Action competitive d'helisoma duryi,wetherby (Planorbidae : Helisomatinae) a l'egard de divers mollusques vecteurs de trematodoses humaines et animales. I. Biomphalaria glabrata,say

Laboratory experiments indicate that Helisoma duryi may be a promising biological control agent of human Schistosomiasis by acting as a predator of very young Biomphalaria glabrata and, when the two planorbid snails are maintained together, in influencing infection rate of Biomphalaria by miracidia of Schistosoma mansoni and their cercarial production.(avec la collaboration technique de R. THOMASSET)     

Studies on the interspecific competition between Helisoma duryi (wetherby) and Biomphalaria camerunensis (boettger). Size-weight relationships and laboratory competition experiments

Biological control of the intermediate hosts of schistosomiasis by means of the introduction of a competitor snail Helisoma duryi has been suggested. In the present laboratory studies the allometric size-weight relationships of H. duryi and Biomphalaria camerunensis were investigated in order to get a tool for estimating the biomass and dry-weight of snails.Competition experiments were conducted and the results showed a marked inhibition of growth and reproduction of B. camerunensis. No conclusions about the competitive interactions were drawn from the present results but experiments are established to elucidate these mechanisms.     

The effect of temperature,darkness, starvation and various food types on growth,survival and reproduction of Helisoma duryi,Biomphalaria alexandrina and Bulinus truncatus (Gastropoda: Planorbidae)

Helisoma duryi has been proposed as a biological control agent in schistosomiasis due to its superiority in laboratory competition experiments with various species of the intermediate host snails. Therefore it was considered important to evaluate the response of this snail species and the intermediate host species, Biomphalaria alexandrina and Bulinus truncatus, to various physical, chemical and biological factors under laboratory conditions in order to obtain information on the similarities in the ecological niches of these species. The factors considered in the present paper are: temperature, darkness, starvation and food. All three species had optimal growth and egg laying at 26–28 °C. Only H. duryi survived for a longer period at 33°C and it was capable of starting egg laying at this temperature although the onset was delayed. However, low temperature (18°C) caused a relatively larger decrease in egg laying of H. duryi than in the other two species. Growth and egg laying was reduced for H. duryi and B. truncatus kept under darkness and B. alexandrina could not tolerate maintenance under darkness. A few days of starvation of juvenile snails had no effect on later growth and egg laying capacity of the survivors, although mortality in B. truncatus was increased. B. alexandrina had a lower tolerance to starvation than the other two species. Egg laying of snails fed only one of the three laboratory food types decreased for all three species in the order: Vov-vov (dog food in dry pellets), Tetramin (fish food) and lettuce. Combinations of lettuce and one or more proteinaceous food types gave optimal growth and egg laying for all three species.     

The evolution of phally polymorphism in Bulinus truncatus (Gastropoda,Planorbidae): the cost of male function analysed through life-history traits and sex allocation

In the hermaphrodite freshwater snail Bulinus truncatus, two sexual morphs, euphallic (regular hermaphrodites) and aphallic individuals without a male copulatory organ, co-occur at various ratios in natural populations. Both aphallic and euphallic individuals can reproduce by selfing, but when outcrossing aphallic individuals can only play the female role. A comparison of life-history traits and sex allocation in these two forms provides the opportunity to investigate the evolution and maintenance of sexual polymorphisms. This study was performed to test whether a reallocation of resources from the lost male function to the female function occurs in aphallic snails at the level of both sex organs (sex allocation) and life-history traits. In a first experiment we compared life-history traits over a whole life-cycle under selfing between the two sexual morphs. In a second experiment, the sex organs were weighed to test for a difference in sex allocation between the two morphs. No difference in resource allocation to female function between the two morphs was observed in either experiment. This is in contrast to patterns frequently observed in sexually polymorphic plants, and in a previous study performed on aphally in the same snail species. We discuss the genetic and physiological hypotheses that could explain these results, and their consequences for the evolution and maintenance of phally polymorphism in B. truncatus.     

