食蚜绒螨对棉花苗蚜的控制作用研究

通过2年的田间调查和小区试验发现:(1)食蚜绒螨与被寄生的棉蚜有翅蚜和无翅蚜在时间—数量分布上具相似性。(2)棉蚜带螨率结果说明,50％有翅蚜可被迁入初期杀死,可使大部分棉蚜繁殖力下降或不能生殖;(3)棉田播种前施肥、浅翻,对食蚜绒螨的发生量不具明显影响;(4)食蚜螨在棉田期其他棉蚜天敌缺少的情况下,填补了此期控蚜天敌时间生态位的空缺,成为棉田生态系统中不可缺少的一员。     

Survey of the parasitoids of the tuliptree aphid,Illinoia liriodendri (Hom: Aphididae), in northern California

A survey of the parasitoids ofIllinoia liriodendri (Monell) in northern California conducted from 1988–1990 revealed the presence of 12 primary and 14 hyper-parasitoid species. The most common primary parasitoid wasAphidius polygonaphis (Fitch), which was imported from the eastern United States in the 1970's and is now established throughout the area. New host records were noted forA. ervi Haliday,A. avenaphis (Fitch), Praon occidentale Baker,P. unicum Smith,Diaeretiella rapae M'Intosh,Lysiphlebus testaceipes (Cresson), andMonoctonus nervosus (Haliday) (all Hymenoptera: Braconidae: Aphidiinae), andAphelinus sp. nr.asychis Walker (Hymenoptera: Aphelinidae). The most common hyperparasitoid species werePachyneuron aphidis (Bouché) andAsaphes californicus Girault (both Hymenoptera: Pteromalidae). New hyperparasitoid host records were noted forPachyneuron californicum Girault on Aphidiine and Aphelinidae spp. andCoruna clavata Walker (Hymenoptera: Pteromalidae) onAphelinus sp.     

Construction and characterization of two rice bacterial artificial chromosome libraries from the parents of a permanent recombinant inbred mapping population

Rice is a leading grain crop and the staple food for over half of the world population. Rice is also an ideal species for genetic and biological studies of cereal crops and other monocotyledonous plants because of its small genome and well developed genetic system. To facilitate rice genome analysis leading to physical mapping, the identification of molecular markers closely linked to economic traits, and map-based cloning, we have constructed two rice bacterial artificial chromosome (BAC) libraries from the parents of a permanent mapping population (Lemont and Teqing) consisting of 400 F9 recombinant inbred lines (RILs). Lemont (japonica) and Teqing (indica) represent the two major genomes of cultivated rice, both are leading commercial varieties and widely used germplasm in rice breeding programs. The Lemont library contains 7296 clones with an average insert size of 150 kb, which represents 2.6 rice haploid genome equivalents. The Teqing library contains 14208 clones with an average insert size of 130 kb, which represents 4.4. rice haploid genome equivalents. Three single-copy DNA probes were used to screen the libraries and at least two overlapping BAC clones were isolated with each probe from each library, ranging from 45 to 260 kb in insert size. Hybridization of BAC clones with chloroplast DNA probes and fluorescent in situ hybridization using BAC DNA as probes demonstrated that both libraries contain very few clones of chloroplast DNA origin and are likely free of chimeric clones. These data indicate that both BAC libraries should be suitable for map-based cloning of rice genes and physical mapping of the rice genome.     

Factors determining the pest status of the rose-grain aphid, Metopolophium dirhodum (Walker), on winter barley in the United Kingdom

To test the hypothesis that early maturation of barley affords it some resistance to cereal aphids, the colonisation, survival, growth, reproduction and emigration of M. dirhodum on barley was measured and compared with previously published results for this aphid on wheat.
Barley plants were colonised as readily as wheat plants. Survival to maturity was similar on both hosts. Relative growth rate was higher on wheat than on barley for most of the season while reproduction was similar on both. Emigration, measured alate production, was significantly higher on mature wheat than on mature barley.
It is proposed that the increase of M. dirhodum populations on barley is normally terminated early in the year directly plant maturation and consequent drying out of the leaves, resulting in the death of aphids. This is different to the situation on wheat, which matures later, and where emigration following plant induced alate induction has been shown to be the major factor affecting the decline in population growth.
These results support the hypothesis that early maturation of barley provides some resistance to M. dirhodum.     

