DANGEROUS INTERNATIONAL FOREST TREE DISEASES 59 



black powdery mass of spores. The spores are brown, subglobose to 

 oval, 1-celled, wall darker, smooth, 4.9-6.1 X 2.7-3.7/*. They are wind- 

 blown and infect trees through wounds caused by pruning or lop- 

 ping of branches. From the stem, the fungus travels into the roots. 

 Secondary spread of the disease occurs through infected roots by 

 root contact and grafting. Owing to long spreading lateral roots, 

 the disease spreads rapidly in plantations. Diseased trees occur in 

 groups. Infected trees are killed in 6 to 8 months. 



Prevention of pruning and lopping will eliminate or reduce pri- 

 mary infection. Secondary spread of the disease may be checked 

 by trenching diseased trees. All dead trees including infected ones 

 should be removed. 



This is the most serious disease of Casuarina in plantations in south 

 India. Trees are attacked mainly in plantations of pure Casuarina 

 with usually 7 years rotation. Losses are high, up to 75 percent mor- 

 tality in some stands. 



Casuarina is indigenous in Australia, the Pacific Islands, and Ma- 

 laya and is also planted in Central and North America. It was in- 

 troduced into south India where it is now naturalized. Export of 

 diseased plant material should be prevented. 



Hosts : Casuarinaceae — Casuarina equisetifolia Forst. 

 Literature: Bakshi, B. K. Mortality of Casuarina equisetifolia 

 Forst. Indian Forester 77 : 269-276. ; 1951. 



Sal Root Rot 



Polyporus shoreae Wakef . A common fungus in sal (Shorea robusta 

 Gaertn.) forests of north India but becomes of economic significance 

 in wet sal type only where annual rainfall is over 75 inches. The dis- 

 ease is encountered on good sites with sal in quality classes I, II, 

 and III (over 100 ft., 80-100 ft., and 60-80 ft, height growth, 

 respectively). 



The fungus attacks healthy uninjured roots and progresses towards 

 the collar but does not normally advance into the stem. Light yellow 

 mycelial felts develop in patches on bark. White pocket rot develops 

 in bark and sapwood. The affected tree shows symptoms of top dy- 

 ing after about three-fourths of the root system is attacked. Dying 

 extends downwards till the tree becomes dead or, as commonly hap- 

 pens, the diseased tree becomes windblown due to decayed roots. Dis- 

 eased trees occur in groups. Sporophores develop at the base of the 

 tree. They are sessile, pileate, brown. 



The disease is serious in wet sal forests of north Bengal and Assam. 

 Healthy, vigorous trees of advanced age are attacked. Mortality may 

 be 20 percent or more. High moisture in soil favors activity of the 

 fungus. Control burning, recommended in silvicultural practice in 

 wet sal forests, will reduce soil moisture and check growth of weeds 

 which thereby reduces disease incidence. Dying and dead trees should 

 be removed and converted, since timber quality is not affected. 



Shorea robusta and other species of Shorea occur in India, Pakistan, 

 Burma, and the Far East. The occurrence of Polyporus shoreae out- 

 side its known range in India should be determined. 



Hosts : Dipterocarpaceae — Shorea robusta Gaertn. 

 Literature : Bakshi, B. K., and Boyce, J. S. Polyporus shoreae root 

 rot of sal. Indian Forester 85 :656-658. 1959. 



687-137 O — 63 5 