Etude enzymologique comparee de souches de aspergillius fumigatus et de a. Fischeri d'origine saprophytique ou isolees de lesions humaines ou animales. Repercussions pratiques d'ordre diagnostique

Resume 14 activités enzymatiques (3 deshydrogénases et 11 hydrolases) ont été recherchées systématiquement sur les électrophorégrammes en gel d'agar des extraits de 2 souches de Aspergillus fischeri et de 14 souches de A. fumigatus (8 isolées de lésions humaines ou animales intitulées souches pathogènes, et 6 souches d'origine saprophytique). La composition enzymatique de A. fumigatus est apparue très polymorphe et sans rapport avec l'origine des souches.D'autre part, l'analyse immunoélectrophorétique de ces extraits antigéniques, par des sérums de lapins hyperimmuns et des sérums de malades atteints d'aspergillose, a montré que l'activité chymotrypsique de type II, supportée par l'arc C, est caractérisée de manière plus fréquente et plus intense lorsque les antigènes provenant de souches pathogènes sont opposés à des sérums de malade.De plus, si cette activité chymotrypsique est révélée avec la même fréquence par une souche saprophyte et une souche pathogène, le nombre de précipitines mises en évidence est apparu significativement plus élevé avec cette dernière.Les antigènes utilisés pour le diagnostic de précipitation en gel devraient donc être, de préférence, extraits de souches pathogènes et leur qualité évaluée par des sérums de malades atteints d'aspergillose.     

Further laboratory studies on the interspecific competition between Helisoma duryi (Wetherby) and the intermediate hosts of schistosoma mansoni sambon: Biomphalaria alexandrina (Ehrenberg) and B. camerunensis (Boettger)

Biological control of schistosomiasis by means of introduction of a competitor, Helisoma duryi, of the intermediate host snails has been proposed. In the present laboratory studies the competitive relationships between H. duryi and two Biomphalaria species were investigated both when direct interference between the two competing species was possible and when not. A reduction of growth and reproduction of Biomphalaria was found when direct interference was involved but the effect of competition was lessened when the two species were separated by a mesh.The data showed that despite continuous presence of food in the aquaria food competition was involved in the direct interference between the two species, while the role of chemical interactions could not be evaluated conclusively from the present experiments.The role of food is discussed.     

Karyological Studies of Biomphalaria tenagophila (d'Orbigny, 1835) (Gastropoda: Planobidae) from Rio de Janeiro,Brazil

The karyotypes of Biomphalaria tenagophila collected from Rio de Janeiro, Brazil were studied using the air-drying method. Somatic cells of this species had 2n=36. The 18 chromosome pairs were identified and classified into 3 groups. The diploid cell has 7 pairs of metacentric, 8 pairs of submetacentric, and 3 pairs of subtelocentric chromosomes. Observed chromosomes ranged from 2.4 to 6.4 µm, and the total length was 122.3 µm. This is the first report on the chromosome of B. tenagophila.     

Host specificity ofPareuchaetes insulata (Lep.: Arctiidae), a biological control agent forChromolaena odorata (Compositae)

Larvae of the arctiid moth,Pareuchaetes insulata, from Florida fed on the leaves ofChromolaena odorata, a serious composite, alien weed in Natal, South Africa. In starvation test trials using 48 plant species,P. insulata completed its development onC. odorata andAgeratum houstonianum. Subsequent attempts to cultureP. insulata on these two plants was only successful onC. odorata. The biology ofP. insulata is similar to that of two other well studiedPareuchaetes species namelyP. pseudoinsulata andP. aurata aurata. Repeated defoliation ofC. odorata byP. insulata could contribute to its control as has been found withP. pseudoinsulata in Guam.Pareuchaetes insulata has been approved for release as a biological control agent ofC. odorata in South Africa.     

Predation rates,survivorship and development ofPodisus maculiventris (Het.: Pentatomidae) on larvae ofLeptinotarsa decemlineata (Col.: Chrysomelidae) andPieris brassicae (Lep.: Pieridae), under field conditions

The mean predation rate per day and the effect of the prey on the development and survival of the various nymphal stages ofPodisus maculiventris (Say) were studied under field-cage conditions. Third instar larvae of the Colorado potato beetleLeptinotarsa decemlineata (Say) and the large white butterflyPieris brassicae (Linnaeus) were used as the prey. The results show that under climatic conditions similar to those occurring in the Thessaloniki region (N. Greece), the 5^th instar nymphs and the adults of the predatorP. maculiventris would be promising agents for the biological control of larvae ofL. decemlineata andP. brassicae.

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Résumé Des recherches de terrain ont été menées afin d'étudier le degré de prédation journalier et l'effet de la proie sur le développement et la survie des différents stades nymphaux deProdisus maculiventris Say en présence de larves du 3^e stade deLeptinotarsa decemlineata (Say) et dePieris brassicae (Linnaeus). Les résultats obtenus montrent que les nymphes du 5^e stade et les adultes du prédateur ont une importante activité prédatrice avec un taux de survie élevé quand ils se nourrissent aux dépens de larves du doryphore ou de la Piéride du chou. Par conséquent, il est très probable quePodisus pourrait être utilisé contre ces ravageurs dans des zones où les conditions climatiques sont proches de celles de la région de Thessaloniki (Grèce du Nord).

