Are Nematodes a Problem in SRI? Directorate of Rice Research, Rajendranagar, Hyderabad-500 030 J.S. Prasad, Ch. Padmavathi, R.M. Kumar, and L.V.Subba Rao

High yields of rice declined in Brazil and China after 3-4 years under aerobic conditions, possibly due to nematodes or toxic substances (Bouman, 2002). Yield differences between aerobic and flooded rice ranged from 8 to 69%, the differences attributed to the build-up of nematodes (Peng et al., 2006). Under controlled irrigation, even small pest problems have great impacts on yields and farmers' income. INTRODUCTION

High yields of rice declined in Brazil and China after 3-4 years under aerobic conditions, possibly due to nematodes or toxic substances (Bouman, 2002).

Yield differences between aerobic and flooded rice ranged from 8 to 69%, the differences attributed to the build-up of nematodes (Peng et al., 2006).

Under controlled irrigation, even small pest problems have great impacts on yields and farmers' income.

Uncontrolled irrigation can be associated with the rice root nematode Hirschmanniella spp. – yield loss 8-23% (Kuriyan and Sheela, 1981) Nematode pests that could be associated with SRI

Controlled irrigation can be associated with the root-knot nematode Meloidogyne graminicola -- yield loss 21-64 % (Rao and Biswas, 1973)

Giant cell formation induced by the root-knot nematode in phloem

Materials and methods Field Experiment – Split Plot Treatments: SRI, Eco-SRI, and Conventional Varieties: Rasi and Jaya Greenhouse studies Treatments: Continuous flooding Optimum moisture (OM) Flooding & OM alternated at weekly intervals

Greenhouse studies

Treatments:

Continuous flooding

Optimum moisture (OM)

Flooding & OM alternated at weekly intervals

H. oryzae in soil as influenced by crop establishment methods

H. oryzae in root as influenced by crop establishment methods

Roots of freshly uprooted plant from a continuously inundated rice field

Roots showing galls developed 7 days after uprooting

Incidence of root-knot nematode at various moisture levels Figures in parentheses indicate √X+0.5 transformed values Treatment No. of galls Root volume Root length (cm) Root weight (g) Control 0.00 (0.707) 1.600 (1.448) 8.080 (2.928) 1.280 (1.333) Continuous flooding 0.760 (1.119) 1.500 (1.413) 14.620 (3.887) 0.682 (1.084) Optimum moisture (OM) 8.80 (3.048) 1.680 (1.476) 3.180 (1.911) 0.650 (1.072) Alternate flooding & OM at weekly intervals 2.32 (1.662) 0.820 (1.145) 15.840 (4.040) 0.560 (1.029) CD (p = 0.05) 0.23 0.088 0.192 0.076

CONCLUSIONS Under aerobic or saturated conditions, more gall formation on the roots by root-knot nematode was observed In conventional rice cultivation, H. oryzae population is more In SRI fields where no water control is possible, there is need to monitor for the root nematode H. oryzae Existing root knot nematode infection may not express itself, but when aerobic conditions prevail, symptoms do appear

Under aerobic or saturated conditions, more gall formation on the roots by root-knot nematode was observed

In conventional rice cultivation, H. oryzae population is more

In SRI fields where no water control is possible, there is need to monitor for the root nematode H. oryzae

Existing root knot nematode infection may not express itself, but when aerobic conditions prevail, symptoms do appear

Use of cono-weeder would destroy the nematodes that have invaded the roots of weed plants The incorporation of weeds and organic nutrients deters movement, migration and infestation by nematode pests Decomposing organic matter promotes beneficial predatory and saprophytic nematode populations Possible impact of SRI cultivation on plant parasitic nematodes

Use of cono-weeder would destroy the nematodes that have invaded the roots of weed plants

The incorporation of weeds and organic nutrients deters movement, migration and infestation by nematode pests

Decomposing organic matter promotes beneficial predatory and saprophytic nematode populations

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