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

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

0102030405060708090

100

Vegetative Harvest Vegetative Harvest

Rasi Jaya

Soil nematodes

Nem

ato

de

po

pu

lati

on

SRI

SRI- Eco

Conventional

H. oryzae in soil as influenced by crop establishment methods

0

50

100

150

200

250

Vegetative Harvest Vegetative Harvest

Rasi Jaya

Nem

ato

de

po

pu

lati

ion

SRI

SRI- Eco

Conventional

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

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)

Optimummoisture (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

Figures in parentheses indicate √X+0.5 transformed values

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

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