Life histories and host specificities of theEchium flea beetlesLongitarsus echii andL. Aeneus [Col. Chrysomelidae]

Two halticine flea beetles,Longitarsus echii Koch andLongitarsus aeneus Kutsch, occurring on the boraginaceous plantEchium plantagineum L. in the western Mediterranean region are potential biological control agents in Australia where the plant has become a weed (Paterson's curse). The adults of both species feed by making “shot holes” in the leaves. The larvae of both species attack the roots ofEchium, those ofL. echii feeding more centrally in the root than those ofL. aeneus which attack the outer cortex and rootlets. Both species are univoltine. The host restrictions of both flea beetles as adults and as larvae were tested using the criteria already established for theEchium leaf minerDialectica scalariella Zeller (Wapshere & Kirk, 1977). This testing established that it would be safe to introduce the 2 insects into Australia for the biological control ofE. plantagineum and they are now under quarantine.     

Host specificity of the two lace bugs,Dictyla echii andDictyla nassata [Hem.: Tingidae] potential biological control agents for paterson's curse (Echium plantagineum)

Two species of lace bugs,Dictyla echii (Schrank) andDictyla nassata (Puton), were tested for host specificity as potential biological control agents for Paterson's curse,Echium plantagineum L. A range of test plants from the family Boraginacea, from related families in the order Laminales and from species of economic importance in Australia which have had inadequate exposure in their countries of origin, were tested under both choice and non-choice conditions. These bugs proved to be oligophagous within the Boraginaceae and attacked a number of Australian native species. Because of this,D. echii andD. nassata are not considered sufficiently specific to release from quarantine and tests were abandoned before completion of the test plant list.

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Résumé La spécificité parasitaire deDictyla echii (Schrank) etD. nassata (Puton) a été étudiée en tant qu'agents de lutte biologique potentiels contreEchium plantagineum L. Dans les conditions de choix et d'absence de choix, une série de plantes ont été testées provenant de la famille des Boraginacées, des familles voisines de l'ordre des Laminales et d'espèces d'importance économique en Australie qui n'avaient pas fait l'objet de tests suffisants dans leur pays d'origine. Ces punaises se révèlent oligophages en ce qui concerne les Boraginacées et s'attaquent à de nombreuses espèces indigènes d'Australie. Pour cette raison,D. echii etD. nassata ne sont pas considérées comme suffisamment spécifiques pour les relacher à partir de la quarantaine et les tests ont été abandonnés avant d'épuiser la totalité des plantes prévues sur la liste.

     

The life history and host specificity of theEchium borer,Phytoecia coerulescens [Col.: Cerambycidae]

The cerambycid stem borerPhytoecia coerulescens (Scopoli) is a possible biological control agent for the weedEchium plantagineum L. in Australia. The adult beetle oviposits at the base of stems ofEchium spp. and a few otherBoraginaceae. The larva damages the flower stem by boring both upwards and downwards and eventually, at the end of the season, girdling the stem at its base. It overwinters in the rootstock of its host plant. It does not attack plants of agricultural importance in the field and host restriction to a small group of boraginaceous plants was confirmed in the laboratory, withEchium spp. as principal hosts. It is therefore considered thatP. coerulescens is a safe agent to introduce into Australia for the control ofE. plantagineum.     

Biology and host specificity ofOncochila simplex [Hem.: Tingidae], a candidate for the biological control of leafy spurgeEuphorbia esula L. “complex”

