Symptoms
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Plants stunted, needles reduced in size, crowns or crown parts dull green, adventitious shoots; plants can be easily pulled out. Roots, initially mainly the fine roots, are damaged by localized feeding or by peeling; larvae of Curculionids are able to girdle fine roots, but never bite through the whole root; cockchafers (grubs), however, are able to bite through. The finest roots are mostly eaten totally.
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Impact
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Older plants commonly withstand even more intense feeding damage. In forest nurseries, young plants can be killed following epidemical propagation. A clear diagnosis often requires work on the site, but, depending on the season, it is necessary to dig into the soil up to 1m in order to find the larvae. Very common are cockchafer grubs, larvae of other Chrysomelidae, Elateridae or some weevils.
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Control
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Carefull change of soil and/or disinfection of the soil with insecticides in nurseries (see official register of Plant Protection). Some of these pests can be controlled by use of biological compounds (microfungi against grubs, nematodes against some weevils), but certain temperatures and degrees of moisture have to be regarded. For plants in pots or buckets the sampling of larvae is recommended.
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Hosts |
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Maple;
All tree species;
Apple;
Birch;
Pear;
Beech;
Boxelder;
Douglas fir;
European mountain ash;
Edible chestnut;
English ivy;
Yew;
Oak;
Wild service tree;
Alder;
Ash;
Ex-Robinia;
Serviceberry;
Spruce;
Lilac;
Forsythia ;
Framire;
Ginkgo;
Tree-of-heaven;
European Hornbeam;
Dogwood;
Hazel;
Hemlock;
Elder;
Hophornbeam;
Pine;
Cherry;
Buckthorn;
Larch;
Thuja;
Privet;
Linden, Lime;
Magnolia;
Redwood;
Giant sequoia;
Mulberry;
Common whitebeam;
Common medlar;
Cotoneaster;
Olive tree;
Poplar;
Bladdernut;
Plane;
Rhododendron;
Leyland cypress;
Rose;
Horse chestnut;
False Cypress;
Japanese Pagoda tree;
Spindle;
Holly;
Fir;
Southern Catalpa;
Elm;
Juniper;
Walnut;
Willow;
Common grape wine;
Hawthorne;
Cedar;
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Affected plant parts
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Root;
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