Egg–larval opiine parasitoids (Hym., Braconidae) of tephritid fruit fly pests do not attack the flowerhead-feeder Trupanea dubautiae (Dipt., Tephritidae)

Abstract:  We investigated the potential impact of three opiine tephritid fruit fly parasitoids: Fopius arisanus (Sonan), Fopius caudatus (Szépligeti) and Fopius ceratitivorus Wharton, on the non-target native Hawaiian tephritid, Trupanea dubautiae (Bryan), infesting flowerheads of the endemic Asteraceae shrub Dubautia raillardioides Hillebrand. The three species are the only known opiine fruit fly parasitoids that attack host eggs (but occasionally attack first instars). F. arisanus , which originated in southeast Asia, is now widely established in Hawaii and elsewhere in the world, while the other two are African species currently in quarantine in Hawaii. In the laboratory, field-collected flowerheads of D. raillardioides containing T. dubautiae eggs and first instar larvae were exposed to naïve female wasps of each of the three Fopius species in the absence (no-choice test) or presence (choice test) of papaya fruit infested with eggs of the Mediterranean fruit fly Ceratitis capitata (Wiedemann), the parasitoids' normal host. All three Fopius species visited the papaya fruit much more often than the flowerheads, and displayed normal ovipositional responses (probing and stinging) on the fruit in the choice test. None of the three parasitoid species showed ovipositional responses to flowerheads in either choice or no-choice tests. As a result, not a single T. dubautiae egg or larva was attacked by any of the three parasitoids, indicating that these parasitoids of pest tephritids are unable to recognize the microhabitats of flowerhead-feeding tephritids. The results suggest minimal risk of non-target impact in these biological control agents.     

Biology and host specificity of the chromolaena stem gall fly, Cecidochares connexa (Macquart) (Diptera: Tephritidae)

Abstract The stem-galling tephritid fly Cecidochares connexa (Macquart) was investigated as a potential biocontrol agent against the weed Chromolaena odorata (L) King & Robinson in Indonesia. Adults were tested in choice and no-choice tests, on 55 non-target plant species in 17 families. No oviposition was recorded on 53 of the species, while oviposition but no larval development was recorded on two. Field releases commenced in 1995 and establishment was immediate. The gall fly is now widely established in most Indonesian provinces, where gall parasitism and predation is generally low.     

The tortoise beetle Physonota maculiventris (Chrysomelidae: Cassidinae) is suitable for release against the weedy Mexican sunflower Tithonia diversifolia (Asteraceae) in South Africa

The biology and host range of the defoliating beetle Physonota maculiventris Boheman (Chrysomelidae: Cassidinae) were studied in quarantine to determine its suitability for release as a biological control agent against Mexican sunflower, Tithonia diversifolia (Hemsl.) A. Gray (Asteraceae), in South Africa. Females laid 5.25?±?0.25 (mean?±?SE) egg batches during their lifetimes, with each batch consisting of approximately 33 eggs. Larvae were highly gregarious as early instars and both larvae and adults fed voraciously, often defoliating the plants completely. The life cycle of the beetle was completed in 67.5?±?7.5 days under quarantine conditions. Among the 58 test plant species subjected to no-choice tests, P. maculiventris developed successfully on T. diversifolia and some sunflower (Helianthus annuus L.) cultivars. However, only minor damage was recorded on non-target species, notably the exotic weed Xanthium strumarium L. and some H. annuus cultivars. Also, survival to adulthood was considerably lower on sunflower cultivars than on the target weed during these tests. During choice tests, P. maculiventris oviposited and developed successfully on T. diversifolia only, with only minor feeding damage on some H. annuus cultivars, suggesting that the beetle’s field host range will be confined to the target weed. Risk analysis also showed that P. maculiventris presents an extremely low risk to non-target plant species (e.g. within the tribe Heliantheae and other close relatives). The study concluded that P. maculiventris is safe for release in South Africa and an application for its release is being considered by the relevant South African regulatory authorities.     

