Insect associates of Ceratocystis albifundus and patterns of association in a native savanna ecosystem in South Africa

Abstract

Species of Ceratocystis Ellis and Halstead s.l. include important plant pathogens such as C. albifundus Morris, De Beer, and M. J. Wingfield that causes a serious wilt disease of non-native, plantation-grown Acacia mearnsii De Wild. trees in Africa. The aim of this study was to identify the insects associated with C. albifundus in South Africa and to consider the means by which the pathogen spreads. Insects were collected weekly for 77 wk in a native ecosystem using modified pitfall traps. Trapped insects were identified, and fungi were isolated using carrot baiting and by plating them onto malt extract agar. Fungi were identified using morphological characteristics and DNA sequence comparisons. Three different nitidulid (Coleoptera: Nitidulidae) beetles, Brachypeplus depressus Erichson, Carpophilus bisignatus Boheman, and Ca. hemipterus L, were collected, of which the most common were the Carpophilus spp. Two Ceratocystis spp., namely C. albifundus and C. oblonga R. N. Heath and Jolanda Roux, were isolated from all three insect species. Insect numbers and fungal isolates decreased significantly in the colder months of the year. Of the two Ceratocystis spp., C. oblonga was most abundant, occurring on 0.5% of the Carpophilus spp. C. albifundus was isolated from 1.1% of the Brachypeplus individuals and from 0.01% of the Carpophilus individuals. This study presents the first record of insects associated with C. albifundus and C. oblonga and provides an indication of environmental influences on fungal and insect populations, which could contribute to future disease management.