Insect Associates ofCeratocystis albifundusand 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.

A diverse assemblage of Ophiostoma species, including two new taxa on eucalypt trees in South Africa

“…Isolation of fungi from insects was done by crushing individual specimens between two slices of carrot and incubating them for five days at 25ºC (Moller and Devay 1968;Heath et al 2009). Fungi were isolated by transferring fruiting bodies (mycelium, ascomata, ascospores) growing on the carrots to 2% malt extract agar (MEA: 20 g/L malt extract and 15 g/L agar, Biolab, Midrand, South Africa and 1000ml sterile deionised water) containing 0.05 g/L of the antibiotic streptomycin sulphate (SIGMA-ALDRICH, Steinheim, Germany).…”

A new sudden decline disease of bullet wood in Thailand is associated with Ceratocystis manginecans

“…The disease may be associated with high temperatures and humidity in the local fields. Stem wounds, such as from pruning the tree to reduce branching, may be visited by insects such as H y p o c r y p h a l u s m a n g i f e r a e, a kno wn ve cto r of C. manginecans in mango (Al Adawi et al 2013) and other beetles known to carry Ceratocystis species (Appel et al 1990;Hayslett et al 2005;Heath et al 2009). …”

New host range and distribution of Ceratocystis pirilliformis in South Africa

“…The fact that haplotypes of C. pirilliformis from GRNP occur in more than one geographic location suggests that anthropogenic activities are closely linked to the movement of the pathogen in South Africa. This is especially when one considers that this pathogen is unlikely to be dispersed so widely by insects over such great distances (Heath et al 2009;Ferreira et al 2010). There are numerous examples of Ceratocystis species that have been accidentally introduced into new areas where they have caused significant economic losses in yield or threaten natural ecosystems (Panconesi 1999;Santini and Capretti 2000;Engelbrecht et al 2004;Tarigan et al 2011;Al Adawi et al 2014).…”

“…Ceratocystis species require wounds to infect hosts that arise from natural or accidental damage to roots or stems (DeVay et al 1968;Roux et al 2007). Some species have also established important symbioses with wood-infesting insects that facilitate their dispersal (Heath et al 2009;Al Adawi et al 2013;Ploetz et al 2013;Soulioti et al 2015).…”