Soil moisture as mortality factor for cutworms, Agrotis segetum Schiff. (Lep., Noctuidae)
1986
Esbjerg, P. (National Research Centre for Plant Protection, Lyngby (Denmark). Dept. of Zoology) | Nielsen, J.K. | Philipsen, H. | Zethner, O. | Oegaard, L.
The extreme fluctuations of cutworm attacks in Denmark have mainly been related to summer rainfall. In the present investigations the influence on the cutworms was split up and dealt with in the following three ways: relative air humidity - pilot experiments in the laboratory: rainfall -semifield experiment with sprinkle irrigation of 2m x 2 m plots. Soil moisture-greenhouse experiments using carrots in pots. No indications were found of the effect of relative humidity or of the effects of falling rain. Soil moisture had a pronounced effect on young cutworms, the mortality of which rose with increasing soil moisture. The experiments showed that young cutworms do not stay permanently on leaves, as described in the literature, but hide in the topmost soil, and this behaviour is disturbed by wet soil. Even though the exact reason for the death of cutworms is still obscure, soil moisture ist clearly a major cause of mortality. This information ist already used for forecasting of attacks. Improvements may, however, be obtained by building a simple dynamic model when further experimental data are available
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