Quarantine host range of Bikasha collaris,a potential biological control agent of Chinese tallowtree (Triadica sebifera) in North America

Chinese tallowtree, Triadica sebifera (L.) Small (Euphorbiaceae), is one of the worst invasive weeds of the southeastern USA impacting coastal wetlands, forests, and natural areas. Traditional mechanical and chemical controls have been unable to limit the spread, and this invasive species continues to expand its range. A proposed biological control candidate, the flea beetle Bikasha collaris (Baly) (Coleoptera: Chrysomelidae), shows high specificity for the target weed Chinese tallowtree. Results from a series of no‐choice and choice feeding tests of B. collaris adults and larvae indicated that this flea beetle was highly specific to Chinese tallowtree. The larvae of B. collaris feed by tunneling in the roots, whereas the adults feed on the leaves of Chinese tallowtree. A total of 77 plant taxa, primarily from members of the tallow plant family Euphorbiaceae, were tested in numerous test designs. Larval no‐choice tests indicated that larvae completed development only on two of the non‐target taxa. Of 80 B. collaris larvae fed roots of Hippomane mancinella L. and 50 larvae fed roots of Ricinus communis L., two and three larvae completed development, respectively. The emerging adults of these five larvae died within 3 days without reproducing. Larval choice tests also indicated little use of these non‐target taxa. Adult no‐choice tests indicated little leaf damage by B. collaris on the non‐targets except for Ditrysinia fruticosa (Bartram) Govaerts & Frodin and Gymnanthes lucida Sw. When given a choice, however, B. collaris adults consumed much less of the non‐targets D. fruticosa (7.4%) and G. lucida (6.1%) compared with the control leaves. Finally, no‐choice oviposition tests indicated that no eggs were produced when adults were fed all non‐target taxa, except those fed G. lucida. These B. collaris adults fed G. lucida leaves produced an average of 4.6 eggs compared with 115.0 eggs per female when fed Chinese tallowtree. The eggs produced from adults fed G. lucida were either inviable or the emerging larvae died within 1 day. These results indicate that the flea beetle B. collaris was unable to complete its life cycle on any of the non‐target taxa tested. If approved for field release, B. collaris will be the first biological control agent deployed against Chinese tallowtree in the USA. This flea beetle may play an important role in suppressing Chinese tallowtree and contribute to the integrated control of this invasive weed.     

Host range testing and life history of the defoliator Hymenomima nr. memor: an unsuitable biological control agent for Schinus terebinthifolia in the U.S.A.

Host range of larvae of Hymenomima nr. memor (Lepidoptera: Geometridae) was examined in quarantine to evaluate its suitability as a biological control of Brazilian peppertree, Schinus terebinthifolia. Brazilian peppertree, S. terebinthifolia is an environmental and agricultural weed from South America that had invaded many subtropical and tropical areas of the world including Florida and Hawaii, USA. Laboratory life history and quarantine host range studies of H. memor were conducted with no-choice feeding tests. These tests included eight species of the Anacardiaceae and one species of Sapindaceae. Larvae of H. memor had five to six instars with each head capsule width increasing by 1.68-X. Development time from neonate to adult was 46.7?±?2.2 days. In host range tests, neonates completed development to the adult stage on all non-target species, except Toxicodendron radicans. Moreover, developmental times were delayed and pupal weights were reduced for larvae fed Spondias purpurea leaves. Due to the broad host range exhibited by H. memor larvae, this species will not be considered as a biological control agent of S. terebinthifolia in the continental U.S.A.     

Research article: life history and host range of Prochoerodes onustaria,an unsuitable classical biological control agent of Brazilian peppertree