     

Host range ofPachycerus cordiger (=P. Scabrosus) (Col.: Curculionidae)

The univoltine weevilPachycerus cordiger Germar (=P. scabrosus Brullé) completes its life cycle on species of Boraginaceae, it is found from western Europe to the Middle East. In southern France, adultP. cordiger were collected feeding on the leaves ofHeliotropium europaeum L.,Echium vulgare L. andCynoglossum creticum Miller, whereas larvae were found feeding externally on the roots of the three plant species from within an earthen cell. BecauseP. cordiger is considered too much of a generalist to be released in Australia, work on the weevil as a potential biological control agent ofH. europaeum has been stopped.     

Action de pesticides chez des insectes en fonction de leur etat physiologique: Etude de 2 insecticides et d'un melange d'herbicides chez les larves aquatiques de cloeon. (Ephemeropteres).

For the larvae of the ephemeron Cloeon, our studies of acute toxicity show that the degradation products of fenthion are more toxic than the insecticide itself.Doses of fenthion and lindane, responsible of a hight mortality, lead to a decrease in the moulting frequency of these larvae. A mixture of herbicides and degradation products of fenthion gave different results.

     

Isolation of Beauveria bassiana and Metarhizium anisopliae var. anisopliae from Boophilus microplus tick (Canestrini, 1887), in Rio de Janeiro State,Brazil

The objective of this work were to isolate and identify strains of entomopathogenic fungi from ingurgitated female Boophilus microplus ticks, collected from the soil in the municipality of Paracambi, Rio de Janeiro State, Brazil. The ingurgitated females were inoculated in the selective medium oat dodine agar (oda), where 49 colonies of Beauveria bassiana (71%) and 20 of Metarhizium anisopliae var. anisopliae (29%) were isolated. These isolated strains characterize for the first time in Brazil the natural occurrence of these species of fungi in this tick, and will be used to conduct bioassays to evaluate the pathogenicity and virulence of these strains for ticks of the genus Boophilus microplus. This revised version was published online in June 2006 with corrections to the Cover Date.     

Biological control of alligatorweed (Alternanthera philoxeroides) with a Fusarium sp.

Alligatorweed (Alternanthera philoxeroidesG.) has become a serious weed in different crops in China. A fungal pathogen was found in Chongqing and Sichuan Provinces and was identified as a species in the Fusarium genus. The fungus produced macroconidia and chlamydospores abundantly on potato sucrose agar (PSA) plates. The bestconidial production and germination and colonygrowth of Fusarium sp. were at 23–31°C and pH 6.7–7.0. Light period and flooding did not affect fungal growth and conidium formation. The herbicides, glyphosate and paraquat, inhibited the fungal development in vitro. The fungus did not affect seed germination and seedling growth of paddy rice, wheat, maize, oilseed rape and broad bean inlaboratory or greenhouse trials. Inoculum density and wetness duration influenced the efficiency of Fusarium sp. to control alligatorweed; a concentration of 1.0 × 10⁵ spores^–1 ml and 12 h of high humidity duration after inoculation produced goodinfections on the weed at 23°C in the laboratory. When the fungus was applied to alligatorweed grown in greenhouse and in the field, good biocontrol efficiency was obtained: the plants started to wilt after four to five (greenhouse) or six days (field), and were killed 9–10 (greenhouse) or 13–14 (field) days after spraying the fungal inoculum. This was similar to the control efficiency resulting from glyphosate treatment. Therefore, this Fusarium sp. appeared to be a good candidatefor further studies and a promising biocontrol agent to manage alligatorweed in some terrestrial and aquatic crops.     

Successful colonization ofEretmocerus debachi (Hym.: Aphelinidae) in the eastern mediterranean citrus region of Turkey

The whitefly,Parabemisia myricae (Kuwana) is one of the most serious citrus pests in the Eastern Mediterranean region of Turkey. In 1986, a host-specific parasitoid ofP. myricae, the aphelinidEretmocerus debachi Rose and Rosen, was imported from California to Turkey and released into citrus orchards along the Eastern Mediterranean coast. In the following yearsP. myricae-populations were rapidly reduced from about 17 whitefly-immature stages per leaf to less than 0.1 stages per leaf in all citrus orchards where the parasitoids were released. Furthermore,E. debachi was shown to be a good disperser and it is well adapted to the climatic conditions in the Eastern Mediterranean region. Since the successful colonization ofE. debachi, the whitefly is no longer a serious pest and it is difficult to find unparasitized individuals in the Eastern Mediterranean region of Turkey.     

