Multiple host use by a sap-sucking membracid: population consequences of nymphal development on primary and secondary host plant species

Aconophora compressa is a gregarious, sap-sucking insect that uses multiple host plant species. Nymphal host plant species (and variety) significantly affected nymphal survival, nymphal development rate and the subsequent size and fecundity of adults, with fiddlewood (Citharexylum spinosum) being significantly best in all respects. Nymphs that developed on a relatively poor host (Duranta erecta var “geisha girl”) and which were moved to fiddlewood as adults laid significantly fewer eggs (mean ± SE = 836 ± 130) than those that developed solely on fiddlewood (1,329 ± 105). Adults on geisha girl, regardless of having been reared as nymphs on fiddlewood or geisha girl, laid significantly fewer eggs (342 ± 83 and 317 ± 74, respectively) than adults on fiddlewood. A simple model that incorporates host plant related survival, development rate and fecundity suggests that the population dynamics of A. compressa are governed mainly by fiddlewood, the primary host. The results have general implications for understanding the population dynamics of herbivores that use multiple host plant species, and also for the way in which weed biological control host testing methods should be conducted. Handling Editor: Robert Glinwood     

Development and feeding of <Emphasis Type="Italic">Tetraphleps galchanoides</Emphasis>, a predator of the hemlock woolly adelgid

Tetraphleps galchanoides Ghauri (Hemiptera: Anthocoridae) nymphs were collected from hemlock woolly adelgid (HWA) Adelges tsugae Annand (Hemiptera: Adelgidae) infested Tsuga sp. in Baoxing, Sichuan, China. First and second stage nymphs collected from foliage shipped from China; were reared to adults and tested for feeding rates and host preferences. They were reared at 5, 8, 12, and 15 ± 1 °C from November to December, January to March, April, and May to June, respectively, in the quarantine laboratory at Virginia Polytechnic Institute and State University. At 8 °C, development time was 15, 20, and 40 days for the N-III, IV, and V nymphal stages, respectively. Adult males lived 83 days with a range of 21–147 days. A single adult female lived for 21 days. At 5 °C, second stage T. galchanoides nymphs consumed 0.8 HWA nymphs per day, and 2.0 HWA nymphs per day at the N-V stage. At 8 °C, consumption of HWA nymphs ranged from 1.3 to 3.4 nymphs per day for the N-III to N-V stages, respectively. Adult T. galchanoides consumed more HWA eggs than HWA adults, pine bark adelgid (PBA) Pineus strobi (Hartig) (Hemiptera: Adelgidae) adults, and eggs in no-choice tests. In choice tests with HWA eggs and PBA eggs, more HWA eggs were eaten. Adult and nymph body measurements are presented for determination of nymphal instars.     

Biology and host range of <Emphasis Type="Italic">Aconophora compressa,</Emphasis> a candidate considered as a biocontrol agent of <Emphasis Type="Italic">Lantana camara</Emphasis> in Africa

The shrub, Lantana camara L. (Verbenaceae), of tropical American origin, is a serious weed in South Africa and is the target of a biological control programme. The stem-sucking membracid, Aconophora compressa Walker (Homoptera: Membracidae), from Mexico was reported to be very damaging and was therefore imported into South Africa for biology and host range studies. The female partially inserts the eggs into the woody portion of actively growing stems, and guards them against potential predators. Nymphs develop through five instars to the adult stage in about 45 days. The adults and nymphs feed on the sap of stems causing the leaves to wilt, the flowers to abort and the gradual dieback of stems. No-choice experiments showed that adult survival, egg production, and nymphal emergence was high on L. camara, and also on related ornamental and indigenous species. The adult reproductive performance was higher on some indigenous Lippia species than on L. camara. Furthermore, the nymphs developed faster on these indigenous species and high rates of reproductive performance on these non-target species were sustained over several generations. In multiple-choice trials, equal or larger numbers of egg batches were recorded from indigenous Lippia species and the ornamental plant, Aloysia citrodora Palau, than on L. camara. The treehopper, A. compressa, poses an unacceptable threat to indigenous Lippia species and has therefore been rejected as a biocontrol agent for L. camara in Africa.     

