东亚小花蝽对西方花蓟马和二斑叶螨的捕食选择性

多食性天敌对猎物的捕食选择性及猎物密度对天敌捕食的干扰作用直接影响到天敌对不同猎物的控制作用.在实验室条件下研究了东亚小花蝽对西方花蓟马和/或二斑叶螨不同虫态的捕食选择性,以及两猎物中一种猎物的密度变化对小花蝽取食另一种猎物的影响.结果如下:东亚小花蝽5龄若虫和成虫对西方花蓟马2龄若虫的捕食选择性均强于对其成虫,对二斑叶螨的选择性为雌成螨>若螨>幼螨.实验中西方花蓟马2龄若虫是东亚小花蝽最喜好的虫态.二斑叶螨雌成螨密度固定为60头/19.63cm2,西方花蓟马若虫密度从10增加到60时显著地减少了东亚小花蝽对二斑叶螨的取食.反之,固定西方花蓟马同样密度,增加二斑叶螨密度却没有显著改变小花蝽对西方花蓟马的取食.此结果进一步表明,西方花蓟马是东亚小花蝽更喜好的猎物.     

Nest site preference and success in a gregarious, ground-nesting bee Dieunomia triangulifera

1. The characteristics of preferred nest sites of the solitary bee Dieunomia triangulifera, which nests gregariously in alluvial soil, were investigated. Nest presence was used as an indication of preference. In those cases where nests were more than a few days old, therefore, this study also investigated nest success. 2. Independent variables tested were soil surface moisture, presence of nesting conspecifics, smooth vs. irregular soil surface, distance to visual landmarks, percentage of vegetation cover, soil compaction, vehicular traffic, soil surface temperature, and light intensity. 3. Bees preferred to nest in moist, compact soil with an irregular surface. More bees nested near visual landmarks and in places with little or no vegetation. They preferred nesting in areas with warmer soil surface temperatures and brighter illumination. The presence of nesting conspecifics did not influence nesting decisions. Vehicular traffic also seemed to have no impact on nest initiation but did seem to have a negative impact on nest success. 4. Although it might seem that ground-nesting bees should not be limited by nesting sites, relatively little of the study area met all their apparent criteria. This might account, in part, for gregarious nesting in this species.     

Odour-mediated preference and prey preference of Macrolophus caliginosus between spider mites and green peach aphids

Abstract  A comparative study between direct prey preference and odour-mediated preference of the predatory mirid bug, Macrolophus caliginosus , was conducted. We used a Y-tube olfactometer to determine the attraction of the predator to herbivore-induced volatiles from Myzus persicae or Tetranychus urticae -infested sweet pepper plants over clean plants and to direct prey odours over clean air. The mirid bugs showed a stronger response to odours from infested plants than to odours from clean plants. The mirids did, however, not seem to exploit odours emitted directly from the prey themselves. Our results further demonstrated that M. caliginosus prefers M. persicae to T. urticae in a direct two-choice consumption test. This preference was, however, not reflected in a similar odour-mediated preference between plant volatiles induced by either of the two preys. Two hypotheses are suggested for this neutral response of the mirids to herbivore-induced volatiles from a preference prey or a non-preference prey.     

东亚小花蝽对西花蓟马和/或二斑叶螨危害豆株的定位反应

多食性天敌对其猎物植物系统的选择是其重要生物学特性之一,决定了对不同猎物控制的有效性。东亚小花蝽Orius sauteri是西花蓟马Frankliniella occidentalis(Pergande)及二斑叶螨Tetranychus urticae的重要捕食性天敌。本文在温室笼罩条件下通过释放东亚小花蝽,而后在不同时间调查其在西花蓟马和/或二斑叶螨危害2d后的豆株及健株上的数量,研究了其定位反应。结果表明:东亚小花蝽显著趋向西花蓟马及由西花蓟马与二斑叶螨同时危害的豆株,而较少趋向二斑叶螨单独危害的豆株及健株。在各处理豆株上,东亚小花蝽的日活动规律中,傍晚时分有离开植株的趋势。     

