Factors affecting orchard colonisation by the black-kneed capsid (Blepharidopterus angulatus (Hemiptera:Miridae)) from alder windbreaks

The colonisation of orchards by Blepharidopterus angulatus (the black-kneed capsid bug) from alder windbreaks was investigated, to determine its use as a biological control agent of orchard pests. The aphid Pterocallis alni provides an abundant and acceptable food for the capsid on alder. The key capsid mortality factor on windbreaks was the loss of adult females through migration. Clipping the windbreak prior to the aphid population peak resulted in male capsids migrating and females remaining, while clipping after the aphid population peak resulted in both sexes migrating to nearby orchards. Guidelines are given for windbreak management as part of a system of integrated orchard pest control.     

The ecology of a scale insect,Aulacaspis tegalensis,on sugar cane in East Africa

• 1 The scale insect, Aulacaspis tegalensis, invaded a sugar estate near Moshi, Tanzania, in 1969.
• 2 The number of fields affected and scale abundance were estimated weekly by weighing eggs sifted from samples scraped from infested cane.
• 3 Abundance increased exponentially with the age of the cane, once mature cane began to develop at the age of six months, and it was also affected by the cane variety.
• 4 The principal source of temporal variation in abundance was weather, especially mean maximum temperature eight weeks before sampling, when the crawlers which gave rise to the females were settling.
• 5 The behaviour of crawlers is affected by temperature, humidity and sunshine.
• 6 Up to 25% of the crop was lost at the height of the infestation.
• 7 Wild natural enemies could not reduce scale numbers to an acceptable level.
• 8 Lindorus lophanthae (Coccinellidae) was introduced from Mauritius in 1971 and may have been responsible for the decline in scales which began after it had become abundant throughout the estate. Since 1972 loss of yield due to scale has been undetectable in the factory.
• 9 The results are discussed in relation to the situation in Mauritius, where L.lophanthae is ineffective and the implications of the studies for the reduction of losses by agronomic methods are detailed.

     

Field manipulation of populations of individual staphylinid species in cereals and their impact on aphid populations

Abstract.

• 1 Four species of staphylinids were caged separately on wheat and their effect on the population development of the grain aphid, Sitobion avenae (F.), was investigated over two seasons.
• 2 A novel field cage design was used to exclude all but the staphylinid species under investigation.
• 3 Predator effects were compared with total-exclusion cages in which all predators and parasitoids were kept out.
• 4 During a high-density phase of aphid population development only Philonthus cognutus (Stephens) significantly influenced aphid population numbers.
• 5 At low aphid densities, Tachyporus obtusus (L.), T.chrysomelinus (L.) and P.cognatus reduced aphid population levels.
• 6 The experiments showed that Tachyporus spp. can reduce the numbers of cereal aphids prior to the exponential phase of aphid population increase and that P.cognatus causes some reduction at both the stages of aphid population growth investigated.

     

Individual growth rates do not predict aphid population densities under altered atmospheric conditions

• 1 Altered atmospheric composition, associated with climate change, can modify herbivore population dynamics through CO₂ and/or O₃‐mediated changes in plant quality.
• 2 Although pea aphid Acyrthosiphon pisum genotypes exhibit intraspecific variation in population growth in response to atmospheric composition, the proximate mechanisms underlying this variation are largely unknown.
• 3 By rearing single (green, pink) and mixed (green + pink) pea aphid genotypes on red clover Trifolium pratense at the Aspen Free Air CO₂ and O₃ Enrichment (Aspen FACE) site, we assessed whether: (i) elevated CO₂ and/or O₃ concentrations alter aphid growth and development and (ii) individual aphid growth rates predict aphid population densities.
• 4 We showed that growth and development of individual green and pink aphids were not influenced by CO₂ and/or O₃ concentrations when reared as individual or mixed genotypes. Individual growth rates, however, did not predict population densities.
• 5 Reared as a single genotype, green pea aphid populations decreased in response to elevated CO₂ concentrations, but not in response to elevated CO₂ + O₃ concentrations. Pink pea aphid populations reared as a single genotype were unaffected by augmented CO₂ or O₃. Populations of mixed genotypes, however, were reduced under elevated CO₂ concentrations, irrespective of O₃ concentrations.
• 6 Herbivore population sizes may not readily be predicted from growth rates of individual organisms under atmospheric conditions associated with global climate change.

