Prospects for biological control of teasels,Dipsacus spp., a new target in the United States

Two closely related teasels (Dipsacales: Dipsacaceae, Dipsacus spp.) of European origin have become invasive weeds in the United States. Common teasel (Dipsacus fullonum L.) and cutleaf teasel (Dipsacus laciniatus L.) have likely been in North America for more than two centuries, having been introduced along with cultivated teasel [D. sativus (L.) Honckney], an obsolete crop plant. There are few records of American insects or pathogens attacking Dipsacus spp. Invasive teasels have recently begun to spread rapidly throughout much of their current range, for reasons that are not yet known. Common and/or cut-leaf teasel have been listed as noxious in five US states and as invasive in 12 other states and four national parks. Because the family Dipsacaceae is an exclusively Old World family, classical biological control is an important component of the overall management strategy of this weed in the US. Field surveys for natural enemies of D. fullonum and D. laciniatus in their native ranges and literature reviews of natural enemies of plants in the family Dipsacaceae have yielded 102 species of insects in six orders, as well as 27 fungi from 10 orders, three mites, one nematode, and two viruses. Due to the biennial nature of these weeds, a strategy to assign highest priority to biological control candidates attacking first-year (rosette) plants has been established. Candidates selected for further study based on this strategy include Chromatomyia ramosa (Hendel) (Diptera: Agromyzidae), Longitarsus strigicollis Wollaston (Coleoptera: Chrysomelidae), Epitrimerus knautiae Liro (Acarina: Eriophyiidae), Euphydryas desfontainii (Godart) (Lepidoptera: Nymphalidae), Erysiphe knautiae Duby (Erysiphales: Erysiphaceae), and Sphaerotheca dipsacearum (Tul. and C. Tul.) (Erysiphales: Erysiphaceae).     

Allantus luctifer (Hymenoptera: Tenthredinidae), a candidate agent for the biological control of Rumex spp.

The dock plant (Rumex spp.) is one of the most problematic pasture weeds worldwide. Allantus luctifer was selected as a potential biological control agent for Rumex spp. Continuous rearing of A. luctifer was carried out from 2005 to 2006, and its general biology is presented in this report. The preliminary host specificity test showed a promising result for using A. luctifer to control Rumex spp.     

Dispersal strategies of Aceria guerreronis (Acari: Eriophyidae), a coconut pest

The dispersal of plant-feeding mites can occur involuntarily, through transportation of infested plant parts, or voluntarily, by walking to new plant parts or to suitable spots where biotic (phoresis) or abiotic (wind, agricultural tools, etc.) factors carry them over long distances. Elucidating the dispersal mechanisms of the coconut mite, Aceria guerreronis Keifer, is important for understanding the process of colonization of new fruits of a same or different plants, essential for the improvement of control strategies of this serious coconut pest. Thus, the objective of this work was to investigate the voluntary dispersal mechanisms of this mite. The hypothesis that the coconut mite disperses by walking, phoresis or wind were tested. The coconut mite was shown to be able to walk short distances between fruits of the same bunch or between bunches of the same plant. Phoresis on insects of the orders Hymenoptera (Apidae), Coleoptera (Curculionidae) and Lepidoptera (Phycitidae) was evaluated in the laboratory and in the field. Although in the laboratory mites were shown to be able to climb onto honeybees, field investigations failed to show these insects as important carriers of the pest, corroborating findings of previous works; however, both laboratory and field investigations suggested the curculionid Parisoschoenus obesulus Casey to be able to transport the coconut mite between plants. Similarly, laboratory and field investigations suggested wind to be important in the dispersal of the coconut mite between plants.     