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.     

Host range evaluation of the leaf-feeding beetle,Zygogramma bicolorata and the stem-boring weevil,Listronotus setosipennis demonstrates their suitability for biological control of the invasive weed,Parthenium hysterophorus in Ethiopia

The invasive weed, parthenium (Parthenium hysterophorus L.) (Asteraceae: tribe Heliantheae), damages agriculture, adversely impacts biodiversity and is hazardous to human and animal health in Ethiopia. The host range of two natural enemies, a leaf-feeding beetle, Zygogramma bicolorata (Coleoptera: Chrysomelidae) and a stem-boring weevil, Listronotus setosipennis (Coleoptera: Curculionidae) was evaluated for biological control of the weed in Ethiopia. The specificity of Z. bicolorata and L. setosipennis was assessed against 29 and 31 non-target plant species, respectively. The host range of Z. bicolorata and L. setosipennis was first assessed using no-choice tests to examine their oviposition and feeding response on non-target plants. Although oviposition by Z. bicolorata occurred on six non-target species in four Asteraceae species in no-choice tests, it was significantly lower than on parthenium and no larvae developed. Zygogramma bicolorata nibbled the leaves of one of the five niger seed (Guizotia abyssinica L. – an oil seed crop closely related to parthenium) cultivars tested, but feeding and oviposition were significantly less than on parthenium. Furthermore, choice tests indicated that Z. bicolorata did not oviposit nor feed on G. abyssinica when parthenium was present. In no-choice tests, L. setosipennis did not oviposit on any of the non-target species assessed. Mean oviposition on parthenium was 39.0?±?3.4 eggs per plant whereas no eggs were laid on any of the 31 species tested. Based on these and other host range tests, permission was obtained to field release Z. bicolorata and L. setosipennis in Ethiopia.     

Host range of Secusio extensa (Lepidoptera: Arctiidae), and potential for biological control of Senecio madagascariensis (Asteraceae)

Secusio extensa (Lepidoptera: Arctiidae) was evaluated as a potential biological control agent for Madagascar fireweed, Senecio madagascariensis (Asteraceae), which has invaded over 400 000 acres of rangeland in the Hawaiian Islands and is toxic to cattle and horses. The moth was introduced from southeastern Madagascar into containment facilities in Hawaii, and host specificity tests were conducted on 71 endemic and naturalized species (52 genera) in 12 tribes of Asteraceae and 17 species of non‐Asteraceae including six native shrubs and trees considered key components of Hawaiian ecosystems. No‐choice feeding tests indicated that plant species of the tribe Senecioneae were suitable hosts with first instars completing development to adult stage on S. madagascariensis (78.3%), Delairea odorata (66.1%), Senecio vulgaris (57.1%), Crassocephalum crepidioides (41.2%), and at significantly lower rates on Emilia fosbergii (1.8%) and Erechtites hieracifolia (1.3%). A low rate of complete larval development also was observed on sunflower, Helianthus annuus (11.6%), in the tribe Heliantheae. However, sunflower was rejected as a potential host in larval‐feeding and adult oviposition choice tests involving the primary host S. madagascariensis as control. Although larvae died as first instars on most test species, incomplete development and low levels of feeding were observed on nine species in the tribes Heliantheae, Cardueae and Lactuceae. Larvae did not feed on any non‐Asteraceae tested, including species with similar pyrrolizidene alkaloid chemistry, crops, and six ecologically prominent native species. Because all species of Senecioneae are non‐native and weedy in Hawaii, these results indicate that S. extensa is sufficiently host‐specific for introduction for biological control. High levels of feeding damage observed on potted plants indicate that S. extensa can severely impact the target fireweed as well as D. odorata, a noxious weed in native Hawaiian forests.     

