IOBC/wprs Bulletin Vol. 28(2) 2005

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the Welsh chafer Hoplia philanthus (Fuessly, 1775) and the Garden chafer Phyllopertha
horticola (L., 1758).
As a secondary damage of the infestation of the grubs but more severe for the landscape
is the damage caused by wild pigs leaving at night the forests for rooting and digging up the
grubs to devour them.
To avoid all the damages in the grassland it became necessary to fight the real cause, to
reduce the grubs to a tolerable level.
Materials and methods
Design of the trial
The last cockchafer flight in the Hessenthal-Mespelbrunn valley was in 2003. The treatment
started at the end of April 2004 to fight the second larval stage after the first hibernation.
In the experiment the grubs should be controlled in three different ways: Firstly in a
mechanical way with a rotary hoe/rotary cultivator, secondly with a biological antagonist, the
entomopathogenic fungus Beauveria brongniartii, thirdly by chemical treatments with the
insecticides Imidacloprid and Carbofuran. In table 1 the six different variants are listed. Every
variant besides var. 6 (Imidacloprid, Gasur) was tested in three plots, each plot being of a size
of 25 metres in length and 9 metres in width. Gasur was tested in a long strip of nearly 150 m
length and 3 m width close-by the other plots. On the day of the treatments the grubs were in
a depth of about 2 centimetres.
Table 1. The different variants of the cockchafer control experiment in the Spessart region Hessenthal-
Mespelbrunn
Var. Variant Concentration (+) milling way of control
1 Untreated control --- no none (natural)
2 Rotary hoe/cultivator --- yes mechanical
3 Beauveria fungus 50 kg/ha no biological
4 Carbofuran (Carbosip) 10 kg/ha yes chem. + mech.
5 Imidacloprid (Confidor) 0,15 kg/ha yes chem. + mech.
6 Imidacloprid (Gasur) 100 ml/100 kg/ha no chemical
In the untreated control only the natural decrease of the grubs’ population caused by
predators, bacterial or fungal diseases could be observed. The Beauveria fungus was applied
in the form of Melocont ® -Pilzgerste. The kernels were brought into the soil by using a special
slit seedling machine. The same seedling machine was used to disperse evenly Imidacloprid
in the Gasur form. In these three variants the turf was not milled.
To apply both Carbofuran and Imidacloprid in the Confidor form into the soil a rotary
cultivator was used. The same rotary hoe was used for milling the mechanically treated plots
to fling up the grubs to the daylight, where they died because of ultraviolet radiation or being
killed of birds. As in the last three variants the turf was completely destroyed after the
treatments the grass has to be reseeded.
For measuring the efficacy of a certain treatment the number of the grubs, the healthy
ones and the fungal infected ones, in the different plots were counted and the results were
compared with the untreated variant. In using a so-called Goettinger frame four times a square
metre of the sod was digged up in every plot and the soil was searched for grubs.