Effects of soil temperature and tuber depth on Cyperus spp. control

Studies were conducted to determine lethal temperatures for Cyperus esculentus and Cyperus rotundus tubers using diurnal oscillations in soil temperature with maxima of 40, 45, 50, and 55 C and a minimum of 26 C. Growth of Cyperus spp. plants was faster at 40 C than at a constant temperature of 26 C. The 45 C treatment delayed Cyperus spp. emergence but was not lethal to tubers. Tuber mortality was 100% for both Cyperus spp. with the 50 and 55 C temperature regimes. Soil solarization with thermal-infrared-retentive (TIR) films resulted in higher soil temperatures than with a 30-μm low-density polyethylene (LDPE) clear film. With TIR films, greater proportions of emerged C. rotundus plants were killed by foliar scorching, and 6 wk of soil solarization was more effective at reducing C. rotundus density than with the LDPE film. Four weeks after film removal, the lowest level of control was obtained with the LDPE film. For C. rotundus tubers planted 5 and 10 cm deep, 62% control was obtained with the LDPE film, and it decreased to 32% with a 15-cm planting depth. The best residual control was 95 and 92% with the 75-and 100-μm TIR films, respectively. With the TIR films, there was no significant change in C. rotundus control with planting depth.