     

Nocturnal activity and resource utilization in the aphid hyperparasitoid, Dendrocerus carpenteri

Abstract.

• 1 Females of the aphid hyperparasitoid Dendrocerus carpenteri (Curtis) search successfully for hosts during both day and night. Oviposition numbers per host patch did not differ significantly between day and night.
• 2 D.carpenteri females also displayed a nocturnal flight activity, showing that they are not only capable of searching on a given host plant but also of dispersing between host plants.
• 3 Nocturnal oviposition activity was mainly influenced by egg load. Females with a high egg load laid more eggs at night than females with a comparatively low egg load. Thus, D.carpenteri females may use nocturnal foraging to compensate for the lack of oviposition opportunities during day.
• 4 D.carpenteri females which foraged continuously for hosts both day and night (= for 24 h per day) benefitted from an 1.4-fold increase in lifetime reproductive success when compared to females which foraged only by day (= for 16 h per day).
• 5 The benefit of night foraging for this species is a significantly increased reproductive success.

     

The food requirements of Blepharidopterus angulatus (Heteroptera: Miridae) as a predator of the lime aphid, Eucallipterus tiliae

The weight of lime aphids consumed by B. angulatus increases at an increasing rate during nymphal development, with the fifth instar contributing 50% of the total consumption. Males and females reach different adult weights, but show no difference in food consumption. The efficiency of conversion of aphid food into body tissues diminishes from the third instar onwards. Females continue to oviposit for 5 weeks at least, laying on average just over one egg per day. The daily food requirements of ovipositing adult females increase as they get older, being more than twice as great as those of fifth-instar nymphs. Nymphs can tolerate a less than optimal food supply, and in the early instars they can compensate for an inadequate diet by converting food into body tissues with increased efficiency. Teneral adult weight is, however, proportional to the weight of food consumed during the fifth instar. B. angulatus can develop successfully on parasitized aphids and can utilise honeydew to prolong survival and, to a limited degree, to increase in weight. Leaf tissue has no significant value as a source of food.

---

Résumé Les besoins alimentaires de B. angulatus ont été étudiés au laboratoire à une température de 14 degrés.Quand B. angulatus est largement approvisionné avec des pucerons du tilleul, sa consommation de nourriture s'accroît de plus en plus au cours du développement, de même que son poids, de sorte que le 5ème stade larvaire absorbe un peu plus de 50% du poids total de pucerons consommés pendant toute la durée du développement larvaire. Ce 5ème stade larvaire est plus long que le 4ème, lequel est également plus long que chacun des trois premiers stades. La consommation journalière est moindre au début et à la fin de chaque stade, en particulier dans les derniers stades.Le prédateur consomme jusqu'à 90% du poids du corps de la proie. Quand les pucerons lui sont donnés en excès, la larve du 5ème stade de B. angulatus tend à tuer plus de proies qu'elle n'en consomme, ce qui sans doute est dû à la stimulation provoquée par la proie.Le rendement de croissance (efficience de la transformation du poids d'aphides absorbés en poids du corps du prédateur) diminue à partir du 3ème stade larvaire (de 46% pour le ler stade à 19% chez les adultes femelles). Au 5ème stade larvaire le rendement de croissance des mâles est significativement plus faible que celui des femelles, de sorte que les mâles sont plus légers que les femelles à l'état de maturité, bien que les deux sexes consomment le même poids de pucerons.Les femelles adultes commencent à pondre environ deux semaines après la mue imaginale et chacune dépose en moyenne 44 ufs, environ 1, 2 par jour. Les besoins alimentaires des femelles adultes en cours de ponte s'accroissent avec leur âge; leurs besoins journaliers en pucerons sont plus de deux fois aussi grands que ceux des larves du 5ème stade.Les larves peuvent supporter un apport en nourriture réduit par rapport à l'optimum.La résistance à la restriction alimentaire est plus grande au 3ème stade larvaire qu'aux ler et 5ème stades. Le ler et le 3ème stade larvaire peuvent compenser une réduction de l'apport alimentaire, par un meilleur rendement de croissance, ce que ne peuvent faire les larves du 5ème stade. B. angulatus peut se développer de façon satisfaisante en se nourrissant de pucerons parasités et momifiés. Il peut aussi utiliser le miellat en cas de disette ce qui lui permet d'accomplir un développement partiel, d'un stade au suivant, mais pas au-delà. En moyenne B. angulatus ne survit pas plus longtemps quand on ne lui offre que de l'eau ou des feuilles de tilleul, l'insecte peut en effet piquer celles-ci, pour lutter contre la dessication.