Host range and impact of the flower-feeding moth,Cochylis campuloclinium – a biological control agent for Campuloclinium macrocephalum,in South Africa

Campuloclinium macrocephalum (Less.) DC. (Asteraceae) (pompom weed), an invader in South Africa and Swaziland, threatens biodiversity conservation, agriculture and tourism in the region. We report on the host range and impact of the flower-feeding moth, Cochylis campuloclinium Brown (Lepidoptera: Tortricidae), the second insect biological control agent to be considered for C. macrocephalum in South Africa. Laboratory host-specificity tests were conducted on 31 Asteraceae species. Field host range studies included 17 non-target Asteraceae species. Results of both C. campuloclinium laboratory and field host-range trials indicated that it is suitably host specific. In laboratory host-range trials, only C. macrocephalum and the closely related native, Adenostemma caffrum DC. (Asteraceae), received feeding damage, while in field host-range trials, the moth was only recorded on the target. Laboratory impact studies showed that C. campuloclinium destroyed a significant number of florets in flower buds (76%) and seeds in mature flowers (54%). Based on evidence from the native range, there appears to be no competitive interactions between C. campuloclinium and the already established stem- and leaf-deforming thrips, Liothrips tractabilis Mound & Pereyra (Thysanoptera: Phlaethripinae). The two insect agents should perform a complementary role of reducing flowering (L. tractabilis) and seed production (C. campuloclinium). Based on the above data, permission for the release of the moth was sought in August 2015.     

广聚萤叶甲成虫取食经历对后续 产卵寄主选择的影响

【背景】取食经历对植食性昆虫的寄主选择行为具有较大影响,影响天敌昆虫寄主专一性测定的设计和结果解释。【方法】采用选择性试验,观察了入侵豚草的重要天敌——广聚萤叶甲成虫羽化后取食不同植物对其后续产卵寄主选择的影响。【结果】与取食豚草的试虫相比,有取食三裂叶豚草、苍耳或菊芋经历的成虫选择苍耳产卵的频次增加,不再对豚草表现出明显的选择偏好性。对产卵识别期的Cox模型分析结果表明,成虫早期取食不同植物,对后续产卵选择有显著影响,成虫羽化后如果先取食豚草或三裂叶豚草,则选择苍耳产卵的倾向显著低于豚草;但如果先取食苍耳、菊芋和农家向日葵,则选择苍耳产卵的倾向与豚草无显著差异。【结论与意义】由此推测,广聚萤叶甲初羽化成虫取食的植物对其后续产卵选择具有较大影响,因而在寄主专一性测定中应关注测试前饲喂的植物种类。     

Chemistry of Cirsium and Carduus: a role in ecological risk assessment for biological control of weeds?

Prediction of host plant range and ecological impact of exotic phytophagous insects, such as insects for classical biological control of weeds, represents a major challenge. Recently, the flowerhead weevil (Rhinocyllus conicus Fröl.), introduced from Europe into North America to control exotic thistles (Carduus spp.), has become invasive. It feeds heavily on some, but not all species of native North American thistles (Cirsium spp.). We hypothesized that such non-target use among native plants could be better predicted by knowledge of characteristic chemical profiles of secondary compounds to supplement the results of host specificity testing. To evaluate this hypothesis, we reviewed the literature on the chemistry of Cirsium and Carduus thistles. We asked what compounds are known to be present, what is known about their biological activity, and whether such information on chemical profiles would have better predicted realized host range and ecological effects of R. conicus in North America. We found an extensive, but incomplete literature on the chemistry of true thistles. Two main patterns emerged. First, consistent chemical similarities and interesting differences occur among species of thistles. Second, variation occurs in biologically active groups of characteristic compounds, specifically flavonoids, sterols, alkaloids and phenolic acids, that are known to influence host plant acceptance, selection, and feeding by phytophagous insects. Surprisingly, sesquiterpene lactones, which are characterisitic in closely related Asteraceae, have not been extensively reported for Cirsium or Carduus. The minimal evidence on sesquiterpene lactones may reflect extraction methods vs. true absence. In summary, our review suggests further research on thistle chemistry in insect feeding is warranted. Also, since the exotic Canada thistle (Cirsium arvense) is an invasive thistle of current concern in North America, such research on mechanisms underlying host range expansion by exotic insects would be useful.     

