Functional responses of the parasitoid,Ertmocerus longipes Compere (Hym., Aphelinidae) to densities of the whitefly,Aleurotuberculatus takahashi David et Subramaniam (Hom., Aleyrodidae) at different temperatures

The present study dealt with the functional responses of the parasitoid,Eretmocerus longipes Compere (Hym., Aphelinidae) to the densities of the whitefly,Aleurotuberculatus takahashi David et Subramaniam (Hom., Aleurodidae) at different temperatures under the laboratory conditions. The results showed that when the initial densities ofA. takahashi-3rd instar were raised from 10 to 320 ind./leaf, the numbers of parasitized nymphs increased as well, ranging from 7.0 to 23.1 at 20°C, 9.8 to 42.9 at 25°C, 6.7 to 39.9 at 30°C, and 1.8 to 8.3 ind./leaf at 35°C, respectively. The Holling Disk Equation was introduced to build up the models of functional responses. The response curves remained type II, although the numbers of parasitized nymphs were significantly different under different temperatures. The suitable initial densities of the host whitefly for parasitization were about 80 individuals per leaf. A negative relation was observed between the initial densities of the whitefly and the parasitization rates by the parasitoid. An increase in the initial densities ofA. takahashi-3rd instars ranging from 10 to 320 ind./leaf resulted in a decrease in the parasitization rate byE. longipes ranging from 70.0% to 7.2% at 20°C, 98.0% to 13.4% at 25°C, 67.0% to 12.5% at 30°C and 18.0% to 2.6% at 35°C with a value of 0.2877 was significantly smaller than that at 20°C with a vlaue of 1.3354, that at 25°C with a value of 1.6465 and that at 30°C with a value of 1.1199, respectively (p<0.01). The handling time (Th) forE. longipes was 0.1521 at 35°C, significantly longer than 0.0510 at 20°C, 0.0289 at 25°C and 0.0320 at 30°C, respectively (p<0.01). The maximum loading number (K) of the parasitized nymphs with a value of 34.5 ind./leaf at 25°C was similar to that with a value of 31.2 ind./leaf at 30°C, about 1.8 times as high as that with a value of 19.6 ind./leaf at 20°C and 4 times more than that with a value of 6.6 ind./leaf at 35°C. It was suggested that temperature affected the functional response by balancing searching rate and handling time. The optimal temperature range for the functional responses ofE. longipes to the densities ofA. takahashi-3rd instar was 25° to 30°C.     

Wirksamkeit des ParasitoidenEretmocerus debachi Rose und Rosen (Hym., Aphelinidae) gegenüber der Wei?en FliegeParabemisia myricae (Kuwana) (Hom., Aleyrodidae)

Die Weiße Fliege,Parabemisia myricae (Kuwana) (Hom.: Aleyrodidae), stellt seit ihrer Verschleppung in die Zitrusanbaugebiete an der Südost-Mittelmeerküste der Türkei im Jahre 1982 eines der größten Probleme im dortigen Zitrusanbau dar. Zu ihrer biologischen Bekämpfung wurde im Jahre 1986 der spezifische Parasitoid,Eretmocerus debachi Rose und Rosen (Hym.: Aphelinidae) aus Kalifornien in die Türkei eingeführt. Der Parasitoid konnte sich nach Massenfreilassungen im gesamten Gebiet sehr gut einbürgern. In der vorliegenden Untersuchung wurde die Wirksamkeit vonE. debachi gegenüberP. myricae in zweijährigen Versuchen in natürlich befallenen Zitrusanlagen und auf künstlich infizierten und exponierten Zitrusjungpflanzen erfaßt.Innerhalb von zwei Wochen konnten auf den exponierten Zitrusjungpflanzen die ersten Parasitoiden festgestellt werden, wobei bis zu 10% derP. myricae-Nymphen und Puparien durchE. debachi parasitiert waren. In beiden Versuchsjahren und an allen 4 Standorten baute sich im weiteren Verlauf der Vegetation keine weitere Weiße-Fliegen-Population auf den Zitrusjungpflanzen auf. Die Populationsdichte vonP. myricae war auf den natürlichen befallenen Zitrusbäumen sehr viel geringer als auf den exponierten und künstlich infizierten Pflanzen. Dennoch traten mit den erstenP. myricae auch sofort durchE. debachi parasitierte Individuen auf. Die Parasitierungsrate erreichte teilweise 100%, so daß die Schädlingspopulation sehr schnell im weiteren Vegetationsverlauf abnahm und es zu keiner erneuten Gradation kam. Selbst auf sehr geringe Dichteerhöhungen derP. myricae-Population reagierte der Parasitoid mit einer erhöhten Parasitierung. Die Untersuchungen zeigten deutlich, daßE. debachi in der Lage ist, sowohl sehr hohe als auch sehr niedrige Populationen der Weißen Fliege in hohem Maße zu parasitieren und dadurch den Schädling erfolgreich zu bekämpfen.     

