Evaluation of crop loss due to abnormal leaf fall disease caused by Phytophthora spp in rubber (Hevea brasiliensis) plantations of the clones RRIM 600, GT 1 and RRII 118 over 14 years revealed 31.66, 8.21 and 7.15 per cent loss respectively. No such loss was observed for the clone RRII 105 in the plantation in south western India. The mean leaf retention in clone RRIM 600 was only 14.32 per cent as against 54.82 in RRII 105. There was a significant and positive correlation between crop loss in the clone RRIM 600 and the leaf fall in the preceding two years. For RRII 105, the depression in yield during the disease season was compensated by the post wintering resurgence in crop production. The weather conditions had more pronounced effect on crop production in this clone than the disease incidence. The adverse effect of disease on the affected clones resulted in poor girthing and lower wood volume at felling. An increase in crop by 2 to 3 per cent compensates for the cost of spraying. Location specific recommenda­tions of clones for disease avoidance could be a useful strategy for higher crop production. 

The study examined factors influencing rubber export from Nigeria using error correction representation procedures with a view to ensure that the short-run dynamics is being integrated with the long-run supply relationship between rubber export and various explanatory variables. The analysis was carried out using time series data collected over 34 years (1970-2003) on the identified key factors that could influence export of the commodity.
The findings confirmed that rubber export was influenced by the producer's price, world price and the exchange rate. In addition, there is high feedback captured by the coefficients of the error correction mechanism. Statistical significance of the error correction terms validates the existence of an equilibrium relationship among the variables in each cointegrating vectors. There seems to be an instantaneous change in the short run equilibrium to long run equilibrium values of the export as a result of policy changes in the regressors. Based on the observations, policy inputs are provided. 

Variations in the length, width and wall thickness of normal wood fibres (NF) and tension wood fibres (GF) were studied at different height levels of four clones viz. Tjir 1, GT 1, RRIM 600 and RRII 105 of Hevea brasiliensis. Length and width of both types of fibres showed a fluctuating trend from pith to periphery. In all these clones the average length of NF was more than that of GF. The variation in length and width of NF and GF between clones and different height levels was not statistically significant. However, highly significant variations were observed in length, width and wall thickness of normal and tension wood fibres within all the four clones. 

The study is an approach to identity the causes of low yields in rubber smallholdings in Sri Lanka through question­naire surveys, field inspections and participatory rural appraisals (PRA). Further, a case study is presented which merges information collected from various data collection procedures including farmers' views. The study was conducted in three major rubber growing districts, viz., Kegalle, Kalutara and Ratnapura. Growth Performance Index (GPI) and Yield Performance Index (YPI) were suggested to identity the existing status of immature and mature holdings. The GPI suggests only 35 per cent of the sample had the required tree girth for successive subsidy payments. Based on the YPI, 73 per cent of the fields have recorded below average yields, mainly due to low proportion of holdings under new improved clones. Awareness and adoption rates of most of the recommendations were low, which may be a great set back on achieving expected targets, although new improved clones and planting material are being distributed among smallholders. The Bayesian Network (BN) model helps to come up with suitable remedial measures to improve the productivity in the smallholder sector of Sri Lanka and is of immense importance in making appropriate policy decisions. 

In an experiment  to assess the fertilizer requirement during immature stage of Hevea brasiliensis clone RRII 105 laid out in an acidic soil of high organic carbon and low P and K status it was observed that 30, 30 and 20 kg/ha/year of N, P₂O₅ and K₂O respectively were sufficient for growth improvement. In the early tapping phase highest yield was observed when 60, 30 and 40 kg/ha/year of the nutrients were applied. Though P build up was noticed in all the plots when it was applied, K and organic carbon contents were not influenced by the treatments. There was no influence of the treatments on leaf N and P status. 

The effect of planting density on rubber (Hevea brasiliensis) was studied in a trial which consisted of five densities as the main plot treatment and two methods of calculating fertilizer requirement by area and plant basis as sub plot treatment. Density of planting had significant effect on girth of plants by the ninth year from planting but the fertilizer treatments did not have any effect. Plants at the lowest density of 420 trees/ha recorded the highest girth increment, bark thickness and percent  tappability. The general plant architecture was also balanced in the lowest density. However, plants at 479 trees/ha and 549 trees/ha also performed reasonably well. Plants in these densities had a comparable girth, bark thickness and percent tappability with those in the lowest density. A density above 549 trees/ha was observed to adversely affect girth, bark thickness and percent tappability