Potential for biological control of Zophiuma butawengi (Heller) (Hemiptera: Lophopidae) in coconut and oil palms using the hymenopterans Ooencyrtus sp.(Encyrtidae) and Parastethynium maxwelli (Girault) (Mymaridae)

The planthopper Zophiuma butawengi (Heller) causes Finschhafen Disorder (FD) of coconut and oil palm in Papua New Guinea (PNG). Field surveys for parasitoids of Z. butawengi were conducted between November 2007 and February 2009. Of the 1,059 egg masses collected, 41% were found to be parasitized by an encyrtid (Ooencyrtus sp.) or a mymarid (Parastethynium maxwelli (Girault)) whilst no parasitoids were recovered from nymphs or adults. Wasps of Ooencyrtus sp. were responsible for 74.8 % of the parasitism with the remaining 24.6 % caused by P. maxwelli. The average progeny produced per egg mass by Ooencyrtus sp. and P. maxwelli was 20 and 23, respectively, both with female biased sex ratios of 70% and 68%, respectively. Parastethynium maxwelli was common on the island of West New Britain but absent from mainland PNG sites, hence offering an opportunity for classical biological control. Laboratory experiments showed that adult longevity of both parasitoids was markedly enhanced by honey and this finding will prove important in future mass rearing attempts for inundative biological control of Z. butawengi. Further experiments involved testing nectar plants as potential food source to the parasitoids. Access to flowers of potential food plants did not significantly improve longevity over a no-food and water treatment. There was a strong response to honey diet, suggesting that screening a wider range of plants is worthwhile to develop conservation biological control.