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     

Characterising insect plant host relationships facilitates understanding multiple host use

Weed biocontrol relies on host specificity testing, usually carried out under quarantine conditions to predict the future host range of candidate control agents. The predictive power of host testing can be scrutinised directly with Aconophora compressa, previously released against the weed Lantana camara L. (lantana) because its ecology in its new range (Australia) is known and includes the unanticipated use of several host species. Glasshouse based predictions of field host use from experiments designed a posteriori can therefore be compared against known field host use. Adult survival, reproductive output and egg maturation were quantified. Adult survival did not differ statistically across the four verbenaceous hosts used in Australia. Oviposition was significantly highest on fiddlewood (Citharexylum spinosum L.), followed by lantana, on which oviposition was significantly higher than on two varieties of Duranta erecta (“geisha girl” and “Sheena’s gold”; all Verbenaceae). Oviposition rates across Duranta varieties were not significantly different from each other but were significantly higher than on the two non-verbenaceous hosts (Jacaranda mimosifolia D. Don: Bignoneaceae (jacaranda) and Myoporum acuminatum R. Br.: Myoporaceae (Myoporum)). Production of adult A. compressa was modelled across the hosts tested. The only major discrepancy between model output and their relative abundance across hosts in the field was that densities on lantana in the field were much lower than predicted by the model. The adults may, therefore, not locate lantana under field conditions and/or adults may find lantana but leave after laying relatively few eggs. Fiddlewood is the only primary host plant of A. compressa in Australia, whereas lantana and the others are used secondarily or incidentally. The distinction between primary, secondary and incidental hosts of a herbivore species helps to predict the intensity and regularity of host use by that herbivore. Populations of the primary host plants of a released biological control agent are most likely to be consistently impacted by the herbivore, whereas secondary and incidental host plant species are unlikely to be impacted consistently. As a consequence, potential biocontrol agents should be released only against hosts to which they have been shown to be primarily adapted.     

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.     

Introduction, Rearing, and Host Range of Aerenicopsis championi Bates (Coleoptera: Cerambycidae) for the Biological Control of Lantana camara L. in Australia

The biology and host range of the cerambycid beetle Aerenicopsis championi Bates, a potential biological control agent for the weed Lantana camara L., were studied. A. championi is a univoltine species associated with L. camara, L. urticifolia, and L. hirsuta in Mexico and Central America. In Mexico, adult emergence occurred in May and June at the start of the rainy season. Larvae fed within the stems over a 9- to 12-month period and caused damage to the plant. The insect was imported into Australia, where a procedure for rearing it in the laboratory was developed. Host-range tests indicated that adults oviposited and larvae commenced development in L. camara and L. montevidensis but not in any of 57 other species tested. A CLIMEX model indicated that most areas infested with lantana in Australia would have a favorable climate for A. championi. Permission to release this insect in Australia was obtained and three small releases were made in southern Queensland in February 1995.     

Influence of initial egg density and host size on the development of the gregarious parasitoid <Emphasis Type="Italic">Bracon hebetor</Emphasis> on three different host species

Bracon hebetor (Say) (Hymenoptera : Braconidae) is a gregarious parasitoid that attacks a variety of important lepidopterous pests of stored product and in the field. In this study the effect of host species, size and larval competition on parasitoid size, survival and development were investigated. In laboratory studies, wasp eggs at a range of densities, were placed on larvae of different weight of three Lepidoptera host species namely Adoxophyes orana (Fischer von Röslerstamm, Tortricidae), Plodia interpunctella (Hubner, Pyralidae) and, Lobesia botrana(Dennis & Schiffermueller, Tortricidae). On A. orana survival of immature parasitoids was very low at all densities and different host weights. On L. botrana survival progressively reduced as egg density increased at both host weights examined for this host. Survival on P. interpunctella was significantly affected by egg density but not by host weight. Initial egg density had a significant effect on the size of emerging adults from each rearing host. Smaller adult parasitoids emerged as egg density per larva increased. Larval host weight of P. interpunctella and A. orana had a significant effect on the size of emerging adult parasitoids mainly at the higher egg densities used in these experiments. The above results of host quality on fitness of parasitoid are discussed.     

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.     

