Jeong-Oh Yang

Effect of Electron-beam Irradiation on Development and Reproduction of Bemisia tabaci, Myzus persicae, Plutella xylostella and Tetranychus urticae

Four major agricultural insect pests, Bemisia tabaci, Myzus persicae, Plutella xylostella and Tetranychus urticae, were irradiated with 30, 50, 70, or 100 Gy electron-beam. Longevity, egg hatching, emergence, and fecundity of the test insects were measured. Hatchability of B. tabaci, P. xylostella and T. urticae declined with increasing irradiation doses, and all B. tabaci and T. urticae eggs were dead at 100 Gy. When eggs of B. tabaci, P. xylostella and T. urticae were irradiated, hatch was inhibited. B. tabaci adults grown from 70 Gy irradiated eggs did not lay eggs. Fecundity of P. xylostella from the 100 Gy irradiated eggs decreased. When B. tabaci, P. xylostella, M. persicae and T. urticae nymphs/larvae were irradiated, the results were similar as those of the hatched eggs. When P. xylostella pupae were irradiated with 100 Gy, fecundity of emerged adults decreased and no eggs hatched. When B. tabaci, P. xylostella, M. persicae and T. urticae adults were irradiated with 70 and 100 Gy, fecundity decreased and egg hatch of B. tabaci was inhibited. However, the longevity of adults did not change and electron-beam irradiation of all developmental stages had no effect on the longevity of adults.

Seasonal occurrence and developmental characteristics of ussur brown katydid, Paratlanticus ussuriensis Uvarov (Orthoptera: Tettigoniidae).

ABSTRACT : This study was performed to investigate the seasonal occurrence, developmental characteristics of each nymphal stages with different temperatures (20, 25, 30℃), longevity and fecundity of ussur brown katydid, Paratlanticus ussuriensis , damaging by outbreaks in the orchard areas of Bitan-ri, Yeongdong, Chungbuk. Paratlanticus ussuriensis occurred from late-March to late-August with peak of mid-May. Newly emerged nymphs appeared from March and do damaged fruit orchards with peak of mid-May when P. ussuriensis existed as 4th and 5th nymphal stages. P. ussuriensis adult occurred from early-June to mid-Aug. with peak of mid-July. Total density of P. ussuriensis was showed highest in mid-May. Paratlanticus ussuriensis goes through nymphal stages to 7th nymph, the ovipositor began exposed to outside from the 4th instar and the body weight increased heavily from this stage and the wings were observed from 6th instar. Developmental period was longer as increased the nymphal stages. Sex ratio of collected insect was showed as 0.57; females more than males. As increased the temperature, developmental period was to be short. Preoviposition was also to be short as 5.0, 4.3, and 3.4 days at 20, 25, 30℃, respectively, and fecundity increased as 69.0, 87.1, and 104.3 at 20, 25, 30℃, respectively. Longevity of male and female at 25℃ was showed the longest with 35.7, and 32.9 days and showed the shortest with 30.1 and 28.1 days at 30℃, respectively. The difference of developmental period in male and female were showed longer in female without relation of temperature. The eggs laid were frequently distributed 3 to 4 cm from soil surface, and showed the behavior laying eggs intensively when early oviposition period.

Differentiation in Feeding Behaviour of Biotypes B and Q of Bemisia tabaci (Homoptera: Aleyrodidae) against Three Insecticides

The feeding behaviors of 2 biotypes (type B and Q) of tobacco whitefly, Bemisia tobaci, were monitored using EPG technique on tomato and pepper plants treated 3 insecticides for controlling whiteflies, for examples, acetamiprid, spinosad and thiamethoxam. After treatment of three insecticides with recommended concentrations to tomato and pepper plants, EPG waveforms were recorded during 6 hours. The characteristic patterns of feeding behaviors investigated were as follows; time consumed by withdrawal of proboscis, total non-penetration time, total stylet pathway pattern time and total phloem feeding time. There was somewhat difference among 3 insecticides tested. As a result of investigation of total duration showed the stylet pathway activity due to the reaction against all tested insecticides, the Q biotype showed fewer time than those from the B biotype. The B biotype showed more frequent stylet pathway activity patterns during whole recording time and a shorter phloem ingestion time than those from the Q biotype. In result of prior up (non-penetration) time representing the reaction against the insecticide treated, the time of B biotype was more faster than that of the Q biotype, so it was considered that the B biotype was more sensitive to the tested insecticides. Therefore, our results revealed a clear difference in feeding behaviour between the B and Q biotypes of B. tabaci. Also, it was investigated that B biotype was susceptible to the 3 insecticides.

