Abstract

Intensive application of manures and fertilisers is one of the chief methods of increasing crop yields. A close relationship between manuring and incidence of pests and diseases has been observed by research workers. The interesting observations made by the author on the influence of manuring on the incidence of the fulgorid-Nilaparvata lugens S on paddy are recorded in this note. The work done on this aspect in India is rather limited. Andrews (1923) remarks that nitrogenous manures should be used with caution. Dealing with the incidence of Helopeltis theivora W on tea, he mentions of a distinct reduction in damage by the bug with the application of potash to the soil. McCollach and Salmon (1923) conclude that silica applied in the form of sodium silicate wards off the Hessian fly-Mayetiola destructor S on wheat. Less (1926) and Evans (1938) mention that the reproduction of aphids is positively correlated with nitrogen and protein contents of the plant. Martin (1940) holds the view that increased applica- tion of nitrogenous manures creates favourable conditions for diseases and that plots not manured with potash are the first to be attacked by insects. Balasubramaniam and Kesava Iyengar (1950) have recorded that the application of groundnut cake and cattle manure has given rise to an increase in incidence of the cotton jassid - Empoasca devastens D.

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