349 



on the number and kinds of weeds surrounding the plantation ; thus 

 the wet spring of 1913, owing to a large growth of weeds, led to a 

 severe outbreak ; while in 1914, the spring droughts and the scarcity 

 of weeds resulted in a very belated and hmited appearance of the 

 pest. The destruction of weeds by ploughing early in spring is 

 accordingly an effective remedy. 



The experiments of 1914 were conducted on two plots, one of which 

 was watered thrice, and the other twice. A detailed description of 

 the plots and the weeds overgrowing them is given. Amongst the 

 latter, special mention is made of Saiissurea amara, L., on the leaves of 

 which the mites breed only in spring until May. In so far as the 

 growth of the plants is concerned, both the dusted and undusted 

 plants of the plot subjected to three waterings were practically of the 

 same height, while of the plants with two waterings the undusted 

 ones were higher than the dusted. Evidently the sulphur affects 

 the growth, and the additional watering gives the plants sufficient 

 strength to withstand this effect. The number of leaves is also 

 reduced by dusting, though at the same time it saves some of them 

 from dropping and by destroying the mites allows the plant to 

 produce more foliage. As to the pest itself, the results tend to show 

 that the absence of sufficient moisture favours its development ; and 

 that dusting with sulphur destroys the mites and decreases the injury 

 to cotton. 



The conclusions as to the effect of the combined dusting and 

 watering on the buds and flowers cannot be summarised, as they 

 are not complete. 



VAN Hall (C. J. J.). Ziekten en Plagen der Cultuurgewassen in 

 Nederlandsch-Indie in 1917, [Diseases and Pests of cultivated 

 Plants in the Dutch East Indies in 1917.] — Meded. Laboratorimn 

 voor Plantenzielden, Buifenzorg, no. 33, January 1918, 42 pp. 



Owing to the wet east monsoon [dry season] of 1916 and the pro- 

 longed rains during the west monsoon of 1917 insect injury was less 

 severe than in previous years. Helopeltis, however, was an exception 

 and did much damage to tea. The locust infestation of teak, Hevea 

 and coconut was negligible, whereas it has been noticeable everywhere 

 in 1915. The inadequate shipping facihties and consequent accu- 

 mulation of produce resulted in greatly increased loss through insects, 

 but the experience of 1916 having led to universal fumigation with 

 carbon bisulphide, tobacco of the 1917 crop suffered little from 

 Lasioderma [serricorne] and Sefomorpha [margalaestriata]. Potatoes 

 were seriously attacked in some districts by a Coccinellid, Ejnlachna 

 sp. Arachis hypogaea planted at the beginning of the east monsoon 

 [about mid- April] was injured by a T}'phlocybid leaf -hopper, about 

 25 per cent, of the crop being lost. 



Cacao suffered less from Helopeltis, and a reduction of infestation 

 was observed in estates where measures were taken against the 

 gramang ant [Plagiolepis longijjes], and the black cacao ant [Dolichoderus 

 bitnberculatiis] was introduced. Borers were unimportant ; Zeuzera 

 was less abundant and Phassns damor was reported once only. In 

 the dry season a Diaspine scale occurred abundantly in some localities 

 and was followed by a fungus infestation. Teak forests were infested 

 as usual by Galotermes tectonae, Duomitus ceramictis, Wlk., and 