     

Ecophysiological aspects of bruchid reproduction. I. The influence of pod maturity and seeds of Phaseolus vulgaris and the influence of insemination on the reproductive activity ofZabrotes subfasciatus

ABSTRACT.

• 1 Economically important bruchid beetles like Zabrotes sub-fasciatus (Boh.) are able to reproduce both in the field before the legume crop harvest – whilst the seeds are still enclosed within pods – and on seeds in storage sites.
• 2 To take into account this reproductive feature, the influence of pods at different stages of maturity and seeds of Phaseolus vulgaris (Lin.) together with the influence of insemination on the reproductive activity of Zabrotes subfasciatus were examined.
• 3 Female fecundity, insemination and ovarian production were studied under laboratory conditions approximating as closely as possible to the thermal and photoperiodic regimes of the Costa Rican region from which the experimental strain originated.
• 4 The three stages of pod maturity used in experiments (fresh green, fresh yellow and dry yellow pods, all non-dehiscent) induced copulations and significantly stimulated oogenesis. Fecundities of females in the presence of pods were low and did not differ from controls.
• 5 The influence of bean seeds on female reproductive activity was more pronounced than that of pods. Contact with seeds led to a marked increase in the number of sexual meetings, ovarian production and egg-laying activity. Under these conditions, eggs are laid directly on the larvae's food.
• 6 Insemination alone stimulated oogenesis but did not induce egg-laying.
• 7 Possible additive or synergistic interactions between host plant information perceived by females, the effects of egg-laying and insemination are suggested to explain the observed results.
• 8 The adaptive value of this form of reproductive regulation by host plant seeds and pods is discussed in terms of the natural history and oviposition behaviour of Zabrotes subfasciatus.

     

Searching by Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and escape behaviour of its aphid and cicadellid prey on lime (Tilia×vulgaris Hayne)

• 1 The paper describes the behavioural interactions between searching larvae of Adalia bipunctata and its aphid and cicadellid prey on lime (Tilia×vulgaris Hayne).
• 2 The frequency with which the predator achieves contact with cicadellid nymphs of differing ages is related to direction of predator approach and predator perception by the cicadellid.
• 3 The success of a coccinellid in contacting and capturing its aphid prey is related to the predator's size and direction of approach, the perception of the predator by an aphid and the latter's ability to escape, the effectiveness of which is discussed.

     

Overdispersion of Allothrombium pulvinum larvae (Acari: Trombidiidae) parasitic on Aphis gossypii (Homoptera: Aphididae) in cotton fields

Abstract.