Decision to superparasitize based on larval survival: competition between aphid parasitoids Aphidius ervi and Aphidius smithi

Oviposition by a parasitoid wasp in an already parasitized host (= superparasitism) may result in larval competition and the loss of offspring. Consequently, in solitary species, the decision to superparasitize should be based on the probability of offspring survival. Females of Aphidius ervi Haliday and A. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae), two parasitoids of the pea aphid, discriminated between conspecific-and heterospecific-parasitized hosts. Both species showed partial preference for aphids previously attacked by A. smithi, a result predicted from the fact that A. ervi is superior to A. smithi in larval competition under most conditions. Females of A. smithi selectively attacked conspecific-parasitized pea aphids when given a choice between these and self-parasitized hosts. Results indicated that females of both species responded to an external pheromone-like marker to discriminate between selfconspecific-and heterospecific-parasitized aphids. In addition, A. smithi may use internal cues to recognize, and avoid oviposition in, aphids previously parasitized by A. ervi.

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Résumé L'oviposition par une guêpe parasite dans un hôte qui a déjà été parasité (= superparasitisme) pourrait conduire à une compétition entre larves et à une perte de progéniture. Par conséquent, dans les espèces solitaires, la décision de superparasiter devrait être basée sur la probabilité de survie de la progéniture. Les femelles de Aphidius ervi Haliday et de A. smithi Sharma & Subba Rao (Hymenoptera: Aphidiidae), deux parasites du puceron du pois, ont discriminé entre les hôtes parasités par des individus de la même espèce et ceux parasités par des individus d'une espèce différente. Les deux espèces de parasite ont montré une préférence partielle pour les pucerons préalablement parasités par A. smithi, résultat qui était prévisible du fait que, dans la majorité des cas, A. ervi est supérieur à A. smithi dans la compétition entre larves. Les femelles de A. smithi ont sélectivement attaqué les pucerons parasités par un individu de la même espèce lorsqu'il leur était donné de choisir parmi ceux-ci et ceux parasités par les même individu. Les résultats indiquaient que les femelles des deux espèces répondaient à une sorte de phéromone externe pour distinguer les pucerons parasités par le même individu de ceux parasités par un individu de la même espèce et ceux parasités d'une autre espèce. En plus, A. smithi pourrait utiliser des signaux internes pour reconnaître et éviter l'oviposition dans les pucerons préalablement parasités par A. ervi.

     

Spatial patterns and sampling plans for cereal aphids [Hom.: Aphididae] killed by entomophthoralean fungi and hymenopterous parasitoids in spring wheat

Cereal aphids infesting spring wheat in southwestern Idaho were surveyed during 1988 and 1989 for the presence of entomophthoralean fungi and hymenopterous parasitoids. Cereal aphids killed by the fungi (cadavers) and parasitoids (mummies) includedDiuraphis noxia (Mordvilko),Metopolophium dirhodum (Walker),Sitobion avenae (F.), andSchizaphis graminum (Rondani). Taylor's power law was used to describe the relationships between mean densities of cadavers or mummies (number per tiller) and associated variances. Except forS. graminum mummies, which were at low levels throughout the growing seasons and tended to be randomly distributed, Taylor's slopes exceeded 1.0 for all the aphid cadavers and mummies, indicating varying degrees of clumping in spatial pattern. The spatial patterns ofD. noxia andM. dirhodum cadavers were similar, simply reflecting those of their own populations, but more aggregated than were their respective mummies resulting from parasitoid attack. The intercepts and slopes from the power law analysis were used to generate functional relationships between the proportion of wheat tillers bearing cadavers or mummies of each aphid species and the mean density, and develop optimal numerical (direct counting) and binomial (presence or absence) sample size curves for both cadavers and mummies of each aphid species.      