南方小花蝽在不同试验空间对西花蓟马的捕食及搜寻效应

【背景】南方小花蝽是一类很有利用前景的捕食性天敌,而有关其在不同捕食空间下对我国局部地区暴发成灾的重要入侵害虫西花蓟马捕食控制效能的研究较少。【方法】在实验室条件下比较研究了南方小花蝽成虫在不同试验空间对西花蓟马成虫、若虫的捕食选择性、捕食功能反应与搜寻效应。【结果】南方小花蝽成虫对西花蓟马若虫的捕食选择性强于成虫;在相同的试验空间,南方小花蝽成虫的日均捕食量随猎物数量的增加而增大,其对西花蓟马成虫和若虫的捕食量在猎物数量为每指形管中60头时最大,分别为15.90和19.30头;而搜寻效应随猎物数量的增加而降低。在各供试条件下,捕食功能反应均符合Holling Ⅱ型方程;南方小花蝽成虫在小饲养容器中对西花蓟马若虫的瞬时攻击率最大,为1.2794;而在大饲养容器中对西花蓟马成虫的瞬时攻击率最小,仅为0.3506,其处理1头西花蓟马成虫的时间约需0.0402d,而处理1头若虫的时间仅需0.0242d。在相同的猎物数量下,南方小花蝽成虫在大饲养容器中对西花蓟马的日均捕食量均低于其在小饲养容器中对西花蓟马的日均捕食量。【结论与意义】南方小花蝽对西花蓟马有很强的捕食效能,对西花蓟马的种群消长具有一定控制作用。本研究旨在为应用南方小花蝽防治西花蓟马积累资料,同时为西花蓟马的综合治理奠定理论基础。     

Pollinator genetics and pollination: do honey bee colonies selected for pollen‐hoarding field better pollinators of cranberry Vaccinium macrocarpon?

1. Genetic polymorphisms of flowering plants can influence pollinator foraging but it is not known whether heritable foraging polymorphisms of pollinators influence their pollination efficacies. Honey bees Apis mellifera L. visit cranberry flowers for nectar but rarely for pollen when alternative preferred flowers grow nearby. 2. Cranberry flowers visited once by pollen‐foraging honey bees received four‐fold more stigmatic pollen than flowers visited by mere nectar‐foragers (excluding nectar thieves). Manual greenhouse pollinations with fixed numbers of pollen tetrads (0, 2, 4, 8, 16, 32) achieved maximal fruit set with just eight pollen tetrads. Pollen‐foraging honey bees yielded a calculated 63% more berries than equal numbers of non‐thieving nectar‐foragers, even though both classes of forager made stigmatic contact. 3. Colonies headed by queens of a pollen‐hoarding genotype fielded significantly more pollen‐foraging trips than standard commercial genotypes, as did hives fitted with permanently engaged pollen traps or colonies containing more larvae. Pollen‐hoarding colonies together brought back twice as many cranberry pollen loads as control colonies, which was marginally significant despite marked daily variation in the proportion of collected pollen that was cranberry. 4. Caloric supplementation of matched, paired colonies failed to enhance pollen foraging despite the meagre nectar yields of individual cranberry flowers. 5. Heritable behavioural polymorphisms of the honey bee, such as pollen‐hoarding, can enhance fruit and seed set by a floral host (e.g. cranberry), but only if more preferred pollen hosts are absent or rare. Otherwise, honey bees' broad polylecty, flight range, and daily idiosyncrasies in floral fidelity will obscure specific pollen‐foraging differences at a given floral host, even among paired colonies in a seemingly uniform agricultural setting.     