• 1 Dispersion patterns of the protelean parasite, Allothrombium pulvinum Ewing, among individuals of an aphid host, Aphis gossypii Glover, were examined during spring 1991 in several cotton fields in Jiangsu Province, China.
• 2 The variance-to-mean ratios (i.e. dispersion index) of larval mites per host were greater than 1, indicating that the mite parasites were overdispersed among aphid hosts. The variance increased with the mean according to the power law, variance = 1.51 mean¹⁰⁶, which explained 99.7% of the variation in the data.
• 3 The negative binomial distribution adequately describes the patterns of larval mite dispersion among aphid hosts in eight out of ten populations. The degree of clumping (1/k) decreased curvilinearly with parasite density (mites per host).
• 4 Mites were more clumped among adult aphids than among immature ones.
• 5 Ecological and evolutionary consequences of mite overdispersion within host populations are discussed. The role of Allothrombium in pest control is also discussed.

     

The population dynamics of the large pine aphid,Cinara pinea (Mordv.)

The large pine aphid, Cinara pinea lives exclusively on Pinus species, where it feeds on the foliated shoots of the current and previous year. The paper describes the development of a computer model designed to simulate the aphid's population dynamics on saplings in the controlled environment of the laboratory, i.e. in the absence of natural enemies. The model was able to account for about 80% of the variation in aphid numbers within and between trees over a three month period. Sensitivity analysis revealed that the number of pine aphids is limited primarily by nymphal emigration, the operation of which is sensitive both to density and to plant quality as reflected in aphid growth rates. Of secondary importance are changes in reproduction acting through increased reproductive delay, again a result of altered growth rates and adult size. Development, too, has an important secondary influence. Contrary to expectation and conventional belief, however, alate production proved to be of negligible importance, either in limiting or regulating population numbers. Alatae are produced in too few numbers and for too short a period to significantly alter the pattern of population change.     

Influence of Experience on the Response of Bathyplectes curculionis (Hymenoptera: Ichneumonidae), a Nonaphidophagous Parasitoid, to Aphid Odor

Bathyplectes curculionis (Thomson) is an introduced natural enemy of the alfalfa weevil in North America. The wasp requires carbohydrate foods as an adult. Adult wasps have increased longevity and fecundity when provided access to pea aphid, Acyrthosiphon pisum (Harris), honeydew in the laboratory, and adults respond positively to the presence of pea aphids in alfalfa fields. However, it is unknown how these wasps find aphid honeydew in the field. In a series of Y-tube olfactometer experiments, we evaluated the response of naïve and experienced adult female B. curculionis to odors from pea aphids, alfalfa, and pea aphids on alfalfa. Naïve adult females did not respond positively to pea aphid odor even when hungry. But adult females were able to learn aphid odor, and the mechanism of learning appears to be associative rather than by sensitization. Naïve females also showed no preference for alfalfa odor but learned alfalfa odor through sensitization. The wasps did not distinguish between alfalfa with aphids and alfalfa without aphids, even after exposure to aphids or alfalfa with aphids. However, they preferred pea aphid odor to alfalfa odor after a feeding experience in the presence of pea aphid odors. But after exposure to mixed odors of aphids and alfalfa while feeding, B. curculionis females preferred the odor of alfalfa to the odor of pea aphids. These results suggest that alfalfa odors mask or override aphid odors when aphids are associated with alfalfa (as happens naturally), thus interfering with the wasp's ability to respond to learned aphid odors. Therefore, although the wasps are capable of learning to find pea aphids and their honeydew in a simplified laboratory setting, it appears unlikely that they do so in the field.     

Ant attendance of the cotton aphid is beneficial for okra plants: deciphering multitrophic interactions

相似文献   

Intraspecific variation of Myzus persicae on sugar beet (Beta vulgaris)

Differences in inherited resistance among seven sugar-beet stocks had similar effects on Myzus persicae clones representing the range of variation in aphid response to resistant and susceptible sugar beet observed in fifty-eight clones collected between 1969 and 1971. Three sugar-beet stocks were consistently resistant. Statistically significant interactions between beet stocks and aphid clones did not indicate the existence of biotypes with specific abilities to overcome resistance. M. persicae clones differed in their vigour of colonizing sugar beet, irrespective of the differences between beet stocks. The readiness of adult aphids to settle determined the size of aphid population produced and included a component related to the response of the aphid clone to sugar beet as a host, and a component related to the resistance ranking of the beet stock. Breeding sugar beet with resistance to aphids will be simplified, as the results indicate that, at present, differences between aphid biotypes need not be considered a problem.     

