Pests| Garden chafer (Phyllopertha horticola) | Pests main menu |
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Adult garden chafers (Phyllopertha horticola) are 8-12 mm long and have red-brown slightly hairy wings with a dark edge. The neck shield is metallic green to shiny black. They appear depending from season to season in the months of May and June, therefore they are easily confused with june beetles. During the first night that the adults are active, mating takes place. That same night the females crawl in the ground and dig to a depth of 10 to 25 cm to deposit their eggs. Approximately 85 % of the eggs are laid during the first night. After the first batch, they fly out in the late morning. The typical low flights right above the grass surface are very characteristic for the garden chafer. During the flight they feed for three weeks on buds and leaves of different broad-leaved cultures. This is called the period of ripening damage which is followed by a second session of egg laying. It can take place in a 3 to 4 km zone around the area of initial egg laying. When the flights get noticed, most of the eggs are already laid. This and the dispersal of adult beetles has the consequence that chemical control against adult garden chafers is impossible. 3 to 6 weeks after the first generation the first larvae appear. These have a brown head and a beige-white body. The young beetle larvae, also called white grubs, immediately begin to nourish themselves with humus-like material. During the second larval stage, they eat root hairs and when they reach the third stage they eat the roots of the lawn and other plants. This way the plant's moisture becomes strongly decreased and the damaged plants eventually die. The life span of the larval stages is 1 year while for other beetle larvae of the same family, like the summer chafer and the cockchafer, it could take respectively 2 and 4 years time. The larvae keep feeding until mid October. As soon as the temperature begins to drop in autumn, most of the larvae move deeper in the soil to hibernate. If the temperature increases in spring, the white grubs pupate in April and from May they reappear as adult garden chafers.
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In the period between July and September the damage can be so severe that entire parts of the lawn die. A well-trained eye can already recognize the place where the grubs are situated by the colour of the grass (less fresh, yellow/brown blades). From July it is obvious that the grass does not grow well on the infected places. It is not uncommon that with a heavy infestation, the turfs are so damaged that they come loose and it is possible to roll them up. Under the turf you find a mass of grubs, sometimes up to 100.
When the grass endures a heavy drought period now as well, these severely damaged areas can completely scorch and die. In addition these grubs are the favoured food of moles skunks and several bird species. The presence of these animals can lead to secondary damage in the grass field.
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