Treena Burgess

Rubus anglocandicans is the most common species of European blackberry in Western Australia (WA) and one of the few weeds of national significance in the south-west of WA. It is a major weed of conservation areas, forestry and agriculture. Exotic strains of the blackberry rust Phragmidium violaceum have been introduced to WA as biological control agents, but in most areas it seems that they are not effective, possibly due to climate. In 2007 while monitoring establishment of the released rust strains, unexplained dead and diseased blackberry plants were discovered at two locations, along the Warren River near Pemberton and the Donnelly River near Manjimup in the south-west of WA. The extent of the disease, with noticeable landscape changes due to the removal of dense blackberry infestations, has lead to it being called ‘blackberry decline’. The organism or organisms responsible for killing the blackberry plants are so effective that within a couple of years previously impenetrable stands of well established blackberry have been completely killed for at least several kilometres from the initial sightings of disease symptoms. We outline the history of the ‘decline’ phenomenon on blackberry in the south-west of WA and discuss some of the possible causes.

Respiration assays are routinely used for investigating microbial metabolic activity in soil, but usually after a period of "conditioning" whereby dry soil is rewetted and incubated for a period of days. We showed that rewetting and incubation of soil with or without amendments cause changes in microbial populations that are dependent on the type of amendment. As these amendments resulted in altered basal respiration levels and SIR profiles, they call into question the suitability of soil conditioning as pretreatment for soil microbial analyses. When testing soils from an experiment involving various amendments we have found that different substances can inhibit, rather than stimulate, respiration following rewetting. We suggest further investigation of "CO2 burst inhibition" for the purpose of developing a method that does not require naturally dry or air dried soil to undergo conditioning prior to a SIR assay.

Most Phytophthora surveys in native ecosystems in Australia have focused exclusively on isolations from samples of soil and symptomatic plant tissue including the extensive vegetation health surveys conducted in Western Australia (WA) (1). The outbreak of P. ramorum in California and Europe, where early detection of an infested area was important to the success of containment and eradication efforts, has popularised the stream surveys in native ecosystems. In Australia, it has recently been used to detect Phytophthora spp. in Victoria resulting in several species being isolated from four streams which varied according to the winter and summer sampling season (2). In our study, the baiting technique was used to survey a wide range of WA’s waterways for Phytophthora spp. during October to early December 2008.

Since the early 1990s there has been a significant decline of E. gomphocephala, and more recently E. marginata, in the tuart forest in tuart woodland in Yalgorup National Park SW Western Australia, although no satisfactory aetiology has been established to explain the decline. Characteristics of the canopy dieback and decline distribution are reminiscent of other forest declines known to involve Phytophthora soil pathogens and indicate that a Phytophthora species may be involved in the decline. In 2007 isolates of Phytophthora multivora, recently described by (1), were recovered from rhizosphere soil of declining or dead trees of Eucalyptus gomphocephala and E. marginata. For E. gomphocephala and E. marginata, the pathogenicity of P. multivora was tested: ex situ on seedlings using a soil infestation method; and in situ on stems using an under bark infestation method.

Recently a survey of endophytes associated with boabs (Adansonia gregorrii) and associated tree species in the Kimberleys, Western Australia has resulted in the description of seven new species in the Botryosphaeriaceae (Pavlic et al. 2008). Additionally several common species of Lasiodiplodia, (L. theobromae, L. pseudoptheobromae and L. parva) were also isolated as endophytes of endemic tree species. Concurrently, surveys in the Ord River Irrigation Area (ORIA) have revealed Mangiferum indica trees showing symptoms of dieback and cankers. In this project we isolated, identified and determined the pathogenicity of fungi associated with these cankers.

Many diseases of Eucalyptus species have emerged as pathogens in exotic plantations. Guava rust (Puccinia psidii), cryphonectria canker (Crysoporthe cubensis) coniotherium canker (Colletogloeopsis zuluensis) and Kirramyces leaf blight (Kirramyces destructans) are all serious pathogens that have not been found in native forests or in plantations in Australia (Burgess & Wingfield 2002; Cortinas et al. 2006; Glen et al. 2007; Wingfield et al. 2001). The susceptibility to these pathogens of Eucalyptus spp. commonly used in exotic plantations is known; however the susceptibility of many Eucalyptus spp. found only in natural ecosystems in Australia is unknown. There are two main uses of sentinel plantations. Firstly, tree species known to be susceptible to different pathogens can be planted within the natural environment to try and trap pathogens from their surroundings. In Australia, taxa trials planted in different environments act as sentinel plantings. By surveying these taxa trials we have collected and described a number of new eucalypt pathogens and reported the presence in Australia of Kirramyces destructans. The second use for sentinel planting is where many tree species are planted in a region known to harbour certain pathogens. In this manner the susceptibility of the different tree species can be determined.