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Shot-hole borer (Xyleborus fornicatus Eichh.) of tea in Ceylon II.—The effect of chemical control on the yield and manurial response of tea

Published online by Cambridge University Press:  10 July 2009

J. E. Cranham ,
P. Kanapathapillai  and
A. Kathiravetpillai
J. E. Cranham
Affiliation:
Tea Research Institute of Ceylon, Talawakele, Ceylon
P. Kanapathapillai
Affiliation:
Tea Research Institute of Ceylon, Talawakele, Ceylon
A. Kathiravetpillai
Affiliation:
Tea Research Institute of Ceylon, Talawakele, Ceylon
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Extract

In 1960–65, six field trials were carried out on tea estates in Ceylon to assess the effect on yield, and on the response of the crop to fertilizer, of dieldrin sprays applied after pruning to control shot-hole borer (Xyleborus fornicatus Eichh.). Periodic sampling was carried out to assess the numbers of borers and their galleries. Yields were recorded by weekly or fortnightly weighings of the green leaf plucked, over pruning cycles of two to four years.

The pattern of the yield increases on the sprayed plots was related to the difference in attack between the sprayed and unsprayed plots. Increases were, in general, small in the first year and much larger in the second year, reaching peak values of 32–58 per cent. (on the yields of successive three-monthly periods recorded) in the late second year, and declining thereafter through the third year as the difference in attack declined. Over the first two years there were marked yield increases in eight of the nine pruning cycles, and these ranged from 11·7 per cent, to 26·3 per cent. There was significant regression (P<0·001) of the percentage increase in yield on the maximum difference in gallery counts. Yield increases in the third year of pruning cycles were also considerable and the results evidence a prolonged effect of the heavy borer attack occurring in the second year.

In one trial there was a significant interaction between the effects of dieldrin spraying and of nitrogen supplied. Control of the borer greatly improved the crop response to nitrogen. Nitrogen application increased the yield but resulted also in a proportionately larger loss of crop from borer attack. There was a small but significant increase in the number of borer galleries on the plots receiving nitrogen.

The evidence on the size and pattern of crop losses caused by the borer suggests that these occur both from shoot breakages and from the direct effect of galleries on the growth of stems.

The significance of the results in relation to estate practice, and the economics of spraying, are briefly discussed.

Type
Research Paper
Information
Bulletin of Entomological Research , Volume 57 , Issue 4 , June 1968 , pp. 619 - 641
Copyright
Copyright © Cambridge University Press 1968

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References

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