Macrolophus caliginosus: Functional response to whiteflies and preference and switching capacity between whiteflies and spider mites

Laboratory experiments were performed with adult female Macrolophus caliginosus Wagner (Heteroptera: Miridae) at 22ºC on bean plants to determine the functional response towards whiteflies, as well as the preference and switching capacity between the two prey species: whiteflies and spider mites. Predation of females presented with first instars of Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) was of a Type III functional response. The observed maximum predation was approximately 75 first instars at high prey densities within a 24-h period. The preference of M. caliginosus females between eggs of T. vaporariorum and Tetranychus urticaeKoch (Acarina: Tetranychidae) changed with the ratio of offered prey. The preference for T. vaporariorum eggs increased non-linearly with increasing proportions of this prey type. The average maximum predation of whitefly and spider mite eggs were approximately 166 and 111 eggs per day, respectively, at the highest ratio of the two preys. The proportion of M. caliginosus females found on the test plants at the end of the experiment increased with prey density suggesting that this mirid spends more time in areas with high prey density. Macrolophus caliginosus females are voracious predators of eggs and first instars of T. vaporariorum as well as of spider mite eggs and may thus be a valuable addition to existing methods of biological control of T. vaporariorum and T. urticae.     

Prey preference of Orius minutus and its functional response in comparison that of O. laevigatus,on Tetranychus urticae

Orius species (Hemiptera: Anthocoridae) are generalist predators of small insects, including thrips, mites, aphids, and scales. Here, we evaluated the prey preference of Orius minutus (L.) on five prey species by comparing it with Tetranychus urticae Koch (Acari: Tetranychidae) as a standard prey. Among five prey species tested, Frankliniella intonsa (Trybom) (Thysanoptera: Thripidae) and Hyalopterus pruni (Geoffroy) (Hemiptera: Aphididae) were preyed on more than T. urticae by O. minutus in a four hour choice test. In a four hour no-choice test, F. intonsa was the most frequently consumed prey, followed by H. pruni, T. urticae, Amphitetranychus viennensis (Zacher) (Acari: Tetranychidae), Eriococcus sp. (Hemiptera: Eriococcidae), and Stephanitis pyrioides Scott (Hemiptera: Tingidae). The functional response of O. minutus in response to various densities of adult T. urticae on kidney bean leaf was compared with that of the commercialized species Orius laevigatus (Fieber). Different numbers of adult T. urticae (5, 10, 20, 40, 80, and 120) were offered to females of both predators for 24 h in a controlled environment of 25.0 ± 0.5 °C, 71.2 ± 5.0% RH, and a 16: 8 h (L: D) photoperiod. Both O. minutus and O. laevigatus exhibited a Type III response according to a logistic regression model. Despite the similar attack rate or handling time found between the two species, predation rate was higher on O. minutus than on O. laevigatus. These results indicate that O. minutus could also play an important role in the biological control of T. urticae as well as F. intonsa and H. pruni.     

Pathogenicity of the Hyphomycete Fungi Verticillium lecanii and Metarhizium anisopliae to the Western Flower Thrips,Frankliniella occidentalis

The pathogenicity of several isolates of the hyphomycete fungi Verticillium lecanii and Metarhizium anisopliae to Frankliniella occidentalis was investigated. Treatment of adult thrips with M. anisopliae resulted in at least 94% mortality at 7 days post-inoculation. In contrast, V. lecanii isolates only gave mortalities of between 20 and 70%. Detailed studies were made on the most virulent isolate of M. anisopliae (275) to determine its efficacy at different doses and temperatures. At 23 C the LC was ca. 3 105 conidia ml-1 after 5 days and the LTs were 50 50 3 and 4.5 days at 10 7 and 106 conidia ml-1 respectively. Temperature influenced fungal virulence to adult thrips; the LT at 18 and 20 C was ca. 4 days and at 23 or 26 C it was ca. 3 days. 50 Larvae were less susceptible to infection than adult thrips (27% versus 100% mortality), presumably due to the inoculum being shed with the exuvium during ecdysis. Conidia of M. anisopliae isolate 275 germinated rapidly on the surfaces of larvae, pupae and adults, with most germlings producing appressoria within 24 h post-inoculation. Fungal elements were present in significant amounts in the body 3 days after treatment.     