A proposal to use plant demographic data to assess potential weed biological control agents impacts on non-target plant populations

Weed biocontrol programs aim to reduce the spread and population growth rate of the target plant while stabilizing or increasing populations of those native species considered under threat by invasive plants. This goal is not unique to weed biocontrol but applies to all other invasive plant management techniques, though such information is rarely collected. Without this information, success of management interventions can be ambiguous, and regulatory agencies, the public, policy makers, funders and land managers cannot be held accountable for chosen treatments. A fundamental reform, including use of demographic studies and long-term assessments, are essential to guide weed biocontrol programs. We propose to add use of plant demography (an assessment of how environmental factors and ecological interactions, for example competition, disease or herbivory, may affect plant populations by altering survival, growth, development and reproductive rates of plant individuals) during host specificity risk assessments of potential biological control agents. Demographic models can refine assessments of potential impacts for those plant species that experience some feeding or larval development during host specificity testing. Our proposed approach to focus on impact on plant demography instead of attack on plant individuals is useful in appropriately gauging threats potential weed biocontrol agents may pose to non-target species after field release.     

Predicting the host range of Nystalea ebalea: Secondary plant chemistry and host selection by a surrogate biological control agent of Schinus terebinthifolia

The safety of weed biological control depends upon the selection and utilization of the target weed by the agent while causing minimal harm to non-target species. Selection of weed species by biological control agents is determined by the presence of behavioral cues, generally host secondary plant compounds that elicit oviposition and feeding responses. Non-target species that possess the same behavioral cues as found in the target weed may be at risk of damage by classical biological control agents. Here we conducted host range tests and examined secondary plant compounds of several test plant species. We studied the specialist herbivore Nystalea ebalea (Lepidoptera: Notodontidae) a Neotropical species, present in Florida as a surrogate biological control agent of the weed, Brazilian peppertree Schinus terebinthifolia, invasive in Florida and Hawaii. We found that the larvae had the greatest survival when fed the target weed, the Neotropical species Spondias purpurea, the Florida native species Rhus copallinum, and the ornamental Pistacia chinensis. Reduced survival and general larval performance were found on the native species Metopium toxiferum and Toxicodendron radicans. Both the volatiles and the allergen urushiols were chemically characterized for all species but urushiol diversity and concentration best predicted host range of this herbivore species. These results provide insight into host selection and utilization by one oligophagous Schinus herbivore. Other potential biological control agents may also be sensitive to plants that contain urushiols and if so, they may pose minimal risk to these native species.     

Isolation and characterization of microsatellite markers for a worldwide invasive weed, Chromolaena odorata (Asteraceae)

? PREMISE OF THE STUDY: Microsatellite loci were isolated and characterized for a worldwide invasive weed Chromolaena odorata (Asteraceae) to elucidate the population genetic structure and invasive history. ? MetHODS AND RESULTS: A total of 14 microsatellite primer pairs were developed using the Fast Isolation by AFLP of Sequences Containing repeats (FIASCO) protocol, and their polymorphism was assessed in two natural populations of C. odorata from Mexico and Trinidad and Tobago. Eleven loci showed polymorphism and eight of these loci were successfully amplified in Ageratina adenophora, another invasive weed related to C. odorata. ? CONCLUSIONS: These microsatellite markers are useful for investigating the population genetic structure and the history of range expansion of these invasive species.     

Occurrence of Physoclypeus farinosus Hendel (Diptera: Lauxaniidae) in flowerheads of Asteraceae (Asterales)

The occurrence of Physoclypeus farinosus Hendel in flowerheads of Asteraceae from different Brazilian localities is presented. The use of this resource by this fly is discussed.     

