Indagini sui fenomeni di moria dei pini in Sardegna con particolare riferimento aPinus radiataD. Don.

Mortality inPinussp. in Sardinia - in particular,P. radiataD. Don - was investigated between 1976 and 1978. Preliminary studies had revealed an association betweenMacrophomina phaseolina(Tassi) Goid. (the causal agent of charcoal root rot disease) with affected plants. The disease occurred on plants of different ages in 24 of the mainP. radiataplantantions and nurseries. In every case, the presence ofM. pllaseolinawas confirmed. The disease varied in spread and severity from rather low to very high values. It was also recorded onP. pineaL.,P. halepensisMill.,P. patulaSchl. et Cham.,P. pinasterSol. andP. nigraArn. ssp.Laricio(Poir.) Palabin Coste. The occurrence of infection, the symptomatological progress of thc disease and microscopic characteristics of affected tissues wcrc invcstigntcd both in the field and in the laboratory. Data concerning the incidence of disease - which first became serious in 1975, showed a low value in 1976 and 1977 and increased again in 1978 - were obtained by field obscrvation and trials in experimental plots. Several strains ofMacrophomina phaseolinawere isolated from affectcd plants. They were very similar morphologically and in their tempe· rature responses. Regarding microsc1erotia size, thcsc strains can bc included in Haigh's «C-type ». Environmental factors favouring the development of the disease were investigated. Analysis revealed that the occurrence of disease in the field can be attributed both to affected plants having come from nurseries and to direct infection due to presence ofCistus monspeliensisin the planting arca. Seeds of otherPinusspecies were disease-free. Some planting systems appear to favour the development of the disease in certain climatic conditions. In particular, a combination of high temperature and prolonged periods of water stress increase infection withM. phaseolina.