Bionomical and host-range studies of the lacebug,Oncochila simplex (Herrich-Shaeffer) (Hemiptera: Tingidae), a candidate for the biological control of leafy spurge (Euphorbia esula L. “complex”) in the United States, were made during the years 1979 to 1982 at the USDA-ARS Rome Laboratory, and during 1981 and 1982 at the USDA-ARS Albany, California laboratory. A total of 26 test plant species, varieties, or population was used. Oncochila simplex overwinters as adults and nymphs at the base of its host, 4 to 5 cm below the soil surface. In the Piacenza area (northern Italy) adults first appeared at the end of March and were present as 5 successive generations until the end of September. In the laboratory, under long day (L: D-16: 8) conditions, reproduction was continuous, amounting to 11 generations during 1981. Each life cycle was completed in 33 to 40 days. The ♀♀ laid eggs under the mesophyll of stems. An average of 175±10.93 eggs per female were produced. Of a sample of 1,580 eggs, 83% were fertile.Oncochila simplex has 4 nymphal instars. Adults lived 50–70 days. In no-choice tests, neonate nymphs ofO. simplex developed on plants of the genusEuphorbia (subgenusEsula) and on lettuce and corn. In field trials, this lacebug completed a generation onEuphorbia lathyris L., but not on lettuce and corn. The development of neonate nymphs under forced conditions on lettuce and corn does not necessarily indicate that these plants are suitable hosts in nature. Our hypothesis of the restricted host range ofO. simplex is also supported by the literature, in which there are no reports of this species from lettuce, corn or other plants of agricultural importance. We conclude thatO. simplex should be introduced as a biological control agent against leafy spurge in the United States.      

Inundative biological control of velvetleaf,Abutilon theophrasti [Malvaceae] withNiesthrea louisianica [Hem.: Rhopalidae]

Niesthrea louisianica Sailer (Rhopalidae) is native from Arizona to Florida north to New York and West to Iowa in the Mississippi Valley. Immatures and adults feed on seeds of malvaceous plants. Velvetleaf,Abutilon theophrasti Medic. (Malvaceae), is a major exotic weed of corn, soybeans, cotton, and sorghum, and is among the hosts forN. louisianica. A laboratory colony ofN. louisianica was established in 1984 using imbibed velvetleaf seeds as the food source. The colony was expanded in 1985 to support field releases in velvetleaf infested fields in the Midwest and New York State. Approximately 83,000 adultN. louisianica were released in 5 States. The insects reproduced and were found more than a kilometer from the release point at some release sites. In areas of establishment, a significant reduction in seed viability was recorded.      

Alaboratory evaluation ofAnthocoris nemorum andA. nemoralis [Hem.: Anthocoridae] as predators ofPhorodon humuli [Hom.: Aphididae]

Anthocoris nemorum (L.) andA. nemoralis (F.) were reared on apterous hop aphids,Phorodon humuli (Schrank), at 20±0.5°C.A. nemorum andA. nemoralis killed an average of 255 and 174 aphids respectively during nymphal development, and the adults killed 37 and 33 per day respectively. Small anthocorid nymphs selectively killed small aphids but adult anthocorids and 5th instar nymphs killed aphids of every size. Mean development times from emergence to final moult were 22 and 16 days forA. nemorum andA. nemoralis respectively.     

Effect of temperature on development and survival ofPristhesancus plagipennis [Hem.: Reduviidae]

The effect of temperature on the rate of development ofPristhesancus plagipennis Walker was determined by rearing individuals under a range of constant temperatures (22.5–35°C). Rates of development changed in a linear fashion from 22.5–30°C. Estimates of lower developmental thresholds were obtained for egg (13.1°C), nymphal (15.5°C) and egg to adult development (15.4°C). Fastest rates of nymphal and egg development occurred at 30 and 32.5°C, respectively. A requirement of 845.7 DD (degree days) was estimated for development from egg to adult. Nymphal survivorship was highest between 25 and 30°C.

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Résumé L'effet de la température sur la vitesse de développement dePristhesancus plagipennis a été déterminé par élevage des insectes dans une gamme de températures constantes allant de 22,5 à 35°C. La vitesse de développment est une fonction linéaire de la température entre 22,5 et 30°C. Le seuil théorique de développement a été estimé à 13,1°C pour l'œuf, 15,5°C pour la nymphe et 15,4°C pour le développement larvaire. Les plus grandes vitesses de développement de l'œuf et de la larve ont été obtenues respectivement à 30 et 32,5°C. 845,7 degrés-jours sont nécessaires pour le développement de l'œuf à l'adulte. La survie des nymphes a été la plus élevée entre 25 et 30°C.