Influence of <Emphasis Type="Italic">Lecanicillium attenuatum</Emphasis> on the development and reproduction of the cotton aphid, <Emphasis Type="Italic">Aphis gossypii</Emphasis>

The activity of entomopathogens on insect pests has been investigated for many species but the influence of entomopathogenic fungi on factors other than mortality relating to population increase has not been frequently studied. The influence of Lecanicillium attenuatum CS625 (=Verticillium lecanii CS625) on development and reproduction of cotton aphid (Aphis gossypii) was investigated. A conidia suspension of the isolate was applied onto first instar nymphs. Increased spore concentration did not significantly affect each nymphal stage, total nymphal period, pre-reproductive period and the age of first larviposition. A significant dose effect on reduction of life span, reproductive period and fecundity was observed in 1st and 3rd instars after spore application. When conidia were applied to 1st instars, life span was significantly reduced to 10.8 and 8.4 days at 1 × 10⁴ and 1 × 10⁸ conidia/ml, respectively from 12.2 days in the control. During the life span, total fecundity was 41 ± 7.3, 26 ± 0.8 and 22 ± 5.7 nymphs per female at 1 × 10⁴, 1 × 10⁶ and 1 × 10⁸ conidia/ml, respectively compared with 51 ± 2.0 nymphs per untreated female. Reproduction period was also significantly shortened with increasing spore concentration. Application of spores to 3rd instars showed a similar trend. However, daily fecundity of individual aphids was not affected by spore dose. It was concluded that the isolate of L. attenuatum is able to affect populations of cotton aphid by reducing life span and total fecundity as well as by killing the aphids directly.     

Assessing host specificity of a classical biological control agent against western corn rootworm with a recently developed testing protocol

Celatoria compressa (Wulp) (Diptera: Tachinidae), a parasitoid of adult chrysomelid beetles in the subtribe Diabroticina in North America, has been selected as a candidate for classical biological control of the alien invader, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae: Galerucinae), into Europe. We conducted host specificity testing to evaluate the fundamental host range of C. compressa and potential risks to native European coleopteran species. Nine potential non-target beetles were tested for host selection with D. v. virgifera in no-choice tests, sequential no-choice tests, choice tests and sequential choice tests in small experimental arenas in a quarantine laboratory. The nine representative non-target species were selected for experimentation based on (1) ecological host range information of C. compressa, (2) ecological similarities to D. v. virgifera, (3) close phylogenetic/taxonomic relationships, (4) safeguard considerations, (5) morphological similarities, geographical distributions, overlap of temporal occurrences with D. v. virgifera and C. compressa, and (6) accessibility and availability. Of the potential nine non-target hosts tested, gravid C. compressa only parasitized a few red pumpkin beetles, Aulacophora foveicollis (Chrysomelidae: Galerucinae), regardless of the presence or absence of D. v. virgifera. However, C. compressa significantly preferred D. v. virgifera (44.6% parasitized) over A. foveicollis (2.7%) in choice tests. Of the 1110 A. foveicollis tested among all experiment types, only 23 were parasitized and only one C. compressa successfully developed from the parasitism, demonstrating that A. foveicollis is a poor host. In conclusion, C. compressa has a fundamental host range restricted to the subtribes Diabroticina and Aulacophorina, and would therefore be unlikely to have a direct impact on indigenous species in Europe.     

Biological control of <Emphasis Type="Italic">Lantana camara</Emphasis> in South Africa: targeting a different niche with a root-feeding agent, <Emphasis Type="Italic">Longitarsus</Emphasis> sp.

