• Korean Journal of Weed Science
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• v.31 no.1
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• pp.71-77
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• 2011

This study was conducted to predict the yield loss of red pepper and to determine the economic weed thresholds levels for red pepper cultivation field from competition with the most serious weeds, Echinochlor crus-galli (L.) P. beauv. (barnyard grass) and Chenopodium album L. (goosefoot) in Youngyang of Korea. Crop yield as a function of weed density was predicted by using a rectangular hyperbola, and their economic threshold levels were determined by using the equation developed by Cousens (1987). The red pepper yield loss models of weeds were predicted as y=317.0 kg/ (1+0.1707x), $R^2$=0.895 in E. crus-galli and y=323.2 kg/(1+0.2900x), $R^2$=0.896 in C. album L.. Economic thresholds calculated using Cousens' equation was negatively related with the competitiveness of weed. Economic thresholds of each weed were calculated as 6.5 plant $100m^{-2}$ in E. crus-galli, and 3.7 plant $100m^{-2}$ in C. album L..

• The Korean Journal of Pesticide Science
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• v.2 no.2
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• pp.102-107
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• 1998

The objective was to know if seed potato farmers in Kangwon alpine area control weeds effectively and use herbicides properly to control weeds. Seed potato farmers in Pyongcbang, Hoengsong, and Kangnung have noxious weeds, such as marsh pepper, lambsquarters, barnyard grass, mugwort, asiatic dayflower, hairy carbgrass, ladysthumb, common chickweed, field horsetail, and common purslain, in their farmyard. These are controlled by a combination of physical and chemical weed control methods. However, several weeds such as marsh pepper, field horsetail and, mugwort are poorly controlled by 2-fold amount of several herbicides, including paraquat, pendimethalin, and metribuzin (58% of the answered). Herbicides are not selected and used in a proper manner by seed potato farmers: most of farmers selected herbicides by their experience (51% of the answered) and dealers recommendation (34% of the answered), while only a few farmers of the answered took advantage of the Farmers Handbook for Herbicide Application. In addition, the selected herbicides, including non-registered ones such as paraquat and fluazifop-butyl, are applying three to five years in a succession. With these improper selection and usage of herbicides, sixty-seven percent of the answered farmers have experienced crop damage and seventy-five percent have poisoning. We conclude that a systemic educational program for the proper selection and use of herbicides is needed for seed potato farmers in Kangwon alpine area.

• The Korean Journal of Pesticide Science
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• v.3 no.3
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• pp.54-59
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• 1999

The objective was to know if corn growers at Hongchcel County, Kangwon-do, where corn is the major agricultural product, control weeds effectively and use herbicides properly to control weeds. Sixty-eight corn growers at Hongchon were participated in this survey. Corn growers have noxious weeds, such as hairy carbgrass, common purslane, lambsquarters, Asiatic dayflower, mugwort and barnyard grass in their corn fields. Forty-four percents of the answered corn growers control weeds by hand weeding, and the others by a combination of physical and chemical methods. Corn growers have a preference of paraquat and alachlor for a pre-emergence treatment (94% of the answered) and of paraquat, glufosinate, glyphosate and fluazifop-P-butyl for a post-emergence treatment (87% of the answered). Corn growers did not select and use herbicides in a proper manner. fifty-four percent of the answered corn fevers selected herbicides by their own experience and 18 percent by neighbors recommendation. Herbicides were not selected and used in a proper manner by corn growers: 54 percent of the answered selected herbicides by the experience of growers and 18 percent by the recommendation of neighbors. In addition, a half of the answered applied over two-fold higher amounts of herbicides than the recommended rate. With these improper- selection and use of herbicides, 37 percent of the answered have experienced the crop damage and 42 percent the herbicide poisoning. We conclude that the development of the educational program for the proper selection and use of herbicides is needed for corn growers in Kangwon-do.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.5
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• pp.405-412
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• 1993

This experiment was conducted to investigate the effects of water depths on seedling stand and early growth of califonia rice varieties, S201, M202, A301, Italico livorno and Korean variety, Hwaseongbyeo, and barnyardgrass (Echinochloa crus-galli) The coleoptile length of rice was longer with deep water depth while for the radicle length shorten. As water depth was increased, the percentage of seedling stand were decreased slightly in rice, while sharply increased in barnyardgrass. Plant height of rice with increasing water depth were longer, whereas that of barnyardgrass reduced significantly with weaker. Tiller number of rice and barnyardgrass were significantly reduced as water depth increased. Dry matter weight and healthy score of rice seedling at 35DAS were highest in 7.5cm water depth followed saturated moisture, 15, and 22.5cm water depth, while for barnyardgrass those were especially negatively affected by deep water depth. These results showed that the seedling stand and early growth of barnyardgrass was highly suppressed by deeper water levels compared with rice. Rice cultivars which are showes growth characteristics in deeper water levels at early growth stage were Italico livorno and S201 in Japonica / Indica.

• Korean Journal of Weed Science
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• v.14 no.3
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• pp.199-211
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• 1994

Butachlor applied pre-emergence at 3.6kg ai/ha inhibited the growth and developments of shoot of barnyardgrass under dry condition, whereas rice was unaffected. Growth of rice and barnyardgrass under water condition was severely inhibited by treatment of butachlor but that of transplanted rice was not affected. The inhibition rate was higher under water condition, in broadcast rice and direct seeded rice than under dry condition, drilled rice and transplanted rice, respectively. The major anatomical response of stem of barnyardgrass seedling to butachlor under dry condition were partial reduction in thickness and collapse of leaf sheath, while not in rice. Broadcast rice on soil under water condition appeared reduction and constriction of leaf primordia thickness, and barnyardgrass formed tubular-like leaves and showed inhibited elongation of apical meristem. On the other hand, transplanted rice did not show these responses.