温度和湿度对B型烟粉虱发育、存活和生殖的影响

研究了采自北京市的B型烟粉虱种群在不同温、湿度条件下的生长、发育和繁殖力参数.结果表明,相对湿度是影响卵、1龄若虫、3龄若虫和成虫发育的主要因素,30%～70%RH是烟粉虱发育的适宜范围.在25℃组合90%、70%、50%和30%RH环境下的种群内禀增长率(rm)分别为0.0499、0.0596、0.064和0.0856.若虫的发育历期随温度的升高而缩短,20～30℃是烟粉虱发育的适宜范围.在1 5℃下从卵发育到成虫需要69.0天,但30℃下则减少到27.7天.当温度上升到35℃时,只有少数个体能发育到3龄.不同龄期对温度的要求有较大的区别,2龄若虫的发育起点温度最低(6.16℃),而卵期所需的有效积温最高(110.22日度).在80%RH配合30、25、20和15℃条件下的内禀增长率(rm)分别为0.0729、0.0673、0.0895和0.0486.     

Oviposition and survival of castor bean whitefly Trialeurodes ricini (Hemiptera:Aleyrodidae) on different host plants

<正>Banker plant system is a new biological control method,including banker plants,alternative food and beneficials.A non-pest herbivore is particularly favored for using as an alternative host for beneficials in this system,and evaluating the potential damage caused by alternative host on the target crops is an important step(Frank,2010).So,the potential     

Host plant preference of Diuraphis noxia (Kurdj.) (Hom., Aphididae)

Host plant preference of the Russian wheat aphid Diuraphis noxia (Kurdj.) was studied on 11 cultivars of 9 plant species: winter barley, spring barley, winter wheat, spring wheat, rye, oat, Triticale, canary grass, red millet yellow millet and maize. Seeds of the host plants were sown in a circle near the edge of pots. The host plant choice was evaluated 24 hours after releasing 55 Diuraphis noxia female adults in the middle of each pot. The suitability of different hosts for aphid development was evaluated 2, 7 and 14 days after infestation based on the mean number of Russian wheat aphid individuals per plant. Red millet, yellow millet and maize were chosen by significantly fewer aphids than grain crops. Winter and spring barley were chosen as hosts most frequently, and the progeny production was also the highest on these plants. The growth rate of D. noxia was significantly affected by the host plants and the date of assessment and their interaction.     

Life table of Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) on cotton whitefly,Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) as prey

Journal of Plant Diseases and Protection - Developmental time, longevity and fecundity of Delphastus catalinae (Horn), a predator of Bemisia tabaci (Genn.), were evaluated under laboratory...     

以豌豆修尾蚜为猎物的大草蛉两性生命表和捕食率

为明确大草蛉Chrysopa pallens (Rambur)的发育、存活、繁殖和捕食能力,利用年龄-龄期两性生命表方法,在25 ℃、光周期L 15:D 9条件下研究了以豌豆修尾蚜Megoura japonica (Matsumura)为猎物的大草蛉的生命表及其捕食率。结果表明:大草蛉雌成虫个体的繁殖力为683.6±55.99粒,种群的内禀增长率、周限增长率、净增殖率和平均世代周期分别为0.1247/d、1.133/d、333.64粒/个体和46.5 d;大草蛉幼虫、雌成虫和雄成虫个体的平均捕食率分别为145.25、1 192.47和669.08头。若考虑存活率,个体的净捕食率为1 026.26头;从猎物种群到捕食者后代的转化率为3.08;种群个体的稳定捕食率和周限捕食率分别为5.49和6.22头。表明以豌豆修尾蚜为猎物时,大草蛉表现出较好的个体发育、种群增长和捕食特性,豌豆修尾蚜可作为大草蛉人工繁殖选择的猎物之一。     

Russian wheat aphid, Diuraphis noxia (Kurdj.) under adverse weather conditions (2001) (Hom., Aphididae)

Cool and wet weather in some periods of the season generally supressed the RWA (Diuraphis noxia Kurdj.) populations in the Czech republic in 2001. However, some sites manifested population levels ranging out of the population mean stated per area, and these sites were also apparently responsible for respective peaks of alate aphids sampled by suction traps. An analysis of these sites determined them to be attributed to some poor quality barley fields in a warmer area of the state. RWA is known to vary in all-over populations in different years, and the year 2001 illustrated its capability of its surviving even unfavourable periods and seasons, remaining well-established in the area.     