The root-feeding flea beetle, Longitarsus sp. (Coleoptera: Chrysomelidae: Alticinae), was studied as a potential biological control agent for Lantana camara L. (Verbenaceae) in South Africa. Host range tests were carried out on 52 plant species in 11 families. Although 11 plant species, all in the family Verbenaceae, supported complete development of Longitarsus sp. during no-choice tests, the beetles showed very strong preferences for L. camara during paired-choice and multi-choice tests. The results confirm that the beetles have a narrow host range, and that under natural conditions they are highly unlikely to utilise plants other than L. camara. In the unlikely event that some of the Lippia spp. are attacked in the field, they are not expected to sustain populations of the flea beetle over time. Attributes that should enhance the biocontrol potential of Longitarsus sp. include: the adults are long-lived and highly mobile; and, the larvae cause extensive direct damage to the roots of L. camara, which could in turn expose the plants to soil-born pathogens. All indications are that Longitarsus sp. could make a substantial contribution to the biological control of L. camara in many countries around the world because the beetles pose no threat to non-target plant species and they damage a part of the plant (i.e. roots) not yet affected by any other agent species.     

Relative host plant species use by the lantana biological control agent Aconophora compressa (Membracidae) across its native and introduced ranges

Aconophora compressa Walker (Hemiptera: Membracidae) was released in 1995 against the weed lantana in Australia, and is now found on multiple host plant species. The intensity and regularity at which A. compressa uses different host species was quantified in its introduced Australian range and also its native Mexican range. In Australia, host plants fell into three statistically defined categories, as indicated by the relative rates and intensities at which they were used in the field. Fiddlewood (Citharexylum spinosum L.: Verbenaceae) was used much more regularly and at higher densities than any other host sampled, and alone made up the first group. The second group, lantana (Lantana camara L.: Verbenaceae; pink variety) and geisha girl (Duranta erecta L.: Verbenaceae), were used less regularly and at much lower densities than fiddlewood. The third group, Sheena’s gold (another variety of D. erecta), jacaranda (Jacaranda mimosifolia D. Don: Bignoniaceae) and myoporum (Myoporum acuminatum R. Br.: Myoporaceae), were used infrequently and at even lower densities. In Mexico, the insect was found at relatively low densities on all hosts relative to those in Australia. Densities were highest on L. urticifolia, D. erecta and Tecoma stans (L.) Juss. ex Kunth (Bignoniaceae), which were used at similar rates to one another. It was found also on a few other verbenaceous and non-verbenaceous host species but at even lower densities. The relative rate at which Citharexylum spp. and L. urticifolia were used could not be assessed in Mexico because A. compressa was found on only one plant of each species in areas where these host species co-occurred. The low rate at which A. compressa occurred on fiddlewood in Mexico is likely to be an artefact of the short-term nature of the surveys or differences in the suites of Citharexylum and Lantana species available there. These results provide further incentive to insist on structured and quantified surveys of non-target host use in the native range of potential biological control agents prior to host testing studies in quarantine.     

Candidates for biocontrol of Macfadyena unguis-cati in South Africa: biology, host ranges and potential impact of Carvalhotingis visenda and Carvalhotingis hollandi under quarantine conditions

Macfadyena unguis-cati (L.) Gentry (Bignoniaceae) was introduced as an ornamental in South Africa, but is fast becoming an important invasive plant in many areas. It is difficult to control the plant chemically and mechanically. The first biocontrol agent, the chrysomelid Charidotis auroguttata (Boheman), has been released. It established at some release sites, but numbers have so far remained low. Additional biocontrol agents were sought to augment C. auroguttata. The potential host ranges of two foliage feeding lace bugs, Carvalhotingis visenda (Drake and Hambleton) and C. hollandi (Drake) (Hemiptera: Tingidae) were evaluated on the basis of nymphal no-choice and adult multi-choice tests involving 23 plant species in 11 families. In no-choice tests, nymphs of both species were able to survive and complete development on M. unguis-cati only, and adults of both species only fed and oviposited on M. unguis-cati during the adult multi-choice tests. Host specificity tests thus confirm that the tingids are highly host specific biocontrol agents, and will not pose risk to any non-target plants in South Africa. A study to determine the potential impact of C. hollandi nymphal feeding on M. unguis-cati showed a significant decrease in the chlorophyll contents of leaves when compared to those of control plants. These studies indicate that, once released, the two lace bug species could contribute significantly to the biological control of M. unguis-cati in South Africa.     