Biology and host range of Ophiomyia camarae Spencer (Diptera: Agromyzidae), a potential biocontrol agent for Lantana spp. (Verbenaceae) in Australia

The life history and host range of the herringbone leaf-mining fly Ophiomyia camarae, a potential biological control agent for Lantana spp., were investigated. Eggs were deposited singly on the underside of leaves. Although several eggs can be laid on a single leaf and a maximum of three individual mines were seen on a single leaf, only one pupa per leaf ever developed. The generation time (egg to adult) was about 38 days. Females (mean 14 days) lived longer than males (mean 9 days) and produced about 61 mines. Oviposition and larval development occurred on all five lantana phenotypes tested. Eleven plant species representing six families were tested to determine the host range. Oviposition and larval development occurred on only lantana and another nonnative plant Lippia alba (Verbenaceae), with both species supporting populations over several generations. A CLIMEX model showed that most of the coastal areas of eastern Australia south to 30°16′ S (Coffs Harbour) would be suitable for O. camarae. O. camarae was approved for release in Australia in October 2007 and mines have been observed on plants at numerous field sites along the coast following releases.     

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.     

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.     

Biology, host range, and risk assessment supporting release in Africa of Falconia intermedia (Heteroptera: Miridae), a new biocontrol agent for Lantana camara

The ornamental hybrid shrub, Lantana camara L. (lantana), is a serious environmental weed and has been targeted for biological control in South Africa since 1961. The established biocontrol agents cause insufficient levels of damage and additional natural enemies are required to reduce the invasiveness of this weed. The lantana mirid, Falconia intermedia (Distant), is a promising new agent that was imported from the Caribbean for life history and host-range studies. The nymphs and adults are leaf-suckers that cause chlorotic speckling, which reduces the photosynthetic capacity of the plant. Biological studies indicate that F. intermedia has considerable biocontrol potential, in that it has a high intrinsic rate of increase, the potential for multiple generations a year, highly mobile adults, and a high level of damage per individual. Host-specificity trials indicated that the lantana mirid has a narrow host range, with L. camara being the most suitable host, but several indigenous African species in the closely related genus Lippia are suitable alternative host plants. Under multiple-choice conditions, adults showed a significant and strong oviposition preference for L. camara over the Lippia species. A risk assessment of potential nontarget effects indicated that three Lippia species could sustain damage levels in the field. The relatively low probability of damage to indigenous species was considered a justified trade-off for the potentially marked impact on L. camara. The regulatory authorities accepted the results of this study and F. intermedia was released against L. camara in South Africa in April 1999.     

The suitability of non-target native mangroves for the survival and development of the lantana bug <Emphasis Type="Italic">Aconophora compressa</Emphasis>, an introduced weed biological control agent

Aconophora compressa (Hemiptera: Membracidae), a biological control agent introduced against the weed Lantana camara (Verbenaceae) in Australia, has since been observed on several non-target plant species, including native mangrove Avicennia marina (Acanthaceae). In this study we evaluated the suitability of two native mangroves, A. marina and Aegiceras corniculatum (Myrsinaceae), for the survival and development of A. compressa through no-choice field cage studies. The longevity of females was significantly higher on L. camara (57.7 ± 3.8 days) than on A. marina (43.3 ± 3.3 days) and A. corniculatum (45.7 ± 3.8 days). The proportion of females laying eggs was highest on L. camara (72%) followed by A. marina (36%) and A. corniculatum (17%). More egg batches per female were laid on L. camara than on A. marina and A. corniculatum. Though more nymphs per shoot emerged on L. camara (29.9 ± 2.8) than on A. marina (13 ± 4.8) and A. corniculatum (10 ± 5.3), the number of nymphs that developed through to adults was not significantly different. The duration of nymphal development was longer on A. marina (67 ± 5.8 days) than on L. camara (48 ± 4 days) and A. corniculatum (43 ± 4.6 days). The results, which are in contrast to those from previous glasshouse and quarantine trials, provide evidence that A. compressa adults can survive, lay eggs and complete nymphal development on the two non-target native mangroves in the field under no-choice condition.     

Host specificity ofAcanthoscelides quadridentatus andA. Puniceus [Col.: Bruchidae] for biological control ofMimosa pigra (with preliminary data on their biology)

The biology and host specificity of the seed-feeding bruchids,Acanthoscelides quadridentatus (Schaeffer) andA. puniceus Johnson, from Mexico were studied in quarantine facilities in Australia. Distinguishing characters in the genitalia of each species are illustrated. Oviposition was recorded on 16 of 73 species of plants tested but larvae died without entering pods or seeds, except onMimosa invisa K. F. P. von Martius andM. pigra L. Larvae entering seeds ofM. invisa died in the first instar. The bruchids were clearly specific toM. pigra and were subsequently released as part of a program for biological control of this weed in the Northern Territory, Australia in April 1983 and thailand in July 1984.      

