Young-Cheol Yang

Insecticidal Activity of Plant Essential Oils Against Pediculus humanus capitis (Anoplura: Pediculidae)

Abstract The insecticidal activity of 54 plant essential oils against female Pediculus humanus capitis De Geer was examined using direct contact and fumigation methods, and compared with the lethal activity of δ-phenothrin and pyrethrum, two commonly used pediculicides. In a filter paper contact bioassay with female P. humanus capitis, the pediculicidal activity was more pronounced in eucalyptus, marjoram, pennyroyal, and rosemary oils than in δ-phenothrin and pyrethrum on the basis of LT50 values at 0.0625 mg/cm2. At 0.125 mg/cm2, pediculicidal activity of cade, cardamone ceylon, clove bud, myrtle, rosewood, and sage oils was comparable with that of the test insecticides. In fumigation tests with female P. humanus capitis at 0.25 mg/cm2, eucalyptus, marjoram, pennyroyal, and rosemary oils were more effective in closed containers than in open ones, indicating that the effect of these oils was largely a result of action in the vapor phase. Neither δ-phenothrin nor pyrethrum exhibited fumigant toxicity. The essential oils described herein merit further study as potential control agents for P. humanus capitis.

Ovicidal and adulticidal activities of Origanum majorana essential oil constituents against insecticide-susceptible and pyrethroid/malathion-resistant Pediculus humanus capitis (Anoplura: Pediculidae).

The toxicity of essential oil constituents from marjoram, Origanum majorana, to eggs and adult females of the susceptible KR-HL and dual malathion- and permethrin-resistant BR-HL strains of human head louse, Pediculus humanus capitis, was examined using contact + fumigant mortality bioassay. Results were compared with those following treatment with two pyrethroid pediculicides, d-phenothrin or pyrethrum. As judged by the lethal time to 50% mortality (LT(50)) values at the exposure rate of 0.25 mg/cm(2), 1,8-cineole (14.1 min) was the most toxic compound, followed by linalool (15.4 min) to KR-HL females. These compounds were faster acting than either d-phenothrin (24.1 min) or pyrethrum (33.4 min). Based on the lethal concentration causing 50% mortality (LC(50)) values, (-)-camphor (0.022 mg/cm(2)) was the most toxic compound, followed by linalool (0.035 mg/cm(2)), (-)-terpinen-4-ol (0.040 mg/cm(2)), alpha-terpineol (0.045 mg/cm(2)), and 1,8-cineole (0.068 mg/cm(2)) against KR-HL females. These monoterpenoids were less toxic than either d-phenothrin (LC(50), 0.0015 mg/cm(2)) or pyrethrum (0.0013 mg/cm(2)). However, the toxicities of these monoterpenoids were almost identical against females from either of the two strains, even though the BR-HL females exhibited high levels of resistance to d-phenothrin [resistance ratio (RR), 667] and pyrethrum (RR, 754). After a 24 h exposure to linalool, BR-HL egg hatch was inhibited 100 and 84% at 0.25 or 0.125 mg/cm(2), respectively, while (-)-terpinen-4-ol caused 94 and 69% inhibition of egg hatch at 0.25 and 0.125 mg/cm(2). alpha-Terpineol caused 88 and 76% inhibition of egg hatch at 0.5 and 0.25 mg/cm(2), respectively. Thus, certain monoterpenoids from O. majorana essential oil, particularly linalool, (-)-terpinen-4-ol and alpha-terpineol, merit further study as potential pediculicides and ovicides for the control of insecticide-resistant P. h. capitis populations as fumigants with contact action.

Larvicidal Activity of Medicinal Plant Extracts Against Aedes aegypti, Ochlerotatus togoi, and Culex pipiens pallens (Diptera: Culicidae)

Abstract The toxicities of methanol extracts from 28 medicinal plant species to early 4th instar larvae of Aedes aegypti, Ochlerotatus togoi {Aedes togoi), and Culex pipiens pollens were determined in the laboratory. Responses varied according to plant and mosquito species. At a concentration of 100 ppm, >90% mortality of the three species was obtained with the extracts of Cinnamomum cassia bark, Illicium verum fruit, Piper nigrum fruit, Zanthoxylum piperitum fruit, and Kaempferia galanga rhizome. P. nigrum fruit extract gave 100% mortality of larvae of Ae. aegypti and O. togoi at 5 ppm and 96% mortality of larvae of C. pipiens pallens at 2.5 ppm. Z. piperitum fruit extract gave 85, 100, and 48% mortality in larvae of Ae. aegypti, O. togoi, and Cx. pipiens pallens at 10 ppm, respectively. The plants described merit further study as potential mosquito larval control agents.