Effects of frequent fish predation on corals in Hawaii

The abundance of lesions from fish bites on corals was quantified at nine shallow reefs in the main Hawaiian Islands. There were on average 117 bite scars m⁻² on Pocillopora meandrina tissue from the barred filefish Cantherhines dumerilii, 69 bites m⁻² on Porites compressa tissue, and 4 bites m⁻² on Porites lobata tissue from the spotted puffer Arothron meleagris. Across sites, the frequency of A. meleagris bites on P. compressa per unit area of living coral cover declined exponentially with increasing coral cover. P. compressa nubbins in two size classes (1–2 cm and 4–5 cm) were transplanted onto six study reefs. Nubbins in the small size class were entirely removed by bites from A. meleagris, while nubbins ≥4 cm were only partially consumed, leaving them able to recover. At sites with abundant P. compressa, predation had little effect on transplanted nubbins; at sites where P. compressa comprised less than 5% of living cover, all nubbins were preyed upon. A. meleagris bite lesions on P. compressa were monitored through time and fully recovered in 42 ± 4 days. A model of the risk of over-predation (a second predation event before the first is healed) decreased exponentially with increasing coral cover and increased linearly with increasing lesion healing time. The increased risk of over-predation at low coral cover could indicate an Allee effect limiting the recovery of coral populations if coral cover is substantially reduced by natural or anthropogenic disturbances.     

The natural hosts for larvae and nymphs of Amblyomma neumanni and Amblyomma parvum (Acari: Ixodidae)

Based on the hypothesis that birds and rodents are important hosts for subadults of the Neotropical Amblyomma neumanni and Amblyomma parvum ticks, a survey of these type of hosts was carried out from July 2004 to March 2006, in Quilino (A. parvum) and Dean Funes (A. neumanni), Córdoba province, Argentina. Additionally, monthly tick counts were performed on cattle and goats with occasional tick search in other domestic hosts. Records of questing height of subadult ticks on vegetation were also carried out monthly. Rodents (n = 123) and birds (n = 122) captured in Dean Funes showed no infestation with A. neumanni. Apart of few nymphs found on horses, all larvae and nymphs of A. neumanni were on cattle with a larval prevalence and mean number of 22.2%, and 7.7 ± 22.52, respectively, and a prevalence of nymphs of 47.8% with a mean of 7.9 ± 18.49. The average questing height of larvae and nymphs of A. neumanni was 23.5 ± 17.1 cm and 30.7 ± 26.7 cm, respectively. A total of 138 rodents and 130 birds were captured in Quilino but the Caviidae rodent Galea musteloides carried 99.3% of larvae and 99.8% of nymphs of A. parvum, and no immature stages were detected on cattle, goat or vegetation. Tick counts on G. musteloides (n = 74) showed a prevalence of 42% and a mean number of 9.9 ± 24.83 for larvae, while nymphal infestation had a prevalence of 56.5% and a mean of 8.7 ± 11.31. Cattle appear to be suitable hosts to sustain the complete cycle of A. neumanni in nature (adult ticks infest cattle too) and questing height of subadults indicates that they are expecting to feed on medium and large-sized mammals, such as cattle and other ungulates. At least in the study site, G. musteloides is the principal host for the survival strategy of A. parvum subadults; adult ticks are common on cattle and goats. These hosts are introduced in the Neotropics but A. neumanni was able to develop a surrogate cycle independent of native hosts while A. parvum still depends on probably primeval hosts to sustain their larvae and nymphs.     

Antibacterial activity of some salt marsh halophytes and mangrove plants against methicillin resistant Staphylococcus aureus

The antibacterial activity of aqueous and methanol extracts of leaves/shoots of five salt marsh halophytes and six mangroves was studied against methicillin resistant, clinical isolates of Staphylococcus aureus. There was a clear comparability between the salt marsh halophytes and mangroves in their antibacterial action. The mangrove plants possessed higher antibacterial potency than the salt marsh halophytes. The highest activity was recorded with the methanol extract of Excoecaria agallocha followed by the methanol extracts of Aegiceras corniculatum, Lumnitzera racemosa and Ceriops decandra. The minimum inhibitory concentration (MIC) values ranged from 0.125 to 4 mg/mL and 1 to 16 mg/mL for methanol and aqueous extracts, respectively. Further separation of active principle from the potent mangrove plant will be useful for the control of drug resistant strains of S. aureus.     