Unsuitability of Charidotis pygmaea for biocontrol of Lantana camara in Africa

The host range of the tortoise beetle,Charidotis pygmaea Klug (Coleoptera:Chrysomelidae), was studied under quarantinelaboratory conditions to evaluate the insect'ssuitability for release as a biological controlagent for the noxious weed, Lantanacamara L. (Verbenaceae) in South Africa.Culturing on the target plant, L. camara,proved problematic with high larvalmortalities. Host-specificity studies showedthat four species in the genus Lantana,and two species in the genus Lippiawere acceptable as host plants. Duringlarval development trials, the insect performedbetter on the indigenous Lantana rugosaThunb. (Verbenaceae) and the introduced,commercially used L. montevidensis(Spreng.) Briq. (Verbenaceae), than on any ofthe weedy South African L. camaravarieties tested. Adult multi-choice trialsindicated that the beetle preferred to ovipositon L. rugosa and L. montevidensis.It is therefore recommended that C.pygmaea not be released against L.camara in Africa.     

Study of pollen brush in selected species of Astragalus L. subgenus Pogonophace Bunge (Leguminosae)

Nine species of Lippia (Verbenaceae) were studied by RAPD markers in order to evaluate the degree of genetic diversity. The following species were collected at the Cadeia do Espinhaço Mountains, Southeast Brazil: L. corymbosa, L. diamantinensis, L. filifolia, L. florida, L. hermannioides, L. lupulina, L. rotundifolia, L. rosella and L. sidoides. The analysis was performed using 18 primers that generated 490 fragments and only one primer was found to be monomorphic in all individuals. The average interspecific genetic distances were similar for all species and higher than the intraspecific genetic distances. Species with narrow occurrence did not show low intraspecific diversity. The molecular data were used to generate an UPGMA dendrogram that showed two major groups with a clear distribution among the species. RAPD analysis was efficient to address the genetic diversity of Lippia species and contributed to understand the adaptation to the environment, conservation and taxonomic implications.     

北京唇形科一新记录属——龙头草属

该文报道了发现于北京市密云区的1种被子植物新记录——荨麻叶龙头草[Meehania urticifolia(Miq.)Makino],其所隶属的龙头草属(Meehania Britton)为北京分布新记录。描述了荨麻叶龙头草的形态特征与生境,凭证标本藏于浙江大学标本馆(HZU)。荨麻叶龙头草于1899年首次发现于日本,是东北亚分布植物,此前在中国仅分布于东北。北京云蒙山发现的分布点,显然是该种目前在中国分布最西的分布点,可能于冰川期从东北亚迁移而来。     

The influence of plant species on attraction and host acceptance inCotesia glomerata (Hymenoptera: Braconidae)

Females of the larval parasitoidCotesia glomerata (L.) use plant-associated cues to locate their lepidopteran host,Pieris rapae L. In this study we investigated the influence of four host plant species,Brassica oleracea var.acephala (‘Vates’ kale),Tropaeolum majus (nasturtium),Lunaria annua (honesty), andCleome spinosa (spider flower), on two components of the host selection process inC. glomerata, namely, attraction and host acceptance. Choice tests in a flight tunnel showed that parasitoids were attracted to some host plant species more than to others in the absence of host larvae.B. oleracea was the most attractive plant species, followed byL. annua, T. majus, andC. spinosa. In previous studies it was shown thatB. oleracea carries highly suitable hosts forC. glomerata and that, in the field, parasitization rates on this plant were the highest. When host larvae were reared on the four host plant species and then transferred to a common substrate (B. oleracea var.capitata, cabbage), plant species that had served as diet for the hosts did not have a significant effect on acceptance for parasitization. Thus, parasitoids were attracted to host plant species differentially, but they did not discriminate among host larvae based on the dietary history of their hosts. ForC. glomerata, it appears that phytochemistry mediates host selection more by influencing parasitoid attraction than it does by affecting host acceptance.     

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.     

