Plant health biosecurity, risk management and capacity building for the nursery industry

Project NY11001 has been a four year funding partnership between the Australian nursery industry, the Queensland Department of Agriculture & Fisheries (DAF), and Horticulture Innovation Australia (HIA). The aim of the project was to provide support to the nursery industry in the area of plant health and biosecurity, including the identification and management of plant diseases and pests through professional diagnostics, skill enhancement of industry through training workshops, and the development of various resources for on-farm biosecurity management

Better understanding epidemiology of Panama disease of banana

This study involved traditional and molecular methods to track the movement of Fusarium oxysporum f.sp. cubense (Foc) in the vascular system of banana. Traditional studies were conducted in the field using naturally-infected Lady finger banana plants, and molecular studies are currently being conducted at UQ using banana plants artificially-inoculated with GFP-transformed Foc isolates in the glasshouse. Panama disease is a polycyclic disease where inoculum causing infection is produced in individual plants infected during the course of the epidemic. This field study clearly demonstrated that the sap produced in such plants will be contaminated with Foc, and will contribute to epidemic build-up if allowed to contaminate the soil. Thus, sap as a source of inoculum is very important when managing disease containment. The study also suggested that the laticifers are not colonised by Foc and that when a pseudostem is cut, the sap from the laticifers is contaminated by inoculum from severed vascular strands and/or associated necrotic tissues. It is difficult to separate these tissues, but results suggest that mycelial fragments may come from severed vascular strands or xylem fluid, and microconidia from necrotic cells adjacent to the vascular bundles. It is anticipated that GFP-transformed isolates being used in the experiment at UQ will provide more definitive evidence on the systemic infection process of Foc in banana. It will determine whether movement in the vascular tissue is via mycelial growth or microconidia, and may explain why the incubation and latent periods for the disease are often so long. Chemical intervention to reduce inoculum levels may be possible but will require much more detailed research. The production of a volatile chemical (bicyclo(4,2,0) octa-1, 3, 5-triene) detected in this study by race 4 strains of Foc in culture is interesting and presents the opportunity for detection of disease by “sniffer” dogs before external disease symptoms are produced. Whether this chemical is produced in infected plants is yet to be determined

Rootstock influences postharvest anthracnose development in 'Hass' avocado

Rootstock studies conducted on ‘Hass’ avocado found that rootstock had a significant impact on postharvest anthracnose susceptibility. This is the first record of such an effect for avocado. The severity and incidence of anthracnose was significantly lower on ‘Hass’ grafted to ‘Velvick’ Guatemalan seedling rootstock compared with the ‘Duke 6’ Mexican seedling rootstock. Differences in anthracnose susceptibility were related to significant differences in concentrations of antifungal dienes in the leaves and mineral nutrients in the leaves and fruits from trees grafted to different rootstocks. Leaf diene concentrations were up to 1.5 times higher in ‘Hass’ trees on the ‘Velvick’ than the ‘Duke 6’ rootstock. In ungrafted nursery stock trees, diene concentrations were around 3 times higher in ‘Velvick’ than ‘Duke 6’ leaves. The ‘Velvick’/‘Hass’ combination also had a significantly lower leaf N concentration, a significantly higher fruit flesh Mn concentration, and significantly lower and higher leaf N/Ca and Ca+Mg/K ratios, respectively. A significant correlation (r = 0.82) between anthracnose severity and skin N/Ca ratio was also evident

Postharvest diseases of mangoes in Fiji

Despite considerable research globally on postharvest diseases of mango, virtually no work has been done to determine the occurrence of these diseases and their causal agents in Fiji. This study is the first major field and market survey of postharvest diseases of mango in Fiji. For the field survey, fruits from five local mango cultivars were harvested at each of five locations. Fruits from five imported cultivars were also harvested from one location in Nadi. For the market survey, vendors were selected at five municipal markets for fruit collection, along with ten roadside stalls. For field and market surveys, fruits were incubated at 23°C and assessed for postharvest disease (incidence and severity of body rots and stem end rots) when ripe. Isolations were made from disease lesions and fungal cultures were identified using multilocus sequence typing. High incidences of body and stem end rots were recorded across all surveys. In the field survey of local cultivars, ?Salusalu? fruits were found to have the lowest severity of body rot and stem end rot on average, while for imported cultivars, ?Nam Doc Mai? had the lowest average severity of these diseases. The market survey showed that ?Salusalu? had a lower incidence of anthracnose on the body of fruit compared to all other cultivars, although it did have a surprisingly high incidence of stem end rot at some localities. Fungal isolates from anthracnose lesions in the field and market surveys were identified as Colletotrichum asianum, C. simmondsii and C. fructicola. C. asianum was the predominant species associated with anthracnose symptoms, accounting for 97% of isolations. Lasiodiplodia theobromae and Neofusicoccum parvum were the predominant species found in association with mango stem end rot symptoms. Other species isolated from mango stem end rot in lesser numbers included L. brasiliensis, N. umdonicola and N. kwambonambiense. All of these fungi represent new reports for Fiji

Pepper spot: A preharvest disease of lychee caused by Colletotrichum gloeosporioides

Pepper spot of lychee was found to be caused by Colletotrichum gloeosporioides

Diseases

This chapter describes the following diseases infecting longan and litchi (Litchi chinensis): soilborne diseases (rot caused by Armillaria mellea, litchi decline, and longan decline); diseases in nurseries (caused by Fusarium, Pythium and Rhizoctonia species); foliar, floral, fruit, stem and preharvest diseases (algal spot caused by Cephaleuros virescens, corky bark caused by F. decemcellulare [Nectria rigidiuscula], downy blight caused by Peronophythora litchii, branch blight and fruit rot caused by Lasiodiplodia theobromae, pepper spot caused by Colletotrichum gloeosporioides [Glomerella cingulata], leaf blight caused by Phomopsis species, Phytophthora-incited diseases, sooty mould and black mildew, witches' broom, and minor foliar and stem diseases); and postharvest diseases (anthracnose caused by Colletotrichum species, stem end rot, and other postharvest diseases). Information on symptoms, morphology of causal agents, vectors (insects and nematodes), and control strategies (mainly cultural and chemical) is provided