Adult chafers are not for the garden practically no danger. Main engaged in wrecking their larvae. In some places, they do make it impossible for the cultivation of blackberries, strawberries and other berries. After mating, the female buried in the soil of from 30 to 50 larvae that has significant harm to the soil. The larvae have a very long life, the average of their development takes about 4 years, but can occur and particular species with a 5 year development cycle.
The main cause damage to the larvae by eating the roots of plants and humus, significantly reducing land fertility. Soil with a lot of the May beetle larvae require much more time to recover minerals. Further, larvae are very resistant to frost in winter because migrate to a depth of 1 meter. After reaching the final stage of development of the larvae begin to massively get out of the ground, causing damage to trees, especially noticeable on plum leaves.
How to determine the threshold of harm?
At cockchafer as in any pest has a threshold hazard and it is one larva per 1 m2 at a depth of 30 cm. But the actual figures are not exact, since it is not tied to the age of the larvae. So the three-year larvae will have a greater harm than annuals. For this reason, the calculated rate is not relevant for strawberries second and third year of fruiting. In this case the yield is reduced by 40-50% due to more older individuals, as compared to 1 year.
How to reduce the harm?
To combat this pest has not yet been displayed no chemicals. Therefore, use a manual method will have to dreary "escape." It consists in the fact that in September, when the plantation planting need to carefully dig the soil. It must be done no later than September, as the beetles in this period is not yet time to pupate. Mass laying of larvae occurs in July, the larvae age 1 to 2 years do not cause much damage, but in 3 years they are able to completely destroy the plantation.
For this simple reason, planters change location berry crops every 3 years, collecting from them only 2 crops. This approach allows albeit not fully, but still retain a large part of the crop. However, it is worth considering that the thus collected 2 harvest only in the southern regions.
Also, reduce the number of larvae can be content plantation before planting under fallow.