• Korean Journal of Weed Science
• /
• v.18 no.2
• /
• pp.146-153
• /
• 1998

This experiment was conducted to clarify the characteristics of germination and emergence of Panicum dichotomiflorum which is a noxious weed species in direct-seeded rice field. P. dichotomiflorum was planted with several treatments such as different depths of irrigation to verifiy the ecological habits of seedling emergence and growth. In order to know the germination characteristics, Panicum dichotomiflorum seeds, pretreated with low-temperature($4^{\circ}C$) stratification for breaking the dormancy, were germinated under different temperature regimes and water potentials. Germination rates of P. dichotomiflorum was increased from 0% of dormant seed to 1%, 35% and 44% by stratification for 21, 28 and 42 days, respectively. Two dominant weed species in directseeded rice fields, Echinochloa crus-galli and Panicum dichotomitlorum, showed different germination habit under different temperature regimes. Echinochloa crus-galli showed more higher germination rate than Panicum dichotomiflorum at relatively low temperature regime(20/$10^{\circ}C$). Both species germinated faster at 30/$20^{\circ}C$ than at 20/$10^{\circ}C$. When the water potential was lowered, germination of Panicum dichotomiflorum was reduced more drastically than Echinochloa crus-galli. The critical water potential for germination of P. dichotomiflorum was -0.7MPa but Echinochloa crus-galli was affected slightly by the same water potential. The results showed that Echinochloa crus-galli can germinate under more wide range of soil water potential than Panicum dichotomiflorum. Emergence of P. dichotomiflorum was highly affected by irrigation depth and the level of water table. When the depth of irrigation water was increased, emergence of P. dichotomiflorum was dragged and emergence rate showed significant difference under the irrigation depth deeper than 6cm. The maximum depth of irrigation water for survival of Panicum dichotomiflorum seedling was 9cm.

• Korean Journal of Weed Science
• /
• v.17 no.4
• /
• pp.413-420
• /
• 1997

In this study, germination characteristics and effect of some chemicals on germination of Trapa japonica $F_{EROV}$ seeds were investigated to obtain a fundamental data for controlling them. When the seeds were stored at low temperature for at least 3 months, their dormancy was completely released with a germinability of above 90%. However, those stored under the room or high temperature condition were never germinated. Germination was best at constant temperature of around $25^{\circ}C$ or at alternate temperature of 25/$15^{\circ}C$ (12 hr-day/12 hr-night), and was nat dependent on light. They could germinate though planted at the depth of 15 cm, but their initial growth were: suppressed with increase of planting depth, especially above 10 cm depth. Germinability was lost when the fresh weight was decreased more than 30%, indicating that the seed is sensitive to dehydration. The freezing at $-20^{\circ}C$ for 1 hr didn't affect germination, but 5 hr treatment completely killed them. Their germination was inhibited by 100% at 100 ppm ABA and slightly inhibited above 25 ppm of butachlor, whereas pyrazosulfuron-ethylnt is likely to control T. japonica physically and herbicide treatment to inhibit germination may not be recommendatory. and bensulfuron-methyl didn't inhibit the germination at the concentration of 100 ppm. Taken together, dehydration treatme is likely to control T. japonica physically and herbicide treatment to inhibit germination may not be recommendatory.

