A simple method for separating beneficial parasitoids of the alfalfa seed chalcid (Bruchophagus roddi) from Alfalfa chaff.
A method was developed to separate diapausing larvae of beneficial hymenopterous species from alfalfa [lucerne] chaff by a pneumatic separator. The parasitoids can then be used as biological control agents against the lucerne seed chalcid, B. roddi. Tetrastichus bruchophagi [Baryscapus bruchophagi] can be obtained from chaff collected during normal seed harvest, by precisely adjusted floating-rate cleaning. Chaff from Kompolt, Hungary, was used to test the method. A chaff fraction collected at floating rates between 25.0-27.5 m3/h (air speed = 2.77-3.05 m/s) by a Petkus K-293 pneumatic separator was found to be rich in lucerne seeds containing diapausing B. bruchophagi larvae, but practically free from seeds infested by non-parasitized B. roddi. Females of the beneficial parasitoids Liodontomerus perplexus [Idiomacromerus perplexus] and Habrocytus medicaginis [Pteromalus medicaginis] were most abundant at floating rates of 35.0-37.5 m3/h. Greatest numbers of I. perplexus males were recorded at 32.5-35.0 m3/h. B. roddi was most abundant between 35.0 and 40.0 m3/h.