First Report of Soybean Cyst Nematode Reproduction on Purple Deadnettle under Field Conditions

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J. Earl Creech, Graduate Research Assistant, and William G. Johnson, Assistant Professor, Department of Botany and Plant Pathology; Jamal Faghihi, Extension Nematologist, and Virginia R. Ferris, Professor, Department of Entomology; and Andreas Westphal, Assistant Professor, Department of Botany and Plant Pathology; Purdue University, West Lafayette, IN 47907-2054

Soybean cyst nematode (SCN, Heterodera glycines) commonly infests soybean (Glycine max) fields in the United States and is a threat to profitable soybean production. In a greenhouse experiment, purple deadnettle (Lamium purpureum) was identified as an excellent host for SCN (4). Purple deadnettle (Fig. 1) is common in Indiana production fields and frequently occurs at very high densities (100 or more plants per m²) (1). Purple deadnettle is a winter annual weed that typically emerges after harvest, over-winters as a small seedling, and completes its life cycle in spring. SCN development does not occur at temperatures below 10°C (2). Thus, the potential interaction between SCN and purple deadnettle is limited to a short period in the fall and the spring when soil temperatures favor both nematode activity and weed growth. An increase in SCN egg densities has been observed in purple deadnettle infested research plots (3). However, the ability of SCN to complete a reproductive cycle on purple deadnettle under field conditions has not been reported.

Fig. 1. Purple deadnettle in a no-till field infested with soybean cyst nematode (Heterodera glycines) in southwest Indiana.

A research site infested with both SCN (HG Type 0) and purple deadnettle was selected at the Southwest Purdue Agricultural Center near Vincennes, Indiana. The field site had been under no-till for three years and contained a Patton silt loam soil. The field was planted with the SCN-resistant soybean cultivar ‘DKB36-51’ and was harvested on 20 September 2004. On 19 October, purple deadnettle plants were removed from the field using a 10-cm-diameter golf-hole cutter to keep the soil around the roots intact. In the Purdue University Nematology Laboratory, purple deadnettle plants were carefully removed from the soil and the roots were rinsed with water. Cysts containing eggs were found attached to the roots of nine of the ten purple deadnettle plants sampled (Fig. 2). The morphology of cysts and juveniles was consistent with SCN. A bioassay was performed to confirm the ability of the nematode to utilize soybean as a host. The SCN-susceptible soybean ‘Williams 82’ was planted in 10-cm pots containing a sterilized 3:1 (v:v) sand-to-soil mix and was inoculated with eggs recovered from the purple deadnettle. Pots were placed in a greenhouse that was maintained at 24 ± 5°C and a 16-h photoperiod supported by metal halide lamps to supplement natural lighting and watered as needed. After 35 days, the roots of the soybean were examined and new cysts containing eggs were found. Based on the distribution of other cyst nematodes in Indiana, the bioassay on soybean, and morphometric observations, we determined the identity of the nematode to be SCN.

Fig. 2. Female of soybean cyst nematode (Heterodera glycines) protruding from a purple deadnettle root.

Management recommendations for SCN include rotation with non-host crops and use of SCN-resistant soybean cultivars. However, these control measures may be inadequate if SCN populations are able to increase on winter annual weeds when susceptible soybean is not present. Future research should be directed toward assessing the influence of winter annual weeds on SCN population dynamics and whether SCN management guidelines should be expanded to include winter annual weed management.

(Purdue ARP Manuscript Number 2005-17676.)

Literature Cited

1. Creech, J. E., and Johnson, W. G. 2004. Soybean cyst nematode and winter annual weeds in Indiana: Distribution and producer concern. Proc. North Central Weed Sci. Soc. 59:143.

2. Hill, N. S., and Schmitt, D. P. 1989. Influence of temperature and soybean phenology on dormancy induction of Heterodera glycines. J. Nematol. 21:361-369.

3. Venkatesh, R., Harrison, S. K., Regnier, E. E., and Riedel, R. M. 2004. Purple deadnettle effects on soybean cyst nematode populations in no-till soybean. Proc. North Central Weed Sci. Soc. 59:56.

4. Venkatesh, R., Harrison, S. K., and Riedel, R. M. 2000. Weed hosts of soybean cyst nematode (Heterodera glycines) in Ohio. Weed Technol. 14:156-160