Under low frequency tapping systems, trees are stimulated from the first year of tapping using ethephon (2.5%) by panel application method to achieve sustainable yield. Number of stimulations to be given varies with clone and frequency of tapping (ref. table T2 on page 35). Use of ethephon is also recommended for medium yielding clones (RRIM 600, GR1, PB 28/59, PB 86, etc.) which are under alternate daily frequency of tapping in C (B1-1) and D (B1-2) panels. Three stimulations per year can be done following panel or lace application method. Concentration of ethephon to be used is 2.5% for panel application and 5% for lace application. Months of application can be April/May, September and November.
In newly opened trees/on trees with tapping resumed after annual rest, or rested during monsoon due to absence of rainguarding, ethephon at 5% (active ingredient) concentration may be applied once (over the lace after two tappings).
Methods of Application
Panel application method (2.5% ethephon applied with a brush made from coconut husk just above the tapping cut on to the recently tapped area to a width of 1.5 cm) is recommended for general use. Lace or groove method of application can also be adopted. In these methods, ethephon (5%) is applied on the cut surface of the bark over the lace or after removing it. Among various methods, panel application is easy, most economic and efficient.
The ready to use formulation of Ethephon available in the market for use in rubber usually contains 10% active ingredient. Five per cent concentration of the active ingredient is as effective as 10%. The 10% formulation can be diluted to 2.5 % (1:3) or 5% (1:1) with palm oil, or coconut oil. Ethephon-39% a.i. available in the market can also be used. However, dilution may be done carefully. The diluted mixture may be stirred frequently while applying. In newly opened trees or trees tapped after rest, first stimulation may be done by lace application of 5% (a.i.) ethephon after the second tapping.
Duration of Continuous Application
There is declining trend in the response to continuous application of ethephon under 100% tapping intensity (S/2 d2). Accordingly, continuous application of ethephon is not recommended for periods of more than three years at a stretch, under d2 frequency of tapping.
Points to Remember
* Do not stimulate trees with TPD symptoms.
* Do not stimulate trees of medium yielding clones tapped daily or trees of high yielding clones tapped alternate daily.
* Do not apply Ethephon on the portion of bark previously treated.
* Do not apply Ethephon during drought period under S/2 d2 and S/2 d3 system.
Under low frequency tapping (d3, d4 & d6), the stimulation schedules recommended will not result in yield decline, any injurious effect or increased panel dryness (brown bast) in the course of time. However, if trees under alternate daily tapping are stimulated for more than two years, there will be increased panel dryness.