Purple Deadnettle (Lamium purpureum) and Soybean Cyst Nematode Response to Cold Temperature Regimes

An experiment was conducted in growth chambers to determine the influence of cold temperature regimes, designed to simulate winter temperature conditions and spring recovery, on the interaction between purple deadnettle and soybean cyst nematode (SCN). The study was a factorial arrangement of treatments with five levels of temperature (20, 15, 10, 5, or 0 C), two levels of exposure time to the temperature (10 or 20 d), and two levels of recovery time at 20 C following exposure (0 or 20 d). In general, purple deadnettle shoot and root growth increased with temperature and time. The ability of purple deadnettle to recover from cold temperatures declined as the length of time that the plant was subjected to the cold temperature increased. SCN juveniles per gram of root at the conclusion of the temperature treatment declined as the temperature increased from 0 to 15 C, likely a result of continued purple deadnettle root growth and the inhibition of SCN hatch, growth, or development at those temperatures. SCN female, cyst, and egg production per gram of root generally increased with temperature and occurred under all temperature regimes. The results of this research indicate that, after hatching, SCN juveniles can survive a period of cold temperature inside the roots of a winter annual and continue development when transferred to warmer temperatures. Therefore, in a field environment, where fall or spring alone may not be sufficient for SCN to complete a reproductive cycle on a winter annual weed, the nematode may be able to reproduce by combining the fall and spring developmental periods.