Biocontrol News and Information
CABI Publishing


March 1997 Vol.18 No.1

The following papers, of biological control interest, will appear in the Bulletin of Entomological Research in the near future.

Species status of two host-associated populations of Aphytis lingnanensis (Hymenoptera: Aphelinidae) in citrus. L.C.P. FERNANDO and G.H. WALTER, Department of Entomology, University of Queensland, Brisbane, Queensland, Australia.

Abstract - Although Aphytis lingnanensis is an important parasitoid of California red scale Aonidiella aurantii, several "races" exist which parasitise white louse scale Unaspis citri. The reproduc-tive status of a white louse scale "race" that originated in Thailand was examined in relation to several populations (from Queensland, California and the Philippines) that parasitise California red scale. None of the wasps from red scale mated with individuals from white louse scale in small cages within ten minutes, whereas control crosses all mated within that time. The two "races" would therefore constitute independent reproductive entities (species) in sympatry in the field, although no consistent anatomical differences could be found between them, even with the aid of discrimi-nant function analysis on the number of setae on the delta region of the forewing and the mesoscutum. Aphytis lingnanensis from California red scale in Queensland mated readily with wasps derived from the same host species in California and the Philippines, and mating took place at random among individuals in mate choice tests. Although such results are equivocal, there are no reasons for suspecting that these different populations of A. lingnanensis from California red scale also comprise more than one species. The results obtained indicate that cross-mating tests designed to quantify reproduc-tive isolation between sexual popula-tions are inappropriate. They should rather be designed to establish whether individuals recognise one another as potential mates. The design of cross-mating tests should therefore consider the usual time to mating, of known conspecifics, under the experimental conditions used.

Seasonal and weather factors influencing the annual flight cycle of Prostephanus truncatus (Coleoptera: Bostrichidae) and its predator Teretriosoma nigrescens (Coleoptera: Histeridae) in Benin. C. BORGEMEISTER, W.G. MEIKLE, D. SCHOLZ, C. ADDA, P. DEGBEY and R.H. MARKHAM, IITA, Plant Health Management Division, Cotonou, Benin.

Abstract - Investigations were carried out in southern Benin on the annual flight cycle and the effects of weather variables on the flight activity of Prostephanus truncatus and its natural enemy Teretriosoma nigrescens. Two seasonal peaks in flight activity of P. truncatus were observed, one between the end of December and the beginn-ing of January and second one bet-ween May and June. Teretriosoma nigrescens showed a single delayed peak in June, approximately six weeks after the major peak of P. truncatus. Flight activity of P. truncatus was only weakly associated with weather characteristics, whereas for T. nigrescens it was associated with precipitation. The possibility that one of the P. truncatus peaks was assoc-iated with dispersal from crowded maize stores and the other with the search for natural woody host plants is discussed.

Characterization of a microsatellite locus in the parasitoid wasp Aphelinus abdominalis (Hymenoptera: Aphelinidae). F. VANLERBERGHE-MASUTTI and P. CHAVIGNY, INRA, Laboratoire de Biologie des Invertébrés, Antibes, France.

Abstract - Primers for DNA amplifica-tion using the polymerase chain reaction were synthesized for a microsatellite locus isolated from a partial genomic library of the aphid parasitoid Aphelinus abdominalis. Screening for genetic polymorphism at this locus in two laboratory strains of this wasp revealed the presence of two alleles different in the number of (GT) and (GGC) repeats. The relative frequencies of the two alleles were not significantly different between the two strains or between diploid females and haploid males. Heterozygosity at this microsatellite locus was estimated to be 0.40, which is within the range in other hymenopteran species. Given that
A. abdominalis is a good candidate for augmentative release programmes in greenhouses against aphids, we suggest that microsatellite markers may have application in discriminat-ing among aphelinid sibling species and strains. The markers provide a means for studying the performance and impact of selected parasitoid lines on pest dynamics in field release experiments.

Studies on the maize stem borer, Busseola fusca (Lepidoptera: Noctuidae) and its major parasitoid, Dolichogenidea fuscivora (Hymenoptera: Braconidae), in eastern Ethiopia. K. YITAFERU and A.K. WALKER, Alemaya University of Agriculture, Dire Dawa, Ethiopia.

Abstract - Studies on Busseola fusca and its major larval parasitoid Dolichogenidea fuscivora were carried out in the field and the laboratory in eastern Ethiopia. Larvae of B. fusca were also parasitized in the field by Bracon sesamiae and Sarcophaga sp., but in low numbers. Parasitism of B. fusca by D. fuscivora is as high as 71% during the dry season (November-March) and approximately 18% in the wet season (June-September). Dolichogenidea fuscivora is active throughout the year. In the laboratory it requires nearly 26 days at 24 ± 1°C to complete the development of one generation (egg to egg laying). Longevity of adults is affected by the availability of food and water. Mating and oviposition reduced the life spans of males and females, respectively. Sixty five to 75 larvae emerged from eggs laid by a single female. The sex ratio ranged from 1:1 to 7:1 (female:male), the average being 5:1.