不同水分处理和密度配置对牛鞭草与狗牙根生长与种间竞争的影响

为合理利用三峡库区消落带优良草本植物进行退化植被恢复,并探索恢复过程中草本植物的最佳混植比例,选取三峡库区消落带适生先锋草本植物牛鞭草(Hemarthria compressa)(H)和狗牙根(Cynodon dactylon)(C)为研究材料,于2016年4月29日在盆栽控制条件下设置3种不同水分条件(对照组——CK组、浅淹组——SF组、全淹组——TF组)、7种配置比例,每盆牛鞭草与狗牙根株数分别按2株进行递增与递减,具体的配比分别为H0C12,H2C10,H4C8,H6C6,H8C4,H10C2、H12C0,比较研究混植条件下牛鞭草与狗牙根在水淹环境中的生长及二者的竞争作用。研究发现:(1)无论在单植还是二者混植条件下,水分胁迫均显著降低狗牙根与牛鞭草生物量,且牛鞭草对水淹胁迫的响应更敏感;(2)狗牙根和牛鞭草的生长均具有明显的密度制约效应,但狗牙根的反应更为强烈;(3)不同水分与密度条件下,混植体系总相对生物量均大于1。在CK组,狗牙根与牛鞭草表现出竞争关系;在SF组和TF组,二者之间的竞争作用减小,表现出一定的促进作用。综合分析本试验不同水分与密度条件下牛鞭草与狗牙根的总生物量、根冠比、竞争系数(相对总生物量),发现常规供水处理下牛鞭草和狗牙根的最佳配置比例为H2C10,而浅水淹和深水淹处理下最佳配置比例为H8C4。研究结果可以为三峡库区消落带不同海拔位草本植被的恢复及管理提供依据,也为生态类型相同或相似地区人工恢复草本植被提供理论参考。     

A molecular phylogeny of the genus Lygodium (Schizaeaceae) with special reference to the biological control and host range testing of Lygodium microphyllum

Lygodium microphyllum, first naturalized in the 1960s, has aggressively invaded forest-dominated wetlands in southern and central Florida. The indeterminate growth of this invasive climbing fern creates thick rachis mats which climb over shrubs and trees smothering the underlying growth and carrying ground fires into the forest canopy. Foreign surveys for natural enemies identified 20 species of insects and two species of mites. Host range testing of three insect species and one mite included five Lygodium species (L. palmatum, L. volubile, L. cubense, L. venustum, and L. oligostachyum) native to the United States and the West Indies. A molecular phylogeny of the genus was conducted using the trnL intron and the trnL-F intergenic spacer of chloroplast DNA to determine the relationship of L. microphyllum to other Lygodium species. Three major clades appeared, one with L. palmatum and L. articulatum (the most basal), a second with L. reticulatum and L. microphyllum, and a third comprising the other species examined. Lygodium microphyllum appeared at the end of a long branch approximately equidistant from all species of interest preventing the correlation of genetic distance and host range behavior. However, inspection of the results of host range experiments showed a relationship between the presence of a related biotype or species of the insect on a related alternate host and the ability of that insect to develop on that alternate host. Ancestral host usage and ecological fitting are examined as possible explanations for the acceptance of L. palmatum by the tested musotimine insects.     

Developmental Host-Specificity of Mozena obtusa (Heteroptera: Coreidae), a Potential Biocontrol Agent for Prosopis Species (Mesquite) in Australia

Mozena obtusa Uhler (Heteroptera: Coreidae) was examined in quarantine for its potential as a biological control agent of Prosopis species (mesquite) in Australia. Trials were conducted on 16 nontarget plant species to estimate its developmental host range. Complete development occurred on all Prosopis species that have become naturalized in Australia as well as on four Australian native species (Neptunia species and Paraserianthes lophantha), although reproductive diapause prevented assessment of subsequent fecundity. Development through the first feeding nymphal instar also occurred on other plant species representing two subfamilies. Nymphal performance was highly variable on both target and nontarget species, possibly because variation in plant nitrogen composition affected plant quality. The correlation between environment, plant nitrogen, and plant quality is likely to be sufficiently strong to determine whether a plant species can support development. Plant quality should therefore be considered when predicting the field host range of M. obtusa and of sap-sucking coreids generally. Nonetheless, our preliminary results suggest that M. obtusa may not be sufficiently specific for release in Australia, although insufficient understanding of its oviposition behavior in the field and the effect of plant quality on development means that its rejection would be premature.