     

Biology and host plant range of the soft scale,Steatococcus new species [Hem.: Margarodidae] for the biological control of the weedCryptostegia grandiflora [Asclepiadaceae]

The soft scale,Steatococcus new species, occurs onCryptostegia grandiflora R. Br. in Madagascar. Studies on its biology and host plant range showed colonies could survive for up to 6 months on some genera in theApocynaceae and indefinitely on many genera in the familyAsclepiadaceae. The species was therefore rejected as a biological control agent forC. grandiflora, a serious weed in northern Queensland, Australia.      

Bionomics ofTrioxys indicus [Hym.: Aphidiidae], a parasitoid ofAphis craccivora [Hem.: Aphididae]: 31. Effect of host haemolymph on the numerical response of the parasitoid

The influence of kairomones on the numerical response of the parasitoidTrioxys indicus against its hostAphis craccivora at its varying density was studied. The kairomones (applied as aqueous extract of the host) significantly enhanced the rate of parasitisation and multiplication and the area of discovery of the parasitoid and also the K-values of mortality of the host at all parasitoid densities introduced (1, 2, 4, 8, 12 and 16 parasitoids) into troughs having about 200 hosts. The sex-ratio of F₁ offspring decreased at lower parasitoid densities and remained more or less unchanged at higher parasitoid densities after the application of kairomones. The present findings indicate that if kairomones are applied properly, the number of hosts destroyed by a stimulated parasitoid will be about 200, twice the number reported earlier, thus fewer parasitoids will be needed to regulate an estimated population of the hosts.      

Interactive behavior ofOrius insidiosus [Hem.: Anthocoridae] andSericothrips variabilis [Thys.: Thripidae]: Predator searching strategies and prey escape tactics

The searching strategies ofOrius insidiosus (Say) exposed to various densities of the soybean thrips,Sericothrips variabilis (Beach), were observed on soybean trifoliolates under laboratory conditions. The effects of prey density on the predator's searching speed and feeding time were evaluated. Predator searching speed and feeding time per soybean thrips declined with increases in prey density. The greatest number of predator-prey encounters occurred on the upper midrib of the soybean trifoliolate. Adult soybean thrips were captured in 45 and 56% of their total encounters with adult male and femaleO. insidiosus, respectively. Running was found to be the primary escape tactic used by soybean thrips in response to attack byO. insidiosus.

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Résumé Les stratégies de recherche deOrius insidiosus (Say) exposé à des densités variées de thrips du soja,Sericothrips variabilis (Beach), furent observées sur du soja à 3 folioles en laboratoire. Les effets de la densité de la proie sur la vitesse de recherche et sur le temps nécessaire au prédateur pour se nourrir furent évalués. La vitesse de recherche et le temps de nourriture du prédateur sur le thrips du soja déclinèrent avec l'accroissement de la densité de la proie. Les rencontres prédateur-proie eurent lieu dans leur majorité dans la partie supérieure de la nervure du soja. Les thrips du soja adultes furent capturés respectivement dans 45 et 65% du total de leurs rencontres avec des males et des femelles adultesO. insidiosus. Courir s'est avéré être la tactique primaire de fuite utilisée par les thrips de soja en réponse aux attaques deO. insidiosus.

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This paper (No. 80-7-204) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

Gryon gnidus,a scelionid egg-parasite ofAcanthomia tomentosicollis [Hem.: Coreidae] in Nigeria

Gryon gnidus Nixon (Hym.: Scelionidae) is an egg-parasite of the pigeon pea coreid,Acanthomia tomentosicollis Stål in Nigeria. The life-cycle is completed in 8–14 days. The parasite is solitary and levels of parasitism in the field vary between 0% and 69%. The parasite is highly host-specific and eggs of other legume-infesting coreids includingAcanthomia horrida Germ.,Anoplocnemis curvipes F.,Mirpeurus torridus Westw., andRiptortus dentipes F. are not attacked. High levels of parasitism were recorded and parasite population build-up followed the trend of host population levels but did not prevent the host populations from reaching economic injury levels.     

The cactus mealybugHypogeococcus festerianus [Hem.: Pseudococcidae] an agent for the biological control ofEriocereus martinii [Cactaceae] in Australia

The mealybugHypogeococcus festerianus (Lizer y Trelles) infests cacti in Northern Argentina and Paraguay, causing deformed and distorted growth of attacked plants. Laboratory studies and field observations demonstrate that it will only infest plants in the sub-familyCereanae of theCactaceae. Its liberation in Queensland, Australia, for the control ofEriocereus spp., was approved in October 1974, and it has since established widely.