The number of tadpoles consumed by the nymphs of the giant water bug <Emphasis Type="Italic">Kirkaldyia deyrolli</Emphasis> under laboratory conditions

Giant water bug Kirkaldyia (=Lethocerus) deyrolli (Belostomatidae: Heteroptera) nymphs consume many individuals of anuran larvae (tadpoles) before they reach adulthood. However, no quantitative data on the number of tadpoles consumed have been made available until now, despite the importance of this data for the conservation of this species. The number of tree frog, Hyla japonica (Hylidae: Anura), tadpoles consumed by nymphs of K. deyrolli was examined under laboratory conditions. The number increased according to the developmental stage of the nymphs; the fifth instar nymphs were the highest consumers. The total numbers consumed by the nymphs throughout development were 155.0 ± 12.8 (average ± SD) and 172.8 ± 9.6 for the males and the females, respectively. Thus, it might be important to maintain high densities of frogs in fields to conserve the population of K. deyrolli into the future.     

Biology and host range of Ophiomyia camarae, a biological control agent for Lantana camara in South Africa

The herringbone leaf-mining fly, Ophiomyiacamarae Spencer, is a promising candidateagent for the biological control of the alieninvasive weed Lantana camara L. in SouthAfrica. During extensive host-specificity testsinvolving 39 test plant species from 12families, survival to adulthood was restrictedto L. camara, L. trifolia, and fourspecies of the closely-related genus Lippia (Verbenaceae) in no-choice tests. However, survival of the immature stages wassignificantly lower on L. trifolia andthe four Lippia species than on L.camara. In addition, O. camaraedisplayed very strong oviposition preferencefor L. camara during paired-choice tests.This narrow laboratory host range suggests thatO. camarae will not pose any risks tonon-target verbenaceous plants if released inSouth Africa. Permission to release O. camaraeinto South Africa was approved by the regulatoryauthorities in 2001.     

Temperature dependence for development of the whitefly predator <Emphasis Type="Italic">Clitostethus arcuatus</Emphasis> (Rossi)

This work aimed to study the biology of Clitostethus arcuatus (Rossi) (Coleoptera: Coccinellidae) under different temperatures and evaluate the optimum temperature for its mass rearing. Studies were carried out in the laboratory at four constant temperatures (15°C, 20°C, 25°C and 30°C), 75 ± 5% relative humidity and a photoperiod of 16 h light:8 h dark, in which C. arcuatus was fed ad libitum with nymphs of all instar of Aleyrodes proletella L. (Homoptera: Aleyrodidae) on Brassicae oleracea L. (var. Costata). The following biological parameters were evaluated: development time and survival rates of pre-imaginal stages, adult longevity (female and male), length of the pre-oviposition and oviposition periods, fecundity, fertility and percentage of egg hatching. Population growth parameters, the lower development threshold and the sum of effective temperatures were estimated. Temperatures ranging from 20°C to 30°C were suitable for the development of C. arcuatus, suggesting that this species is well adapted to the temperatures usually found inside greenhouses or in open fields in temperate regions. Although the intrinsic rate of natural increase and doubling time were similar at 25°C and 30°C, the temperature of 25°C was shown to be the most suitable for mass rearing and development of populations under field conditions, since the percentage of egg hatching and the accumulated survival rates of the pre-imaginal stages were the highest. Considering the estimated lower threshold for pre-imaginal development (7.9°C) and the sum of effective temperatures [293.6 degree-days (°D)], it is predicted for Ponta Delgada (Azores, Portugal) that the first adults of C. arcuatus should emerge by the first fortnight of February and that up to 12 generations per year can occur.     

Coal Dust Pollution Effects on Wetland Tree Species in Richards Bay,South Africa

In this study, the effects of coal dust on four, sympatric, wetland tree species in Richards Bay Harbour were investigated. We tested the hypothesis that leaf micromorphology influenced dust accumulation and that coal dust occluded stomata and reduced photosynthetic performance of three mangroves, Avicennia marina, Bruguiera gymnorrhiza and Rhizophora mucronata, and a mangrove associate, Hibiscus tiliaceus. To investigate leaf micromorphology, leaf blade material of the four species was prepared following standard procedures and viewed under scanning electron microscopy. Gas exchange and chlorophyll fluorescence measurements were made at saturating light (>1000 μmol m⁻² s⁻¹) and high temperature (>25 °C) on leaves that were either covered or uncovered with coal dust. There was no evidence of occlusion of stomata by dust. Dust accumulation in A. marina and H. tiliaceus was exacerbated by the presence of a dense mat of trichomes on the undersurface of the leaves, as well as by the sticky brine secreted by salt glands in the former species.Coal dust significantly reduced CO₂ exchange, Photosystem II (PS II) quantum yield and electron transport rate (ETR) through PS II in A. marina and H. tiliaceus but not in the other two mangroves. Reduction in photosynthetic performance was attributed to reduction in light energy incident on the photosynthetic tissues.     

Host plant influences pathogenicity of Beauveria bassiana to Bemisia tabaci and its sporulation on cadavers

Laboratory bioassays were conducted to determine host plant effect on pathogenicity of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill. (Ascomycota: Hypocreales) to the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Fourth instar B. tabaci reared on cucumber, tomato, melon, green pepper, potato, eggplant, marrow, cabbage, bean or cotton, were treated with 1 × 10⁷ conidia/ml B. bassiana EABb 93/14-Tp isolate. Mortality caused by B. bassiana significantly increased with time and it was significantly affected by the host plant on which the nymphs were reared. Mean mortality of nymphs 8 days after inoculation ranged between 52.3±7.3 for nymphs reared on cotton and 91.8±5.8 for nymphs reared on cucumber. Average survival times of nymphs treated with the fungal suspensions were also significantly influenced by the host plant, with a mean of 4.7±0.1 days for nymphs reared on cucumber, 6.6±0.2 days for cotton and 6.9±0.1 days for green pepper. The production of newly formed conidia was also affected by host plant and varied from 111000±8600 conidia/cadaver for nymphs reared on cotton to 597000±28000 conidia/cadaver for those reared on melon.     

The trimorphic flea-beetle, <Emphasis Type="Italic">Alagoasa extrema</Emphasis>, not suitable for biocontrol of <Emphasis Type="Italic">Lantana camara</Emphasis> in Africa

The biology and host range of the flea-beetle, Alagoasa extrema (Harold) (Coleoptera: Chrysomelidae: Galerucinae: Alticini), was studied under quarantine laboratory conditions to evaluate the insect’s suitability for release as a biological control agent for the noxious weed, Lantana camara L. (Verbenaceae), in South Africa. Identification of this species proved noteworthy. The adults of A. extrema display three freely interbreeding and very distinct colour morphs, which can be confused with no less than 11 species of Alagoasa found in Mexico and the southwestern U.S. Initially, specimens were identified as two species of the genus Alagoasa Bechyné, i.e. A. quadrilineata (Harold) and A. extrema. Thirteen additional Alagoasa species and Kushelina petaurista (F). that can be confused with A. extremabased on external morphology of adults or larvae are discussed. Favourable biological characteristics included long-lived adults, several overlapping generations per year, and high adult and larval feeding rates. Observations from the insect’s native Mexican range and studies in South Africa suggest that A. extrema would probably be more suited to subtropical, rather than temperate areas in Africa. Host-specificity studies showed A. extrema to be an oligophagous species, capable of feeding and developing on several non-target species, especially two indigenous, African Lippia species (Verbenaceae). The host suitability of these indigenous species was only marginally lower than that of L. camara, and the potential risk to them was deemed to be too high to warrant release. It was therefore recommended that A. extrema be rejected as biocontrol agent for lantana in Africa.     

