Ho-Yul Choo

Nematocidal Screening of Essential Oils and Herbal Extracts against Bursaphelenchus xylophilus

Five essential oils and 15 herbal extracts were evaluated to control Bursaphelenchus xylophillus in laboratory. The essential oils from clove plant (Syzygium aromaticum), mustard (Brassica integrefolia), thyme (Thymus vulgaris), and Pelargonium inquinans were found to be highly promising and gave excellent control of the nematodes at all the time of exposure. Among them, the least one gave 91.3% mean mortality rate at 24 hours of exposure time, which is highly significant from the control. While in the second study, most of the methanol (Desmodium caudatum, Paulownia coreana, Auckulandia lappa, Sophota flavescens, Aloe sp., Rheum palmatum, Zingiber officinale, Magnolia officinalis, and Eugenia caryophyllata), hexane (Torreya nucifera, Pharbitis nil, Prunus mume, Melia azedarach, and Xanthium strumarium), and hot water (Cinnamomum cassia) herbal extracts killed the nematodes, but in varying degrees compared to the control. Only one extract was found to be promising viz Magnolia officinalis which found to be statistically different from the control and gave mean mortality of 72, 82.3, and 85.3 % for 24, 48, and 72 hours exposure, respectively. Further screening was conducted for M. officinalis with concentrations of 1,000, 100, and 10 ppm against the same species of nematode with the same time of exposure. However, it gave an excellent result for 1,000 ppm for all time of exposure, whereas for the 100 and 10 ppm it gave mean mortality of 39.5 and 25.8% for the time 72hrs, respectively that were statistically different from the control.

Biological Control of Tobacco Cutworm, Spodoptera litura (Lepidoptera: Noctuidae) by Steinernematid and Heterorhabditid Entomopathogenic Nematodes

Five effective strains against tobacco cutworm, Spodoptera litura (Lepidoptera: Noctuidae), Steinernema carpocapsae (GSN1), Steinernema sp. (GSNUS-10), Steinernema sp. (GSNUS-14), Heterorhabditis bacteriophora Hamyang (HbH), and Heterorhabditis sp. (GSNUH-1) were selected among 14 isolates of Korean entomopathogenic nematode in laboratory tests. values of above five strains against tobacco cutworm were various by different nematode strains and developmental stages of tobacco cutworm. value of S. carpocapsae (GSN1) was the lowest by infective juveniles (Ijs) and 2nd instars of tobacco cutworm was most susceptible. Pathogenicity of five effective strains against tobacco cutworm depends on nematode strain, concentration, and application times. The most effective strain was determined as S. carpocapsae (GSN1). Two or three times of applications were effective regardless of nematode strain, or concentration. Efficacy of S. carpocapsae (GSN1), Steinernema (GSNUS-10), Steinernema (GSNUS-14), and Heterorhabditis (GSNUH-1) was variable depending on nematode strain, concentration, application times, and host variety. S. carpocapsae (GSN1) was the most effective and inoculation of 100,000 infective juveniles per m2 (720,000 Ijs/7.2

Development of Economical Artificial Diets for Greater Wax Moth, Galleria mellonella (L.)

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Pathogenicity of Entomopathogenic Nematode, Steinernema carpocapsae GSN1 Strain (Rhabditida: Steinernematidae) against Tebenna issikii (Lepidoptera: Choreutidae)

This research was carried out to develop economical artificial diets of the greater wax moth, Galleria mellonella (L.). Diets were mixed with malt or sugar instead of whole honey for cheaper ones. fecundity, developmental period, pupation rate, emergence rate and adult longevity of G. mellonella depending on diet were examined. The head width and length of larvae were not significantly different among diets tested. However, the weight of larva was the heaviest, 255.5 mg, at 1/2 honey + 1/2 malt diet and lightest, 144.3 mg, at sugar diet. The weight of pupa was also the heaviest at 1/2 honey + 1/2 malt representing 196.7 mg. Larval period was the shortest at honey diet as 30.9 days but the longest at sugar diet as 36.5 days. Pupation and emergence rates were over 79.3% at all diets. The longevity of mated females was ranged from 6.3 to 8.0 days and those of mated males ranged from 7.9 to 11.2 days. The highest number of eggs, 1269, was obtained at sugar diet. Artificial diets replaced by rice bran, malt, and sucrose reduced costs compared with wheat bran plus honey diet. The cost of rice bran was only 10% of wheat bran. Honey was much more expensive than malt and sugar, that is 6 and 13 times, respectively.

