Comprehensive studies were conducted (during 1998, 1999 and 2000) to determine effectiveness of various control methods including varietal resistance, mechanical, cultural and chemical control by integrating them in all possible combinations on different varieties of sugarcane for the control of top borer of sugarcane (Scirpophaga nivella F.) Role of weather and morpho-physico-chemical plant factors were also determined on selected varieties of sugarcane showing resistant, susceptible and intermediate behaviour. Ten varieties of sugarcane viz… CP-43/33, L-118, COL-54, COJ-114, Triton, CP-72/2086, CP-77/400, BL-4. SPSG-26 and BF-162 were screened out on the basis of top borer infestation at tillering stage during 1998. Amongst these, CP-43/33 and L-118 showing susceptible, BF162 and SPSG-26 showing resistant and CP-72/2086 showing intermediate responses were selected for final screening during 1999. Morpho-physico chemical plant factors as well as quality of sugar were determined to see their affects on the pest infestation. Different control methods were applied for the control of top borer at three different places on resistant (BF-162) and susceptible variety (CP-43/33) of sugarcane during 2000. The results are summarized as under:
None of the variety was found completely immune against the pest infestation at tillering as well as at maturity stages.
CP-43/33 was susceptible while BF-162 was found resistant variety during both the study years i.e. 1998 and 1999 on the basis of tillering and maturity stages. 1st week of May showed maximum tillering infestation followed by 1st week of April, 1st week of July and 3rd week of July during 1998. Similarly during 1999, last week of March showed maximum pest infestation followed by last week of July and 2nd week of May.
Pest infestation at tillering stage as well as maturity stage was higher during 1998 as compared to1999.
Abiotic factor did not show significant contribution in the fluctuation of pest infestation during 1998, 1999 and on cumulative basis. However, the contribution of these factors were calculated to be 12.9, 61.1 and 13.5 per cent during 1998, 1999 and on cumulative basis, respectively.
All the morpho-physico-chemical plant factors differed significantly among varieties except total minerals and manganese.
Plant height, cane girth, leaf area and leaf sheeth hairiness showed negative and significant correlation, whereas thickness of leaf lamina and moisture contents showed positive and significant correlation with the pest infestation at tillering stage.
The coefficient of determination value was 96.1 per cent when all the morpho-physical plant characters computed together for multivariate regression models.
Leaf area appeared to be the most important factor followed by leaf hairiness with variance value of 22.08 per cent in first component.
Total minerals manganese and copper contents did not show significant correlation with the pest infestation whereas nitrogen, potassium, calcium, magnesium and ferrous contents manifested positive and significant contribution with the pest infestation. Phosphorous, carbohydrates, fats and zinc contents produced significant and adverse effect on the pest infestation at tillering stage.
The chemical plant factors showed significant influence on pest infestation contributed 96.5 per cent role when computed together for multivariate regression models.
Zinc contents with contrasting behaviour appeared to be the most important character with co-efficient value of 0.764 followed by Ferrous with positive sign. The variance value was determined to be 68.53 per cent. But in second component Ferrous with positive sign was important, followed by potassium with contrasting behaviour. The variance value was 26.44 per cent.
The effect of borer infestation was significantly negative on POL, Brix contents of CES. The coefficient of determination value was 0.821, obtained by computing Fiber contents POL, Brix and CCS factors together for multivariate regression models.
Brix appeared to be the most important factor in first component followed by POL, CCS and Fiber contents. All the factors showed positive response. The variance value was 89.56 per cent. In the second component Fiber was appeared to be the most important factor followed by CCS with contrasting behaviour. The variance value was 6.88 per cent.
During 2000, application of trash mulching at the time of sowing proved to be the most effective treatment followed by Furadan, removal of dead hearts + spike thrust at 15 days interval, hand collection of egg masses at 15 days interval, and cutting of shoots at 15 days interval.
Application of Thiodan did not prove an effective treatment showing minimum protection level (3.03% as against 62.87% in trash mulching) against top borer on sugarcane.