Biology and Host Specificity of the Stem Galling Weevil Conotrachelus albocinereus Fiedler (Col.: Curculionidae), a Biocontrol Agent for Parthenium Weed Parthenium hysterophorus L. (Asteraceae) in Queensland, Australia

The stem-galling weevil Conotrachelus albocinereus Fiedler has been investigated as a potential biological control agent against parthenium weed ( Parthenium hysterophorus L.) in Australia. Adults were tested in multiple-choice feeding and oviposition tests on 56 plant species in 51 genera. No feeding or oviposition was recorded on any non-target plant except annual ragweed ( Ambrosia artemisiifolia L.), a closely related weed. Field releases of the weevil in Queensland, Australia, commenced in 1995 and establishment has been recorded at several sites.     

Eutreta xanthochaeta (Diptera: Tephritidae) is unsuitable for biocontrol of Lantana camara in Africa

The stem-galling fly, Eutreta xanthochaeta, was evaluated as a potential agent for biocontrol of the invasive alien plant, Lantana camara, in Africa. Multi-choice trials showed an approximately equal oviposition preference for indigenous Lantana and Lippia species, and the target weed. They were also found to be about equally suitable for fly development. Finally, population sustainability studies indicated that the fly has about as much potential to persist on these indigenous plants as on the target weed. It was concluded that E. xanthochaeta is insufficiently host specific to use for biocontrol of L. camara in Africa.     

Distribution of Insect Attacks in Biological Control of Weeds: Infestation of Centaurea virgata Flowerheads by a Gall Fly

The success of biological control efforts to reduce weed density through release of insects may depend as much on the distribution of insect attacks among individual plants or plant parts as on the mean level of infestation. We used an index of dispersion to describe the distribution of Urophora quadrifasciata (Diptera: Tephritidae) galls among squarrose knapweed (Centaurea virgata) flowerheads at 18 west central Utah sites in the first 5 years following introduction of the biological control agent. Two thirds of the samples showed a significantly aggregated distribution of galls among flowerheads. Statistical analysis showed that site and year accounted for relatively small proportions of the variance in the index of dispersion. The degree of gall aggregation among flowerheads was positively correlated with the mean flowerhead quality (mean number of seeds per flowerhead; P = 0.013) and tended to be negatively correlated with the mean fly density per flowerhead at a site in a given year (P = 0.097). Our data suggest that higher quality flowerheads, and possibly higher quality plants, are preferentially attacked by U. quadrifasciata and therefore are more heavily subject to reduced reproductive potential through biological control. However, an aggregated distribution of fly attacks may undercut the potential of the fly to reduce seed production by the weed population as a whole. Understanding both the distribution of insect attacks among individual plants and the behavioral mechanisms producing such distribution patterns is important to the biological control of weeds.     

Effects of Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) growing conditions and nutrient content on the performance of a leaf-mining fly,Hydrellia purcelli Deeming (Diptera: Ephydridae)

Host plant quality for insects used in weed biological control influences their performance and hence their ability to suppress target host populations. Determining the specific response of these insects to the quality of their host is important because phytophagous insects have variable tolerances of the different constituents of host plant quality, most notably dietary nitrogen (N), but also other physical and chemical components. The invasive aquatic weed Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) was cultivated under varying nutrient conditions to determine the influence of plant quality on immature survival, development, larval mining, reproductive output and adult longevity of a leaf-mining fly Hydrellia purcelli Deeming (Diptera: Ephydridae). Additionally, field-collected H. verticillata was included in the investigations to assess the potential performance of H. purcelli in the field. Variation in plant tissue N and phosphorus (P) concentrations had no effects on larval survival, female fecundity, or adult longevity, but high levels of N and P were associated with reduced immature development times and higher body mass of females. Overall, plant quality factors not measured in this study appeared to have a greater impact on the performance of the fly, rather than dietary N and P. The results provided insights into optimal mass-rearing conditions for H. purcelli and the potential performance of the fly in the field in South Africa. Furthermore, the results demonstrate the importance of considering other aspects of plant quality for insect agents, in addition to dietary N and P, when developing mass-rearing protocols or predicting their potential impact in the field.     