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Résumé La cochenille farineuseHypogeococcus festerianus (Lizer y Trelles) infeste les cactus dans le nord de l’Argentine et le Paraguay, causant chez ces plantes, des déformations et une croissance anormale. Les observations faites dans la nature et en laboratoire montrent qu’elle s’attaque exclusivement aux plantes de la sous-famille desCereanae de la famille desCactaceae. Son introduction en Australie a été approuvée en octobre 1974, et elle s’est largement établie depuis.

     

A note onSaissetia privigna [Hem.: Coccidae] in Pakistan and the breeding of its natural enemies

During a survey for the parasites and predators ofSaissetia privigna De Lotto, 4 additional species of natural enemies, namelyAnysis saissetiae (Ashm.),Metaphycus citricola Annecke & Mynhardt,Eublemma sp. andPullus coccidivora Ayyar were recorded in Pakistan.Aneristus ceroplastae How. andEncyrtus lecaniorum Mayr, which are known to be important parasites of this scale, were bred onS. privigna andPulvinaria sp. cultured on fruits ofCucurbita maxima in the laboratory.A. ceroplastae was introduced into France and proved useful in controllingCeroplastes rusci (L.) on citrus.

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Résumé Au cours d'une campagne de recherche de parasites et prédateurs deSaissetia privigna De Lotto au Pakistan, on a trouvé 4 espèces supplémentaires d'ennemis naturels;Anysis saissetiae (Ashm.),Metaphycus citricola Annecke & Mynhardt,Eublemma sp. etPullus coccidivora Ayyar.Aneristus ceroplastae How. etEncyrtus lecaniorum Mayr, connus comme parasites importants de cette cochenille, ont été élevés surS. privigna etPulvinaria sp. multipliés en laboratoire sur des fruits deCucurbita maxima. A. ceroplastae a été introduit en France et s'est révélé efficace pour la lutte contreCeroplastes rusci (L.) sur citrus.

     

The introduction and establishment of parasites of citrus blackfly,Aleurocanthus woglumi in Florida [Hem.: Aleyrodidae]

Three species of laboratory-reared parasites of citrus blackfly,Aleurocanthus woglumi Ashby, were released at Fort Lauderdale, Florida in 1976 following discovery of this citrus pest in residential properties there.Amitus hesperidum Silv. andProspaltella opulenta Silv. were recovered 6 weeks after release and sharp increases in the rate of parasitism were observed throughout the season. Seven months after the initial release, 100% parasitism of citrus blackfly pupae was observed at some release sites, and 95% of the original release sites were found positive for the parasite. Observations after 1 year showed significant levels of parasitism over a large area. The rapid establishment and increase of these parasite species indicate that environmental conditions and the host at Fort Lauderdale are suitable for these species and that they may well provide control of the pest.     

Greenbugs [Hom.: Aphididae] forced from host plants byLysiphlebus Testaceipes [Hym.; Braconidae]

In a laboratory study 150 sorghum plants were infested with greenbugs,Schizaphis graminum (Rondani), of ages 1, 3, and 5 days in densities of 5, 10, and 20 aphids per plant. Seventy-five of these infested plants were exposed to mated femaleLysiphlebus testaceipes (Cresson), and the number of aphids leaving each plant in a 4-hr period was recorded. Of the 75 plants exposed to parasitoids, an average of 41.0% of the aphids left the plants, compared to 0.9% from the 75 control plants. Twenty-six of the 75 parasitoids used in the experiment were inactive in the presence of aphids, showing no interest in searching for hosts. The number of inactive parasitoids was inversely related to the number of aphids per plant. When only those plants exposed to active parasitoids were considered, an average of 62.8% of the aphids left. To determine the fate of greenbugs leaving plants on hot, sunny, summer days, a small field test was performed in which greenbugs were knocked from plants onto soil exposed to direct sunlight. Air temperature was ca. 29°C and soil temperatures ranged from 45°C to 54°C. Twenty-four greenbugs were knocked to the soil, and all of them ceased activity within 10 seconds and were apparently dead.     

