[Oulema melanopus L.: yield losses in winter wheat [Switzerland]]
1996
Jossi, W. | Bigler, F. (Eidg. Forschungsanstalt fuer Agraroekologie und Landbau (FAL), Zurich (Switzerland))
Injury by the cereal leaf beetle, Oulema melanopus L., is caused by the reduction of assimilating leaf surface and increased attack by fungal diseases. Optimal periods for evaluating the larval densities in view of possible treatments are the developmental stages "appearance of flag-leaf" (DC 37-39), when insect growth regulators are used, and "ear emergence" (DC45-55) for use of any other insecticides. One larva destroys approximately ten % of the surface of the flag-leaf, which causes a yield loss of five to seven % per stalk. The economic injury level is reached with 1 larva per stalk on average. At DC 37-39 the number of larvae is to be multiplied by two and at DC 45-55 20 % must be added to the number of larvae counted, because only 50 % and 80 % of the eggs, respectively are hatched at this time. In general chemical treatment is justified only on farms which grow winter wheat on a high-intensity level
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