Short-distance dispersal behavior and establishment of the parasitoid Gonatocerus ashmeadi (Hymenoptera: Mymaridae) in Tahiti: Implications for its use as a biological control agent against Homalodisca vitripennis (Hemiptera: Cicadellidae)

The egg parasitoid Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae), was introduced into French Polynesia as a biological control agent to control the invasive plant feeding pest Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). The short-distance dispersal of G. ashmeadi was monitored as part of the biological control program. G. ashmeadi showed exponential dispersal capacity with 47 m/day being a minimum estimate of its natural rate of spread at high host densities (>150 nymphs per minute of sweep net sampling) in urbanized areas at sea level, which were characterized by a high diversity of exotic ornamental plants. This rate of spread contrasted starkly with almost nonexistent establishment and dispersal where host densities were very low (<2 nymphs per minute of sweep net sampling) at high elevation (800 m) with relatively undisturbed native vegetation. Survey results across different altitudes revealed an effect of vegetative diversity and host density on the measurable mobility and establishment of G. ashmeadi. In contrast, no significant influence of wind direction was found on G. ashmeadi dispersal rate or direction. Survey results for G. ashmeadi from French Polynesia suggest that the best release establishment strategies for classical biological control of H. vitripennis are: (1) many small releases where host density is high, or (2) larger and fewer releases where host densities are low.     

Searching and Oviposition Behavior of Anagrus atomus L. (Hymenoptera: Mymaridae) on Four Host Plants of Its Host, the Green Leafhopper Empoasca decipiens Paoli (Homoptera: Cicadellidae)

Anagrus atomus L. is an important egg parasitoid of the green leafhopper Empoasca decipiens Paoli. In this study the ability of the parasitoid to locate and parasitize its host was investigated on four host plants, i.e., broad beans (Vicia faba L.), sweet pepper (Capsicum annuum L.), cucumber (Cucumis sativus L.), and French beans (Phaseolus vulgaris L.). For each plant species, the behavior of the parasitoid was observed on E. decipiens infested and noninfested plants. Searching and oviposition behavior were characterized by drumming, probing, and resting. Parasitoids spent significantly less time on non-infested than infested plants, 274.5 and 875.7 s, respectively, and no probing behavior was observed on non-infested plants. Frequency of resting behavior was significantly greater on non-infested than on infested plants. Total foraging time was significantly longer on infested than on non-infested plants, indicating that A. atomus females can efficiently discriminate between leaves with and without infestation. Parasitism of A. atomus was influenced by parasitoid density, with the highest parasitism rate (64.0%) obtained at a density of 10 A. atomus females/0.1356 m² but the number of parasitized eggs per female and the searching efficiency decreased with increasing parasitoid density.     

Host Specificity of the Argentine Root-Boring Weevil, Heilipodus ventralis (Coleoptera: Curculionidae), a Potential Biocontrol Agent for Snakeweeds (Gutierrezia: Asteraceae) in Western North American Rangelands—U.S. Quarantine Tests

Native snakeweeds, especially Gutierrezia sarothrae (Pursh) Britton and Rusby and Gutierrezia microcephala (DC.) A. Gray, are among the most widespread and damaging weeds of rangelands in the western United States and northern Mexico. The genus long ago spread to southern South America, where further speciation occurred. We have found several species of insects in Argentina that damage other species of snakeweeds there and are possible candidates for biological control in North America. The first of these, the root-boring weevil, Heilipodus ventralis (Hustache), was tested in Argentina and then sent to the USDA-ARS Insect Quarantine Facility at Temple, Texas, for host specificity testing on North American plants. We tested H. ventralis on 40 species of the family Asteraceae, in 19 tests of five types, using 686 adults and 365 larvae. Host specificity increased from adult feeding, to ovipositional selection, to larval development. At Temple, adults fed mostly on 6 species of the closely related genera Grindelia, Gutierrezia, and Gymnosperma, but with substantial feeding on four other genera of the two preferred subtribes Solidagininae and Machaerantherinae and on Baccharis in the tribe Baccharidinae, with lesser feeding on the subtribe Asterinae, all in the tribe Astereae, and on 1 species in the tribe Anthemideae. Females oviposited primarily on the same 6 species but very little on plants outside the 2 preferred subtribes. Larvae developed only on 9 of the 29 U.S. plant species tested, 6 within the two preferred subtribes and on Brickellia and Aster in other tribes. Only 5 species of three genera appear to be potential true hosts of H. ventralis in North America, on which all stages of the life cycle, adult feeding, oviposition, and larval development, can take place; these are Gymnosperma glutinosum (Spreng.) Less., Gutierrezia grandis Blake, Gut. microcephala, Gut. sarothrae, and Grindelia lanceolata Nutt. None of these genera contain species of economic or notable ecological value; the few rare species appear to be protected by habitat isolation from attack by H. ventralis. H. ventralis, therefore, appears sufficiently host specific for field release in North America. This is the first introduced biocontrol agent to be approved for release in a continental area to control a native weed.     