Comparison of feeding behavior of B and Q biotypes of Bemisia tabaci (Hemiptera: Aleyrodidae) against red pepper and tomato varieties.

Nymphal development of the B and Q biotypes of Bemisia tabaci was normal on all seven tomato varieties tested. However, their nymphal development was different on red pepper varieties. B biotype was not normally developed on nine red pepper varieties tested. On the contrary, Q biotype was normally developed, but its adult emergence rate was very low in Nokkwang variety than in other eight varieties. The EPG analysis of the feeding behavior of Bemisia tabaci showed that B and Q biotypes had different duration of phloem phases on red pepper. Q biotype showed longer phloem phases than B biotype. On Nokkwang variety, Q biotype had short phloem phases and did not prefer to feed on Nokkwang variety. Interestingly, Q biotype was found to have long duration of phloem phases on eight red pepper varieties, but B biotype did not prefer to feed on red pepper varieties. However, both biotypes did not show any difference in feeding time on tomato varieties.

Synergistic Effects of Oxygen on Phosphine and Ethyl Formate for the Control of Phthorimaea operculella (Lepidoptera: Gelechiidae)

ABSTRACT Phosphine (PH3) and ethyl formate (EF) are two potentially powerful postharvest fumigant insecticides.We investigated the effectiveness of both PH3 and EF as fumigants at all developmental stages of the potato tuber moth Phthorimaea operculella Zeller, and we also studied the synergistic effects of these fumigants under controlled atmospheres of 50 and 80% oxygen (O2). The larval stage of P. operculella was the most susceptible to fumigation with PH3 at both 5°C and 20°C. All of the developmental stages showed greater susceptibility to PH3 at 20°C than at 5°C, whereas the susceptibility of adult P. operculella to this fumigant was not affected by temperature. The toxicity of EF did not differ with temperature for any of the P. operculella developmental stages. The atmospheric oxidation of PH3 increased the toxicity of this fumigant toward all developmental stages at both temperatures. In contrast, no differences in toxicity were observed for oxidized EF compared with EF alone at any developmental stage. In conclusion, using fumigation tests, we showed that atmospherically oxidized PH3 was much more effective against P. operculella than PH3 alone, demonstrating a synergistic effect for this fumigant and O2. Therefore, treatment with PH3 and high concentrations of O2, as described in this study, could be useful for managing the postharvest pest P. operculella.

Preliminary trials of the ethanedinitrile fumigation of logs for eradication of Bursaphelenchus xylophilus and its vector insect Monochamus alternatus

BACKGROUND The nematode Bursaphelenchus xylophilus and its insect vectors from the Monochamus genus are major global quarantine pests of timber products. Owing to the phase-out of methyl bromide for plant quarantine and preshipment treatments, an alternative fumigant is essential. Based on preliminary laboratory studies on the efficacy of ethanedinitrile (C2 N2 ) to B. xylophilus and Monochamus alternatus, three quarantine trials were conducted at three dosages and three temperatures. Potential for inhalation exposure was assessed by monitoring atmospheric C2 N2 in relation to the threshold limit value. RESULTS Concentration × time products (Ct) of 398.6, 547.2 and 595.9 g h m-3 were obtained for each trial. A 100% mortality of B. xylophilus and M. alternatus larvae at 23 ± 4 °C and 10 ± 4 °C occurred with a load factor of pine logs of 46% and at 3 ± 1 °C with a load factor of 30%. During all fumigations, atmospheric levels of C2 N2 20 m downwind were below the TLV. During aeration, levels 10 and 5 m downwind were below the TLV after 0.4 and 1 h respectively. CONCLUSION For the purpose of quarantine or phytosanitary treatment, specific doses of C2 N2 at the trial temperatures could control B. xylophilus and M. alternatus larvae without significant inhalation risk to workers.

Efficacy and Phytotoxicity of Phosphine as Fumigants for Frankliniella occidentalis (Thysanoptera: Thripidae) on Asparagus

The insecticidal activity of phosphine (PH3) and ethyl formate (EF) toward Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) and their phytotoxicity to asparagus were evaluated. Both the PH3 and EF fumigants showed higher lethal concentration and time (LCT) values at lower temperatures. The LCT99 values of PH3 and EF at 5°C in a 12 liters desiccator for 4 h showed the following ranking: eggs (64.69 mg·h/liter for PH3 and EF indicating phytotoxicity to asparagus), nymphs (5.54 and 17.48 mg·h/liter, respectively), and adults (3.83 and 14.67 mg·h/liter, respectively). The adsorption of PH3 was approximately 11% at 2°C and 13% at 5°C, whereas the adsorption of EF increased sharply to 88% at 2°C and 97% at 5°C. The hatching rate of F. occidentalis eggs was approximately 95% at all locations (top, middle, and bottom) in the presence of 4 mg/liter PH3 at 5°C in a 0.65-m3 fumigation chamber for 24 h. However, extension of the treatment to 48 h resulted in 100% inhibition of egg hatching. The atmospheric level of PH3 decreased below the threshold limit value after 80 min, and phytotoxicity was not observed. The results revealed that EF is highly absorbed by asparagus and is not suitable as a fumigant, but PH3 is a suitable alternative to the fumigant methyl bromide for the control of western flower thrips in asparagus.

