This study was conducted to establish effective weed control technologies and pesticide usage safety management methods for the prevention of repeated pesticide treatments. A decennial weed distribution investigation in rice paddy fields was conducted, along with a quadrennial pesticide usage investigation on rice and classification of rice herbicide mechanisms.
The first chapter of this study regards a decennial weed occurrence investigation. This investigation was conducted until the fifth investigation in 2013, to see rice paddy weed change for 50 years, establish weed control technique and predict future weed occurrence.
1. In the 2013 rice paddy weed investigation, perennial weeds had increased for a lengthened reproduction period with early rice-planting. Furthermore, perennial weed tuber survival resulting from tillage reduction and tuber spread from agricultural machines of trust farming companies had increased.
2. Barnyard millet had a dominant portion of 6.9% in 1970, 9.0% in 2000 and 17.3 in 2013. Although annual weeds showed decreasing trends, barnyard millet is increasing not only from the increase of organic rice fields but also occurrence of resistant strains to ACCase-inhibitors in Chungnam/Jeonnam/Jeonbuk.
3. Herbicide resistant weeds are increasing in numbers of species and occurrence areas. Occurring species increased from one in 1998 to 11 in 2012. Occurrence area expanded from 10,000 ha in 1998 to 176,870 ha in 2012.
4. Increases in barnyard millet numbers, the predominance of perennial weeds over annual weeds, the increase in herbicide resistant weeds species/area, and the proliferation of foreign weeds due to climate change and crop changes can be expected.
The second chapter is about quadrennial pesticide usage investigation on rice. This investigation was conducted until the fifth investigation in 2015, to identify pesticide usage patterns in rice and to suggest the improvement of pesticide safety control. One hundred twenty-nine ingredients and 358 products of domestic-registered herbicides have been classified into 9 reaction patterns and 23 sites of action according to HRAC criteria. These pesticide mechanisms are provided to farmers for prevention of repeated pesticide usage and herbicide-resistant weed occurrence.
1. Observance of pesticide safety usage regulations has not improved. Observance rate was 52~53% for method/usage and 43~57% for protective gears. Although registration has an agroworker hazard assessment component, it is important to develop convenient protective gear and to educate farmers on wearing gear properly.
2. Pesticide crop damage and poisoning is not decreasing, it was reported as 8~18% for crop damage and 6~11% for poisoning during the last 5 years. Crop damage is caused by a disregard of label instructions, such as, mixture availability, application season, and dose; therefore, education is needed on use safety guidelines. Spraying with no protective gears in strong sunlight or prolonged periods are major causes of poisoning,; thus, protective gear development and farmer education are required.
3. In decreasing pesticide usage in rice (a.i. kg ha-1),mostreductionresultsfromfungicidesandinsecticidesreductionswhileherbicideusageremainssteady.Declineisobservedinfungicide(2.7→1.3 →1.0 kg) and insecticide (2.2 →1.3 →0.8 kg) but herbicide use is expected to stay still in spite of expected big changes (1.5 →0.9 →1.3 kg).
4. Sulfonylurea herbicide usage has rebounded after a decline (0.05 →0.03 →0.04kg). Out of the 15 rice herbicides used in 2015, 9 SU herbicides were used among 11 registered SUs. SU increase in 2015 is from use of metazosulfuron, which was registered in 2011 and is user friendly for direct spraying. Frequency is decreasing by constant education and substitution with low resistance pesticides.
5. One hundred twenty-nine domestically registered pesticides have been classified into 10 activity mechanisms categories (e.g. fat composition hindrance, amino acid disturbance, photosynthesis hindrance, etc.) and 22 affiliations (accetyl carboxylase inhibition, branched-chain amino acid inhibition, etc.) according to HRAC criteria. Pesticide mechanisms written on product labels is stipulated to prevent herbicide-resistant weed occurrence. This information of pesticide mechanisms will be provided to farmers for prevention of repeated pesticide usage to reduce herbicide-resistant weed occurrence.