A new genus of Cryphonectriaceae isolated from Lagerstroemia speciosa in southern China

Numerous species in the Cryphonectriaceae have been recorded on the Myrtales and many of these are economically important pathogens of Eucalyptus. Some species have also recently been shown to be endophytes of native Myrtaceae and to have undergone host jumps to infect Eucalyptus species established as exotics in plantations. Recent surveys in the GuangDong and HaiNan Provinces of South China reveal the presence of a species of Cryphonectriaceae associated with cankers on trees of Lagerstroemia speciosa (Lythraceae, Myrtales). Fungal structures were observed on the surface of dead bark covering cankers and on branch stubs. Multigene phylogenetic analyses were conducted based on DNA sequence comparisons of the partial LSU gene, ITS region of the nuclear ribosomal RNA gene and two regions of the β‐tubulin (BT) gene. The results revealed the presence of a previously undescribed genus and species in the Cryphonectriaceae. The fungus is described here as Chrysomorbus lagerstroemiae gen. et sp. nov. Inoculation tests showed that it is an aggressive pathogen on L. speciosa and that it can also infect Eucalyptus.     

Biology of Litosermyle ocanae in Colombian Pinus patula plantations

Plantations of Pinus spp. in Colombia are severely damaged by various phasmid (Phasmatodea: Diapheromeridae) insects. Of these, Litosermyle ocanae is one of the most serious defoliators. Since 1988, several outbreaks have been recorded in Pinus patula plantations, resulting in substantial economic losses. The aim of this study was to determine the life cycle of Litosermyle ocanae in P. patula plantations in Colombia. In addition, we assessed the population levels of L. ocanae and the presence of natural enemies of L. ocanae in these plantations. The development of L. ocanae was monitored under controlled conditions, and population fluctuations and the presence of natural enemies was assessed from field-collected eggs and field observations. The results showed a total life cycle of 225 d and 235 d for males and females, respectively, and a complete fourth instar nymph cycle of 121 d and 116 d for males and females, respectively. The sex ratio was 1:1.7 female to male. Females laid an average of 112 eggs. The number of eggs peaked in November and the most dominant natural enemy observed was a parasitoid wasp Adelphe sp. (Hymenoptera: Chrysididae). The results provide important information for the management of L. ocanae in P. patula plantations.     

Population variation in traits of Deladenus siricidicola that could influence the biocontrol of Sirex noctilio in South Africa

Deladenus siricidicola is the primary biocontrol agent of the invasive woodwasp, Sirex noctilio. The nematode is mass-reared in culture on the S. noctilio symbiotic fungus, A. areolatum, but can also be induced to convert into its infective form in culture. The aim of this study was to explore the level of variation among a collection of D. siricidicola strains to convert into the infective form in culture. In addition, we measured variation in growth of the nematode on a strain of A. areolatum that is commonly used for laboratory rearing. Both traits could influence laboratory rearing and efficiency in the field. The 22 strains from three countries showed significant variation in the frequency of conversion into the infective form in culture. Even genetically uniform strains from South Africa displayed a range of variation in this trait. There was also significant variation in the growth of D. siricidicola on A. areolatum. These results emphasise the importance of considering variation in traits in D. siricidicola that could influence a biological control program. They also provide tools that could be used to screen larger collections of D. siricidicola for variation in traits linked to virulence and reproduction.     

High diversity and clonality are hallmarks of Fusarium circinatum in South Africa

Pitch canker on plantation-grown Pinus species, caused by the fungal pathogen Fusarium circinatum, first appeared in the western and southern Cape regions of South Africa. However, outbreaks have subsequently been reported from the major plantation growing regions of KwaZulu-Natal and Limpopo in the eastern, summer rainfall regions of the country. It is more than 10 years since the last detailed population genetics studies on F. circinatum in the region were conducted. To shed light on the population biology of F. circinatum in this region of South Africa, we used microsatellite markers and mating-type assays to study a collection of 296 isolates from different nurseries and plantation sites. Our results showed that populations in the region are highly diverse, but strongly interconnected, with various genotypes shared across nursery and plantation collection sites. In contrast to nursery populations, those associated with pitch canker outbreaks were characterized by the presence of relatively small numbers of dominant genotypes that were generally widespread across the region. Opposite mating-type individuals occurred in most of the isolate collections, but multilocus linkage disequilibrium analyses pointed towards clonality being the main reproductive mode of F. circinatum in the region. Most of the pathogen's genetic variation could probably have resulted from multiple different introductions into the country and more specifically, into the summer rainfall region. Because the spread and establishment of invasive pathogens are typically driven by aggressive clones, the results of this study provide important considerations for current and future Pinus disease management strategies.