• Korean journal of applied entomology
• /
• v.59 no.1
• /
• pp.15-22
• /
• 2020

Two tephritid fruit flies are infesting pumpkins in Korea. Both are classified into genus of Zeugodacus. The striped fruit fly, Z. scutellata, males are attracted to a lure called Cuelure (CL), which has been used to monitor the occurrence of this fruit fly in the crop field. In contrast, no effective male lure was not developed to monitor the pumpkin fruit fly, Z. depressa. Protein diet lure has been used to attract females of most fruit flies. The addition of terpinyl acetate (TA) was effective to increase the attractiveness of Z. depressa. This study aimed to monitor the occurrence of Z. depressa in pumpkin field with TA-protein diet lure. To validate the efficiency of TA-protein diet lure, Z. scutellata was monitored in a year of 2019 using CL and TA-protein diet lures, and the yearly monitoring data were compared. The occurrence patterns derived from both lures were similar except late season after October. The extended catches of TA-protein diet lure might be explained by the adult diapause induction of Z. scutellata at late September. Monitoring Z. depressa with TA-protein diet lure gave two peaks at mid July and August-September, in which more than 80% catches were females. Based on the attractiveness of TA-protein diet lure, its wettable powder with an addition of spinosad insecticide was formulated and sprayed to pumpkin crops. After 7 days post-spray, the control efficacy recorded more than 70%. However, the control efficacies decreased as the time progressed after the spray. These results demonstrated the application of TA-protein diet lure for monitoring occurrence of Z. depressa in pumpkin-cultivating field conditions. The wettable powder containing spinosad can be applied to develop a new control agent against two pumpkin fruit flies.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.4 no.3
• /
• pp.151-158
• /
• 2002

In Korean high yielding varieties developed by crosses between indica and japonica rice, the most limiting factor for yield increase may be attributed to the less number of tillers per unit area. The goal of this study is to find out the effect of the environmental factors as well as cultivation practice on the development and increase of tillers of Dasanbyeo, the high yielding indica / japonica hybrid cultivar. The effect of temperature was examined with 3 different light intensity, 220,600, and 1220 $\mu$㏖/s/$m^2$, respectively. For all the experiments, the leading japonica variety in Korea, Hwaseongbyeo, was used fur the check cultivar for the comparison with Dasanbyeo. The increase of the tillers was more prominent in Dasanbyeo than in Hwaseongbyeo at 220 $\mu$㏖/s/$m^2$ of light intensity, while the similar increase of tiller no. was found at 600 $\mu$㏖/s/$m^2$ of light intensity treatment. However, Hwaseongbyeo showed more rapid increase of tiller at 1220 $\mu$㏖/s/$m^2$ of light intensity. The mean number of the primary tiller ranged 5 to 7 in Dasanbyeo, and 2 to 7 in Hwaseongbyeo, showing greater variation in the latter case. However, the secondary tiller number ranged from 2 to 13 for the former, and 2 to 12 for the latter. The earliest initiation of tiller node of Dasanbyeo and Hwaseongbyeo was observed on 6 and 4 days after transplanting(DAT), respectively, at 600 $\mu$㏖/s/$m^2$ of light intensity, while 10, and 7 DAT, respectively, at 1,220 $\mu$㏖/s/$m^2$. No cultivar difference was observed at 600 $\mu$㏖/s/$m^2$ with the 18 DAT. The ratio of effective tiller was lower in Dasanbyeo, ranging from 47 to 55% than in Hwaseongbyeo, ranging from 72 to 100%.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.16 no.4
• /
• pp.396-402
• /
• 2014

The spring season in Korea features a dynamic landscape with a variety of flowers such as magnolias, azaleas, forsythias, cherry blossoms and royal azaleas flowering sequentially one after another. However, the narrowing of south-north differences in flowering dates and those among the flower species was observed in 2014, taking a toll on economic and shared communal values of seasonal landscape. This study was carried out to determine whether the 2014 incidence is an outlier or a mega trend in spring phenology. Data on flowering dates of forsythias and cherry blossoms, two typical spring flower species, as observed for the recent 60 years in 6 weather stations of Korea Meteorological Administration (KMA) indicate that the difference spanning the flowering date of forsythias, the flower blooming earlier in spring, and that of cherry blossoms that flower later than forsythias was 30 days at the longest and 14 days on an average in the climatological normal year for the period 1951-1980, comparing with the period 1981-2010 when the difference narrowed to 21 days at the longest and 11 days on an average. The year 2014 in particular saw the gap further narrowing down to 7 days, making it possible to see forsythias and cherry blossoms blooming at the same time in the same location. 'Cherry blossom front' took 20 days in traveling from Busan, the earliest flowering station, to Incheon, the latest flowering station, in the case of the 1951-1980 normal year, while 16 days for the 1981-2010 and 6 days for 2014 were observed. The delay in flowering date of forsythias for each time period was 20, 17, and 12 days, respectively. It is presumed that the recent climate change pattern in the Korean Peninsula as indicated by rapid temperature hikes in late spring contrastive to slow temperature rise in early spring immediately after dormancy release brought forward the flowering date of cherry blossoms which comes later than forsythias which flowers early in spring. Thermal time based heating requirements for flowering of 2 species were estimated by analyzing the 60 year data at the 6 locations and used to predict flowering date in 2014. The root mean square error for the prediction was within 2 days from the observed flowering dates in both species at all 6 locations, showing a feasibility of thermal time as a prognostic tool.