Response of Three Hymenopteran Parasitoids Introduced for Fruit Fly Control to a Gall-Forming Tephritid,Procecidochares alani(Diptera: Tephritidae)

The response of three larval–pupal parasitoids,Diachasmimorpha longicaudata(Ashmead),Diachasmimorpha tryoni(Cameron), andTetrastichus giffardianusSilvestri, to the Hamakua pamakani gall fly,Procecidochares alaniL., was determined in the laboratory. We also observed responses of these parasitoids to their normal rearing hosts,Bactrocera dorsalis(Hendel) andCeratitis capitata(Weidemann).D. tryonilanded on pamakani galls or on dishes containingP. alanilarvae as frequently as on dishes containingC. capitata.In contrast,D. longicaudataonly rarely landed on the galls.D. tryoniandD. longicaudataoviposited in galls in fewer than 1% of our observations.D. longicaudataprobedP. alanilarvae as frequently asB. dorsalislarvae, but no parasitoid offspring were observed.D. tryonioviposited more frequently inC. capitatathanP. alani.NoD. tryonideveloped inP. alanilarvae.T. giffardianuslanded on pamakani galls andP. alanilarvae more frequently than any other host substrate. In contrast,T. giffardianusentered galls with artificially opened windows one time in 10 observations. We observed 12% parasitism ofP. alanilarvae dissected from the galls and 20% of parasitismP. alaniin the windowed galls. We discuss the implications of our results for future augmentative or classical biological control studies.     

Host-specificity of a root borer,Bembecia chrysidiformis [Lep.: Sesiidae], a potential control agent forRumex spp. [Polygonaceae] in Australia

Bembecia chrysidiformis (Esper) [Lep.: Sesiidae] was examined for its natural history and specificity toRumex spp. (Polygonaceae) which are weeds in Australia. Adults of this southern European insect appear in late spring to summer. Eggs are laid on the dried, seed bearing stems of perennialRumex plants. The larvae tunnel inside the root during summer through to the next spring. In nature, the larvae are round inRumex species of the subgeneraRumex andAcetosa. In host-specificity tests with 1st instar larvae, the roots of a number of genera within thePolygonaceae were attacked. Larvae died on a range of plants from other families except inPersea americana Miller(Lauraceae), Helianthemum nummularium (L.) Miller (Cistaceae) andQuercus ilex L. (Fagaceae) where larvae fed on the stems. The insect was judged safe for release in Australia by assessing aspects of its biology, its known host plants, and the lack of reported attack on other plants.      

Allorhogas pyralophagus [Hym.: Braconidae], a gregarious external parasite imported into texas,USA, for biological control of the stalkborerEoreuma loftini [Lep.: Pyralidae] on sugar cane

Allorhogas pyralophagus Marsh is a recently discovered doryctine braconid with potential for field trials against stalk borers infesting both large- and small- stemmed Graminacea. This external gregarious parasite was originally reared fromEoreuma loftini (Dyar) larvae infesting Johnson grass [Sorghum halepense (L.) Pers.] and sugar cane (Saccharum officinarum L.) from the states of Sinaloa and Nuevo Leon, Mexico. The parasite is easily reared in the laboratory using a wide range of host larvae [Diatraea spp.,E. loftini, Chilo sp. andTryporyza nivelli (F)]. Hosts are placed in grass stems or paper straws for exposure to ovipositing females.A. pyralophagus has been field released and recovered from the following hosts infesting sugar cane:E. loftini andD. saccharalis (F.) in Texas.Diatraea spp. in Trinidad,D. rufescens in Bolivia andT. nivella in Sumatra, Indonesia. Approved as Contribution No. TA-20743 of the Texas Agricultural Experiment Station.