Atrazine resistant weeds in Thailand
2002
Duangporn Suwanagul(Kasetsart University. Bangkhen Campus, Bangkok (Thailand). Faculty of Agriculture. Department of Agronomy) E-mail:[email protected] | Rungsit Suwanaketnikom(Kasetsart University. Bangkhen Campus, Bangkok (Thailand). Faculty of Agriculture. Department of Agronomy)
Atrazine has been used in corn fields in Thailand since 1970. Major areas for corn production are in the Central and North-Eastern parts of Thailand. Surveys of atrazine resistant weeds as well as test for atrazine resistance were conducted In June 1997 to August 2000 in five North-Eastern and two central provinces of Thailand. Euphorbia heterophylla and Amaranthus gracilis were among the major weeds found in the corn fields. The test of atrazine was either as pre-and post-emergence. Euphorbia heterophylla populations showed no evidence of resistance. However, there were some weeds that survived atrazine application. The offsprings of the surviving weeds were not resistant to atrazine at any rates tested. Meanwhile, Amaranthus gracilis was found to be resistant to atrazine at the rate up to 20 kg ai/ha. Studies on the above ground and soil seed bank in the corn fields where atrazine had been applied for over ten years found a great number of A. gracilis populations. However, a number of underground weed seeds were greater than the weeds that emerged from the soil. Seed germination for the resistant weeds was very low, while for germinated susceptible seeds were quite high.
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