Velvetleaf: A Plant with Adverse Impacts on Insect Natural Enemies

Abstract

We investigated the effect of velvetleaf, Abutilon threophrasti L., leaf age and glandular trichome exudate on Eretmocerus eremicus n. sp. Rose & Zolnerowich parasitism of silverleaf whiteflies, Bemisia argentifolii Bellows & Perring, in the greenhouse. The impact of glandular trichome exudate on entrapment of natural enemies in the field also was examined. Parasitism of whiteflies in the greenhouse was minimal and 31% of the parasitoids released to attack whiteflies were found entrapped in exudate of glandular trichomes and died. In the field, velvetleaf is a source of mortality to natural enemies and significantly more natural enemies were entrapped in glandular trichomes of control plants than on plants that were wiped to remove glandular exudate. Behavioral observations revealed that Eretmocerus in small arenas located fewer whitefly hosts on leaf disk of velvetleaf compared with the number of hosts located on glabrous or pubescent melons, Cucurbita melo L. Parasitoids accessing velvetleaf spent much of their time off the leaf disk, grooming, presumably to remove the exudate that was encountered on the leaf. As such, less overall time was spent searching velvetleaf for hosts compared with time spent searching melons.