Effect of inoculation concentration on pathogenicity, development, propagation and body length of entomopathogenic nematode, Steinernema arenarium (Nematoda: Steinernematidae).

Entomopathogenic nematode, Steinernema carpocapsae GSN1 strain was evaluated for the environmentally sound control of Tebenna issikii (Lepidoptera: Choreutidae) in the laboratory. The corrected mortality of Tebenna issikii larvae was 100% at the 40 infective juveniles (Ijs)/larva 3 days after treatment with S. carpocapsae GSN1 strain in Petri dish. value of S. carpocapsae GSN1 strain against Tebenna issikii was 5.7 Ijs. The mean penetration numbers of Ijs of S. carpocapsae GSN1 strain at the 5, 10, 20, 40 and 80 Ijs/larva in a Tebenna issikii larva were 1.4, 1.4, 3.2, 5.6 and 11.9 Ijs/larva, respectively. However penetration rate of Ijs of S. carpocapsae GSN1 strain at 5 Ijs/larva was the highest among other nematode concentrations. Progeny of S. carpocapsae GSN1 strain in a Tebenna issikii larva was higher with increasing nematode concentration.

Two New Species of Tylenchorhynchus Cobb, 1913 (Nematoda: Belonolaimidae) from Sudan

Effect of inoculation level on pathogenicity, development, and propagation of entomopathogenic nematode, Steinernema arenarium was investigated using the last instar of great wax moth, Galleria mellonella. Pathogenicity of S. arenarium was higher with increasing inoculation level representing 82% at the rate of 5 infective juveniles (IJs) while >98% at the rate of >10 IJs. The number of IJs penetrated into the host was 2.7, 5.0, 7.4, and 12.2 at the rate of 5, 10, 20, and 40 IJs, respectively while 24.3 at the rate of 80 IJs and 40.2 at the rate of 160 IJs. Inoculation level did not affect female adult size (4,616 to 6,444 ) while affected male adult size (1,600 to 1,934 ). The rate of stunted female adults was 70.2% at the inoculation level of 80 IJs and 63.7% at the inoculation level of 160 IJs. The number of progenies was 20,431, 26,696, 47,943, 50,516, 58,701, and 74,235 at the rate of 5, 10, 20, 40, 80, and 160 IJs, respectively. The body lengths of IJs were different depending on inoculation level ranging from 636 to 1,496 .

Susceptibility of the Alfalfa Weevil, Hypera postica (Coleoptera: Curculionidae) to Korean Entomopathogenic Nematodes in Laboratory Assays

Two new species of Tylenchorhynchus Cobb, 1913 from sugar cane fields in Sudan, T. sudanensis and T. elamini are described and illustrated. T. sudanensis is characterized by rather medium body size female, L= 0.692 ㎜ long with rather medium stylet length of 20 ? 23 ㎛. While T. elamini is characterized by medium body size female, L = 0.61 ? 0.78 ㎜ long, medium stylet length of 16 ?19 ㎛. Different characters of two new species are discussed. In addition, vital measurements and brief descriptions of two species are presented.

Survey on Pest Management Practice and Scheme of Increasing Income in Sweet Persimmon Farms in Korea

Laboratory tests were conducted to determine the susceptibility of the alfalfa weevil, Hypera postica to Korean entomopathogenic nematodes, Steinernema carpocapsae GSN1 strain (ScG), S. glaseri Dongrae strain (SgD), Heterorhabditis bacteriophora Hamyang strain (HbH), and Heterorhabditis sp. Gyeongsan strain (HeG) at the petri dish assay. The larval mortality of H. postica was significantly different depending on nematode species and treatment concentration. SgD and HeG strain were more effective against H. postica larva than ScG and HbH strain. When SgD and HeG strain were treated with the rate of >20 infective juveniles (ijs) per alfalfa weevil larva, mortality was ca. 77.5-100% at the late instars of H. postica in 3 days. The number of established nematode was significantly different depending on nematode species, whereas number of progeny was not significantly different. The mean number of established us of SgD strain in a host was the highest at 80 ijs by 30.2. The highest progeny number of HeG strain was 2,671.5 with 80 ijs. All nematode strains were not parasitic entirely to H. postica adults. These results show that alfalfa weevil late larva is highly susceptible to Korean entomopathogenic nematodes in the laboratory