The life history and host range of the South American defoliator Prochoerodes onustaria (Lepidoptera: Geometridae) were examined to determine its suitability as a classical biological control agent of the invasive weed Brazilian Peppertree, Schinus terebinthifolia, in the U.S.A. Larvae were collected feeding on S. terebinthifolia in Brazil and were colonised and tested in quarantine. Life history observations indicated that 54% (n?=?63) of larvae reared on S. terebinthifolia leaves survived to adulthood and 65% of adults (n?=?34) required five instars. Development time from eclosion to adult did not differ by sex: males required 42.9?±?1.1 days and females required 41.1?±?0.9 days. No-choice host range tests were conducted on 11 species in two families (Anacardiaceae and Sapindaceae), including U.S.A. native, commercial, and ornamental species. Larvae completed development on all species, although survival differed significantly among them. Larvae fed Anacardium occidentale, Cotinus coggygria, Dodonaea viscosa, and Mangifera indica demonstrated higher survival than those on S. terebinthifolia, whereas survival was reduced among larvae fed Metopium toxiferum and Comocladia dodonaea. Consumption was significantly greater on M. toxiferum than on the other species. The results presented here suggest that P. onustaria is highly polyphagous, feeding and completing development on members of two related plant families, and is not suitable for biological control of Brazilian peppertree in the U.S.A.     

Host range of the leaf-tier Tentamen atrivirgulatum Metz (Lepidoptera: Gelechiidae); an unsuitable candidate for biological control of Brazilian peppertree

ABSTRACT

The life history and host range of the South American leaf-tier Tentamen atrivirgulatum Metz, 2019 (Lepidoptera: Gelechiidae) was evaluated to determine its suitability for classical biological control of invasive Brazilian peppertree, Schinus terebinthifolia, in the USA. Larvae were collected during a survey in the native range of Brazil feeding on Brazilian peppertree. A quarantine colony was established and no-choice tests were conducted to determine the host range of this species. The results of these tests indicated that the larvae fed and completed development on seven of the eleven non-target species tested. Percent survival on these non-targets ranged from 20% to 100%. Larval survival was 50% when fed the target weed Brazilian peppertree. When larvae were fed leaves of these non-targets, pupal weights were significantly lower only for those fed Pistacia chinensis. Development time to the pupal and adult stages did not differ with larval diet. These no-choice results indicate T. atrivirgulatum larvae have a broad host range and thus this species will not be developed as a biological control agent for Brazilian peppertree in the USA.     

Quarantine host range studies with Lophyrotoma zonalis, an Australian sawfly of interest for biological control of melaleuca, Melaleuca quinquenervia, in Florida, U.S.A.

The Australian melaleuca tree, Melaleuca quinquenervia (Cav.) S. T. Blake (Myrtaceae), has naturalized in southern Florida,U.S.A., and is now one of that regions most important weeds.Primarily a weed of wetlands, it also infests neighboring drierareas. Current efforts to restore the South Florida ecosystem arethreatened by the continuing range expansion of melaleuca andother weeds. In an effort to supplement the current chemical andcultural control methods for melaleuca, a search for potentialbiological control agents was begun in Australia in 1986. Thesawfly, Lophyrotoma zonalis, was determined after extensive fieldand laboratory studies to have potential as a biological controlagent. Larvae of L. zonalis eat leaves and occasionally defoliatelarge trees in Australia. Host range studies were conducted in aFlorida quarantine facility with native and cultivated plantspecies. Multi-choice and no-choice oviposition tests wereconducted with 36 species in the Myrtaceae and with 18 species inother families. Larvae developed to prepupae and adults from theeggs oviposited on 23 species of Myrtaceae only on 3 species ofbottlebrushes, Callistemon. Medium-sized larvae were tested forfeeding on bouquets of plant cuttings and on potted plants. Theyare the stage that might wander from defoliated trees. Noticeablefeeding, but much less than on melaleuca, was restricted to theMyrtaceae, except for a few individual larvae that fed on waxmyrtle, Myrica cerifera. Medium-sized larvae became prepupae onlyon Melaleuca decora (73%) and on wax myrtle (10%). However,neither species received eggs in the oviposition tests. Thesestudies confirmed the narrow host range of L. zonalis aspreviously reported from field and laboratory studies inAustralia.     

