Severe summer may affect leaves and basal bark tissue of small plants, resulting in their drying up. This has to be prevented by appropriate protection measures. In the case of budded stumps, shade has to be given by using shade baskets and also by mulching using dry leaves and plant parts. Usually shade baskets made of bamboo or plaited coconut leaves are used, the baskets having 45-60 cm height and 30-45cm diameter. Plants raised in polybags may not require this type of shading.
Mulching is usually done using dried leaves, grass, cover crops etc. Mulching is ideal for maintaining soil moisture and soil temperature, to increase the organic matter content in the soil and to prevent weed growth.
White washing should be adopted from the second year of planting till the canopy closes in order to protect the stem portion of the plants from sunburn. For this the brown stem portion between the bud union and the first branch is whitewashed using lime. This is done based on the principle that white surfaces will not absorb too much of heat. For whitewashing using quick lime, copper sulphate need not be added. Using china clay, mud etc will not serve the purpose.
Precautions have to be taken, as the chance of fire is very high in rubber plantations during summer and hence fire belts have to be made around the plantation. This is done by removing all vegetation like bushes and also removing all dried leaves in an area of 5-7 m width around the plantations, in the form of a belt, so that even if a fire occurs outside the plantation, it will not spread into the plantation. All other possible precautions against fire should be taken, as it will always be beneficial. The fire belt has to be cleaned frequently of dried leaves, which may accumulate in this area. It is advisable to insure plantations against natural hazards like fire and storm.
Other protection measures
Cattle should not be allowed into rubber plantations. Cattle may feed on rubber plants and also cover crops thus destroying them besides damaging the superficial root system of rubber plants. Fencing around the plantations or constructing retaining walls can be useful.
The most important aspect to be taken care of while establishing a new plantation is the protection of young rubber plants especially in the initial two to three years. Anything that may suppress the growth of the rubber plants during this period may adversely affect its growth in future and will consequently affect the economic stability of the crop in later stages. However better care is given in later situations for such plants, they may not improve from the setback that occurred in the initial growth phases.
Shading for polybag plants
In order to protect the young polybag plants kept in open spaces, from drying in severe summer, shade has to be necessarily given. Plaited coconut leaves that permit passage of sufficient light can be used to partially cover the sides and top portions of the polybag nursery.
To ensure vigorous growth of the young rubber plants in the nursery, in summer season, regular irrigation is recommended. Irrigation should be given only in the morning and evenings. For nurseries spread over large areas it is advisable to divide the area into blocks and then irrigate the blocks by rotation depending on the availability of water. For irrigating polybag plants in the nursery the ideal time is evenings.
Controlling leaf diseases
Incidence of leaf spot and birdís eye spot on the leaves of young plants in the nursery is common in summer season. These diseases are caused by fungi and can be controlled effectively by application of 1% Bordeaux mixture.
Powdery mildew disease
If refoliation of trees in the plantations extends over a long time, there is the possibility of repeated incidence of powdery mildew in the young developing foliage and also in the polybag plants. During the period of refoliation in plantations, it is advised to apply Sulphur dust (325 mesh size) at the rate of 11-14kg per hectare. This can be applied 3-6 times during this period, at an interval of 7-14 days.
A mixture of 70% Sulphur and 30% talc is recommended and this should be applied using a dusting machine. For young plants and polybag plants, wettable sulphur (Sulfex) at the rate of 10 g in 4 liters of water should be applied once at an interval of 7-10 days using sprayers.
Spraying of wettable sulphur and Bavistin on alternate days at an interval of 7-14 days and application of 5g Bavistin and 1.25 g wettable Sulphur together in one liter of water also is very effective.