DEAD-TOP OFPINUSSPP. IN VICTORIAN PLANTATIONS

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Abstract
Field surveys of several Forests Commission pine plantations revealed the presence of dead-top in some areas. The evidence suggested that the disorder was. associated with moisture stress during hot, dry summer months in Pinus spp. growing on shallow soils with a high tree density. Affected sites usually had exposed northern or westerly aspects. The first symptoms' appeared in late summer or early autumn. Experimental work in the glass-house designed to closely simulate field moisture stress conditions during the hot summer months, has reproduced the deed-top condition in young trees of Pinus radiata D. Don. Tree recovery has been demonstrated when the moisture stress was relieved by watering. Similar conditions of moisture stress during the winter produced a general wilting and dying of the trees instead of dead-top symptoms. Results suggest that under field conditions a reduction of tree population would alleviate the trouble. A plantation at Beechworth severely affected with dead-top was heavily thinned in 1951 and has since shown no evidence of the disorder. No primary association between the fungus Diplodia pinea Kickx. and dead-top was established in a pathogenicity test using Pinus radiata as the host plant.

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