Farmers can make their own mixture and use it as and when required for controlling infestation in coconut. Given below are some simple steps for making the mixture.
Dissolve one kg of powdered copper sulphate in 50 litres of water in a mud pot or plastic bucket. Dissolve one kg of lime in 50 litres of water (lime solution).
Pour the copper sulphate solution into the lime solution slowly and slowly stir. To detect presence of more copper dip a new steel knife into this solution.
If a brownish coat appears on the knife then add more lime solution. Keep repeating the procedure till the brown coat no longer forms on the knife. Presence of free copper is injurious to plants, hence to test for the excess copper if any,
After preparing the solution it is advisable for farmers to use it immediately as it loses its efficacy with lapse of time. However, if mixture is to be preserved for the next days add 50 to 100 g sugar or jaggery into the 100 litre solution.
Drenching of diseased coconut palms with one per cent borax solution thrice a year is effective in reducing the intensity of Thanjavur wilt disease. Drench the pits with one per cent bordeaux mixture before planting coconut seedlings.
Bordeaux paste consists of the same ingredients as those of bordeaux mixture but it is in the form of a paste.
It is generally made by dissolving 100 gms of copper sulphate and 100 gms of quick lime each in 500 ml of water separately.
Remove infested tissue
Removal of affected tissues on the coconut stem with a chisel and smearing with warm coal tar or bordeaux paste over the chiselled portion controls stem bleeding.
If the disease is detected when the central shoot withers, application of 10 per cent bordeaux paste after thorough cleaning and removal of infected plant parts can reduce further spread.
The treated portion has to be covered with a plastic sheet to prevent washing of the paste during rains.
Spraying one per cent mixture twice a year reduces leaf rot infestation. Spray must be in fine mist form otherwise it will coalesce and trickle down without sticking properly on the nut surface.
(M. Surulirajan, Asst prof & K. Rajappan, Associate prof, , Coconut Research Station, Veppankulam, Thanjavur, email: firstname.lastname@example.org, phone: 04373- 260205.)