Controls on Chemicals and Residues

The Tea Research Institute (T.R.I.)

Ceylon as it was in the 1800’s ventured into coffee as the first British plantation crop, established to create the funds needed by the Governor of the island to fund the costs of undertaking the infrastructure needed. Unfortunately, not long after it’s establishment, disease in the form of Hemileia Vastatrix struck the crop. Because of a lack of a proper established research station, no effective treatment to combat the disease was available and between 1848 and 1870 coffee declined and by the 1880’s tea had emerged as the new plantation crop and coffee had been wiped out as an effective crop. I am not going into the human disaster this caused for both the planters and their workers here but it was extreme and sufficiently extreme for Sir Arthur Conan Doyle to comment on it in his short story, ‘De Profundis’ published in 1892. As planters recovered with tea, they made sure that this could not happen again and in 1925 the Tea Research Institute was born and funded. To-day it is a huge organization with seven sub stations and today recognized as one of the most important tea research stations in the world.

Shot-Hole Borer Beetle:

In the 1950’s spraying with chemicals was the standard response to disease control not just in Ceylon but also around the world. The Shot-Hole problem revealed itself when the branches if the tea bush started breaking and falling off as the tea pluckers walked between the bushes and were found to have little holes bored into the wood. Spraying Dieldrin on the bushes when pruning took place was promoted to the planters as the control. However it created as many problems as it solved, by killing the Braconid Wasp (Macrocentrus Hormonae) which parasitized the Tortrix moth. This led to not only this area being infested but to the problem spreading for lack of beneficial effect of the Braconid wasp as a controller. In the late 1960’s the TRI decided that there was a need to create a different approach to disease control and one of ‘Bio’ control was created. This was partly due to consumer demands for foods that were not contaminated by harmful residues.
The TRI set-up a strict licensing programme, which required the chemical importing companies like Baurs to submit any chemical they wished to import to the TRI testing programme for three years of asessment. If the chemical passed their testing and was considered acceptable, the TRI would issue a licence for its import. Alongside this, the TRI encouraged estates to plant areas of beneficial plants and trees that ere known to support populations of beneficial insects for natural control, also mentioned in the section on Fairtrade and Organic certification.The estates had been planting Marigold plants along paths and field boundaries for some years before this for the control of Eel worm Now small spinneys of beneficial bushes and trees sprouted wherever room could be found for them.
If an estate has a serious attack of any disease it is bound to report this to the TRI. Depending on the situation, a field officer would visit the problem and assess the population of beneficial insects, if as is usually the case only minor adjustments are needed to increase the population, no chemical solution is required. Should the matter be very serious, a recommended programme of treatment might recommended for a given number of days with a licensed chemical and marketing of the tea from area suspended with leaf being plucked and thrown to the ground. Once the chemical is stopped and the beneficial insect population is back to a satisfactory level,the leaf from one plucking round is thrown away and then marketing can continue. To-day, as a result of this strict control, Shot-hole borer is no longer the problem that it was.

Blister Blight

This largely appears in wet, misty conditions and in the hills we can experience periods of mist rolling in and over the fields. Within the mist are large numbers of spores that settle on the tea leaves, mainly affecting the younger shoots with blistering that curls up the young shoots and then turn them black. The accepted treatment is to spray the fields with a copper sulphate solution immediately after a plucking round has taken place. At one time a systemic spray was allowed but as this is a very expensive treatment, it is rarely if ever used.

