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Methyl bromide alternatives: A planter's point of view

by Chaminda Gunaratna , Asst. Manager, Rangalla Estate, Rangalla

In the tea nursery management, there are many pest and disease problems encountered. Nematode is one such pest that causes heavy damages especially at elevation from 600-1800m. Most common nematode pests are:

1. Root knot nematodes, Meloidogyne spp.

2. Root-lesion nematode, pratylenchus loosi

3. Burrowing nematode, radopholus similis

Main source of infestation is the infested nursery plants. In addition, irrigation water too causes contamination in nurseries (Gnanapragasam, 1982).

Methyl bromide fumigation was the most preferred method in controlling nematodes. However, with the restriction of Methyl bromide use either chemical or biological disinfestation methods will have to be adopted to control nematodes.

Other than chemical control methods, biological methods are preferred in modern pest control operations due to the environmental problems encountered in chemical usage. Two non-chemical disinfestation methods have been studied at the nursery at Rangalla Estate, Rangalla. Those were used together with poly-tunnels to increase the growth performance of tea plants.

Rangala estate nursery has a capacity of 100,000 plants. The main tea clones used in the estate nursery are TRI 2025 and DG39. Both these clones are susceptible to tea nematodes. 70% of the nursery area comes under high shade with agro shading (Synthetic net), remaining 30% coming under low shade with Kekille.

Nematode control

Both P. Loosi and R. Similis could be found in the nursery which is situated at mid elevation. Fumigation with MeBr was started in early 1990s to control the nematode infestation. Used dosage was 1 lb/soil cube. It is kept for 48 hours complete the fumigation. Though, there should be a period of 7 to 14 days to release excess gas, it was observed that excess gas is removed within 7 days. Good results were obtained from MeBr fumigation of Nursery soil.

However, it is difficult to practise fumigation during wet weather periods. As alternatives to the MeBr fumigation soil solarization and refuse tea addition to tea bags (as organic amendment) were practised in the nursery, since the TRI started experiments at Rangalla nursery.

Alternatives used by the nursery Soil solarization

Filled nursery bags are covered with a 300-500 gauge (3-5 mil) polythene, keeping a gap above nursery polythene bags. The gap between polythene and nursery bags were made up by placing a row of nursery bags on top of vertical bags. Edges of the polythene were completely buried in the soil to create a sealed enclosure.

The bags were allowed to solarize for a period of 6-8 weeks. Five hours of sun shine a day is needed to achieve best results. Rainy periods should be avoided with proper nursery plan.

Addition of 1-2 gram of urea per bag was found to give better results under integrated pest management. Addition of urea increases nutrient level in the soil, soil microbial population and it has a nematicidal activity too.

Use of tea waste

Organic amendments are reported to be effective in controlling soil borne pests including nematode infestation. Based on this principle, tea waste decomposed for more than 6 months were used in preparing nursery bags for planting tea cuttings. Tea waste was added up to 50% on volume basis and to the bottom half of the bag.

For the easiness of filling bags, first half of the bag was filled with soil and the remaining half was filled with decomposed tea waste. The bag was then turned upside down so that tea waste layer was in bottom. The filled bags were allowed to settle for one week, with daily watering. After planting the cuttings other normal nursery practices were adopted regularly.

Poly-tunnel

As a different approach to enhance growth of VP cuttings, the planted bags were covered with a mini poly-tunnel which is of a height of 2 1/2 to 3 feet. The planted cuttings were kept in the polytunnel for 45 days watering was not practised during this period. Condensed water vapour which sticks on to the polythene sheets were disturbed and made to fell down on nursery plants by lightly tapping the polythene.

Discussion

Solarization: This method proved to be a little expensive in comparison to addition of tea waste to the nursery bags. However, this consume less labour requirement than addition of organic amendments to nursery bags. However, this method cannot be practised in areas with less sun shine hours per day. In other areas too, it is necessary to avoid rainy season to achieve best results.