Host specificity of <Emphasis Type="Italic">Tectococcus ovatus</Emphasis> (Hemiptera: Eriococcidae), a potential biological control agent of the invasive strawberry guava, <Emphasis Type="Italic">Psidium cattleianum</Emphasis> (Myrtales: Myrtaceae), in Florida

Strawberry guava, Psidium cattleianum Sabine, is a woody tree or shrub native to coastal southeastern Brazil. Strawberry guava was introduced into Florida in the late 1800s as an ornamental species. The plant escaped cultivation and is invading natural areas throughout the southern half of the state. In addition to negative effects on Florida’s native ecosystems, strawberry guava also is a preferred host of the Caribbean fruit fly, Anastrepha suspensa Loew (Diptera: Tephritidae). In total, 57 plant species representing 21 families were included in the host range tests. First instar nymphs of Tectococcus ovatus Hempel fed on two closely related guava species, Brazilian guava (Psidium friedrichsthalianum O. Berg), and Costa Rican guava (Psidium guineense Sw.). However, none of the nymphs completed their development on these two non-target species. The results of the host specificity tests suggest that T. ovatus is a suitable candidate for classical biological control of strawberry guava in Florida.     

Laboratory host range testing of Lilioceris sp. near impressa (Coleoptera: Chrysomelidae) – a potential biological control agent of air potato,Dioscorea bulbifera (Dioscoreaceae)

Air potato, Dioscorea bulbifera, is an invasive, herbaceous, climbing vine, which dominates invaded native vegetation in Florida. The fortuitous discovery of Lilioceris sp. near impressa defoliating D. bulbifera vines and feeding on the bulbils (aerial tubers) in the Katmandu Valley of Nepal initiated a project to assess the potential of this leaf beetle for biological control of air potato in Florida. Quarantine host specificity tests were conducted on 41 plant species in 24 families and 13 orders, with 26 species outside of the Dioscoreaceae and 15 species within the Dioscoreaceae. Adults test fed (nibbled) on 4/12 of tested Dioscorea species, but no larval feeding or development occurred on any plant other than the target, D. bulbifera. The larvae feed gregariously and quickly skeletonize offered leaves of air potato. Air potato bulbils that received any feeding damage to the primary meristematic region did not sprout. The ability of the beetle larvae and adults to feed on the bulbils is important because in Florida, the plant rarely flowers or produces fruit, so these aerial tubers are the primary means of persistence and spread. The adults can live for several months without food. This extremely specialized herbivore from part of the weed's native range appears to have great promise as a biological control of air potato.     

Biology and host range of Heterapoderopsis bicallosicollis: a potential biological control agent for Chinese tallow Triadica sebifera

Chinese tallow, Triadica sebifera, is an invasive weed that infests natural and agricultural areas of the south-eastern USA. A candidate insect for biological control of Chinese tallow has been studied under quarantine conditions. The biology and host range of a primitive leaf-feeding beetle, Heterapoderopsis bicallosicollis, were examined between July 2008 and February 2010. H. bicallosicollis adults fed on 16 of 29 non-target species and survived >10 days on all 29 species, more than the number of days that adults survived when deprived of food. Additionally, adult feeding, oviposition and partial larval development occurred on a Florida endangered species, Heterosavia bahamensis. These data indicated that H. bicallosicollis adult feeding and oviposition may not be limited to the target weed and included several valued North American natives. Therefore, as its release could pose unacceptable risks, testing of this species was discontinued and the quarantine colony destroyed.     

Host range of the defoliator Strepsicrates sp. is too broad for biological control of the invasive weed Rhodomyrtus tomentosa

In its native range the invasive weed, Rhodomyrtus tomentosa is host to a suite of herbivores. One, Strepsicrates sp. (Lepidoptera: Tortricidae), was collected in China in 2014, introduced under quarantine in Florida, USA, and tested against related species to determine its host range and suitability for biological control. In no-choice tests, neonates fed and completed development to the pupal stage on several species of Myrtaceae, including the target weed R. tomentosa, the exotics Melaleuca quinquenervia, and Eucalyptus camaldulensis, and three native species, Eugenia axillaris, Mosiera longipes and Morella cerifera (Myricaceae). Due to the broad host range exhibited in quarantine testing, this species will not be pursued as a biological control agent of R. tomentosa.     

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.     

