Charles Adarkwah, Daniel Obeng-Ofori, Sabine Prozell, Matthias Schöller, Christoph Reichmuth, Carmen Buettner:
Potential of the Parasitic Wasp, Lariophagus distinguendus (Förster) (Hymenoptera: Pteromalidae) as a Biological Control Agent for Sitophilus zeamais Motschulsky (Coleoptera: Curcuilionidae) in Stored Maize

CHARLES ADARKWAH^1,4, DANIEL OBENG-OFORI², SABINE PROZELL³, MATTHIAS SCHÖLLER³, CHRISTOPH REICHMUTH⁴, CARMEN BUETTNER^1
1Humboldt-Universität zu Berlin, Institute for Horticultural Sciences, Phytomedicine, Germany
²University of Ghana, Crop Science, Ghana
³Biological Consultants Ltd., Germany
⁴Federal Biological Research Centre for Agriculture and Forestry (BBA), Institute for Stored Product Protection, Germany

The parasitic wasp, Lariophagus distinguendus is an ectoparasitoid of several beetle species that feed on durable stored products. The potential using L. distinguendus for the biological control of S. zeamais was assessed in maize stored in storage cylinders. The host finding behaviour of the parasitoid was studied in maize stored in various vertical depths in the cylinders. Holes of 3 mm diameter were drilled through PVC pipes of 20.5cm length and 20 mm diameter. The pipes were inserted into the holes in the cylinders. An acoustic detector served to identify the maize kernels that contained 3 weeks old larvae of S. zeamais. Uninfested maize kernels were filled into the cylinder to depths of 20, 25, 30, 35, 40, 45, 95 and 100cm, respectively. For depths of 20, 25 and 30cm, 25 adult L. distinguendus aged between 0-14 days were released; for 35, 40 and 45cm, 30 adult L. distinguendus were released while for 95 and 100cm, 100 adult L. distinguendus of the same age were released, each on top of the uninfested maize. Each treatment was repeated three times with control without parasitoids. L. distinguendus adults that entered the pipe and the wire mesh cage to parasitise the S. zeamais infested maize kernel were collected and placed in a 250 ml glass jars. The emergence of S. zeamais was recorded in both L. distinguendus treated and untreated maize weekly until the 6^th week. L. distinguendus penetrated and infested S. zeamais stored in the cylinders at the various depths. This showed that L. distinguendus was able to find its host in the cylinder with infested maize kernels and produced F1 offspring. L. distinguendus also significantly reduced the emergence of S. zeamais in stored maize. The significance of these results with respect to the suitability of L. distinguendus for the biological control S. zeamais is discussed.

Keywords: Maize, parasitic wasp, storage

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Contact Address: Carmen Buettner, Humboldt-Universität zu Berlin, Institute for Horticultural Sciences, PhytomedicineBerlin, Germany, e-mail: carmen.buettneragrar.hu-berlin.de