• Korean Journal of Agricultural Science
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• v.11 no.1
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• pp.61-67
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• 1984

In an attempt to obtain a basic information to develop methods of an effective chemical control and disease forecasting of panicle blast of rice, effects of conidial number of the causal fungus, Pyricularia oryzae, collected in different periods and the rate of leaf blast occurrence on the occurrence of panicle blast were investigated. Conidial number the fungus collected in 5 days before and after heading date were closely related with panicle blast occurrence. But no relationship was obtained between the occurrence rate of leaf blast and that of panicle blast. Considering the incubation period of the disease, we presume that the most effective application periods of chemicals are 5-10 days and 10-15 days before heading, when immediate effective chemicals and slow effective chemicals are applied, respectively.

• Korean journal of applied entomology
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• v.44 no.4 s.141
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• pp.337-339
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• 2005

In Iksan, Korea, Parnara guttata Brener et Grey spend three generations per year, 1st generation adult emerged mid to late May from pupa developed from overwintered larva in weeds on bank around rice paddy field or on hillside and moved to rice paddy field to lay eggs on leaves of rice. The damage to rice by 2nd generation larva began to increase late July and reached peak from mid to late August. The 3rd generation adults were observed early to mid September and flew away from rice paddy field. There was significant relationship between the transplanting time and the occurrence of P. guttata in rice paddy fields. P. guttata preferred the rice transplanted in late season in paddy field. Insecticide treatment on late July about a week before the peak larval occurrence reduced the damage by P. guttata up to 91.2%, whereas the treatment on early August was a lot less effective reducing only 57.2% of the damage.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.544-549
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• 2018

Thrips populations were monitored in field-cultivated pepper at Gochang, Jeonbuk province, Cheongyang, Chungnam province, and Goesan, Chungbuk province during the field growing seasons of 2017 to 2018, respectively. We classified and quantified thrips population in each plot and year. Most of the monitored thrips were composed of three species: Frankliniella intonsa, F. occidentalis, and Thrips tabaci, respectively. F. intonsa was the dominant species in all the monitoring season. The density of thrips was increased from late June in each field and year with the highest density being recorded in mid-July. Based on the results, management strategy of thrips in red peppers should be evaluated from early June with monitoring and appropriate controls.

• Korean journal of applied entomology
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• v.43 no.2
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• pp.103-109
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• 2004

Seasonal occurrence of Japanese gall-forming thrips, Ponticulothrips diospyrosi Haga et Okajima, and its damage pattern on leaves and fruits were studied at sweet persimmon orchards in Gimhae (orchard A, B) and Changwon, Gyeongnam. Korea in 2002 and 2003. Monitoring adults by yellow sticky traps and inspecting each developmental stage in damaged rolled-leaves revealed that the overwintered adults moved to sweet persimmon orchard from late April to late May, and oviposited inside the rolled leaves. Adults developed from the eggs showed peak occurrence of the first generation adults in early to mid June. Inspection of rolled leaves indicated that the peak occurrences of eggs, nymphs, and pupae of the first generation took place in early to mid May, late May to early June, and early June, respectively. Each developmental stage showed the second small peaks in the late season. Results suggest that most thrips live a single generation per year, but a small portion may develop to the second generation in persimmon orchards. The percent of damaged leaves was highest in Changwon orchard at 9.7％ in early June. Percentage of damaged fruits increased from 0.84％ in early June to 30.2％ in early September in Gimhae B orchard. It was found that the closer the persimmon trees were to the edge of the orchard, the worse damaged the leaves were. Appropriate timing for incorporation of control measures were discussed in relation to the seasonal occurrence of adults.

• Korean journal of applied entomology
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• v.48 no.1
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• pp.21-27
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• 2009

Paromius exiguus (Distant) has caused serious damage by pecky grains around Gimpo paddy fields in 2001. We conducted field and laboratory studies to determine the seasonal occurrence and age distribution of P. exiguus on the three major host plants. The overwintering P. exiguus was found mainly on the basal part of gramineae weeds in various localities. After overwintering, in mid-May, the adults aggregated on the grain parts of Imperata cylindrica, laid their eggs and nymphs developed into adults on the same host plants. By the time, the Calamagrostis epigeios colony had newly occupied I. cylindrica areas, the nymphs and adults of first generation had already moved to the second host. The second generation of P. exiguus, after having completed its life cycle on C. epigeios, the newly emerged adults migrated to the rice plants and other gramineae weeds in early August. Afterwards, they complete its third generation cycle where they can move to the overwintering site again. P. exiguus has the five nymphal stages and each nymphal stage could be determined by head or prothoracic width. On the I. cylindrica and O. sativa hosts, the age distribution of P. exiguus showed a simple structure as each stage ratio increased stepwise with time. But in case of C. epigeios, as the newly emerged adults and immature nymphs continuously migrate after a month from the I. cylindrica, the age structure became remarkably complex. The peak nymphal density was observed when the ratio of third and forth instar was the highest in the population. The finding about the specific age structure on each generation of the insect would be very useful in control decision making on the major host plants. It is also important to consider the host's specificity to pesticide sensitivity in relation to various nymphal stages.