Strategies for the biological control of invasive willows (Salix spp.) in Australia

Abstract  Willows ( Salix spp.) are Weeds of National Significance in Australia where a large number of taxa are naturalised in temperate regions and can cause serious environmental degradation of riparian and wetland habitats. Several species are of economic or ornamental value and conflicts of interest could arise with planning their suppression. Biological control of six willow species ( S. alba L., S. cinerea L . , S. fragilis L., S. nigra Marshall, S. viminalis L., S . x  rubens Schrank) is under consideration in Australia using three approaches based on targeting different morphological structures. A rich phytophagous biota associated with Salix in their regions of origin indicate a range of organisms are available for development as biological control agents. Implementation strategies will depend on the host species targeted for biological control, their reproductive strategies, the level of control required to reduce environmental impacts and the level of conflict of interest associated with a biological control program.     

Biology of Amblyseius largoensis (Muma) (Acari: Phytoseiidae), a potential predator of Aceria guerreronis Keifer (Acari: Eriophyidae) on coconut trees

Aceria guerreronis Keifer is considered one of the main pests of coconuts around the world. Amongst the Phytoseiidae recorded on this crop, Amblyseius largoensis (Muma) has been reported in association with A. guerreronis. In order to verify whether A. largoensis feeds on A. guerreronis, the biology of this predator was evaluated on different food sources, including A. guerreronis. Three types of diet were tested [Tetranychus urticae Koch + castor bean (Ricinus communis L.) pollen + honey at 10%, A. guerreronis + pollen + honey, and only A. guerreronis], determining its development, survivorship, oviposition, sex ratio and longevity at 27 degrees C, 60 +/- 5% RH 12 h photophase. Fertility life tables were constructed. The duration of the immature phase was lower when feeding only on A. guerreronis, while fecundity was higher when feeding on a prey + pollen + honey. There was no difference in relation to survivorship of the immature stages between the three diets. Parameters of fertility life tables were higher when the diet included A. guerreronis or T. urticae + pollen + honey, although the predator was able to complete its life cycle and reproduce when feeding exclusively on A. guerreronis. The results suggest that A. largoensis preys upon A. guerreronis under natural condition and that it might play some role in the control of the latter.     

Micro-morphological alterations in young rosette leaves of Dipsacus laciniatus L. (Dipsacaceae) caused by infestation of the eriophyid mite Leipothrix dipsacivagus Petanovic et Rector (Acari: Eriophyoidea) under laboratory conditions

The present study describes micro-morphological and histological changes to rosette leaves of the native Eurasian plant species Dipsacus laciniatus (Dipsacaceae) provoked by infestation of the eriophyid mite Leipothrix dipsacivagus Petanovic et Rector. Conspicuous injuries to the leaf tissue were induced by mites feeding on leaves of D. laciniatus rosettes that were propagated from seed under laboratory conditions. Anatomical injuries extended into epidermal cells on the upper and lower leaf surface as well as to the mesophyll layer of infested D. laciniatus leaves. Statistical analysis (by ANOVA and MANOVA) showed significant differences between control and infested plants, particularly in total leaf thickness. The most striking change observed was the decrease in thickness of infested leaves, beginning from the 8th week, associated with the progressive replacement of epidermal cells with an acellular layer. Measures of mite density on test leaves indicated that mites vacated leaves as russeting symptoms intensified. They also appeared to vacate all leaves, whether symptomatic or not, after populations peaked 10–12 weeks after infestation. Comparisons were made between these studies and those on naturally infested, field-collected D. laciniatus plants, as well as with similar studies of other mite-plant interactions.     

Redberry mite, Acalitus essigi (Hassan) (Acari: Eriophyidae), an additional biological control agent for Rubus species (blackberry) (Rosaceae) in Australia

Abstract  Acalitus essigi , the eriophyoid mite that causes red berry disease in Rubus species (Rosaceae), was collected from the fruits of three species of weedy blackberry, R. anglocandicans , R. laudatus and R. ulmifolius , in south-west Australia. This is the first record for this species in Western Australia and these plants appear to be new host records for A. essigi , which causes uneven ripening of fruit. Information on the mite is reviewed in the context of determining its potential as a biological control agent for Rubus species, especially those that are not susceptible to Phragmidium violaceum (Uredinales), the rust fungus being released against species of European blackberry in Australia. Published records also show that A. essigi will attack a wide range of Rubus species including species of North American origin that currently escape biological control in Australia. It may also be useful for preventing the spread of commercial varieties of Rubus (e.g. raspberry and loganberry) that have escaped to become weedy. However, the mite may have limited dispersal ability and thus require redistribution.     

