Questioni have several trees aprox 4years old and they are covered with red spots on the leaves i have tried the garden centres in spain for advice without success iam thinking of cutting them down and burning ten eucaliptus all badly infected any suggestions regards john
AnswerEucalyptus rust (Puccinia psidii)
Puccinia psidii, a rust fungus native to South and Central America and the Carib-bean, causes a serious leaf and shoot disease of a wide range of Myrtaceae (ten generaand 33 species) including Psidium gujava (guava), Syzygium aromaticum (clove), Pimento.
Leaf spots caused by P. psidii on EucalyptusThe fungus attacks foliage, inflorescences andyoung, succulent twigs of the hosts. The initialsymptom of the disease is appearance of tiny,circular, yellowish powdery eruptions on the leafor stem surface. These eruptions turn a distinc-tive egg-yolk yellow color in a few days. Theinfection loci expand in due course and becomenecrotic and spread over the entire leaf, stem,shoot and fruits. Leaves and stem can bedeformed by the disease and growing tips candie back if the infection is severe. Defoliation andDried and shrivelled leaves of Eucalyptusfollowing severe infection by P. psidiiis considered to be one of the serious threats to eucalyptsand other members of the Myrtaceae in Australia and othercountries in the Asia-Pacific region and elsewhere (e.g.,Africa and Europe) where eucalypts and other members ofMyrtaceae are grown.
The occurrence of the disease will also have indirect effects on native fauna and humanlifestyles.Spores of P. psidii are very small and can remain viablefor months. The disease can spread from country tocountry through movement of infected plant material suchas seeds, nursery stock and germplasm, spores on timberand wood packing, people carrying spores on clothing,shoes, equipment and contaminated freight containers.Wind-borne seeds are one major source of inoculum. To prevent spread of the rust from its native range, it is necessary to strengthen quarantine measures and import conditions, create public awareness, carry out surveillance pro-grams for early detection of outbreaks, and analyse andblock pathways through which incursions can occur.
Fungicides can be successfully employed for disease control in eucalypt nurseriesand on coppice growth. Application of mancozeb (a protectant fungicide) 10 days prior toinfection has been effective in preventing the occurrence of the disease.
Other controls used are Lime-sulfur spray: Very dilute applications of lime-sulfur liquid spray (calcium polysulfide) applied repeatedly during the time infections appear, can stop the spread and growth of leaf rust fungi. Lime-sulfur stinks, however, like rotten eggs. It is relatively non-toxic, though. Full strength solutions for spraying when woody plants are dormant can burn foliage on growing plants, so use very dilute solutions.