Effect of Starvation on the Searching Path of the Predatory Bug <Emphasis Type="Italic">Deraeocoris Lutescens</Emphasis>

As physiological factors may influence the predatory behavior of insects, this study was designed to evaluate the possible impact that hunger has on the search path of a polyphagous predator: Deraeocoris lutescens Schilling (Heteroptera: Miridae). D. lutescens was fed a diet of Rhopalosiphum padi (Linné) (Homoptera: Aphididae) nymphs and Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs at 21±1 °C and a photoperiod of 16:8 (L:D). After moulting, third and fifth instar nymphs and adults were placed in Petri dishes containing an abundant food source for 24 h. After 24 h, the food was removed and groups were randomly assigned to increasing periods of prey deprivation. Each D. lutescens nymph or adult was placed at the center of an empty arena and its searching path was recorded to calculate different path parameters and to determine the type of movement mode adopted. Results show an effect of starvation on both nymphal and adult D. lutescens searching paths. Satiated third instar nymphs manifested an intensive search path whereas fifth instar nymphs and adults adopted an intermediate one. When starved, the extensive search path appeared early in young nymphs, and later in the last instar nymphs and adults, according to the degree of prey deprivation.     

Establishment potential of the predatory mirid <Emphasis Type="Italic">Dicyphus hesperus</Emphasis> in northern Europe

The predatory mirid Dicyphus hesperus Knight (Hemiptera: Miridae) is native to North America. The species has been used for the control of glasshouse whitefly on aubergine in the Netherlands, and is currently being evaluated for continued and wider release in Europe. Field and laboratory studies were conducted on a population collected from southern California, USA, to assess the cold tolerance and potential for outdoor establishment under prevailing northern European climates. The supercooling points (whole animal freezing temperatures) of nymphal and adult insects were around −20°C. The lethal temperatures (LTemp₅₀) of non-diapausing nymphs and adults and diapausing adults were close to their respective freezing temperatures at −17.6, −17.6 and −19.2°C. At 5°C, the LTime₅₀ was 54, 101.7 and 117.5 days for fed nymphs, non-diapausing and diapausing adults respectively. When first instar nymphs were placed in the field in winter, starved samples died out after 70 days, but 5% of the fed nymphs survived until the end of winter (140 days) and developed to adult on return to the laboratory. After a similar 5-month field exposure, 50% of fed diapausing adults and 15% of fed non-diapausing adults were still alive at the end of winter, whereas starved diapausing adults died after 140 days. On return to the laboratory after 5 months in the field, both diapausing and non-diapausing adults mated and laid eggs, forming viable populations. Overall, the field and laboratory experiments indicate that this population of D. hesperus is able to enter diapause and that winter temperatures are not a barrier to establishment in northern Europe.     

Risk to non-target plants from Charidotis auroguttata (Chrysomelidae: Coleoptera), a potential biocontrol agent for cat’s claw creeper Macfadyena unguis-cati (Bignoniaceae) in Australia

The potential of the leaf beetle Charidotis auroguttata as a biocontrol agent for cat’s claw creeper Macfadyena unguis-cati (Bignoniaceae), an environmental weed in Australia, and risk to non-target plants was evaluated under quarantine conditions. In no-choice tests, C. auroguttata adults and larvae fed on many plant species across different families, but egg to adult development occurred only on the target weed. However, when neonate larvae from the target weed were transferred onto Myoporum boninense australe (Myoporaceae), a non-target native plant, 11.7% completed development, as compared to 95% of larvae that completed development on the target weed. Larval development on this non-target species also took twice as long as on the target weed. No larvae completed development on other test plants. In choice tests, leaf area consumption by adults and larvae was significantly more on the target weed than on other plants, and oviposition occurred only on the target weed. In the no-choice demography trials, adults laid eggs from the second week after emergence on the target weed, with an average of 0.286 eggs/female/day, resulting in an 18-fold increase in the adult population over 16 weeks. On My. boninense australe adult survival remained high, but oviposition commenced only from the 10th week after emergence with an average of 0.023 eggs/female/day, and none of the eggs developed into adults. In the choice demography trials, oviposition on the target weed was evident from the fourth week onwards, while on the non-target plant oviposition commenced only from the 14th week. Only 10% of total adults and 11.3% of total eggs were found on the non-target plant, and none of these eggs developed into adults. Although the biocontrol agent can ‘spill-over’ from the target weed to the non-target native plant and cause adult feeding damage, the non-target plant could not sustain a viable insect population on its own. This agent was not approved for field release in Australia due to perceived risk to non-target species.