Bioecology of the fungus Sphaeropsis sapinea dyko & Sutton - agents of pinus species decline
Authors: Milijasevic Tanja 
Published: September 2009

Sphaeropsis sapinea is a cosmopolitan fungus, identified in more than 50 countries of the world, on all continents, but it is primarily the species of warm lands. It is also a polyphagous fungus recorded from 11 coniferous genera. The most endangered and the most frequent host plants are Pinus species - it occurs on 48 pine species, among which the most susceptible are Pinus Radiata, P. nigra, P. sylvestris, P. ponderosa, P. resinosa, P. mugo, P. pinaster and P. elliotti. The greatest damage is caused on the introduced Pinus species and on those cultivated in artificial plantations, shelterbelts and in urban environments. In Yugoslavia S. sapinea is widely distributed both in the continental and in the Mediterranean parts. It was identified from ten pine species and six hosts from other coniferous genera. By the study in our country, the new hosts of this fungus were detected - Pinus jeffrey, P. peuce and P. heldreichii. The most endangered species in our country is Austrian pine, both in urban environments, and in plantations The symptoms of the disease are bud wilt, curling, stunting and necrosis of current year shoots and needles, dieback of top shoots, parts of crown or tree tops, branch and stem bark canker, root collar rot on the young plants in nurseries and their dying. This fungus also prevents seed germination of Pinus species and causes blue sap stain of the freshly cut wood, although sap stain was also observed on standing trees. More rarely it causes root rot and crown wilt of Pinus species. The main symptoms of infection, both of young plants and older trees, are the dieback of current year shoots S. sapinea can penetrate through buds, bark of young shoots and needles. The critical time of infection is the period from mid April to mid May. Then infection mainly penetrates through the bark of young shoots, which results in their dying. Infection through the needles occurs mainly at the time of their sudden growth or during summer months. The first visible symptoms of infection of the young shoots are in the form of brown necroses, resin bleeding and several short pairs of needles at the place. S. sapinea can infect male and female flowers, current year and second-year cones. The pycnidia with mature conidia can form on the shoots, needles, first-year and second-year cones during the year of infection. The first mature fructifications are mostly formed in the bark of young shoots, in the zone of infection, and they were recorded in late June at the earliest. They were recorded on the cones at the beginning of the third decade of July. Pycnidia are formed in the bark, on the needles and on the second-year and older cones, on male and female flowers, as well as on the cones in the first year of development. The size of S. sapinea conidia on different Pinus species is very variable throughout the world and ranges widely from 16.8-55.0?7.0-21.0 ?m. Our study shows that the size of pycnospores in our country is also variable and it ranges 14.8-51.4?9.7-20.2 ?m The optimal temperature for spore germination and germ tube growth is 27?C, and the optimal temperature for mycelial growth on the media PDA and MEA is 28?C. The formation of fruiting bodies in the culture is affected by light and the presence of sterilised needles on the mycelium The correct and timely control measures can contribute to reduce the consequences of this serious disease, by the combined application of silvicultural and chemical measures. Chemical control is recommended in the nurseries, severely infected plantations and in urban environments. The fungicides which showed the greatest efficiency are the preparations based on copper and Benomil.