Identification of Hevea clones is tedious but very essential for research and for cultivation. Studies on seed coat sculpturing using scanning electron microscope (SEM) have revealed that seed sur­face pattern is characteristic and constant for a given species or a group of species. An attempt was made to identify some popular clones by seed coat sculpturing under SEM. The seed surface of clone RRII 105 is areolate and areoles are granulated and well differentiated. Areoles have various sizes and shapes in Tjir 1. The seed surface of Gl 1 is verrucated with cloudy pattern whereas in PB 260 it is smooth psilate. In PB 312, the seed surface is rough with granules but in KRS 128 it is faintly reticulate with cloudy pattern. SEM studies have elucidated significant variation among clones for seed coat pattern. Hence seed coat micro morphology can be used as a vital parameter in the identification of Hevea clones. 

Corynespora leaf fall (CLF) disease caused by Corynespora cassiicola (Berk & Curt) Wei. is currently considered as one of the major leaf diseases of Hevea brasiliensis in South and South East Asian countries. Chemical control of this disease by high volume spraying in mature plantations is ex­pensive. Field experiments were conducted from 1998 to 2000 to assess the efficacy of oil-dispers­ible and dust fungicide formulations in controlling the disease. Four oil-dispersible fungicides viz. mancozeb 75 % powder, mancozeb 50 % liquid, copper oxychloride (COC) 56 % powder and mancozeb 50 % + COC 15% (mixed powder) and three dust fungicides viz. hexaconazole 2 % carbendazim 1.5 % and tridemorph 1.5 % were tested. Mancozeb 75 % powder and mancozeb liquid formulations were found to be more effective treatments among the oil-dispersible fungi­cides. COC 56% ODP and mancozeb + COC mixed formulations also gave significant control of the disease. Hexaconazole 2 % and carbendazim 1.5 % were found to be superior among the dust formulations. Dusting during refoliation period is more advantageous for controlling CLF disease as compared to spraying of Oil-dispersible fungicides. 

The effect of low winter temperature on CO₂ assimilation and associated gas exchange parameters and growth under agro-climatic conditions of Tripura in North-East India was studied in five dif­ferent Hevea clones grown in polybags. The study was conducted in three different periods viz., pre-winter, winter and post-winter. There was about 50% reduction in net CO₂ assimilation rate in winter compared to the pre-winter and post-winter periods. There was a clear low temperature ­induced photoinhibition of photosynthesis in winter indicating the harmful effects of high photo­synthetic photon flux densities (PPFD) in the stress period. Such photoinhibitory effects on the young plants could be reduced by partial shading. Apparent quantum yield (ɸ_c) of CO₂ assimila­tion was also lower in winter than in the pre- and post-winter periods. However, under cold stress, ɸ_c was relatively high in partial shade with values similar to the post-winter period. Overall growth was more in the plants grown under partial shade and this has been found to be due to the mainte­nance of photosynthesis for longer duration than in open conditions in the winter period. Differen­tial capacities in net photosynthetic rates under prevailing low temperature conditions were no­ticed among the clones. 

Seasonal activity of vascular cambium and bark anatomical parameters related to latex yield such as thickness of soft bark, latex vessel rows, height and width of ray cells in Hevea brasiliensis were studied for two consecutive annual cycles. Climatic variations have Significant influence on cam­bial rhythm. With the onset of rain in April-May, the cambium started to divide periclinally to produce daughter cells, which differentiated into secondary vascular tissues. Mean maximum thickness for the cambial zone was the highest during monsoon (June-September) and least during summer (February-May). Bark thickness was high during July to October and low during Febru­ary to May. The number of latex vessel rows in the soft bark was higher during the monsoon season and declined gradually in the succeeding months to a considerably lower number during the sum­mer. While ray height showed significant variation between seasons, width did not. Starch grains varied considerably both in size and distribution in bark, cambium and wood with seasonal fluc­tuations and were not located in the soft bark during January to March. Calcium oxalate crystals were found throughout the year in the bark with abundance in the month of June, November and February. Depletion of crystals was noticed in August, January and May. The role of reserve metabolites and especially that of crystals in plant metabolism is discussed.

Influence of different girth at opening for tapping (40, 45, 55, 60 and 65 cm) of Hevea brasiliensis trees belonging to three clones viz., GT 1, PB 217 and PB 235 on growth, yield and physiological function were studied over a period of ten years in South Eastern Cote d'Ivoire. Opening girth of 40-50 cm for the clone GT 1 and 50 cm for PB 217 and PB 235 was observed to be ideal. This girth achieved at six years after planting corresponded with the physiological maturity of Hevea.

In order to find out the number of rounds of weeding required for a satisfactory year-round control of Mucuna bracteata in planting strips, a trial consisting of eight treatments was laid out. Manual slashing was compared with three doses of Glyphosate, Paraquat in combination with 2, 4-D Na salt as well as Paraquat alone and two levels of 2,4-D. It was observed that Paraquat (0.43 kg a.i./ha) + 2,4-D (1.0 kg a.i./ha) and 2,4-D (1.0 kg a.i./ha) gave significantly better control. Seven rounds of spraying during the period of observation (692 days) were required for effective weed control. Economic analysis of the different treatments revealed that application of 2,4-D (1.0 kg a.i./ha) costs only Rs.4649/- as against Rs.16557/- for manual slashing. It is therefore concluded that growth of M. bracteata on the planting strips can be effectively and economically controlled with the use of 2,4-D.