Russian wheat aphid, Diuraphis noxia (Kurdj.) under adverse weather conditions (2001) (Hom., Aphididae)

Cool and wet weather in some periods of the season generally supressed the RWA (Diuraphis noxia Kurdj.) populations in the Czech republic in 2001. However, some sites manifested population levels ranging out of the population mean stated per area, and these sites were also apparently responsible for respective peaks of alate aphids sampled by suction traps. An analysis of these sites determined them to be attributed to some poor quality barley fields in a warmer area of the state. RWA is known to vary in all-over populations in different years, and the year 2001 illustrated its capability of its surviving even unfavourable periods and seasons, remaining well-established in the area.     

Within-field refugiums of Russian wheat aphid, Diuraphis noxia (Kurdj.) in cereals (Hom., Aphididae)

An analysis of the Russian wheat aphid (RWA) (Diuraphis noxia Kurdj.), overpopulated due to extraordinary weather conditions (2000) in the Czech Republic, enabled the identification of several within-field situations ouside of the routine approach. This group, classified as within-field refugium, includes variation due to field relief, some injuries caused by the use of machinery, the unharvested field margins and, last but not least, the volunteer plants. Differences between the RWA populations in these situations and the normal grove are presented and recommended to be taken into consideration in the research on RWA population dynamics and movement.     

First records of the ash whitefly Siphoninus phillyreae Haliday (Hemiptera,Aleyrodidae) in Belgium

In recent years, a whitefly species has become more abundant in Belgian pear orchards, and a survey over six locations in the province of Limburg in 2017 showed it to be exclusively Siphoninus phillyreae Haliday, the ash whitefly. Although the puparia of the species are fairly easy to recognize in the field, S. phillyreae most probably has previously been overlooked but present in Belgium. Although the species is an important pest in some parts of the world, so far no significant damage has been observed in Belgian pear orchards. This is the first report of this pest in Belgium.     

Distribution and history of Russian wheat aphid, Diuraphis noxia (Kurdj.) in the Carpathian Basin (Hom., Aphididae)

The Carpathian Basin has been classified as one of the model areas of Russian wheat aphid (=RWA), Diuraphis noxia (Kurdj.), expansion from the southeast to Central Europe. Explorations in 2002 as well as the summarized information published earlier centered the evidence for RWA in the northern and northeastern parts of the area and its occurrence was detected and verified in the area up to the submountains of the Carpathian Mountain Range. The history and distribution peculiarities of RWA in the Carpathian Basin and area are reviewed and discussed.     

Insecticide resistance in Egyptian populations of the cotton whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae)

Three collections of Bemisia tabaci were taken from cotton and vegetable crops at the beginning of the growing season in Egypt. These displayed marked resistance to the carbamates carbosulfan (ca 20- to 50-fold) and aldicarb (ca 40- to 80-fold) and moderate resistance to the pyrethroids cypermethrin (ca 10- to 30-fold) and lambda-cyhalothrin (ca 10- to 25-fold). They displayed no resistance to the organophosphates profenofos and pirimiphos-methyl, or to imidacloprid. Another population, collected at the end of the growing season, differed markedly in its response. In this population, resistance to carbosulfan remained high (ca 40-fold), resistance to profenofos and cypermethrin was increased (ca 20- and 50-fold respectively) and a slight resistance to imidacloprid was detected (ca 6-fold). Resistance to cypermethrin and profenofos was shown to be similar among adults and nymphs. Irrespective of collection date, none of the populations showed resistance to pyriproxyfen. These Egyptian populations were compared with two representative Israeli populations. The differences between their resistance profiles is discussed in terms of their collection date, their geographical proximity and the patterns of insecticide use at their sites of collection.     

Increase of Russian wheat aphid, Diuraphis noxia (Kurdj.) in hot and dry weather (2000) (Hom., Aphididae)

Two hot and dry weather periods during mid-spring and early summer caused severe drought-stress to barley groves in many districts of the Czech Republic in 2000. Although not generally taken into consideration as an injury-increasing factor, the Russian wheat aphid (=RWA), Diuraphis noxia (Kurdj.), was discovered to contribute significantly to injury in the ripening stage of spring barley as well as to the substantial decrease of yield (up to 30–40% of the calculated mean, in some districts). RWA increased considerably not only in the lowland banker areas but also in the higher altitudes, values in the latter case then manifesting those found in the lowland banker areas in the previous years.     