Taxonomy and biological control: Neoseiulus cucumeris (Acari: Phytoseiidae), a case study

The predatory mite Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) is an important biological control agent of thrips and other small pests worldwide. Yet, despite its economic importance, this species is poorly defined taxonomically and cannot be reliably separated from other species on the basis of morphology alone. Neoseiulus cucumeris has been reported from Australia, although considerable confusion exists as to whether the Australian material is actually N. cucumeris or a presumed endemic species, Neoseiulus bellinus (Womersley). A morphological investigation of N. bellinus and several geographical 'strains' of N. cucumeris demonstrated that: (i) N. bellinus is a distinct species, the males of which can be morphologically separated from those of N. cucumeris , using setal and cheliceral lengths and number of teeth on the fixed digit; and (ii) N. cucumeris , or a morphologically identical species, is present in Australia. Despite behavioural differences, there are no significant morphological differences between the 'strains' of N. cucumeris . Biosystematic research is a more reliable method of species separation, and such a method is suggested for future work with phytoseiid mites.     

Diapause in the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae), a biological control agent for tamarisk (Tamarix spp.)

The tamarisk leaf beetle, Diorhabda elongata Brullé deserticola Chen, was collected in northwestern China and has been released in the western United States to control tamarisk (Tamarix spp.). Characteristics of diapause and reproductive development in D. elongata were examined to improve management as a biocontrol agent. Under long days, 16:8 (L:D) h, males began to emit aggregation pheromone within 2-3 d of adult emergence, mating occurred, and females oviposited within 7 d of adult emergence. Under short days, 12:12 (L:D) h, males did not emit pheromone, mating did not occur, and both males and females entered reproductive diapause marked by inconspicuous gonads and hypertrophied fat body. Ovaries of diapausing females lacked vitellogenic oocytes, and the ovarioles were clear and narrow, whereas reproductive females had enlarged ovaries with two to three yellow oocytes per ovariole. Diapausing males had thin, transparent accessory glands and ejaculatory ducts, whereas reproductive males had thick white accessory glands and white opaque ejaculatory ducts. Sensitivity to diapause-inducing photoperiods extended into the adult stage. Reproductive females ceased oviposition, resorbed oocytes, and entered diapause when switched from long to short days. Diapause-destined insects ceased feeding and entered the leaf litter 10-20 d after adult emergence, whereas reproductive insects remained on the plants and fed for at least 30 d. Reproductive insects exhibited dispersal behaviors, such as attempted flights, whereas diapause-destined insects did not show dispersal behaviors. Information gained from these studies will be used to better manage populations in the field and to improve rearing and storage in the laboratory.     

Use of polypropylene bags for mass rearing Neoseiulus baraki (Acari: Phytoseiidae), a predatory mite of Aceria guerreronis Keifer (Acari: Eriophyidae)

An efficient, low cost and practicable mass rearing method for the predatory mite, Neoseiulus baraki Athias-Henriot (Acari: Phytoseiidae) was developed using a bag made of two-ply polypropylene (gauge 150, 24 cm × 36 cm) sheets. Introducing 20 N. baraki females into the bag produced a mean number 5218 ± 212.10 offspring in 6 weeks with a 260-fold increase of the initial population.     

