Helia 2003 Volume 26, Issue 39, Pages: 93-100
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Diabrotica virgifera virgifera leconte, a new sunflower pest from America
Horváth Zoltán, Hatvani Attila
The occurrence and subsequent damage caused by Diabrotica virgifera virgifera LeConte in the corn belt of Northern Bácska have been monitored since 1995. Pheromone traps first indicated the presence of imagoes in 1997. In 1999 imagoes appeared in great numbers in cornfields. In 2000, their swarming was massive again, but not as massive as in 1999. Assessments were performed in 2001, too. In 1999, surprisingly, the imagoes attacked both commercial cornfields and hybrid seed plots, both with very high intensity. Commercial sunflowers adjacent to the cornfields, even sunflower hybrid seed plots, were attacked by the pest. In 2000, again, it attacked sunflower field with in significant numbers. Investigations conducted so far have made it unambiguous that sunflower fields are primarily visited by female imagoes. The extent of damage and population density showed decreasing intensities going from the edge of a field towards its center. In 1999 (12 July), for instance, even 10 to 12 imagoes could be seen feeding on sunflower at the edge of a field while he count was only 4 imagoes per plant 50 m inside the field. Female imagoes peel or sometimes punch the petals of the sunflower. While pollen is their favorite feed, they also consume nectar (this form of damage becomes clear on sterile female plants). In fertile flowers of the male rows, the imagoes reduce the fertilizing potential by consuming pollen. Thus they probably cause quantifiable economic loss as well. With regard to the high proportion of female imagoes (80% to 85%) we should assume that the sunflower as nourishing plant has favorable physiological effects on egg count intensity of egg laying and the fecundity of the clear that the story may be about a kind of "finishing’ step of the ovulation nourishment. However, no egg laying was observed in the sunflower field. Further studies are necessary to better understand how this species causes damage in sunflower crops.
Keywords: Diabrotica virgifera virgifera, Acanthoscelides pallidipennis, "Csalomon", LEM and PAL