Oviposition preference and larval performance of monarch butterflies (Danaus plexippus) on two invasive swallow-wort species

The potential of two invasive herbaceous vines Vincetoxicum nigrum (L.) Moench and Vincetoxicum rossicum (Kleopow) Barbar. (Asclepiadaceae) to reduce monarch butterfly (Danaus plexippus L.) (Lepidoptera: Nymphalidae, Danainae) populations was investigated by evaluating oviposition selection in adult monarch butterflies and larval feeding preference in choice tests comparing the native host plant of monarch butterflies, Asclepias syriaca L. (Asclepiadaceae) and the two non‐indigenous Vincetoxicum species. In both choice and no‐choice tests, no eggs were oviposited on either of the two Vincetoxicum species whereas over 66 eggs per female were oviposited on A. syriaca plants. All first instar larvae allowed to feed on A. syriaca for 48 h survived while a significantly lower proportion survived on V. rossicum (44%) and V. nigrum (14%). Mean weight of larvae that did survive on the Vincetoxicum species was significantly lower than the mean weight of larvae that fed on A. syriaca. The mean weight of surviving larvae, however, did not differ between the two Vincetoxicum species. The mean proportion of leaves consumed by larvae feeding on A. syriaca was significantly greater than the mean proportion of leaves consumed by larvae feeding on either Vincetoxicum species. Findings from this research indicate that V. rossicum and V. nigrum are not viable hosts of monarch butterflies and are likely to pose little direct threat to their populations as oviposition sinks. The ability of these highly aggressive plants, however, to out‐compete and displace the native host of monarchs, A. syriaca, may pose a more serious threat. The potential of monarch populations to adapt to the two Vincetoxicum species as host plants over the long‐term is discussed.     

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.     

Maintenance of a narrow host range by Oxyops vitiosa; a biological control agent of Melaleuca quinquenervia

Host range expansion in insect herbivores is often thought to be mediated by several factors, principal among them are secondary plant metabolites. In weed biological control, the host range of a prospective agent is one of the most important considerations in its implementation. Extensive host testing tests seek to determine the behavioral acceptance and nutritional value of different test plant species to the potential agent. A list of test plants is compiled that comprises species that are close taxonomic relatives of the target weed plus other species of economic or ecologic importance. The host testing of the Melaleuca quinquenervia biological control agent Oxyops vitiosa indicated that larvae would accept and complete development on the Australian target weed M. quinquenervia, two Australian ornamental species, Callistemon citrina, Callistemon viminalis (all Myrtaceae). However, the larvae did not complete development when fed a North American species Myrica cerifera (Myricaceae). The study reported here confirms these results and examines the nutritional and performance differences in O. vitiosa larvae fed leaves of these species. The leaf quality factors, percent moisture, percent nitrogen, toughness, and terpenoid content were related to larval survival, performance and digestive indices. The results indicate that plant quality among the Myrtaceae species was generally similar and correspondingly larval survival, performance and digestive indices differed little when larvae were fed leaves of these species. However, significant differences occurred in the plant quality of the North American M. cerifera compared with the Australian species which had leaves with the lowest percent moisture, lowest leaf toughness, highest percent nitrogen. This species, however, is not a physiological host as none of the neonates survived to pupate. When third instars were switched to M. cerifera from their normal host M. quinquenervia reductions were found in survival, biomass gain, digestive efficiency, and conversion of digested food to insect biomass. The marginal acceptance of this North American native plant in laboratory bioassays appears related to the terpenoid chemistry that has similarities to the taxonomically unrelated host M. quinquenervia. However, the high larval mortality corresponds to several novel terpenoids that are not present in the host. For weed biological control host testing these results indicate that M. cerifera is a poor host for O. vitiosa. Additionally, future test plant lists should include plants with secondary metabolites similar to the target weed as these compounds may constitute behavioral cues that are relevant to these specialized herbivores.     

Do exotic generalist predators alter host plant preference of a native willow beetle?