The population dynamics of the stinging nettle aphid, Microlophium carnosum (Bukt.)

• 1 Populations of Microlophium carnosum on patches of perennial stinging nettle, Urtica dioica increased rapidly during April and May to reach their peaks in June. The decline in numbers was equally rapid and very small populations persisted into autumn; parthenogenetic over-wintering was recorded.
• 2 Suboptimal ambient temperature and mortality due to natural enemies contributed mainly to the post-peak development of aphid populations.
• 3 The combined effects of intraspecific competition and a deterioration in the food quality of the host plant appeared to be the major factors determining the temporal pattern of aphid abundance.
• 4 Variation in the size of populations between the three sampled sites was correlated with differences in the food quality of nettles as indicated by aphid mean relative growth rate.
• 5 Each nettle patch has a particular ‘carrying capacity’ for aphids, within which a biennial fluctuation between relatively large and small aphid populations appeared to be emerging at most of the sites investigated. A natural or aphid-induced cycle in host plant quality, or alternatively, the persistent effects of intraspecific competition over several generations, may explain this fluctuation.

     

The role of intra-specific mechanisms and predation in regulating the numbers of the lime aphid,Eucallipterus tiliae L.

Summary Analysis of changes in numbers of the lime aphid, Eucallipterus tiliae L., reveals that there is an overcompensated density dependent factor acting within years, and an inverse density dependent factor acting between years. Because of its effect on the aphid's rate of development and reproduction the variation in temperature from year to year acts as a density disturbing factor.There is no evidence from laboratory experiments to suggest that the quality of its food influences the numbers of the lime aphid. However, qualitative changes in the aphid following period of aphid abundance are shown to be important in the overcompensated density dependent response. The more prevalent insect predators influence the regulating process as they eat most of the aphids that remain after an aphid population has declined from a very high level of abundance. Their action results in a more overcompensated response than would occur in their absence.     

Productivity modifications to flour beetles (Coleoptera: Tenebrionidae) by gamma radiation (60Co) of one or both sexes and by the addition of radiated males or females to population

The effects on productivity by the addition of various numbers of radiated adult males or females to populations of two densities were determined for two species of flour beetles. Modifications in productivity after exposure to gamma radiation from⁶⁰Co included:

1. females of T. confusum were sterilized by an exposure between 2620 to 5230 R.
2. females of T. castaneum were not sterilized by 10, 200 R.
3. males were not sterilized by 10, 200 R.
4. sterile females may serve as depositories for normal sperm thereby reducing the productivity. Addition of such females to populations of flour beetles did not reduce the numbers of progeny.
5. since sterile females did not suppress population development, and since they destroy grain and cereal products, they should be eliminated from control programs featuring the sterile insect release technique.
6. population density decreased the numbers of progeny.

The use of the sterile insect release technique to control insects of stored grain products does not seem likely with present day sanitary standards since large numbers of insects need be added to effect control.     

The effect of prey density and host plant characteristics on oviposition and fertility in Anthocoris confusus (Reuter)

• 1 Anthocoris confusus females show the greatest egg production when fed on eight adult Aulacorthum circumflexus per day. Prey densities below six result in a marked fall off in egg production.
• 2 Low prey densities result in reduced egg fertility and a decrease in oviposition period.
• 3 A.confusus females oviposit on those parts of a broad bean plant which support the highest aphid densities. This increases the probability of survival of the emerging nymphs.
• 4 Females are also able to distinguish between young, fully turgid, plants and older, more flaccid, plants and oviposit preferentially in the younger ones. Thus the eggs develop before the plant dies.

