Mj. Steinbauer, HOST-PLANT PHENOTYPE AND THE IMPACT AND DEVELOPMENT OF CARMENTA-MIMOSA, A BIOLOGICAL-CONTROL AGENT OF MIMOSA-PIGRA IN AUSTRALIA, Biological control (Print), 13(3), 1998, pp. 182-189
The influence of host plant phenotype on the impact caused to Mimosa p
igra L, (Mimosaceae) plants by the feeding activity of larvae of Carme
nta mimosa Eichlin and Passoa (Lepidoptera, Sesiidae) and the relation
ship between plant phenotype (through plant quality) and larval develo
pment were investigated under controlled conditions. Plants grown unde
r conditions of reduced light availability were most prone to the detr
imental effects of the feeding activities of C. mimosa larvae. The rel
ative growth rate (RGR) of most plant phenotypes could be reduced when
infested with C. mimosa larvae compared to uninfested plants, Small p
lants infested with C, mimosa and grown under reduced light availabili
ty exhibited significant reductions in RGR sooner than large plants gr
own in full sun. The physical quality of stems was correlated with the
severity of impact, i.e., whether stem breakage occurred. Little larv
al-induced mortality of plants was observed, suggesting that vascular
tissues remained sufficiently intact to allow translocation. Systemic
stem death arose through infection by secondary pathogens. Differences
in biomass of infested versus uninfested plants of all phenotypes wer
e associated with the loss of stems and to a lesser extent leaves, The
phenotype of plants had a significant effect on the development of C.
mimosa larvae. Larvae in stems of plants with good access to reserves
of soil moisture reached more advanced stages of development sooner t
han did those in plants which were often water stressed. This response
was mediated through the combined influence of availability and nutri
tional quality of food. The implications of these findings to the impa
ct of this agent in the field and the factors which may significantly
influence its population dynamics are discussed.