Use of Tea Waste: Addition of tea waste, to the bottom half of nursery bag benefited plant growth in many ways. It improved both physical and chemical parameters of nursery medium. Since, tea waste is less dense material (0.1 g/ml) with compared to soil, it promotes aeration and drainage of the bag. This resulted in enhanced root growth.

Ultimately, it resulted in better developed root system with more feeder roots. Nutrient content of the tea waste increased the nutrient status of the nursery medium. The tea waste is believed to increase the soil microbial population which influences better growth in nursery plants. Since half of the nursery bag was filled with tea waste, cost for soil collection could be reduced and this is a more suitable method for the nurseries which have the problem of finding suitable soil for nursery.

Poly-tunnel: Poly-tunnel is very useful in protecting VP cuttings and plants from rain and wind damage. This is very important in areas with high intensity rain fall. Due to the improved and controlled nature of environment inside the polytunnel, early rooting and shooting were observed. Another important observation was the uniformity among the plants. Poly-tunnel helps to protect plants from pest and diseases. Polytunnels also eliminates the need for watering in the first few months.

Since no nematode infection were seen in the nursery plants raised under above treatments without any methyl bromide fumigation, it could be concluded that the treatments are effective and can replace MeBr fumigation. Construction of mini polytunnel is an added advantage for nurseries as it produces more uniform plants quickly.

Workshops on personal health and hygiene

A series of workshops were conducted in around 30 Schools within Colombo and suburbs on Personal Health and Hygiene by Reckitt Benckiser, makers of Dettol.

The morning sessions were conducted for primary grade students on proper guidelines on hand wash to eliminate germs. The afternoon sessions were devoted to senior students getting insight in to the scientific de-germination and prevention of common infection and mitigation of decease causing germs.

This project, 'Suwa Shakthi' which is the first of its kind undertaken by the private sector is guided by a medical professional, Dr. Asela Anthony while Mrs Roshani Fernando is the consultant.

"Every child has a right to good health and medical research points out that most deceases affecting children on a regular basis are bacteria related mainly due to lack of personal cleanliness," said Mrs. Fernando.

"The aim of Suwa Shakthi is to teach children good health habits through enjoyable means."

'Green Sri Lanka National Environmental Award 2001'

The second annual awards ceremony conducted by the South Asian National Environment Committee (SANEC) of Sri Lanka in co-ordination with the Federation of Wild Life Conservation (FWC) titled "Green Sri Lanka National Environmental Award 2001" was held recently. Caltex Lubricants Lanka Limited won the Gold award for its projects while S-Lon Lanka walked away with the Silver and Bronze being taken by CIC Paints.

The Federation of Wild Life Conservation (FWC) is currently carrying out various environmental projects educating the general public about our wild life in our National Parks through a leaflet project. A special recycling projects for Schools and the development work in Catchment areas. Also a booklet on environmental pollution has been published.

Apart from these Hoardings communicating unique messages such as why we need to protect our environment was also carried out.

Another project proposed is the Baseline participatory project. Here, the FWC has received approval to plant trees in open areas to trap toxic fumes emanating from vehicles.

Since this is the entrance to the Colombo city the project will help the community to have a cleaner environment with a pleasing sight of 'green' as well. To implement many of the above activities planned by the (FWC) assistance from the private sector is needed. This is where companies such as Caltex come in.

Caltex has worked very closely with the FWC in carrying out various awareness campaigns such as the leaflet and hoardings project. Kishu Gomes Managing Director of Caltex said: "We don't work for awards. But, it is certainly good to be recognised for our efforts in trying to contribute towards the protection of our environment. We get all the support and commitment from the FWC in implementing our projects. We are definitely happy & will continue to do our part towards the environment."

Currently a national plan is being prepared by the National Environment Authority of Sri Lanka headed by P. B. Weeraskera in collaboration with the Central Environment Authority, Department of Wild Life Conservation, Forest Deportment, Coast Conservation Authority and the Federation of Wild Life Conservation, for which projects the funding is done by companies such as Caltex, CIC paints, Stan Lanka, Millers, Carson and Cumberbatch, Unilevers and Hayleys.

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