Life cycle and host specificity of the heliotrope weevil,Pachycerus cordiger (=Madidus auct.) [Col.: Curculionidae]

Pachycerus cordiger Germar (Curculionidae: Cleonini) is a potential agent for the biological control ofHeliotropium europaeum L. (Boraginaceae) in Australia. Adults feed on the leaves and larvae feed on the main roots of the weed within an earthen cell. These is one generation per year. Adults overwinter in the cells before emerging in late spring when they begin to feed, mate and oviposit on their host plants from late May until late July. Seven Boraginaceae and 31 economically important crop species were tested using adults and 1^st instar larvae.P. cordiger was found to be specific to the Boraginaceae. Field observations strongly suggested that the weevil is restricted to summer-annualHeliotropium species. A widespread egg parasite,Caenocrepis? bothynoderi Gromakov [Hymenoptera: Pteromalidae], caused up to 18% mortality.     

A new host record forTachinaephagus zealandicus [Hym.: Encyrtidae]

Tachinaephagus zealandicus Ashmead was reared from puparia ofProtocalliphora n. sp. [Dip.], representing a new host record for this parasitoid. The habitat ofProtocalliphora is qualitatively different than those of all previously recorded hosts for this parasitoid.T. zealandicus has been imported from Australia and New Zealand and this record strengthens the belief that it has become established in California.     

Life tables and intrinsic rate of natural increase ofPediobius furvus [Hym.: Eulophidae] onChilo partellus [Lep.: Pyralidae]

In the present studies, life table data and intrinsic rate of natural increase (r_m) of the eulophid pupal parasitoid,P. furvus (Gahan) were obtained fromChilo partellus (Swinhoe) at a constant temperature of 26.7±0.6°C, 52.3±2.7% RH in the laboratory. Development of immature stages took 19.1±0.3 days; adult females lived for 7.9±3.3 (range, 2–13) days and produced a mean of 91.9±22.4 progeny per female, with a sex ratio of 1:2.9 (♂:♀). The intrinsic rate of natural increase (rm) was 0.2558/female/day; the net reproductive rate (R₀), 237.25; the capacity for increase (r_c) of 0.252; and the finite rate of increase (λ) of 1.29/female/day; thus, each female contributed 231.42 individuals to the population in a mean generation time of 21.38 days.      

Effect of parasitism byAscogaster reticulatus [Hym.: Braconidae] on growth of the host,Adoxophyes sp. [Lep.: Tortricidae]

The developmental interaction between the egg/larval parasitoid,Ascogaster reticulatus Watanabe (Hymenoptera: Braconidae) and its host,Adoxophyes sp. (Lepidoptera: Tortricidae) was examined. Prior to the egress of a final-instar parasitoid larva from the 4^th-instar host larva, host weight decreased by 22% from the maximum weight. The final body weight of a host larva was 27% of the maximum weight of a healthy 5^th-instar host. Food consumption was significantly reduced in both 3^rd-and 4^th-instar parasitized larvae compared with healthy ones. In the 4^th instar, a parasitized larva consumed 28% less artificial diet and produced less frass than a healthy larva. The growth rate of the endoparasitoid larvae greatly increased after their host's molt to the 4^th instar. Parasitoid larval volume increased 40 fold in the 4^th-instar host.      

Synchrony and impact ofAmitus hesperidum [Hym.: Platygasteridae] on its host,Aleurocanthus woglumi [Hym.: Aleyrodidae] in southern Florida

The synchrony of the citrus blackfly (CBF)Aleurocanthus woglumi Ashby and its parasitoidAmitus hesperidum Silvestri was studied in southern Florida.A. hesperidum adults emerge from 4th instar nymphs 160–300 thermal units after CBF adults. This insured excellent temporal synchronization between the parasitoids and the early CBF instars they prefer since egg to 3rd instar nymph in CBF takes 380 thermal units. AlthoughA. hesperidum parasitized only 29% of the surviving 4th instar CBF, it was the factor responsible for the observed decline in the CBF population level in southern Florida.