Increase of Russian wheat aphid, Diuraphis noxia (Kurdj.) in hot and dry weather (2000) (Hom., Aphididae)

Two hot and dry weather periods during mid-spring and early summer caused severe drought-stress to barley groves in many districts of the Czech Republic in 2000. Although not generally taken into consideration as an injury-increasing factor, the Russian wheat aphid (=RWA), Diuraphis noxia (Kurdj.), was discovered to contribute significantly to injury in the ripening stage of spring barley as well as to the substantial decrease of yield (up to 30–40% of the calculated mean, in some districts). RWA increased considerably not only in the lowland banker areas but also in the higher altitudes, values in the latter case then manifesting those found in the lowland banker areas in the previous years.     

Spring aphid-parasitoid (Hom., Aphididae, Hym., Braconidae) associations and interactions in a Mediterranean arable crop ecosystem, including Bt maize

Conspecific and heterospecific associations of aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) were used to determine the interactions between crops forming the main arable crop ecosystem (wheat, alfalfa, isogenic and [Bt Bacillus thuringiensis] transgenic maize) in an irrigated area in Catalonia, Spain. Species composition and instars of parasitized aphids (mummies) were used to detect the parasitoid population movements between the crops and proved interactions (alternation) between the crops, including transgenic maize. Parasitoid interactions were species-dependent, appearing in the movements between alfalfa-wheat-maize in the individual species. Aphidius ervi Hal., A. rhopalosiphi DeSt.-Perez, A. uzbekistanicus Luzh., Lysiphlebus testaceipes (Cress.) and Praon volucre (Hal.) were classified as key-stone species in the target agroecosystems in the area. No differences were found in aphid-parasitoid associations on Bt transgenic maize and isogenic maize for aphid species composition and associated parasitoid guild.     

Variations in acaricidal effect of wettable sulfur on Tetranychus urticae (Acari:Tetranychidae): effect of temperature,humidity and life stage

Under laboratory conditions, the acaricidal effect of wettable sulfur is influenced by climatic conditions and the stage of development of Tetranychus urticae. Its ovicidal effect results from the combined action of temperature and relative humidity (RH). Wettable sulfur becomes effective at 27.5 degrees C and 75% RH. Beyond this threshold, the acaricidal effect increases with rising temperature or humidity, to become complete at a temperature of 35 degrees C and 90% RH. Within the range of temperatures and humidities 20 degrees C/30% RH and 35 degrees C/90% RH the mortality of immatures (from protonymphs to teleiochrysalis) was total. Under similar experimental conditions, females usually died before the end of the experiment. Temperature and relative humidity increased the adulticidal potential of wettable sulfur. The fecundity of the sulfur-treated females and the viability of their progeny was found to depend on temperature and RH. According to the same climatic conditions, eggs were less susceptible than females, which were in turn less susceptible than juvenile stages.     

Investigations on side-effects of the mixed biocide GCSC-BtA on different predators of Plutella xylostella (L.) (Lep., Plutellidae) in southeastern China

The present paper deals with laboratory studies on side-effects of the mixed biocide GCSC-BtA on Plutella xylostella (L.) (Lep., Plutellidae) and its predators, e.g. Amblyseius longispinosus (Evans) (Acari, Phytoseiidae), Erigonidium graminicola (Sundvall) (Araneae, Linyphiidae), Orius similis Zheng (Het., Anthocoridae) and Coccinella septempunctata L.(Col., Coccinellidae), in comparison to the commercial insecticides, e.g. Abamectin, Tebufenozide, Dichlorvos, Cartap and Lambda-cyhalothrin.The results showed that GCSC-BtA was highly toxic to the 3^rd instar of P. xylostella with 91.18% mortality, followed by Cartap with 84.38%, Abamectin with 78.00%, Tebufenozide with 75.57%, Lambda-cyhalothrin with 63.75% and Dichlorvos with 50.86% mortality. On the other hand, GCSC-BtA was found to be comparatively less toxic to the predators, causing 31.11%, 13.33%, 11.54% and 6.00% mortalities in A. longispinosus, E. graminicola, O. similis and C. septempunctata, respectively. For comparison, the mortalities recorded for Abamectin, Tebufenozide, Dichlorvos, Cartap, Lambda-cyhalothrin were 72.94%, 55.55%, 70.00%, 53.26% and 98.85% in A. longispinosus, 46.51%, 55.10%, 60.00%, 46.00% and 73.68% in E. graminicola, 22.00%, 16.00%, 35.71%, 26.78% and 81.03% in O. similis, 15.55%, 19.64%, 28.00%, 16.66% and 41.79% in C. septempunctata, respectively.