Reduction of the European corn borer in grain-maize by harvesting
1989
Langenbruch, G.A. (Biologische Bundesanstalt fuer Land- und Forstwirtschaft, Darmstadt (Germany, F.R.). Inst. fuer Biologische Schaedlingsbekaempfung) | Lorenz, N.
In a field trial near Darmstadt the reduction of the larvae of the European corn borer in grain maize by harvesting was tested. In three variants the combine harvester was fitted with a chopper which worked contrarotating and guaranteed a thorough tearing of the stalks (combine A). In a further variant a different machine with a chopper rotating in the direction of the wheels of the combine (combine B) with usual adjustment was tested. Although 60-90 per cent of the plants (variety Dea, 760 larvae/100 plants) had broken stems, in all variants a clean harvest without remarkable crop losses was possible. At harvest (14th October 1988) 90 per cent of the larvae were found in the plants and 10 per cent in broken parts on the ground. 26 per cent of the larvae in the plants were found in the lowest parts of the stalks (below 10 cm). When the stubbles had a length of about 14 cm, 26 per cent of the larvae survived the harvest by combine A and 54 per cent by combine B. When the chopper of combine A was put at its lowest position (length of the stubbles only 7 cm) 21 per cent of the larvae survived. In spite of 10 t dead weight (4 t on each front-wheel) there was no higher larval mortality in the wheel track than beside it. This can be explained by the wet and soft soil and by extreme hardness of the stalks of Dea. With a view to an integrated control of the European corn borer we conclude, with regard to former results, that a thorough tearing of the stalks by a picker combined with a rotary cultivator and a subsequent clean ploughing will be sufficient to decrease populations of the European corn borer. But soil management without ploughing needs a further step of control (e.g. a release of Trichogramma wasps), even when a contrarotating chopper is used, to avoid progress of the insect
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