Polyphenic wax production in Abacarus hystrix(Acari: Eriophyidae), and implications for migratory fitness

Abstract. . Wax production in the grass-feeding eriophyid Abacarus hystrix (Nalepa) is seasonally variable; enlarged lateral and dorsal bands of wax filaments develop in adults of summer generations. Wax filaments increase the total surface area of summer-generation mites, without a concomitant increase in cuticular surface-to-volume ratio. Genetic and environmental interactions in changes in the rate of wax production were examined. High temperatures, but not changes in photoperiod, were found to stimulate increased rates of wax production. The degree of wax filamentation was independent of the genetic origin of mites, hence filaments are polyphenic, rather than polymorphic, in origin. The role of wax filaments in the regulation of water-loss and in drag maximization were experimentally investigated. The relative survival of waxed and unwaxed mites was compared at various temperature and humidity combinations, and the influence of wax filaments on surface drag was assessed by comparing the slopes of regression lines of cuticular surface area relative to terminal velocity of waxed and unwaxed mites. Significantly greater survival times in waxed compared to unwaxed mites at low relative humidities suggest mat wax filaments have a function in the regulation of water-loss. Significantly lower mean terminal velocities in waxed mites indicated that total drag relative to cuticular surface area was greater in waxed than unwaxed mites, probably as a result of increased skin friction generated by wax filaments. The increased non-cuticular surface area created by wax filaments may be advantageous during summer-migrations of A.hystrix by increasing wind shear stress on the mites at the leaf margin, enhancing buoyancy while air-borne and reducing the rate of desiccation-induced mortality.     

Pyemotes tritici (Acari: Pyemotidae), a potential biological control agent of Anagasta kuehniella (Lepidoptera: Pyralidae)

The feasibility of utilizing Pyemotes tritici as a biological control agent against the Mediterranean flour moth, Anagasta kuehniella was investigated. The results from experiments designed to assess the effect of P. tritici on cohorts of A. kuehniella of different ages were not significant. They suggested that moth larvae were most severely affected if physogastric P. tritici females were introduced 10 days after moth eggs were added to the experimental arena. In part II, the impact of various densities of P. tritici on flour moths indicated that complete destruction of cohorts of 400 A. kuehniella larvae was achieved by adding about 80 female P. tritici 10 days after the eggs were laid or 6 days after the larvae hatched. Half the above density of pyemotid mites gave inconsistent, but at times complete control.     

Host specificity ofAceria (Eriophyes) malherbe, [Acari: Eriophyidae], a biological control agent for the weed,Convolvulus arvensis [Convolvulaceae]

The host specificity of the gall mite,Aceria (Eriophyes) malherbe (Nalepa), from Greece was studied under quarantine conditions at Albany, California USA. Of the species, ecotypes, or strains tested, onlyConvolvulus andCalystegia spp. supported gall formation and mite reproduction. Although 2 of the native, North AmericanCalystegia species that served as laboratory hosts are threatened or endangered species,A. malherbe is considered safe for release in the USA as a biological control agent of the weed,Convolvulus arvensis (L.).      

Safety assessment and potential of Cecidophyes rouhollahi (Acari, Eriophyidae) for biological control of Galium spurium (Rubiaceae) in North America

Abstract:  Galium spurium L. (Rubiaceae), native to Europe, is an increasingly serious annual weed of cultivated crops in the prairie provinces of Canada. The gall mite Cecidophyes rouhollahi Craemer (Acari, Eriophyidae), originally found on the related plant species Galium aparine L. in southern France, was evaluated as a potential biological control agent for G. spurium . In greenhouse tests, C. rouhollahi caused severe stunting and complete prevention of seed production by G. spurium . Host specificity tests showed that C. rouhollahi developed only on three closely related annual Galium species in the Kolgyda section. No native North American Galium species were attacked, with the exception of G. aparine . A review of available information on G. aparine suggests that it is probably an introduced species in North America. It has been reported that a related gall mite attacking G. aparine might be associated with a plant virus. A series of tests on a greenhouse colony of G. spurium infested with C. rouhollahi showed no evidence of viral infection. On the basis of these results, C. rouhollahi has been approved for field release against G. spurium in Canada.     

