Possible non-target feeding by the bugweed lace bug, Gargaphia decoris (Tingidae), in South Africa: field evaluations support predictions of laboratory host-specificity tests.

摘要

The presence or absence of nontarget feeding by the bugweed lace bug (Gargaphia decoris) was examined at a release site near Howick, KwaZulu-Natal, South Africa where the insect population has persisted since October 1999. Surveys of all nontarget Solanum species, which were growing adjacent to or in the understorey of the bugweed (S. mauritianum) infestation, were carried out monthly from January 2001 to May 2002. The nontarget plants included two native species (S. cf. linnaeanum and S. nodiflorum), two exotic species (S. pseudocapsicum and S. viarum) and one cultivated species (S. tuberosum, potato). The stand of potatoes arose fortuitously from old tubers that had been discarded in the S. mauritianum stand, while the remaining plants grew naturally. During the survey, some 113 adult G. decoris were collected, of which 95.6% were recovered on S. mauritianum. On rare occasions, adults were recovered on S. cf. linnaeanum and S. pseudocapsicum, but not on the remaining nontarget species. Besides S. mauritianum, feeding was observed only on S. cf. linnaeanum where very low levels of damage were recorded. Oviposition was never recorded on any of the nontarget species, with egg batches and nymphs recovered only on S. mauritianum. The results clearly showed that all nontarget species attracted significantly fewer G. decoris and suffered significantly less feeding damage than S. mauritianum, indicating that at the current "ambient" population levels of G. decoris in South Africa, there is no reason to expect nontarget damage to be more than incidental and negligible.