• Korean Journal of Weed Science
• /
• v.16 no.2
• /
• pp.81-87
• /
• 1996

Seeds of rice, cv. Ilpoom, and barnyardgrasses(Echinochloa crus-galli, vars. oryzicola, crux-galli, and praticola) were sown for a characterization of their responses to temperature during emergence under a dry direct-seeded condition. A laboratory-made aluminum block apparatus for emergence-temperature control conferred a linear continuous temperature gradient from 10 to $30^{\circ}C$ to the seeds from cooling to heating ends of the apparatus. The lowest temperature for emergence was $12.3^{\circ}C$ for rice cv. Ilpoom, and $11.0^{\circ}C$ for the three varieties of Echinochloa spp.. Percent emergence of rice increased sharply with an increase in temperature by ca. $20^{\circ}C$, then leveled-off, while those of barnyardgrasses increased almost linearly with temperatures up to $30^{\circ}C$. In rice the time required for emergence after seeding was shortened exponentially with increased temperature while those for barnyardgrasses were shortened almost linearly from 11 to $30^{\circ}C$. The temperature-response characteristic of rice in emergence-speed was almost the same among those for the 1st emergence, emergence by 25, 50, 75%, or average emergence time. At $13^{\circ}C$, $346.7^{\circ}C$ days of accummulated temperature(26.67 days) were required for the 1st emergence in rice while 131.7, 136.0, and $138.7^{\circ}C$ days(10.13, 10.46, and 10.67 days) were required for the 1st emergence in E. spp., vars. crus-galli, praticola, and oryzicola, respectively. Greater cold tolerance and increasingly faster emergence of barnyardgrasses than rice below $20^{\circ}C$ seem to render the barnyardgrasses as much more competitive than rice at lower temperatures.

• Korean Journal of Weed Science
• /
• v.8 no.3
• /
• pp.309-316
• /
• 1988

Several experiments were conducted to investigate the achene viability and growth characteristics of Eclipta prostrata (L.) L. No dormancy and no after-ripening requirement were found for E. prostrata achenes. When achenes were stored at room temperature, germination did not decrease with up to 5 months storage. Large differences in loss of viability of E. prostrata achenes occurred when different dehydration methods were used. Immediate dehydration resulted in high viability, but slow dehydration resulted in severe loss of viability. Achene viability at shallow burial depths (5 and 10 cm deep) was lower under upland soil conditions than under lowland soil conditions. Seedling growth was greatly reduced when flooding to a depth of 10 cm occurred at or before the 4-leaf stage. Flooding after the 4-leaf stage stimulated stem elongation. Branching started from the second week and usually terminated at the tenth week. Leaf size was determined by the branch which are related to the assimilate supply. Flowering of E. prostrata started during the fifth week after emergence, and mature achenes were produced from the sixth week. Ten to 14 days were needed for the achenes to mature. About 14,000 achenes were produced on each plant. Achene production per week increased from the sixth week to the tenth week and thereafter it declined. The average number of achenes per inflorescence decreased with delay in flowering.