Herbicide Influence On Soybean Cyst Nematode (Heterodera glycines) Reproduction in Henbit (Lamium amplexicaule) Roots.

Soybean cyst nematode (SCN) is the most yield limiting disease of soybeans in the United States. Henbit is a prevalent winter annual weed species in no-till fields and is reported to be an alternative host of SCN. A greenhouse study was conducted to evaluate how the development of SCN on henbit roots was affected by herbicide mode of action and time of application. Ten days after transplanting henbit seedlings in pots filled with 750 ml of sterilized soil, 1,000 SCN eggs were inoculated in each pot. At 7, 14, and 21 days after inoculation (DAI), henbit plants were sprayed with recommended doses of either glyphosate or 2,4-D. At 28 DAI, the total number of SCN cysts and eggs, and plant shoot and root dry weights per pot were determined. Henbit root and shoot biomass increased as the time of application was delayed. Glyphosate reduced root biomass more than 2,4-D, but no differences in shoot biomass were detected. The number of SCN cysts per plant and eggs per cyst increased as the application time was delayed from 7 to 21 DAI. Glyphosate reduced the number of cysts found on henbit roots more than 2,4-D, especially at earlier application times. On plants treated with glyphosate, SCN-females produced only half the number of eggs of SCN-females on plants treated with 2,4-D, regardless of time of application. These results indicate that the early control of henbit plants, especially with glyphosate, may reduce SCN reproduction potential in SCN infested fields. In a side field study conducted at 8 locations in Nebraska, the majority of the henbit seedlings (>95 %) emerged by end-October/mid-November, indicating that henbit control after crop harvest in the North Central region of the USA would be the ideal time to manage this weed and consequently reduce potential SCN reproduction.