Efficacy of Spray Formulations Containing Binary Mixtures of Clove and Eucalyptus Oils Against Susceptible and Pyrethroid/Malathion-Resistant Head Lice (Anoplura: Pediculidae)

ABSTRACT The control efficacy of clove, Eugenia caryophyllata, and eucalyptus, Eucalyptus globulus, essential oils and 15 formulations containing these essential oils alone (8, 12, and 15% sprays) and their binary mixtures (7:3, 5:5, and 3:7 by weight) against adult females of insecticide-susceptible KR-HL and dual malathion - and permethrin-resistant BR-HL strains of head louse, Pediculus humanus capitis (De Geer), was examined by using contact plus fumigant and human hair wig (placed over the head of mannequin) mortality bioassays. In contact plus fumigant mortality bioassay, essential oils from eucalyptus (0.225 mg/cm2) and clove (1.149 mg/cm2) were less effective than either d-phenothrin (0.0029 mg/cm2) or pyrethrum (0.0025 mg/cm2) based on 6-h median lethal concentration values. However, the efficacies of eucalyptus and clove oils were almost identical against females from both strains, despite high levels of resistance of the BR-HL females to d-phenothrin (resistance ratio, 667) and pyrethrum (resistance ratio, 754). In human hair wig mortality bioassay, eucalyptus oil spray treatment gave better control efficacy than either spray treatment with clove oil alone or their binary mixtures, Thus, eucalyptus applied as 8% sprays (15 or 20 ml) appears to provide effective protection against pediculosis even to insecticide-resistant head louse populations. Once the safety issues resolved, covering the treated hair and scalp with bath shower cap or hat would ensure the fumigant action of the essential oil.

Insecticidal activities of their components derived from the essential oils of Cinnamomum sp. barks and against Ricania sp. (Homoptera: Ricaniidae), a newly recorded pest

BACKGROUND Insecticidal activities of Cinnamomum cassia and Cinnamomum zeylanicum oils and their components are not known against Ricania sp. Insecticidal activities of major components derived from C. cassia and C. zeylanicum oils were examined in spray and leaf-dipping bioassays against Ricania sp. nymphs and adults. RESULTS The LC50 value of C. cassia and C. zeylanicum oils was 37.66 and 72.62 mg L-1 , respectively, in leaf-dipping bioassays against Ricania sp. nymphs, and 77.38 and 134.86 mg L-1 in spray bioassays against Ricania sp. adults. The insecticidal activity of C. cassia oil was 1.74-1.93 times greater than that of C. zeylanicum oil. When examined by gas chromatography mass spectrometry, the cinnamaldehyde content of C. cassia and C. zeylanicum oils was 80.20% and 46.32%, respectively. Based on the LC50 values of cinnamaldehyde, hydrocinnamaldehyde and 4-hydroxy-3-methoxycinnamaldehyde against Ricania sp. nymphs and adults, cinnamaldehyde (LC50 , 31.25 and 62.43 mg L-1 ) demonstrated the most potent insecticidal activity, followed by 4-hydroxy-3-methoxycinnamaldehyde (172.19 and 212.77 mg L-1 ) and hydrocinnamaldehyde (275.05 and 318.63 mg L-1 ). CONCLUSION The findings revealed that C. cassia oil, C. zeylanicum oil and cinnamaldehyde have potential value in the management of Ricania sp. and could be valuable as effective insecticides.

Food Protective Effects of 3-Methylbenzaldehyde Derived from Myosotis arvensis and Its Analogues against Tyrophagus putrescentiae

The potential abilities of 3-methylbenzaldehyde derived from Myosotis arvensis oil and its structural analogues to act as new acaricide and mite kit (mite color deformation) against Tyrophagus putrescentiae (Schrank) were evaluated in the present study. Based on the LD50 values, 2,4,5-trimethylbenzaldehyde (0.78 μg/cm3) had highest vapor action against T. putrescentiae, followed by 2,4-methylbenzaldehyde (1.14 μg/cm3), 2,5-dimethylbenzaldehyde (1.29 μg/cm3), 2-methylbenzaldehyde (1.32 μg/cm3), 2,3-dimethylbenzaldehyde (1.55 μg/cm3), 3-methylbenzaldehyde (1.97 μg/cm3), and 4-methylbenzaldehyde (2.34 μg/cm3). The color deformation of seven methylbenzaldehyde analogues mixed with 2,3-dihydroxybenzaldehyde against T. putrescentiae showed mite color deformation, from coloress to reddish brown, and valuable to distinguish with the naked eye. In addition, there was no antagonistic interactions between 2,3-dihydroxybenzaldehyde and the methylbenzaldehyde analogues. These finding suggests that the methylbenzaldehyde analogues could be developed as dual functional agent to protect from fall in the commercial value of stored food products.