Ki-Su Ahn

Monitoring of Acaricide Resistance in Two-Spotted Spider Mite (Tetranychus urticae) Populations from Rose Greenhouses in Korea

Laboratory studies were conducted to determine the effects of six acaricides on the eight field populations of two spotted spider mite, Tetranychus urticae, collected from rose greenhouse. There were considerable differences in susceptibility depending on the acaricides treated and on the regions from which the population was collected. The local resistance ratios in the egg stage were lower than those of female adults. The population with a resistance ratio higher than 10 with respect to an acaricide was regarded as the resistant population to the acaricide. The resistant populations in female adult stage include ‘Buyo’ and ‘Chilgok’ populations to abamectin, ‘Buyo’ and ‘Gimhae’ populations to acequinocyl, ‘Buyo’ and ‘Jeju’ populations to bifenazate, and ‘Gimhae’ population to emamectin benzoate. All populations to milbemectin showed small susceptibilities variation (RR <10). The resistant populations in egg developmental stage include six populations except for ‘Koyang’ and ‘Gumi’ populations to abamectin, all populations to acequinocyl and etoxazole, seven populations except ‘Buyo’ population to bifenazate, seven populations except for ‘Gimhae’ population to emamectin benzoate, and ‘Jeju’, ‘Chilgok’ and ‘Gimhae’ populations to milbemectin. However, ‘Jincheon’ and ‘Buyo’ populations were more susceptible to both milbemectin and bifenazate than susceptible strain. The eggs and adults of all field populations showed low resistance to milbemectin among the acaricides tested

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.

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.

Characteristics on the Pollinating Activity of Korean Native Bumblebee, Bombus ignitus Smith (Hymenoptera: Apidae) in the Peach House

The pollinating activity of bumblebee, Bombus ignitus was investigated at the blossom of Peach [Prunus persica (L.) Batsch] planted in vinyl house. The major time of foraging activity by B. ignitus was between 08:00 and 7:00, and the peak time of pollinating activity by B. ignitus was 11 :00 in the peach vinyl house from February 28 to March 5 in 2002. The rate of fruit set and the rate of marketable fruit by foraging activity of B. ignitus were much better than artificial pollination, and the effect of labor reduction by the pollinating activities of B. ignitus released against th e artificial pollination was took remarkable profits over 93%. Therefore, the foraging activity of B. ignitus in peach vinyl house brought satisfactory results among the rate of fruit set, the rate of marketable fruit and the effect of labor reduction against the artificial pollination.