Host-range testing of Eucryptorrhynchus brandti (Coleoptera: Curculionidae), a candidate for biological control of tree-of-heaven, Ailanthus altissima

Ailanthus altissima (Mill.) Swingle, tree-of-heaven, is an invasive species native to Asia. It first was introduced into the United States in the 1700 s and now is distributed throughout much of North America. Mechanical and chemical controls are current suppression tactics, however, implementation is costly. A weevil, Eucryptorrhynchus brandti (Harold), was identified in China and imported for quarantine testing in 2004 as a potential biological control agent. Host specificity tests on adult feeding, larval development, and oviposition of this weevil were conducted from 2007 to 2011 on A. altissima and 29 nontarget species. Eucryptorrhynchus brandti adults fed significantly more on A. altissima foliage when compared with all test species. Range of means for feeding on A. altissima was 32.5-106.5 mm(2)/adult/d. In no-choice tests, Simarouba glauca DC, Leitneria floridana Chapm., and Citrus limon (L.) Burm. F., had feeding rates of only 10, 49, and 10%, respectively, compared with the level of feeding on A. altissima. The mean range of adult feeding by E. brandti on all other test species was <7% of feeding on A. altissima (0.0-3.3 ± 5.0 mm(2)/adult/d). In the no-choice larval inoculation tests, larval development only occurred in two of 10 L. floridana seedlings compared with seven of 10 A. altissima seedlings. In the no-choice oviposition tests, oviposition and subsequent larval development did not occur in L. floridiana, whereas all seven A. altissima seedlings supported oviposition and subsequent larval development. The weevil did not appear to be a threat to L. floridana or any other nontarget species tested. Therefore, we conclude that Eucryptorrhynchus brandti is highly host specific to A. altissima.     

Biology ofAllothrombium pulvinum (Acariformes: Trombidiidae), a potential biological control agent of aphids in China

Allothrombium pulvinum Ewing is a common natural enemy of aphids and other small arthropods in China. It is univoltine species. The eggs hatch in spring, nymphs emerge in early summer, and adults emerge in autumn. Larvae are ectoparasites of aphids, whereas deutonymphs and adults are free-living predators of aphids, spider mites and some lepidopterous eggs. Adults hibernate in soil during winter and females lay their eggs in spring. In the laboratory the duration of immature stages is 74 days at 20–30°C. Larvae kill their host within 1–3 days when the mite load of the host is 2 or more. They decrease the reproductive rate of adult aphids and arrest the development of early-instar aphid nymphs when the mite load is 1. Larvae are capable of controlling the host population growth when the level of parasitism is high. Owing to its wide occurrence,A. pulvinum could be a potential candidate in the biological control of aphids. It is suggested that its impact on the host pest be evaluated in IPM programs in the future.     

Efficacy of indigenous predatory mites (Acari: Phytoseiidae) against the citrus rust mite Phyllocoptruta oleivora (Acari: Eriophyidae): augmentation and conservation biological control in Israeli citrus orchards

The citrus rust mite (CRM), Phyllocoptruta oleivora (Acari: Eriophyidae) is a cosmopolitan key pest of citrus, inflicting severe economic damage if not controlled. In Israel, CRM damages all citrus cultivars. International regulation and increasing control failures of CRM led growers to seek sustainable biological control solutions such as acarine biological control agents. Laboratory studies conducted in Israel have indicated that the indigenous predator species Amblyseius swirskii, Iphiseius degenerans, Typhlodromus athiasae and Euseius scutalis (all Acari: Phytoseiidae) can potentially control CRM. Our general objective in the present study was to bridge the gap of knowledge between laboratory studies and the lack of control efficacy of these species in commercial orchards. Predator augmentation in the field showed that although predator populations increased immediately following releases they later decreased and did not affect CRM populations. When A. swirskii augmentation was combined with a series of maize pollen applications, A. swirskii populations were enhanced substantially and continuously but again CRM populations were not affected. Growth chamber studies with CRM-infested seedlings, with or without a maize pollen supplement, indicated that pollen provisioning led to population increase of E. scutalis and A. swirskii but only E. scutalis significantly lowered CRM populations. Control with E. scutalis was confirmed in the field on CRM infested seedlings with pollen provisioned by adjacent flowering Rhodes grass. While experiments in mature citrus orchard showed that pollen supplement usually increased predator populations they also indicated that other factors such as intraguild interactions and pesticide treatments should be taken into account when devising CRM biological control programs.     

