A greenhouse study was conducted to determine the effect of henbit and purple deadnettle density on weed biomass accumulation and soybean cyst nematode (SCN) reproduction. SCN did not impact shoot or root dry weight of purple deadnettle, henbit, or soybean. Foliar and root biomass of henbit and purple deadnettle were comparable but the biomass per stem was higher for purple deadnettle. Shoot and root biomass per pot of henbit and purple deadnettle at corresponding plant densities were statistically similar and were generally higher with increasing plant density. Henbit produced a greater number of stems than purple deadnettle and the least number of stems for both species existed at low densities. Purple deadnettle allowed for more SCN reproduction than did henbit. Weed densities also influenced SCN cyst and egg production but the results were species dependent. The highest SCN reproduction per pot was supported at low to moderate densities of purple deadnettle but at moderate to high densities of henbit. These results suggest that purple deadnettle should be more aggressively managed than henbit in management programs for SCN, but that henbit, especially at high densities, can support SCN reproduction at levels near those of purple deadnettle.

Nomenclature: Henbit, Lamium amplexicaule L. LAMAM; purple deadnettle Lamium purpureum L. LAMPU; soybean Glycine max (L.) Merr. ‘Williams 82’ and ‘PI437654’