• Research in Plant Disease
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• v.20 no.2
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• pp.119-125
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• 2014

Root-knot nematodes represent a significant problem in cucumber, causing reduction in yield and quality. To develop screening methods for resistance of cucumber to root-knot nematode Meloidogyne incognita, development of root-knot nematode of four cucumber cultivars ('Dragonsamchuk', 'Asiastrike', 'Nebakja' and 'Hanelbakdadaki') according to several conditions such as inoculum concentration, plant growth stage and transplanting period was investigated by the number of galls and egg masses produced in each seedling 45 days after inoculation. There was no difference in galls and egg masses according to the tested condition except for inoculum concentration. Reproduction of the nematode on all the tested cultivars according to inoculum concentration increased in a dose-dependent manner. On the basis of the result, the optimum conditions for root-knot development on the cultivars is to transplant period of 1 week, inoculum concentration of 5,000 eggs/plant and plant growth stage of 3-week-old in a greenhouse ($25{\pm}5^{\circ}C$). In addition, under optimum conditions, resistance of 45 commercial cucumber cultivars was evaluated. One rootstock cultivar, Union was moderately resistant to the root-knot nematode. However, no significant difference was in the resistance of the others cultivar. According to the result, we suggest an efficient screening method for new resistant cucumber to the root-knot nematode, M. incognita.

• Korean journal of applied entomology
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• v.16 no.3 s.32
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• pp.155-161
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• 1977

During 1976 the effects of insecticide placement in the root zone of the rice plants were evaluated for control of rice insect pests in the screenhouse and in the paddy field at Suweon. The methods of insecticide placement included the use of encapsuled formulation and injection of liquid formulation. In screen house experiments, the root' zone placement of carbofuran was highly effective up to 30 days after treatment against the striped rice borers (Chilo sujppressalis) and up to 17 days after treatment against the small brown planthopper(Laodelphax xtriatellus) and the brown planthopper (Nilaparvata lugens), while the root-zone placement of omethoate and disyston were ineffective. In field experiments, the injection in every other row by the liquid applicator designed at IRRI was less effective for control of the striped "'rice borers and the small brown planthoppers than the caupsule placement. The single root·zone placement of liquid carbofuran, however, seemed to be equal in 'effectiveness to two broadcast applications of carbofuran and diazinon. In the plots treated at 5 days after transplanting, incidence of the dead hearts by the striped rice borers was much lower than in the plots treated at the 18 days after transplanting.

• Korean Journal of Weed Science
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• v.3 no.2
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• pp.166-173
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• 1983

To investigate the varietal differences of weed competitive functions under the three different seasons of transplanting, rice cultivars Milyang 23 and Sadominori were used with seven weeding methods, namely, weedy check, weed-free, once weeding at 3, 6, 9, 12 weeks after transplanting, and two times weeding at 3 and 9 weeks after transplanting, respectively. As a result, weeding stages and times for the proper weeding efficacies and reasonable rice productivities by respective weed group and total weed flora were estimated. Also, the constructive characteristics for yield formations under the different competitive conditions as affected by various cropping patterns were discussed.

• Korean journal of applied entomology
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• v.45 no.1 s.142
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• pp.67-74
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• 2006

Korean entomopathogenic nematodes were introduced into cultural management of turfgrasses to enhance white grub control in golf courses for saving labour and expenses and contribution to giving safe playing and working places for golfers and superintendents by environmentally friendly control strategy. The turfgrass height influenced efficacy of entomopathogenic nematodes. Efficacy was higher at short turfgrass both in pot using Galleria mellonella larvae and in golf courses using 2nd instar of Exomala orientalis and Ectinohoplia rufipes as baits. Aeration increased the efficacy of entomopathogenic nematodes which were lower virulent. Pre-aeration was more effective than post-aeration. Exomala orientalis larval population was reduced 80.4 and 66.0% in the pre-aeration and post-aeration with entomopathogenic nematode, Steinernema carpocapsae Pocheon strain compared to 35.4% in the no aeration treatment.

• Korean journal of applied entomology
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• v.18 no.1 s.38
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• pp.55-61
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• 1979

Since rice high yielding practices with blast resistant varieties induced severe and earlier infestation of sheath blight recently, it is strongly suggested to spray at least 10 days earlier than the present recommendation and more than 2 sprays from early July to early August seems to be essential for the efficient control of sheath blight in the future. Among organo-arsenic fungicides, MAFe (Neo Asozin) is known as the most effective and economic as well as with the advantages of free phytotoxicity and safe residure on rice, and applications of the mixed formulation with other fungicide and insecticide is suitable for the one-hit control of rice diseases and insect pests in connection with cooperative mass control system. Present level of arsenic $(As_2O_3)$ residue in .ice is summarized as 0.2ppm to 0.65 ppm in highest average, and there are more possibilities of extensive MAFe fungicide uses for the efficient and economic control of this disease. During the past few years, the acreage of sheath blight control has been extended several times while the increase of the fungicides used for sheath blight showing about 10 times in quantity and mort than 15 times in amount, and also the fungicide cost estimated for the control is differ from 1 to 12 billion 1on by the use of MAFe or antibiotic fungicide in a year.