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Keywords:

  • host location behaviour;
  • info chemicals;
  • kairomones;
  • oviposition;
  • parasitoid;
  • pest–host complex;
  • Scirpophaga incertulas ;
  • Trichogramma japonicum ;
  • wind tunnel

Abstract

The yellow stem borer, Scirpophaga incertulas Walker (YSB), infested rice plants emit chemicals through the surface of their infested stems. These induce attractant activity and cause arrestment responses and ovipositional stimulation in its egg parasitoid, Trichogramma japonicum Ashmead. Laboratory experiments on short-range host searching and oviposition were performed to assess the how these crude stem extracts and their fractions influence the biological control efficiency of Trichogramma. The activity of these chemicals as long-range attractants was confirmed through wind tunnel bioassays. Stem borer-infested plant extracts had enhanced the parasitization rate of T. japonicum, whereas host eggs treated with the extract from undamaged stems or solvent-treated control failed to evoke changes in the parasitoid’s behaviour. A preliminary GC-MASS analysis indicated the presence of several hydrocarbon compounds. The analysis also revealed qualitative and quantitative differences between the chemical profiles of the infested and non-infested plants. We hypothesized that herbivore-induced plant chemicals are released through the stem surfaces and attract T. japonicum, even over long distances. These cues elicit parasitoid arrestment on pest-damaged plants and subsequently lead to the successful parasitization of the stem borer.