Biological Control of Thrips on Ornamental Crops: Interactions Between the Predatory Mite Neoseiulus cucumeris (Acari: Phytoseiidae) and Western Flower Thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on Cyclamen

Difficulties in controlling outbreaks of Western flower thrips, Frankliniella occidentalis, have obstructed the widespread adoption of biological control in many ornamental crops. The efficacy of the predatory mite, Neoseiulus cucumeris, in controlling F. occidentalis on two cultivars of cyclamen was tested in glasshouse experiments. The establishment and development of F. occidentalis populations was compared in three treatment introductions of N. cucumeris (50, 200 and 350 mites m -2 per week) and an untreated control. F. occidentalis were sampled in the flowers over eight weeks and counted into different life stages. No differences were observed between the two cultivars. All treatments with the predator resulted in a decline in numbers of F. occidentalis compared to the untreated control. Although the proportion of first instar F. occidentalis was similar in all treatments, the level of control varied with the number of N. cucumeris introduced. Lower populations of F. occidentalis, combined with a more rapid decline in their numbers, were observed at the 200 and 350 mites m -2 rates. Numbers of F. occidentalis remained low in the 350 N. cucumeris m -2 rate and the proportion of second instar F. occidentalis in the samples was consistently lower than in the other treatments. Trap counts of adult F. occidentalis were strongly correlated with the numbers of both adult and total F. occidentalis in flower samples. High inoculative releases of N. cucumeris early in the flowering cycle followed by frequent low introductions of predators should provide a strong basis for preventative control of F. occidentalis and other thrips species on cyclamen.     

Prey stage preference and feeding behaviour of Oligota kashmirica benefica (Coleoptera: Staphylinidae), an insect predator of the spider mite Tetranychus urticae (Acari: Tetranychidae)

We studied the prey stage preference and feeding behaviour of the first to third instar larvae and adult females of Oligota kashmirica benefica Naomi (Coleoptera: Staphylinidae), a predator of the spider mite Tetranychus urticae Koch (red form) (Acari: Tetranychidae), on leaves of the kudzu vine (Pueraria lobata (Wild.) Ohwi (Leguminosae)) under laboratory conditions. The number of mites eaten increased with the growth of predator larvae. Third instar larvae preyed on all stages of spider mite, whereas first instar larvae preyed mainly on immobile stages (eggs and quiescent stages). The predator larvae showed two types of foraging behaviour (active searching and ambush behaviour) when targeting the mobile stages (larval, nymph and adult stages of prey). Although no difference was found in the number of prey consumed by adult females and third instar larvae of the predator, the adult females mainly attacked and consumed the immobile stages.     

Impact of Entomopathogenic Nematodes on Different Soil-dwelling Stages of Western Flower Thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), in the Laboratory and Under Semi-field Conditions

The impact of entomopathogenic nematodes (EPN) on mortality of soil-dwelling stages of western flower thrips (WFT), Frankliniella occidentalis (Thysanoptera: Thripidae) with different insect stage combinations was studied in the laboratory and under semi-field conditions. In laboratory experiments, the efficacy of Steinernema feltiae strain Sylt (Rhabditida: Steinernematidae) at a concentration of 400 infective juveniles (IJs) cm -2 was tested against different proportions of soil-dwelling stages of WFT, i.e. late second instar larvae (L2), prepupae and pupae. Soil was used as the testing medium. S. feltiae significantly affected the mortality of all soil-dwelling life stages of WFT at all tested insect stage combinations. The proportion of late L2 in the population negatively correlated to EPN-induced mortality. WFT prepupa and pupa were similarly susceptible to S. feltiae and their proportion in the population did not affect the EPN-induced mortality under laboratory conditions. The highest mortality (80%) was recorded when the population consisted only of prepupae and/or pupae. In the semi-field study, the impact of S. feltiae , S. carpocapsae strain DD136 and Heterorhabditis bacteriophora strain HK3 (Rhabditida: Heterorhabditidae) ( H. bacteriophora ) at concentrations of 400 and 1000 IJs cm -2 was evaluated against WFT reared on green beans, Phaseolus vulgaris L., as host plant in pot experiments in a controlled climate chamber. All tested EPN strains at both dose rates significantly reduced the WFT populations. Up to 70% reduction of the WFT population was obtained at the higher EPN concentration.