Fumigation Activity of Ethyl Formate and Phosphine Against Tetranychus urticae (Acari: Tetranychidae) on Imported Sweet Pumpkin

Abstract This study investigated an alternative fumigant for imported sweet pumpkin. Laboratory fumigations with ethyl formate (EF) and phosphine (PH3) alone and in combination were conducted at different temperatures in 12-liter desiccators to determine their efficacy and synergism against adults and eggs of two-spotted spider mites (Tetranychus urticae Koch), a major pest of sweet pumpkins; larger scale fumigations with EF were also performed to evaluate the impact of EF fumigation on the postharvest quality of sweet pumpkin and EF absorption. EF fumigation of 4 h achieved 100% control of both adults and eggs at 10°C. Efficacy of EF also increased with temperature. Conversely, PH3 fumigation for 4 and 6 h was not effective against either adults or eggs, and no synergism between EF and PH3 was observed. In larger scale fumigation tests, EF at 60 g/m3 for 4 h resulted in 100% control of both adults and eggs at 10°C, without causing injury to the sweet pumpkins. These results suggest that EF has the potential to be a safe and effective alternative to methyl bromide fumigation for controlling two-spotted spider mites on sweet pumpkin.

Concurrent application of ethyl formate and 1-methylcyclopropene to control Tetranychus urticae on exported sweet persimmons (Diospyros kaki Thunb. ‘Fuyu’): Application of ethyl formate on persimons

Extending the shelf life of fruits during post‐harvest storage and eradicating pests associated with quarantine issues could together comprise the key steps toward expanding the exportation of sweet persimmon in South Korea. Here we firstly investigated the concurrent application of ethyl formate (EF), a methyl bromide alternative fumigant, which is currently considered a beneficial and safe fumigant in quarantine use, and 1‐methylcyclopropene (1‐MCP), an anti‐ethylene compound that is broadly used in post‐harvest systems, on sweet persimmon. We also suggest the proper fumigation methods to be follow when using these compounds. Tetranychus urticae, an important quarantine pest, was inoculated under the calyx of sweet persimmon, and the fruits were then fumigated using 35.0 mg L−1 of EF for 6 h before and after treating with 1.0 μL L−1 of 1‐methylcyclopropene for 24 h under storage conditions of 5°C. Our results showed that concurrent treatments with 1‐MCP and EF could be suitable for commercial purposes by extending shelf life, delaying color changes and softening, and offering complete control of the target pest, Tetranychus urticae.

Comparison of Cuticular Hydrocarbons of Different Developmental Stages of the Spot Clothing Wax Cicada, Lycorma delicatula (Hemiptera: Fulgoridae)

Aliphatic cuticular hydrocarbons (CHCs) of different developmental stages of the spot clothing wax cicada, Lycorma delicatula (Hemiptera: Fulgoridae) were analyzed using GC and GC-MS. The numbers of carbons in the major CHCs of each developmental stage 32, 33, 28, 38, 37 in the egg, 1st, 2nd, 3rd, and 4th instar nymphal stages, and adults, respectively. The cuticle of Lycorma delicatula contains mainly methyl-branched 9-methylheptacosane (15.11%) in the egg stage, and a high proportion of n-heptacosane in nymphal stages (15.75, 22.42, 25.04, and 23.11 % in the 1st, 2nd, 3rd and 4th instars, respectively). In contrast, male and female adults had high proportions of n-nonacosane (13.42 and 16.55%). The chemical constituents of CHCs were classified into five groups (n-alkanes, monomethylalkanes, dimethylalkanes, trimethylalkanes, olefins) and group profiles of each developmental stage were compared. Egg surface was composed mainly monomethylalkanes (45.39%), a saturated hydrocarbon. Nymph CHCs consisted primarily of n-alkanes (37.63 to 46.12%). There was a difference between adult male and female CHCs. However, both contained n-alkanes and monomethylalkanes. CHCs with trimethyl or double bonded structure were rare in all stages.