Impact of feeding by Neochetina weevils on pathogenicity of fungi associated with waterhyacinth in South Africa
Journal of Aquatic Plant Management
Department of Zoology and Entomolog, Rhodes Uniersity, PO Box 94, Grahamstown 6140, South Africa
Feeding damage by arthropods is known to render water-hyacinth plants vulnerable to diseases. During this study, six South African fungal isolates (Alternaria eichhorniae Nagraj and Ponappa, A. alternata [Fr.] Keissler, Acremonium zonatum [Sawada] Gams, Fusarium oxysporum Schlecht, F. solani [Mart.] Sacc, and Myrothecium roridum Tode ex Fr) were tested for their disease-causing potential against waterhyacinth (Eichhornia crassipes [Mart.] Solms-Laubach; Pontederiaceae). They were applied to waterhyacinth in two treatments: on plants with feeding scars of weevils (Neochetina sp.; Coleoptera: Curculionidae; treatment W+) and on plants with no insect feeding damage (W-). The W+ plants were more prone to fungal infection as compared to W- waterhyacinth. A disease index (DI) of damaged plants varied significantly with different pathogens. By 45 d after treatment, DI was significantly higher in F. oxysporum (91.8 and 46.6%) and A. eichhorniae (87.6 and 65.8%) for W+ and W- waterhyacinth, respectively, followed by A. zonatum (56.6 and 50.6%), F. solani (43.6 and 27.0%), and A. alternata (26.6 and 12.6%). Lowest DI was observed in plants applied with M. roridum (21.8 and 10.0%). This study shows that to improve the biological control of waterhyacinth in South Africa, all available agents including native fungi should be released at all sites.
Acremonium (Ascomycota); Alternaria; Alternaria alternata; Alternaria eichhorniae; Arthropoda; Coleoptera; Curculionidae; Eichhornia crassipes; Fungi; Fusarium oxysporum; Hexapoda; Myrothecium roridum; Neochetina; Pontederiaceae