forest garden and can thus therefore also help with nötviveln.

Chicken apple silvopasture
Höns kan eventuellt hjälpa med att hålla nötviveln i schack.

I could imagine it in the small scale also can work with tarpaulins posted in the hazel bushes when the larvae begin to crawl out of the nuts. When they fall down on the tarpaulin and become easy prey for various predators (or hens). Furthermore, the ground is kept under the tarpaulin dry, which should make it more difficult for the larvae that still manages to get past the tarpaulin to drill into the earth.

resistant varieties

Another strategy to prevent attacks by curculio nucum can be to plant varieties nötviveln not like. It seems that'skalets thickness, hardness and how quickly, that is, early in the season, shell begins to harden, the main factors that affect how large the attacks of curculio nucum becomes [2, 8]. Since nötviveln get started quite late in the season, the varieties of which the skin hardens quickly then a big advantage. And the shell is too hard and thick towards the end of the season it will be difficult for the vivellarverna to chew out the nuts. Varieties of field trials has been shown to be resistant to curculio nucum is: 'Camponica', 'Halle'sche giant Sap, 'Nocchione', 'Tonda di Giffoni' och 'Tonda Gentile delle Langhe'. All these can be grown without the need for pesticides, even in areas where nötvivelpopulationen is very large [8]. For me it is very gratifying to see that 'Halle'sche Riesennuss' are among the most resistant varieties, since it also has proven to be the best variety purely in terms of production in our farms. 'Cosford' that we also have a number of larger specimens of, however, has proven to be the most susceptible variety in several studies, where more than a quarter of the nuts were infested curculio nucum.

Halle'sche Riesennuss, Hall's Giant, Merveille de Bollwiller
Den gamla sorten ‘Halle’sche Riesennussär en av de mest motståndskraftiga mot nötvivel och är dessutom härdig och relativt högavkastande.

The resistant varieties 'Nocchione', 'Tonda di Giffoni' and 'Tonda Gentile delle Langhe' bloom all very early [6], so the question is whether they are suitable to grow in our climate. The variety 'Camponica' I have not been able to find much information about. Om någon odlar dessa italienska sorter i Norden skulle jag bli mycket intresserad av att få ta del av erfarenheterna med dem.

References

[1] pale, I. and C. Tuncer. Biological control and morphological studies on nut weevil (Weevils nuts 50. Col., Curculionidae). in VI International Congress on Hazelnut 686. 2004.
[2] Guy, L., N. Valentini, L. role, G. Me, and L. Tavella, Early nut development as a resistance factor to the attacks of Curculio nucum (Coleoptera: Curculionidae). Annals of applied biology, 150(3): p. 323-329, 2007.
[3] Nylinder, B., Nötodling southern Sweden – with focus on hazel, 2013.
[4] Paparatti, B. and S. Hope. Biological control of hazelnut weevil (L. nut weevils, Coleoptera, Curculionidae) using the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill.(Deuteromycotina, Hyphomycetes). in VI International Congress on Hazelnut 686. 2004.
[5] Peters, A., J. Sarraquigne, B. Blum, and S. Kuske, Control of the hazelnut borer, weevils nuts, with entomopathogenic nematodes. IOBC WPRS BULLETIN, 30(1): p. 73, 2007.
[6] Solar, A. and F. Printing, Characterisation of selected hazelnut cultivars: phenology, growing and yielding capacity, market quality and nutraceutical value. Journal of the Science of Food and Agriculture, 91(7): p. 1205-1212, 2011.
[7] Tuncer, C. and O. Ecevit. Current status of hazelnut pests in Turkey. in IV International Symposium on Hazelnut 445. 1996.
[8] Valentini, N., S.T. Moraglio, L.G.C. role, L. Tavella, and R. Botta, Nut and kernel growth and shell hardening in eighteen hazelnut cultivars (Corylus avellana L.). 2015.
[9]  Walton, V.M., The. Chambers, and J.L. Olsen, Hazelnut pest and beneficial insects: an identification guide. 2009.

4 thoughts on “Manage curculio nucum in hazelnut orchards”

  • Hi!
    I only have a few shrubs, but can share my observations. We had about 20% nötvivel 2016, 10% 2018 and max 1% 2019. It also varies greatly between years. 'Hall Fritzsche giant’ and 'Webb Cob'. Completely without giftspruteri.

    This is a terraced garden in the Netherlands, with plenty of small birds and squirrels but. (But the mice stole enough 100 nuts found urätna under the woodpile when the wood was uppeldad…)
    It will be interesting to see how it looks next year!

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