263 



•of blight when no other complicating disease is present, the correspon- 

 dence between the first appearance of blight and the first generation 

 of froghoppers, and the periodicity of the blight. The spread of 

 injury from the original point of infection indicates the possibihty 

 of some toxin or enzyme being introduced into the plant. Root 

 disease plays an important part as a secondary factor. 



The most important factor in determining the prevalence of blight 

 is the humidity just above and just below the surface of the ground. 

 A table indicates the known effect of moisture on the cane, the root 

 fungi, the froghopper and its enemies. 



The essential preventive against blight is to keep the soil and crop 

 in such condition that no encouragement to the breeding of froghoppers 

 is produced. To this end, drainage should be improved, and should 

 be kept in working order even on land temporarilv abandoned. Pen 

 manure and lime are required on almost all land^ in Trinidad. The 

 tilth and depth of the surface soil requires careful attention. Only 

 plant and first ratoon canes should be grown on lands that prove 

 constantly liable to blight, until the soil can be worked into better 

 condition. Graminaceous crops are not recommended for rotation, 

 but Leguminous crops have given success, particularly Bengal beans! 

 cowpeas, and sword beans ; yams and sweet potatoes also may be used'. 



Direct remedial measures are the destruction of eggs by the removal 

 of dead leaves about ten days after the maximum numbers of any 

 generation, the rubbish being carried to the pens and later used as 

 pen manure. Weeding should be done at the same time. Burning 

 destroys the eggs, but is a wasteful method. Spraying is not prac- 

 ticable. Hand collection of nymphs and adults is possible but tedious. 

 Spraying with kerosene emulsion has been suggested, but has not been 

 tried in the field. Light traps catch many adults, but only about 1 per 

 cent, of these are females. The adults can be caught in large numbers 

 by the use of nets in late evening and early morning. Trials are being 

 made with nets drawn by mules. Natural enemies should be encouraged 

 wherever feasible and watch should be kept for possible new ones. 



SiMMONDs (H. W.) & Knowles (C. H.). a Disease of Clidemia hirta 

 in the Lower Rewa District.— Af/;?/v. Circ. Information Fiji Dept 

 Agric, Suva, i, no. 1, Januarv 1920, pp. 9-12. TReceived ^9th 

 March 1921.] ^ rt- . 



A disease said to be killing a weed, Clidemia hirta, appears to be 

 first brought about by Nematodes, Heterodera sp., and then continued 

 by fungi. There is no doubt that in the areas affected the weed is 

 dymg out, and valuable crops such as paspalum and reeds are now 

 replacmg it. In the poorer class of land under consideration the cost 

 of clearmg would be prohibitive. The general use of this organism • 

 as a means for checking Clidemia'm Fiji is deprecated, as Nematodes 

 are known pests of cultivated plants there. 



SiMMONDs (H. W.). Report on Mission to Tahiti to investigate the 

 Parasites of the Coconut Scale with a View to their Introduction 

 into Fiji. — Mthly. Circ. Information Fiji Dept A^ric Suva i 

 no. 7, July 1920, pp. 133-138. [Received 29th March 1921.] 



The author left Fiji for Tahiti early in 1920 in search of parasites of 

 Aspidiotns destructor. 



At Tahiti the scale is almost entirely confined to the coast and is 

 most common m places exposed to the prevailing winds, which appear 

 to protect It somewhat against its very frail winged enemies. ]\lanv 