     

Cereal aphids, their parasites and predators caught in cages over oat and winter wheat crops

The trapping of alate aphids in emergence cages each 1 yd² (0–83 m²) over cereal crops from mid-June to the end of July, 1964 to 1971, always revealed colonies of cereal aphids within the crop. Four species, Sitobion avenae, S. fragariae, Metopolophium dirhodum and Rhopalosiphum padi occurred every year in different proportions. Alate aphids from winter wheat were most numerous in 1968 and fewest in 1967. Alatae developed slightly earlier in cages than in the field and peak catches were a few days earlier than in a nearby 12-2 m suction trap. Cereal aphid colonies were adversely affected by bad weather in May, e.g. in 1969, and by predators. Coccinellidae (chiefly Propylea 14-punctata) were the dominant predators in 1971 and 1968, Syrphidae in 1966, 1971 and 1968 and Chrysopidae in 1970. Parasites belonging mainly to the genus Aphidius were numerous every year. When hyperparasites such as Asaphes vulgaris, Lygocerus sp., Conostigmus sp. and Phaenoglyphis sp. were abundant as in 1967, they affected numbers of aphids in the current year and increased them in the following year (1968), possibly by hindering early, heavy parasitism. Hyperparasites could have an important influence in fluctuations of cereal aphid populations from year to year. Aphids of one species or another are always present in cereal crops in sufficient numbers during the summer months to provide copious quantities of honey dew, and this is unlikely to be a limiting factor in the biology of the wheat bulb fly, Leptohylemyia coarctata.     

A population study in Jamaica on adult Sceliphron assimile (Dahlbom) (Hymenoptera: Sphecidae)

Abstract.

• 1 A mark–recapture study on the sphecid wasp Sceliphron assimile (Dahlbohm), analysed by Jolly's stochastic method (1965), was made from 3 December 1974 to 22 February 1975 at Green Bay, St Catherine, Jamaica.
• 2 Population levels in an 18.2 ha study area fluctuated about a mean of 281 for males, 259 for total females and 87 for reproducing females, while the probable carrying-capacity for these reproductives was about 104.
• 3 Mean estimated daily survival rates were 0.903 for males, 0.924 for total females and 0.945 for reproducing females. For the first two categories these rates decreased (p < 0.02) during the study, probably reflecting increasing emigration. Reproducing females probably do not emigrate and their survival did not significantly decrease.
• 4 Minimum age was linearly related to wing wear (r=+0.69, P < 0.001) and the latter associated with the progressive maturation and ageing of the ovaries. All surviving females become parous by middle age.
• 5 The mean rate of fecundity in the field was dependent on female age and was reduced during prolonged drought. Curves of total achieved fecundity appropriate to realistic survival rates give 4.2–16.8 eggs/female. The Jamaican mean was 9.6 ± 2.3 and that for Green Bay 8.6.
• 6 The proportion of females in the Green Bay population was 0.48 ± 0.03 while 0.55 was expected at emergence.
• 7 A cyclic budget is used to estimate immigration and emigration, and these were important causes of population change.
• 8 For Jamaica, only an estimated 28% of females survived to nest.

     

The life history and population biology of an intertidal aphid,Pemphigus trehernei Foster

• 1 The fluctuations in the density and composition of populations of Pemphigus trehernei, an aphid that lives on the roots of the halophyte Aster tripolium, were followed on an area of saltmarsh on the north Norfolk coast between 1971 and 1973.
• 2 The aphid has a typical Pemphigus life-cycle, but the emphasis is on the non-sexual anholocycle. Many diapausing aphids overwinter on the marsh and relatively few alates fly to or from it.
• 3 The aphids are confined to the top 11 cm of soil and are highly aggregated: the dispersion of the population can be fitted to the negative binomial. The absolute density of the populations is relatively low, with a mean value of about 2000 aphids/m² of available marsh area.
• 4 Temperature, host-plant growth and fungal attack are probably the most important factors affecting seasonal population fluctuations. Up to 50% of the populations may be infected with the fungus Metarrhizium anisopliae, which is widespread in the soil.