Environmental factors affecting sethoxydim efficacy on glyphosate-resistant and -susceptible biotypes of Eleusine indica
T.S. ChuahA, S. SalmijahB and B.S. IsmailB
A Faculty of Agrotechnology and Food Science, Kolej Universiti Sains dan Teknologi Malaysia, Mengabang, Telipot, 21030 Kuala Terengganu, Terengganu, Malaysia.
B School of Environmental and Natural Resource Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor, Malaysia.
Glasshouse experiments were conducted to evaluate the interaction between shading levels and watering frequency before and after sethoxydim treatment on the growth of glyphosate-resistant (R) and -susceptible (S) biotypes of Eleusine indica. The efficacy of sethoxydim on the R and S biotypes at 0.30 kg a.i. ha-1 was not affected by reduced soil moisture level after herbicidal application. However, water stress experienced by the R and S biotypes both before and after sethoxydim treatment could reduce sethoxydim control by 7-20%. Control of the R and S biotypes with sethoxydim was lower at 0% shade than 60% shade, with both biotypes showing 51-72% and 78-80% shoot dry weight reduction at 0 and 60% shade, respectively. The R biotype was more susceptible to sethoxydim application than the S biotype when both biotypes experienced water stress before the herbicidal treatment, irrespective of the soil moisture level after the herbicidal treatment. Field experiment was conducted to examine the effects of dry and wet seasons on sethoxydim efficacy. The results showed that sethoxydim provided 90% control of the R and S biotypes during the wet season (350 mm) whereas control of both biotypes by sethoxydim was reduced by 30-50% during the dry season (139 mm).
Plant Protection Quarterly (2006) 21 (1) 10-13.