Ginseng foliar diseases are typically controlled by spray application using periodic schedules. Few disease warning systems have been used for effective control of ginseng foliar diseases because ginseng is grown under shade nettings, which makes it difficult to obtain weather data for operation of the disease warning system. Using weather data measured outside the shade as inputs to an empirical leaf wetness duration (LWD) model, LWD was estimated to examine if operation of a disease warning system would be feasible for control of ginseng foliar diseases. An empirical model based on a fuzzy logic system (fuzzy model) was used to estimate LWD at two commercial ginseng fields located in Gochang-gun and Jeongeup-si, Korea, in 2011 and 2012. Accuracy of LWD estimates was assessed in terms of mean error (ME) and mean absolute error (MAE). The fuzzy model tended to overestimate LWD during dew eligible days whereas it tended to underestimate LWD during rainfall eligible days. Still, daily disease risk ratings of the TOM-CAST disease warning system, which are derived from estimates of wetness duration and temperature, had a tendency to coincide with that derived from measurements of weather variables. As a result, spray advisory dates for the TOM-CAST disease warning system were predicted within ±3 days for about 78% of time windows during which the action threshold for spray application was reached. This result suggested that estimates of LWD using an empirical model would be helpful in control of a foliar disease in a ginseng field. It was also found that a spray application time model using meteorological observations may prove successful without the requirement of leaf wetness sensors within the field. Development of empirical correction schemes to the fuzzy model and a physical model for LWD estimation in a ginseng field could improve accuracy of LWD estimates and, as a result, spray advisory date prediction, which merits further studies.

This study was conducted to establish a weed management system based on the sequential application of pre-emergence (PRE) and post-emergence (POST) herbicides for soybean production in Primorsky krai. Field experiments were conducted for two years in a field located in Bogatyrka, Primorsky krai, Russia (N43°49′, E131°36′). No herbicide application resulted in significant soybean yield loss, 0.03–0.3 t ha−1, which is more than 91.6% yield loss compared with that of the weed-free plot. The PRE application of acetochlor showed good weed control efficacy (greater than 90% weed control) with acceptable soybean safety (less than 10% soybean damage), while the other PRE herbicides performed poorly in terms of weed control. The POST application of bentazon + acifluorfen, bentazon, and imazamox at 30 days after soybean sowing (DAS) showed good weed control efficacy with good soybean safety. Neither the PRE nor POST application alone showed a sufficient soybean yield protection, resulting in much lower soybean yield than the weed-free plot. The sequential application of acetochlor (PRE), followed by either bentazon + acifluorfen (POST) at 30 DAS in 2012 or bentazon + imazamox (POST) at 60 DAS in 2013 showed the best performance in soybean yields, 1.7 t and 1.9 t ha−1, respectively, provided with 724.5 US$ and 1155.6 US$ ha−1 of economic returns. For alternative PRE herbicides of acetochlor, which is now banned, our tests of the sequential application of S-metolachlor with other POST herbicides and the sole application of other PRE herbicides revealed that S-metolachlor and clomazone could also be considered. Our results thus demonstrate that the sequential applications of PRE and POST herbicides should be incorporated into the weed management system for soybean production in Primorsky krai, Russia.

ABSTRACT:The mixing cycle-dependent degree of dispersion and degree of mixing of a calcite (calcium carbonate) agglomerate in high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE) matrices upon stretching was investigated using three different techniques: mechanical property, morphological behavior, and image analyzer analyses. The mechanical properties analyzed in terms of the tensile strength and maximum elongation resulted in that the second mixing was the best for giving a better property for all systems except the LDPE system, which exhibited no significant difference between the second and third mixings. The morphological behavior of the three compounds were different, but no distinctive difference was observed to differentiate the degree of mixing from system to system. The number-, weight-, and z ϩ 1-average diameters of the air hole and the aspect ratio upon the stretching and mixing cycle were calculated to analyze the degree of mixing of the calcite-filled composites. As a consequence, no difference in the average diameter of the air hole was obtained among the three systems, but the aspect ratios of the air hole varied significantly. Thus, the degree of dispersion and the degree of mixing may be influenced by the average calcite agglomerate size, the average diameter of the air hole, and the aspect ratio upon stretching and mixing cycles. Those factors would be formed by the difference in chemical characteristics upon various microstructures of polyethylene and its molecular weight and molecular weight distribution.

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