Cm. Mannion et Rk. Jansson, WITHIN-ROOT MORTALITY OF CYLAS-FORMICARIUS (COLEOPTERA, APIONIDAE) BYENTOMOPATHOGENIC NEMATODES, Journal of economic entomology, 86(3), 1993, pp. 722-729
Within-root mortality of sweetpotato weevil, Cylas formicarius (F.), b
y six strains of entomopathogenic nematodes in the families Steinernem
atidae and Heterorhabditidae (Steinernema carpocapsae [Weiser] [=Neoap
lectana carpocapsae, Steinernema feltiae] All and Mexican strains; Ste
inernema feltiae [Filipjev] [=Steinernema bibionis] N-27 strain; Stein
ernema glaseri [Steiner]; Heterorhabditis bacteriophora Poinar [=Heter
orhabditis heliothidis] HP88 strain; and Heterorhabditis sp. FL2122 st
rain [an undescribed nematode isolated in Florida]) was tested in seve
ral buried-root bioassays. The ability of nematodes to locate and kill
weevils, and the location within the root where infection occurred, w
ere measured. In addition, mortality of the weevils in roots that were
artificially infested in the laboratory was compared with mortality i
n naturally infested roots from the field using two concentrations of
one nematode (S. carpocapsae Mexican strain). In general, the heterorh
abditid nematodes caused higher levels of mortality within the root th
an the steinernematids. Heterorhabditis sp. FL2122 strain killed the h
ighest proportion of weevils in the shortest period of time. Similar d
ifferences among nematodes were seen in the inner portion (1/2 radius)
of the storage roots, as well as in the outer portion. Although weevi
l mortality in the artificially infested roots was greater than in the
naturally infested roots, the trends in mortality were similar; we ob
served increased mortality in the nematode treatments compared with th
e control and no difference in mortality between the two nematode conc
entrations.