Feeding behaviour of the staphylinid beetle Tachyporus hypnorum in relation to its potential for reducing aphid numbers in wheat

Aphid consumption by larval and adult Tachyporus hypnorum (Coleoptera: Staphylinidae) in different reproductive states was compared under laboratory conditions. Post-overwintering (spring/summer) adults had a higher consumption rate of first/second instar Sitobion avenae (Hemiptera: Aphididae) than did overwintering adults. Choice experiments incorporating Isotoma viridis (Collembola: Isotomidae) and Sciara thomae (Diptera: Mycetophilidae) as alternative prey items showed that T. hypnorum had a strong preference for aphids at a range of prey frequencies. Numbers of aphids consumed were reduced when leaves infected with Erysiphe graminis f.sp. tritici (powdery mildew of wheat) were offered to beetles with aphids in choice experiments. Behavioural studies of adult T. hypnorum showed that foraging rates on wheat plants increased with increasing amounts of both mildew and aphids on plants. Feeding upon only the conidia of E. graminis was observed. Results are discussed in relation to previous data derived from gut dissection, to a field survey of alternative foods and to the phenology of T. hypnorum in relation to that of aphids in the wheat crop.     

Embryogenesis and oögenesis in alate virginoparae,gynoparae, and oviparae of the aphid Myzus persicae, in relation to photoperiod

The study reports on the effects of prenatal and/or postnatal exposures to short-night or long-night conditions, and of crowding, on embryogenesis and oögenesis in alate virginoparae, gynoparae, and oviparae of a holocyclic strain of the green peach aphid, Myzus persicae, from Yakima, Washington State.In alate virginoparae raised at a density of 10–20 per radish seedling in a short-night regime (8 hr darkness per diem), 3–4 embryos occurred in each of their 10 ovarioles, when the aphids attained adulthood. More than 30 larvae were deposited by most of these alatae. However, in young adult gynoparae, raised at these densities in a long-night regime (15 hr darkness per diem), only one viable embryo (a presumptive ovipara) occurred per ovariole. The follicle containing this embryo was followed by 1–2 abnormal follicles in each ovariole, and the number of larvae deposited by a gynopara was generally less than 10. In young adult oviparae similarly raised under a long-night regime, only one egg typically occurred in each of their 10 ovarioles, and the eggs deposited by an ovipara (only after it had mated) generally numbered less than 10. Alate virginoparae and gynoparae contained an additional embryo in some of their ovarioles when these morphs were raised at a lower density (1–5 per plant).Presumptive gynoparae partially developed the reproductive features of alate virginoparae when transferred to a short-night regime at birth; the converse was true when presumptive alate virginoparae were transferred to a long-night regime early in larval life. Oviparae maintained in short nights from before birth developed the appearance of apterous virginoparae but still produced eggs rather than embryos. However, their oögenesis was enhanced and eggs (10–20) were deposited by them without prior mating. Under all regimes tested, oviparae were always deposited early in the larviposition sequence of their alate mothers, and the number of oviparae deposited never exceeded 15.The possible involvement of juvenile hormone in the regulation of these events and the ecological significance of the results are discussed.     

Juvenile hormone and photoperiodically controlled polymorphism in Aphis fabae: Postnatal effects on presumptive gynoparae

Long days (short nights) (LD 16:8) and high temperatures (> 15°C) have an apterizing effect on the short day (LD 12:12) induced, presumptive gynopara of Aphis fabae. Transfer of presumptive gynoparae to long days (15°C) or to 25°C (short days) at varying times during postnatal development demonstrate that the adult form is determined by the second day of the second instar, i.e. 5 days after birth at 15°C. Transfer on day 1 induces maximum apterization with the proportion of aphids affected decreasing with age at transfer.Apterization induced by long days immediately after birth can, to some extent, be cancelled by return to short days but only up to day 4. Thus long days are morphogenetically more potent than short days at the beginning of larval development. At temperatures above 15°C the proportion of aphids apterized increases almost linearly.Apterized insects can be distinguished from juvenilized insects in the fifth-instar. Topical application of juvenile hormone (JH) induces both apterization and juvenilization of presumptive gynoparae but at different times during larval development, JH treatment during the early-instars promotes apterization but induces little juvenilization, whereas maximum juvenilization, without apterization, is produced by middle-instar treatment. The apterizing effects of JH are, thus, not due to its neotenic action.The response profile of JH-induced apterization is similar to that observed with long days and 25°C. It is suggested that such conditions increase endogenous JH levels in A. fabae. The three naturally occurring JH's differ in activity in the order JH I > JH II > JH III. Both long-day and JH-apterized insects switch from the normal ovipara production of the adult gynopara to vivipara production.