1 Selection can favour herbivores that choose host plants benefitting their offspring either by enhancing growth rates or by increasing larval defences against native predators. For exotic predator species that feed on herbivores, their success with invading new habitats may depend upon overcoming defences used by native prey. Whether exotic predators can alter herbivore host choice has remained unexamined. Therefore, we compared the efficacy of larval defence by Chrysomela knabi (a native beetle species) that had fed on two native willow hosts: Salix sericea (a phenolic glycoside (PG)-rich species) and Salix eriocephala (a PG-poor species), when attacked by exotic generalist predators. In addition, the preference and performance of C. knabi on S. sericea and S. eriocephala was examined.
2  Chrysomela knabi preferred and performed better on S. sericea. In a common garden, adult C. knabi were nine-fold more common and oviposited five-fold more frequently on S. sericea than on S. eriocephala . In the laboratory, adult feeding preference on leaf discs and survival rates of larvae were both greater on S. sericea , and time to pupation was shorter.
3  Chrysomela knabi larvae produced significantly more salicylaldehyde when fed S. sericea leaves than when fed S. eriocephala leaves. Additionally, those larvae with greater salicylaldehyde had reduced predation by two exotic generalist predators, Harmonia axyridis larvae and juvenile Tenodera aridifolia sinensis .
4 The results obtained in the present study suggest that selection favoured the preference of C. knabi for PG-rich willow plants because larvae grew and survived better and that selection by common exotic generalist predators would reinforce this preference.     

Molecular comparisons of native range collections of Gadirtha fusca,a potential biological control agent of Chinese tallowtree

Chinese tallowtree, Triadica sebifera (L.) Small (Euphorbiaceae), is one of the worst invasive weeds of the southeastern USA impacting coastal wetlands, forests, and natural areas. A proposed biological control candidate, the defoliating moth Gadirtha fusca Pogue (Lepidoptera: Nolidae) shows high specificity for the target weed Chinese tallowtree. A total of 13 field sites were sampled in the native range of this herbivore species. To determine if all individuals were the same taxon, molecular DNA analyses were conducted of these collections. These included collections from 2012, 2015 and 2016, from three regions and two adult color morphs. Molecular COI analysis was performed on thirty colonized individuals from these collections. The results of this analysis arranged all taxa into a single clade with average genetic divergence values of 0.3%. Comparison of these G. fusca sequences and those from other Gadirtha spp. all had divergence values that were equal to or exceeded 5%. These results indicate that all the G. fusca collections were a single species and they were distinct from other known members of this genus.     

Greater impact of host plant species on oviposition of a willow leaf beetle <Emphasis Type="Italic">Plagiodera versicolora</Emphasis> Laicharting (Coleoptera: Chrysomelidae) during the adult stage than in developing larval stage

In some herbivorous insects, such as Coleoptera and aphids, not only the host species of larvae, but also those of adults should be considered as key determinants of potential fecundity because oviposition is affected by the quality of host species during both larval and adult stages. This study examined the relatively greater impact on host species of the larval or adult stage on oviposition of the willow leaf beetle Plagiodera versicolora Laicharting (Coleoptera: Chrysomelidae). We conducted an experiment using a 2 × 2 experimental design, in which either of two different host plant species was fed in larval and adult stages. Females fed on a locally unavailable host Salix eriocarpa in the adult stage did not lay any eggs, but those fed on the locally available host S. babylonica laid 67–75 eggs on average, irrespective of larval host species. Such reproductively inactive females fed S. eriocarpa as an adult host recovered reproductive activity within 3 weeks after changing the host species to S. babylonica. This result indicated that the host species fed in the adult stage had a greater impact on oviposition than in the larval stage.     

Non-selective feeding and oviposition behaviour of Cryptocephalus trifasciata (Coleoptera: Cerambycidae: Cryptocephalinae) precludes its use as a biological control agent for downy rose myrtle (Rhodomyrtus tomentosa)*

Downy rose myrtle (Rhodomyrtus tomentosa), a southeast Asian native shrub, invades natural areas in Florida and Hawaii, where it forms dense, impenetrable thickets. We tested the host affinity and survivorship of a case-bearing beetle, Cryptocephalus trifasciata on R. tomentosa and related species. C. trifasciata adults and larvae fed, oviposited and/or completed development on all non-target species tested (N?=?11). C. trifasciata has a broad host range and is unsuitable for use as a biological control agent.     