Parasitus bituberosus (Acari: Parasitidae), a possible agent for biological control ofHeteropeza pygmaea (Diptera: Cecidomyiidae) in mushroom compost

The prey items accepted byParasitus bituberosus Karg included all immature instars ofHeteropeza pygmaea Winnertz, first and second instars ofLycoriella solani together with its eggs, and compost nematodes and springtails. A preference was shown by deutonymphs for first-instarH. pygmaea, whereasHistiostoma feroniarum andPygmephorus sp. were not accepted. Adult mites, especially females, appeared to be even more voracious predators on first-instarH. pygmaea than were deutonymphs or protonymphs. The mite preventedH. pygmaea from reaching high populations in both laboratory-scale and small commercial-scale compost units; it also reduced populations of free-living nematodes in the latter. The distributions ofH. pygmaea and the mite throughout the compost in growing-bags were investigated and found to parallel each other. The mite was able to penetrate all parts of the compost. There was no evidence that it damagedAgaricus bisporus, and it was never found on harvested caps.     

Neozygites abacaridis sp. nov. (Entomophthorales), a new pathogen of phytophagous mites (Acari,Eriophyidae)

A new entomopathogenic fungus, described here as Neozygites abacaridis n. sp. (Zygomycetes: Entomophthorales), has been found on the mites Abacarus hystrix, Aculodes dubius, and A. mckenziei (Acari: Eriophyidae). It differs from other Neozygites species affecting mites by its small, globose primary conidia, short-ovoid, smoky coloured capilliconidia, and very short capillary conidiophores-which are usually not longer than the spore length. This pathogen infected mite individuals in autumn (from mid-August until mid-November) on Lolium perenne, Agrostis stolonifera, and Festuca rubra. It caused 0.5-1% host's mortality in the vicinity of Siedlce (Eastern Poland) and up to 2-8%, on an average in Puszczykowo (Wielkopolski National Park near Poznań), where its prevalence on some plants reached 13%.     

Host specificity of different populations of the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae), a biological control agent of saltcedar (Tamarix spp.)

The leaf beetle, Diorhabda elongata (Brullé) sensu lato, was released in 2001 for the classical biological control of exotic saltcedars, a complex of invasive Tamarix species and hybrids. It did not establish at sites south of 37°N latitude where summer daylengths are below the critical photoperiod of the northern-adapted populations of the beetle that were released. Therefore, we assessed the host specificity of four D. elongata populations collected from more southern latitudes in the Old World (Tunisia, Crete, Uzbekistan, and Turpan, China). All populations were similar to each other and the previously released populations of D. elongata in their host specificity. Larval/pupal survival for all populations was 34–100% on Tamarix test plants, 0–76% on native Frankenia plants (both in the order Tamaricales), and 0% on the remaining 28 species of plants on which all the larvae died as 1st instars. D. elongata laid high numbers of eggs on saltcedar, generally fewer eggs on athel (a moderately valued evergreen species of Tamarix) except for Uzbekistan beetles, and few to no eggs on three species of Frankenia. Few to no adults were found on Frankenia plants which also were poor maintenance hosts. The release of any of the four D. elongata populations in the southern US and northern Mexico should pose no risk to plants outside the order Tamaricales and a low risk to native, non-target Frankenia plants. Athel may be less damaged than saltcedar.