Introduction

The rice root-knot nematode (Meloidogyne graminicola) is an important pest in South and Southeast Asian rice production systems, and has been reported in rice growing regions of southern Brazil and West Africa. Though predominately associated with rice, a population of M. graminicola from Pakistan was found to cause equal or greater root damage on wheat and sorghum than on rice (10). Recently, it has been detected at high levels in rice-wheat rotation areas of India (4, 5), Nepal (9), and Bangladesh (6), where both of these important cereal crops are hosts. The lifecycle of M. graminicola can be as short as 19 days (3), but has been reported to vary between 26 to 51 days, depending on temperature (2).

Yield damage potential of M. graminicola is greatest under nonflooded, upland, rice growing conditions. Upland rice yield losses between 12 and 33% in Thailand (1), and between 28 and 87% in Indonesia (7), occurred under naturally infested field conditions. In studies simulating upland conditions, yield losses caused by M. graminicola varied from > 20% at 8,500 J2 per pot (11), to nearly 70% at 1 J2 per cm3 soil (8).

Depending on the timing and duration of soil flooding, deepwater, lowland-rainfed, and irrigated rice systems are also vulnerable to damage by M. graminicola. Although unable to penetrate roots under flooded conditions, M. graminicola juveniles can survive long periods in flooded soils and rapidly invade roots once flooding ceases (3). Root infection of deepwater rice seedlings, in the early pre-flooded period, was found to later prevent infected plants from growing above the floodwater resulting in substantial yield losses from submergence (3). M. graminicola is a concern in lowland-rainfed and irrigated rice systems as flooding is often intermittent and drought at rice flowering is common. In a field study on lowland-rainfed rice in Bangladesh, rice yield was 16 to 20% lower in plots where no nematicide was applied compared to when the nematicide furadan was applied to both the rice seedbed nursery and the mainfield to control M. graminicola (unpublished).

	Growth of rice seedlings in M. graminicola-infested
	soil in Bangladesh. The plot on the left was treated
	with furadan 5G to control nematodes; the plot on the
	right received no nematicide.

	Growth of rice plants at tillering stage in an M. graminicola
	infested field in Bangladesh.

References 1. Arayarungsarit L. 1987. Yield ability of rice varieties in fields infested with root-knot nematode. IRRN 12: 14

2. Bridge J. 1990. Nematode parasites of rice. In Plant Parasitic Nematodes in Subtropical and Tropical Agriculture, ed. M Luc, RA Sikora, J Bridge, pp. 82-107. London: CAB International

3. Bridge J, Page S. 1982. The rice root-knot nematode, Meloidogyne graminicola, on deep water rice (Oryza sativa subsp. indica). Revue de Nematologie 5: 225-32

4. Gaur HS, Khan E, Sehgal M. 1993. Occurrence of two species of root-knot nematodes infecting rice, wheat, and monocot weeds in Northern India. Annals of Plant Protection Sciences 1: 141-2

5. Gaur HS, Singh J, Sharma SN, Chandel ST. 1996. Distribution and community analysis of plant parasitic nematodes in rice growing areas of Haryana, India. Annals of Plant Protection Sciences 4: 115-21

6. Miah SA, Shahjahan AKM, Hossain MA, Sharma NR. 1985. A survey of rice disease in Bangladesh. Tropical Pest Management 31: 208-13

7. Netscher C, Erlan. 1993. A root-knot nematode, Meloidogyne graminicola, parasitic on rice in Indonesia. Afro-Asian Journal of Nematology 3: 90-5

8. Plowright RA, Bridge J. 1990. Effect of Meloidogyne graminicola (Nematoda) on the establishment, growth and yield of rice cv. IR36. Nematologica 36: 81-9

9. Sharma SB, Pande S, Saha M, Kaushal KK, Lal M, et al. 2001. Plant parasitic nematodes associated with rice and wheat based cropping systems in Nepal. International Journal of Nematology 11: 35-8

10. Soomro MH, Hague NGM. 1992. Effect of Meloidogyne graminicola on root growth of wheat and sorghum. Pakistan Journal of Nematology 10: 119-26

11. Tandingan IC, Prot JC, Davide RG. 1996. Influence of water management on tolerance of rice cultivars for Meloidogyne graminicola. Fundamental and Applied Nematology 19: 189-92