Classical Biological Control Program Research Articles

Psyttalia lounsburyi (Hymenoptera: Braconidae), potential biological control agent for the olive fruit fly in California

The African parasitoid Psyttalia lounsburyi (Silvestri) was evaluated as part of a classical biological control program directed at the olive fruit fly, Bactrocera oleae (Rossi), in California, USA. Experimental assessment using three non-target species provided some evidence that P. lounsburyi restricts its host use to B. oleae. Female P. lounsburyi preferentially searched olives infested with mature third-instar B. oleae, over other non-target plants, but most offspring were reared from olives containing younger (second through young third instar) B. oleae larvae. Developmental time (egg to adult) and adult longevity were significantly affected by temperature and sex, with males tending to develop faster and females living longer, especially in the lower ranges of temperatures tested. The mean longevity of adult female P. lounsburyi was greatest when honey was available and lowest when they were provided water alone or nothing. The presence of hosts significantly decreased longevity. Females produced an average of 10.2 ± 2.6 progeny during their lifetimes, which was lower than expected for a parasitoid adapted to B. oleae and may be a consequence of increased fruit size—the result of cultivation and selection—reducing parasitoid effectiveness on cultivated vs. wild fruit, as well as constraints on oviposition behavior imposed by experimental design. The results are discussed with respect to the use of P. lounsburyi as a biological control agent for olive fruit fly in California.

Pre-introductory risk assessment studies of Gonatocerus ashmeadi (Hymenoptera: Mymaridae) for use as a classical biological control agent against Homalodisca vitripennis (Hemiptera: Cicadellidae) in the Society Islands of French Polynesia

Homalodisca vitripennis (Germar) (=H. coagulata [Say]) (Hemiptera: Cicadellidae) invaded French Polynesia in 1999. A classical biological control program against H. vitripennis was initiated in 2004 aiming to introduce the exotic egg parasitoid Gonatocerus ashmeadi (Girault) (Hymenoptera: Mymaridae) to the Society Islands archipelago. Prior to any release, two risks were assessed: (a) continued uncontrolled H. vitripennis spread and proliferation in French Polynesia, and (b) non-target impacts by G. ashmeadi on indigenous French Polynesian cicadellids. The primary risk of H. vitripennis is its potential to vector the lethal plant bacterium, Xylella fastidiosa. While the presence of X. fastidiosa in French Polynesia has not yet been demonstrated, the presence of uncontrolled H. vitripennis greatly elevates the risk of a disease outbreak and thus represents a major threat for numerous plant species. Assessing the risk of G. ashmeadi introduction for native cicadellids first required an inventory of the Cicadellidae of the Society Islands, resulting in at least 14 cicadellid species (nine not previously recorded). The risk to these species of attack by G. ashmeadi was assessed using four criteria: (1) their phylogenetic relationships to known hosts of G. ashmeadi, and their similarity in (2) body size, (3) egg laying biology, and (4) ecology. All indigenous cicadellid species found were considered to be at low risk of attack because they differed greatly from all known hosts for G. ashmeadi: (1) none of the indigenous species are in the tribe Proconiini, (2) all were very small and, when possible to determine, (3) lay tiny single eggs, which (4) are deposited on the undersides of leaves of trees. These results persuaded the French Polynesian Government that the benefits of establishing G. ashmeadi for H. vitripennis control outweighed the serious potential risks associated with either delaying release or not releasing G. ashmeadi in French Polynesia. Releases of G. ashmeadi in Tahiti began in May 2005.

First records of Gonatocerus dolichocerus Ashmead, Palaeoneura sp., Anagrus sp. (Hymenoptera: Mymaridae), and Centrodora sp. (Hymenoptera: Aphelinidae) in French Polynesia, with notes on egg parasitism of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae)

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) [= H. coagulata (Say)] (Hemiptera: Cicadellidae: Proconiini), invaded Tahiti in 1999 and at the time of writing this pest was widespread in French Polynesia being extremely abundant in Tahiti and Moorea. Homalodisca vitripennis is a major threat for agriculture and biodiversity. In 2004, a classical biological control program against H. vitripennis was initiated with the goal of introducing and establishing the exotic egg parasitoid Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae) in French Polynesia. As part of the preliminary studies for this program, a survey was conducted of existing natural enemies, in particular egg parasitoids of H. vitripennis. Pan trap surveys and monitoring parasitism of H. vitripennis egg masses was performed in Tahiti. The results of the pan trap surveys provide the first record of the presence of Gonatocerus dolichocerus Ashmead (Hymenoptera: Mymaridae) in French Polynesia, but surveys of H. vitripennis egg...

