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Performance and implementation potential of the MCA disruption technique for control of WCR (Western Corn Rootworm)

In the experiments within the DIABROTICA project period, orientation disruption effects of MCA on WCR (Western Corn Rootworm) were visible, but variable. In general, a reduced number of beetles is attracted for a few days to different trap types in MCA treated versus untreated fields.

Throughout the research in Southern Hungary it was obvious that after each MCA application there were more or less pronounced peaks of orientation disruption after MCA coated grits have been distributed. These peaks varied somewhat with trap and bait type and were also susceptible to variation in temperature and wind direction/wind speed.

As to success with demonstrating mating disruption itself, we are now less optimistic than in 2000 to demonstrate this effect in addition to orientation disruption. On first sight, no impact of MCA on the mating status of females was demonstrated. Frequency of sperm deposition in females spermathecae did not differ significantly between treated fields and control.

Further research during subsequent field seasons should therefore concentrate on formulation techniques and on prolonging the lifetime of granular formulations. Sticky material will be added to the MCA/acetone/granular mixture in order to coat the grit surface with an additional cover reducing the volatility of MCA and making the granule stick to plants. We assume that we can then prolong the viability of the MCA release by a factor of 2-3.

The general evaluation of the granular formulation has to be done in a holistic approach. Many independent factors have to be considered to merge into the final result, a stable, inexpensive, easy to prepare and long lasting formulation. In the original proposal we promised to investigate ‘orientation disruption’ of WCR. During the review and budget approval process at Brussels our proposal wording was changed to ‘mating disruption’ which is of course a related concept. It is, however, much harder to prove experimentally. The difficulty of proof has been discussed by the authors in their first report at the meeting in April of 2000 at Mezohegyes.

As to significantly reducing the mating of Diabrotica virgifera virgifera, great care may be needed to have the disruption tools in place and working at the very first appearance of the female beetles. Males are in the field about a week to 10 days prior to females. Males are ready to mate any receptive female appearing at the scene and releasing her sex pheromone lure. Assuming that MCA will disrupt mating, we may not be able to see the effect since 100% of the females we possibly can catch in the field may already be mated before they come in contact with the upper parts of the corn plants where the MCA is concentrated.

As a tool to get a handle on these females, we established emergency cages in the corn field. Yet, based on our present experience, we would have to monitor each cage 24 hours a day in order to prevent any early mating upon emergence, a task requiring considerably more man power than we had available so far.

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Reported by

Justus-Liebig-University of Giessen
Ludwigstrasse 21
35390 Giessen
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