Host specificity of Metriona elatior, a potential biological control agent of tropical soda apple, Solanum viarum, in the USA

The leaf beetle Metriona elatior from Brazil-Argentina was screened in the Florida (USA)State quarantine facility as a potential biological control agent of tropical soda apple, Solanum viarum, a recently arrived weed species. Multiple-choice host-specificity tests were conducted in small cages (60 cm × 60 cm × 60 cm) using 95 plant species in 29 families. Adults fed heavily on the main target weed (S. viarum), and on turkey berry,Solanum torvum (noxious weed of Asiatic origin); fed moderately on red soda apple, Solanum capsicoides (weed of South American origin), and eggplant, Solanum melongena (economic crop); and fed lightly on aquatic soda apple, Solanum tampicense (weed of Mexican-Caribbean-Central American origin), and onsilverleaf nightshade, Solanum elaeagnifolium(native weed widely distributed). M.elatior adults laid 84 to 97% of their egg masses onS. viarum, and 3 to 16% on S. melongena. Non-choice host-specificity tests were also conducted in quarantine in which M. elatior adults and neonate larvae were exposed to 17 and 19 plant species, respectively. Tests with the neonates indicate that this insect was able to complete its development on S. viarum, S. torvum, S. melongena, and S. capsicoides. Although some adult feeding and oviposition occurred on S.melongena in quarantine on potted plants in small cages, no feeding or oviposition by M. elatiorwas observed in field experiments conducted in Brazil. Surveys in unsprayed S. melongena fields in Argentina and Brazil indicated that M. elatioris not a pest of S. melongena in South America. The evidence obtained from the South-American field surveys, Brazil open-field experiments, and Florida quarantine host specificity tests indicate that M. elatior causes significant feeding damage toS. viarum, and does not represent a threat to S. melongena crops in the USA. Therefore an application for permission to releaseM. elatior against S. viarum in the USA was submitted in October 1998. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biology and host range of Omolabus piceus, a weevil rejected for biological control for Schinus terebinthifolius in the USA

Surveys for biological control agents of the invasive weed Schinus terebinthifolius (Anacardiaceae) discovered two Omolabus weevils (Coleoptera: Attelabidae) feeding on the plant in its native range. Molecular and morphological analysis indicated that one of these species consistently fed on the target weed and the other species fed more broadly. Aspects of the biology and host range of the more specific species, Omolabus piceus (Germar) were examined to determine its suitability as a biological control agent of S. terebinthifolius in the USA. Adults feed on newly formed leaves, and eggs, larvae and pupae develop in curled fragments of leaves, called nidi. Larvae consumed an average of 11.3 (±0.4) mg throughout their development which required 15.1 (±0.2) days. An average of 31.6 (±2.7) eggs were laid per female during their 23.8 (±2.2) day lifetime, after a 3.4 (±1.0) day preoviposition period. In no-choice tests, O. piceus adults fed and oviposited on all tested native North American, Caribbean and agricultural Anacardiaceae species except for M. indica. The field host-range of O. piceus, as determined by samples of host use in the native range, included three Schinus, two Lithrea and one Anacardium species. Therefore, we do not recommend O. piceus for biological control of S. terebinthifolius in the USA. However, the utilization of this species in other infested areas such as Hawaií and Australia should be considered.     

Influence of plant size and species on preference of Cyrtobagous salviniae adults from two populations

Adults from two populations (Brazil and Florida) of Cyrtobagous salviniae were bioassayed to determine if they exhibited a preference for either Salvinia minima or Salvinia molesta. Adults did not discriminate between host species in initial tests that evaluated the tertiary growth form. Further tests which compared two growth forms (primary and tertiary) as well as plant species, found that adults from the Brazil population consistently preferred larger (tertiary) plants without regard for host species. Weevils from the Florida population showed a similar, but less distinct, pattern of preference. Although adults from the Florida population survived equally well and experienced a similar pre-oviposition period on both plant species, they laid more eggs in S. molesta. Adults from the two populations differ in size: Brazil weevils were larger, which may explain their sensitivity to plant size as compared with the smaller Florida adults. Narrower rhizomes in S. minima may restrict usage of this species by the larger weevils, whereas smaller larvae may be better able to burrow in a wider range of plant sizes. Both weevil populations should be suitable biological control agents for use in programs targeting S. molesta.