In this section are abstracts of recent papers that may be of interest to the DBM working group.
Selection of egg parasitoids of the genus Trichogramma (Hymenoptera:Trichogrammatidae) to control the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)
Wen Qing ZHANG1,2, Sherif A. HASSAN1
1. Federal Biological Research Center for Agriculture and Forestry,
Institute for Biological Control,Heinrichstr. 243, 64287 Darmstadt, Germany
2. State Key Laboratory for Biocontrol & Institute of Entomology,
Zhongshan University, Guangzhou 510275, ChinaABSTRACT
The host acceptance/preference, reproductive capacity on target host and searching ability on relevant plants were used to select effective Trichogramma species/strains for use in the biological control of the diamondback moth Plutella xylostella (L.). All 18 Trichogramma strains tested parasitized eggs of both the rearing host Sitotroga cerealella and the target host P. xylostella. Much more eggs of the rearing host were parasitized compared to the target host and large differences were found between the strains. With T. chilonis/Chi-C93 and T. ostriniae/Ost-C91, the difference of parasitism between the two hosts was not statistically significant. T. nerudai/Ner-Ch99 and T. pretiosum/Pre-E81 also parasitized relatively high numbers of the target host eggs compared to the other strains tested. The lifetime fecundity on the target host was 32.8 by T. chilonis and 30.0 by T. nerudai, which were significantly higher than those of T. pretiosum and T. ostriniae. The female longevity of the 4 strains did not differ significantly. The emergence rate and the percentage of females were highest with T. nerudai, followed by T. chilonis. Cage experiments with potted cabbage plants to test the searching behavior of Trichogramma showed that when P. xylostella eggs were offered on plastic foil and artificially attached to cabbage leaves, parasitism was very low. In contrast, when P. xylostella eggs were naturally laid on the cabbage plants before Trichogramma was released, significantly more eggs were parasitized. The percent parasitism of the eggs by T. chilonis and T. nerudai were 8.3% and 6.0% respectively when 10 females were exposed to the eggs for 24 h. The percentage increased to 22.0% and 18.0% respectively when the exposure time was prolonged to 48 h. No significant difference was found between the two strains but T. chilonis parasitized more eggs. Based on these results, T. chilonis/Chi-C93 and T. nerudai/Ner-Ch99 were selected as candidates for use in the biological control of the diamondback moth.