Host specificity assessment and potential impact of Megamelus scutellaris (Hemiptera: Delphacidae) on waterhyacinth Eichhornia crassipes (Pontederiales: Pontederiaceae)

The delphacid Megamelus scutellaris Berg was evaluated for host specificity and potential impact as part of a biological control program targeting Eichhornia. crassipes. Survival and development of adults and nymphs were used as metrics with no-choice, two-choice, nymph transfer, and sustainability tests conducted under quarantine conditions. A total of 69 plant species were tested including 12 from the Pontederiaceae (including E. crassipes). Additionally, 27 native and 5 exotic associated wetland species and 11 economic species were tested. Megamelus scutellaris exhibited a high level of oviposition and developmental fidelity to E. crassipes by failing to sustain populations on any non-target test plant past the F₁ generation. Nymph transfer tests which simulated potential spill-over events found that survival was virtually non-existent on associated wetland plants, regardless of taxonomic relatedness, including on Pontederia cordata, an important and widespread native species. Eichhornia crassipes plants exposed to two consecutive generations of feeding produced 66.9% less biomass and 73.4% fewer leaves than those in the controls. We conclude that Megamelus scutellaris is safe to release on E. crassipes in the United States.     

Predictability of pathogen host range in classical biological control of weeds: an update

Before an exotic pathogen can be released as a classical biological control agent the likely positive and negative outcomes of that introduction must be predicted. Host range testing is used to assess potential damage to non-target plants. To-date 28 species of fungi have been released as classical biological control agents against weeds world-wide. These pathogens have been reported infecting only six non-target plant species outdoors and all of these incidents were predicted. Many more non-target plant species developed disease symptoms in glasshouse tests than in the field. Consequently, data from other sources are needed to ensure potential agents are not prematurely rejected. Predictions of pathogen host range to date have been sufficiently accurate to prevent unpleasant surprises. Exotic pathogens are a safe and useful tool for weed control, especially in natural areas rich in valued non-target species.     

Pre-release evaluation of absolute spillover impact risk of Physonota maculiventris (Chrysomelidae: Cassidinae) on non-target plant species Helianthus annuus (Asteraceae) and Zea mays (Poaceae) in South Africa

The tortoise beetle, Physonota maculiventris (Coleoptera: Chrysomelidae), a candidate biological control agent of Tithonia diversifolia (Hemsl.) A. Gray (Asteraceae) was screened for spillover risks on non-target plant species in South Africa. Studies were conducted to measure the absolute feeding damage and reproductive performance of P. maculiventris on non-target plant species, Helianthus annuus L. (Asteraceae) and Zea mays L. (Poaceae). The influence of spillover on generational build-up performance on the non-target plant species was also investigated. Adult female beetles were switched from T. diversifolia at 14 (actively feeding colony) or 24 (gravid colony) days to the non-target species. Likewise, as a backup or control, female beetles were exposed to H. annuus in a no-choice situation and switched to T. diversifolia and Z. mays. Feeding damage, adult longevity and egg production of P. maculiventris were significantly lower on H. annuus, compared to those metrics on T. diversifolia. Gravid P. maculiventris adults switched from T. diversifolia on the 14th day after emergence laid a few egg batches on the leaf surfaces of Z. mays, but no signs of feeding were observed. Furthermore, the population of P. maculiventris significantly increased by 11.7 fold (26.8–312.5 adults) between the first (F1) and second (F2) generations on T. diversifolia, while on the non-target, H. annuus, it decreased from 6.3 to zero (0). The study concludes that P. maculiventris will sustain its populations entirely on the target, T. diversifolia population stands associated with or without H. annuus and Z. mays cultivations at different scales in South Africa.