Garden Chafer(Phyllopertha horticola)
The adults are 8-12 mm long and quite harmless.(Phyllopertha horticola)
Foto: Magnus Gammelgaard
The larvae are, when they appear underneath the grass carpet in great numbers, much more harmful. (Phyllopertha horticola)
Foto: Clemson University - USDA Cooperative Extension Slide Series, , www.forestryimages.org
The use of nematodes is today a very common method for controlling the garden Schafer.
Insect pathogenic nematodes are very small microscopic worms. They are in nature to be found in the soil. The nematodes penetrate the larvae of the garden Schafer, multiply and at last the larvae dies. To get good results, it is very important to follow the guidelines distributed along with the product.
It should be mentioned that latest conclusions in trial reports from Denmark concerning nematodes for controlling garden Schafer, not have been very convincing. Using nematodes for controlling larvae of vine weevil has been much more successfully.
Reports from the latest years have shown that garden Schafer in lawns and golf courses has been a rising problem.
If it is caused by higher level of attack/number of weevils, greater lawns at houses or on golf courses, or the mild winters, is difficult to determinate. It is just bad to see a quite new lawn to be eaten from below.
The beetles belongs to the Family Scarabaeidae, which also includes some of the largest beetles in Denmark (may-bug's, Rhinoceros Beetle,....)
The beetle is not so large as those species previous mentioned, 8-10 mm long. The wings are reed brown, slightly hairy, with a dark edging.
The back of the head is metallic, shining black.
The beetles can bee observed in May-June. The males and females swarm just above the grass level to mate. The first night after mating the females dig themselves 10 to 25 cm into the soil where they are placing 85 % of their eggs.
The following morning the beetle's flies further just above grass level. During the next 3 weeks the rest of the eggs are laid from a distance of 3-4 km from the starting place. When the beetles first are observed they often have laid the main part of their eggs.
After 3-4 weeks the first larvae hatches and immediately begins to eat up the small root hairs. When they reaches the 3. Larvae instars, they are capable to consume large grass roots and now, the damage is serious.
The larvae are typical C-shaped, 5- 20 cm long, white pale, with a brown head and dark abdomen. The larvae have 3 pair of legs.
The duration of the developing time is shorter than for many of the other family members like maybugs and Rhinoceros Beetle's. It only takes one year a generation. For the maybugs I takes 4 years.
As mentioned the larvae eats from newly hatched to the middle of October. When the soil temperature begins to drop, the dig themselves deeper in the ground and are impossible to reach with any control measures.
The turf is turning yellow. Later big flakes can bee drawn from the lawn, without using much power. A well-trained eye are at an early time, capable to spot where the larvae are to be found, just by the chancing of grass colour. That is very important when you are trying to control the larvae attack without having to treat the whole lawn.
Under the lawn you often can find the larvae in large numbers, up to 100 in a single spot.
Heavy attacks are often to be seen in sandy and porous soils. There are a lot of reports from the western part of Jutland. The larvae are doing best in sandy soils especially if they are also dry. An old advice has therefore been to use a roller for making the ground more compact. An ordinary garden roller filled up with water is perhaps to light. Better it is with a homebuilt one with concrete, but it needs more pulling!
Mixing a large amount of sand in the soil before sowing is not a good idea if you live in an area with reported problems with garden Schafer. On the other hand it is recommended to add a few centimetres of compost to the lawn every year. After some years the amount of humus in the soil will rise.
Covering the surface of the lawn with net can be done if the lawn is at a limited size and should be done when you se the first beetles. The type of net used when growing vegetables can be used.
Merit Turf used on golf courses has been shown to have very good controlling the garden Schafer.
The insecticide Baythion used for controlling ants, are told to have an effect on beetles, but it is not legally approved for this area.
Addresses where you can reed more about the garden Schafer: