Leatherjackets as pests of grasslands - their biology and control

1. In the northwestern part of Germany Tipula paludosa, T. czizeki, T. oleracea, T. vernalis and Pales maculata occur. T. paludosa and T. czizeki seem to be economically most important species. 2. The different life-tables are described. 3. The determination of genera and in some cases of species can be done by comparing the morphology of the last segments of the abdomen with L2 - L4. For the subfamily Tipulinae the determination of species is done using adults. 4. Between 1955 and 1985 in Weser-Ems gradations occurred in 1955, 1962, 1966, 1976 and 1983/84. 5. The soil influences the density of larvae by its varying capacity to retain water. 6. The climatic conditions are most important since the moisture content of the top soil-layers strongly influences the mortality of the egg-and L1 stage1482s and possibly the hatching of the adults as well. 7. The Tipulid larvae are omnivorous but show a preference for dicot species. 8. They are able to move and migrate to better suited locations in the vicinity. 9. Cannibalism in the larvae is proved, but seems to be connected with a diminished ability of the individual to defend itself. 10. A list of natural enemies is given. 11. In the literature several diverging economic thresholds are given, which are based on different methods of density-assessment as well. Values for the early control of tipulid larvae in late autumn and early winter are lacking. 12. The type of distribution of the larvae reminds of the negative binomial distribution and makes assessment of actual densities difficult. Values for the necessary number of samples (cores) per hectare (not field irrespective of its size) are still lacking. 13. The application of calcium cyanamide can diminish the density of eggs ans L1. Its possible use for control is discussed. 14. The early control of larvae by insecticides in late autumn/early winter is recommended. The number of in Germany approved active ingredients for this purpose is considered not satisfac