This study quantified the role of seed contamination as a source of weedy rice infestation and spread in four provinces in Sri Lanka. Seed samples were collected from farmers in these provinces and tested for weedy rice contamination. The results showed that the majority of farmers used their own seed or seeds from neighboring farmers, which were contaminated with 19-73% weedy rice seeds. This means farmers were seeding 46,000 to 60,000 weedy rice seeds per hectare. The study concluded that contaminated seed paddy is a main source of weedy rice infestation and spread in the studied areas due to farmers' lack of awareness about weedy rice and use of certified seeds.

1. Quantifying role of seed contamination as a source
of weedy rice infestation and spread in Sri Lanka:
A case study in eastern, northern, north-central and
southern provinces.
R.M.U.S. Bandara 1, A.P. Bentota1, R.S.K. Keerthisena 1, T.K. Illangakoon 1, J.K.
Galabada 1,2, B. Marambe 3, S. Sivanason4, S. Nirojan4, Y.B. Iqbal 5, R.F. Hafeel 6,
H.M.S. Herath 6, H.M.M.K.K.H. Dissanayaka 1, Y.M.S.H.I.U. De Silva1, B.G.C.A.
Gamlath 1, S.G. Kaushalya 1,2 and V. Kumar
1 Rice Research and Development Institute, Batalagoda, Ibbagamuwa, Sri Lanka
2 Socio Economics and Planning Centre, Department of Agriculture, Peradeniya, Sri Lanka
3 Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Sri Lanka
4 Rice Research Station, Paranthan, Sri Lanka
5 Rice Research Station, Sammanthurai, Sri Lanka
6 Rice Research Station, Ambalantota, Sri Lanka
7 International Rice Research Institute, Los Baños, Philippines
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2. INTRODUCTION:
• Recently many farmers from heavy rice production areas such
as Ampara, Vavuniya, Kurunegala, Mathara, Puttalama
complained that their paddy fields cannot be cultivated due
to weedy rice problem and they informed that their yield
losses due to the weeds range on 50-100%.
• It was appeared in those area more than 30 years back with
negligible extent but today is became a serious problem in
these areas due to poor cultural management practices,
shortage of water, increase of direct seeded method and lack
of knowledge of these threaten plants.
• This problem was first reported in Sri Lanka 1997 in Ampara
district Today it was spreading irrespective of agro ecological
zones and an alarming rate, treaten food security in the
country.
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3. INTRODUCTION CONT..
• At present, Department of Agriculture, Sri Lanka has
recommended an Integrated Package for Weedy Rice
Management (IWRMP) combining following activities;
1. Identification of weedy rice,
2.Killing of weedy rice plants before land preparation,
3.Ploughing and allowing weedy rice seeds to germinate and
killing seedling,
4.Proper land preparation,
5.Use of quality seed paddy,
6.Use of an effective crop establishment methods (row seeding
or parachute method or transplanting or water seeding),
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4. INTRODUCTION CONT..
7.Application of pre-emergent herbicides,
8.Manual weeding,
9.Use of weeder in between rows,
10.Rouging of panicles,
11.Use of clean machineries,
12.Application of contact herbicides on weedy rice panicles
at flowering stage and
13.Crop rotation.
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5. OBJECTIVE:
• Still farmers’ awareness on weedy rice and weedy rice
management is less. Seed paddy is a one of the main
source of weedy rice infestation in general.
Therefore, this study was conducted to
quantify the role of seed contamination as a source of
weedy rice infestation and spread and to gather
information on farmers’ awareness on weedy rice and
weedy rice management.
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6. MATERIALS AND METHODS:
• Twenty six (26) farmers representing Northern Province,
• 22 farmers representing southern province,
• 18 farmers representing North-central province and
• 25 farmers representing Eastern province were selected for
the study.
• 500g of seed paddy samples were collected from the same
seed lot farmers using for sowing their crop.
• A structured questionnaire with basic information of
farmers and their crop management practices were filled
from each farmer when collecting seed paddy samples.
• Seed samples were processed in the laboratory and weedy
rice seed contamination were quantified.
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7. RESULTS AND DISCUSSION:
Table 01: Seed rate, seed source, yield reduction and percentage contaminated in Jaffna,
Ampara and Matara
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Parameter Jaffna
(N=26)
Ampara
(N=25)
Matara
(N=22)
Seed rate 160 165 100
Seed source (%)
Own seed/neighboring farmer 54 12 100
Certified/registered 34 4 0
Govt/pvt 8 80 0
Do weedy rice reduce yield
Yes 70 88 100
No 0 4 0
Don't know 30 8 0
Yield reduction by weedy rice (%) 30 19 46
% seed sampled contaminated 19 44 73
No. of seeds/kg rice seed 334 (53440) 280 (46200) 592 (59200)

8. CONCLUSION:
• Results of survey analysis revealed that the majority of
farmers are poorly aware on weedy rice and its control
measures.
• The majority of farmers using their own seed paddy
contaminated with weedy rice seeds rather than using
certified seeds.
• Results of laboratory analysis revealed that seed paddy of
selected paddy farmers had contaminated 19-73% during the
season studied.
• In another words farmers are seeding 46,000 to 60,000 seeds
of weedy rice per hectare.
• It is clear that seed paddy is one of the main sources of
weedy rice infestation and spread in studied area. 8

9. REFERENCES:
• Abeysekara A.S.K., Herath H.M.S., Wickrama U.B., Nugaliyadde L, Johnson
D.E., 2010 Germinability, Viability and Longevity of weedy rice and
cultivated rice in abandoned rice field in Sri Lanka. Proceedings of 3rd
International rice congress, 8-12 November 2010 in Hanoi Vietnam.
• Abeysekara A.S.K., Herath H.M.S., Wickrama U.B., Nugaliyadde L., Johnson
D.E., 2010 Morphological Variation of Weedy rice in Sri Lanka.
Proceedings of 3rd International rice congress, 8-12 November 2010 in
Hanoi Vietnam.
• Abeysekara A.S.K., Herath H.M.S., Wickrame U.B., Nugaliyadde L. and
Iqbal, Y.B. 2010. Weedy rice: a threat to direct seeded rice culture in Sri
Lanka. Proc. Rice Symposium 2010. Department of Agriculture,
Peradeniya, Sri Lanka.
• Darshana KVWS, Silva MKR, Abeysekara A.S.K. and Nugaliyadda L. 2007
Weedy rice in southern Sri Lanka: abundance, diversity and farmer
awareness. Proc. 21st Asian Pacific Weed Sci. Soc. Conf., 2-6 October 2007,
Colombo Sri Lanka. pp 74-77.
• Ahangangoda D.A., Abeysekara A.S.K., Nugaliyadde L. 2008. Some
biological aspects of weedy rice. Final year research project. Faculty of
Agriculture, University of Ruhuna.
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10. Thank You
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