Poria

This is the attacking of the roots of the tea bushes by a mass of strands of fungal mycelium, it is called ‘Red Root Disease’, having rotted large number of the roots, the tea bush dies within a field of tea. This problem is a left over from the days when the Crown lands that were purchased for the planting of coffee. The traditional method of clearing the forested Crown Lands was for a gang of workers to half cut through the trees on lines up a hillside and then to finally cut down the trees along the top point selected for the field, causing a domino effect of trees crashing down upon each other. Any suitable timber that the planter required for use in setting up the estate, such as housing for workers and a small hut for the planter were preserved and the rest set alight in the hope that the fire would burn out the roots of the trees. A number of planters at some expense employed elephants to pull out the roots and others left them to rot.
During my time the traditional treatment was to have a gang of Poria workers who understood the seriousness of the work. On Le Vallon we had an agreement with the Unions that any persons found carrying or removing Poria infected material from a field could face instant dismissal. The problem was costing the estate hundreds of thousands of Rupees. The gang would carefully clear the dead bus and an area around it to include two healthy bushes deep around it. Set up an oil drum in the centre of a 6 foot high hessian screen where any chopping was done, to avoid infected material escaping.Then the whole area was dug to a depth of three feet and any roots thicker than a pencil were removed and burnt. The whole process took the gang several weeks to complete. Once the site had been dug over a mason and his helper (Kai-al) were appointed to terrace the area with stone ridging. A large infection area might need two or three layers of terracing. Once this was completed the area was planted with Guatemala grass a tall fleshy grass, that was lopped regularly and laid to add humus to the soil. After two years of rehabilitation, the area could be supplied with tea plants from the tea nursery and slowly brought back to production. This form of treatment cost Rs.5,700/= per acre on the days when there were Rs.13/= to the U.K. £.

TEA RESEARCH INSTITUTE (TRI) PORIA FUMIGATION TRIAL AT LE VALLON GROUP – 1961-1962:

In 1961 Redlich of the TRI visited Le Vallon (L.V.) Group to set-up two trial plots with me. We selected areas in L.V. Division No: 9 field where PH was 6.0 and also L.V. No: 10 field where the PH was 5.2. This was to trial a new system of fumigating the soil using a heavy duty gun with a pump handle delivering Dichloropropane-Dichloropropene mix (D.D.), instead of the lengthy, costly and laborious system explained above.
1. In June 1961, the designated areas had their bushes winched out and recorded. The infected bushes plus two surrounding healthy tea bushes and all surface roots were burnt at site.
2. Prior to fumigating it was necessary to dampen the soil and to have nearby to hand a sufficient number of old wet manure sacks or a large quantity of Guatemala grass (a tall fleshy leaved grass) on standby to cover the soil as fumigation took place.
3. The sites were lined to mark out 1 foot squares and fumigation was carried out on 28th. and 29th. June. The lining was carried out to leave a 2 foot barrier space from the surrounding healthy tea bushes. The rates of fumigant used are recorded in the PDF link below along with the results of the trial.
4. The gun delivered the fumigant to varying depths between near surface at 8 inches, as well as 1 foot and 2 feet in depth, at the points where the lines crossed. It is extremely important that this work is not undertaken in a period when rain is expected.
5. Tephrosia plants were planted across the sites in November 1961.
6. Planting of V.P., tea plants can and did take place five months after treatment.

Whilst various levels of treatment were undertaken as shown in the results in the PDF link below. We came to the opinion that the fumigation should be carried out at the 20 ML level. At that level 2,000 Lbs of fumigant was used, at a cost of Rs.4,000/= per acre. as explained above for the cost of  the traditional system, at the time of the trial there were Rs.13/= to UK £1 Sterling.
50 estates were known to have a Poria problem at that time, which was a total of 57,680 acres, 10 % of the total tea area.

It is my understanding that this is the system that has been adopted and is in use to day.

Summary

HISTORY OF RESIDUE LEVELS IN CEYLON TEAS:

In 1997 the Chairman at the International Standards Organization (I.S.O.) meeting in Colombo, stated that Ceylon teas were the cleanest in the world as far as pesticides and residues were concerned. This statement was repeated at the Organizations meeting in Calcutta in 1999, gain in Mombassa in 2001, Hangzhou in 2003 and Hamburg in 2005. So, the world were confirming the success of the steps taken by the T.R.I. Those International reports continue to this day reporting on residue levels in teas from all producing countries with Ceylon teas maintaining their reputation in this field.

In 2003 the European Union (EU) declared a maximum residue level (MRL) of 0.01 Mg/Kg. This set the standards that all producing areas had to work to.
China was using high levels of pesticides and herbicides with a massive build up in the soil and this has taken a number of years for them to first comply with International scrutiny and then to meet acceptable levels of residues.

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