Understanding the Ghost of Cactoblastis Past: Historical Clarifications on a Poster Child of Classical Biological Control

ABSTRACT The applied ecological discipline of classical biological control (CBC) has a long history, bolstered by some spectacular successes in the management of pest insect and plant species. A major poster child of CBC is the control of prickly pear (Opuntia spp.) in Australia by the moth Cactoblastis cactorum. In this article we investigate the idiosyncrasies of this CBC program and relate it to contemporary CBC, highlighting the intensive rearing and spatially extensive distribution effort critical to the rapid success of this project. We also emphasize the importance of the sociopolitical and economic context of the Opuntia CBC program and its role in its success. We use these historical clarifications to temper the expectations of equivalent successes in future CBC projects. Cactoblastis cactorum has recently invaded North America, and its threat to native cacti is of concern. We examine the global use of this moth as a biocontrol agent to clarify the nature of the hazard that it may pose as an inva...

Comparative assessment of the parasitoid community of Delia radicum in the Canadian prairies and Europe: A search for classical biological control agents

As a precursor to a classical biological control programme for Delia radicum in spring-seeded (“summer”) canola (oilseed rape) in Canada, communities of parasitoids of D. radicum in summer canola in Canada were compared with those in brassica vegetables and several types of canola in Europe. Weekly samples of immature D. radicum were collected from sites in Canada and Europe and reared individually to determine identity and importance of parasitoids. On both continents, the most frequently encountered parasitoids were the larval–pupal parasitoid Trybliographa rapae and the pupal parasitoid Aleochara bilineata. In Canada, Aleochara verna was common at some sites, and in Europe, Aleochara bipustulata was common at some sites. Parasitoid communities were separated primarily by the relative importance of T. rapae and A. bilineata in puparial samples: in Canada, the ratio of A. bilineata parasitism to that of T. rapae was higher than in Europe. The negative correlation of these species may be related to the degree of synchrony of A. bilineata parasitism with its host. In Canada, A. bilineata parasitism occurred early relative to host availability and this timing is deleterious to T. rapae already within the host. In Europe, T. rapae was favored during multiparasitism because A. bilineata parasitism was synchronized with, or delayed, relative to its host’s availability. The only important parasitoid in Europe that was not found in Canada was A. bipustulata, which most frequently occurred in summer canola in Europe, suggesting that it could be suited to the same crop in Canada. Consequently, A. bipustulata is being considered as a candidate biological control agent.

Monitoring populations of Galerucella birmanica (Coleoptera: Chrysomelidae) on Brasenia schreberi and Trapa natans (Lythraceae): Implications for biological control

In classical weed biological control programs, traditional choice or no-choice tests may reveal an insect’s fundamental, but not its ecological host range. Although seldom quantified, the magnitude of interactions between the insect and the non-target plant species is an important consideration in the selection of biocontrol agents that demonstrate an ability to develop on non-target plants. An Asian leaf beetle, Galerucella birmanica is a potential biocontrol agent against water chestnut, Trapa natans, an invasive aquatic plant in North America. Water shield, Brasenia schreberi is a native aquatic plant in North America that is an occasional host of the beetle in China. The population growth and development of G. birmanica was monitored on B. schreberi for 7 months (up to six generations) under indoor caged conditions in China. The insect was able to sustain a population on B. schreberi, however, its population size was significantly smaller than that on T. natans, the usual host. After 4 weeks, beetle populations were 10 times lower on B. schreberi than on T. natans. On B. schreberi larvae developed more slowly and pupae and adults were smaller than on T. natans. The results show that G. birmanica will use B. schreberi but is unlikely to develop large, sustaining populations on this plant if it is introduced and released in North America, but this needs to be confirmed through additional field studies.

CITRUS LEAFMINER, PHYLLOCNISTIS CITRELLA (LEPIDOPTERA: GRACILLARIIDAE), AND NATURAL ENEMY DYNAMICS IN CENTRAL FLORIDA DURING 2005

Abstract After the citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), invaded Florida in 1993, the endoparasitoid Ageniaspis citricola Logvinovskaya (Hymenoptera: Encyrtidae) was introduced in 1994 in a classical biological control program. Subsequent to its establishment, only limited information has been obtained regarding the seasonal abundance of A. citricola and its host in central Florida citrus groves. During 2005, we monitored replicated plots treated with oil or imidacloprid once on 23 Jun 2005, along with untreated control trees, in a Polk County commercial Valencia orange grove on a weekly basis when tender new growth (= flush) was available. As expected, CLM abundance in the early spring flush was nearly undetectable due to the lack of suitable flush during winter when CLM populations decline nearly to zero. Also as expected, A. citricola was not found during this time. During the second flush (Jun through Jul) CLM populations increased and A. citricola appe...

Molecular and field analyses of the fortuitous establishment of Lipolexis oregmae (Hymenoptera: Aphidiidae) in Jamaica as a natural enemy of the brown citrus aphid

The brown citrus aphid, Toxoptera citricida (Kirkaldy), is a serious pest of citrus because it efficiently transmits citrus tristeza closterovirus (CTV). The invasion of Jamaica's citrus by T. citricida resulted in serious economic losses and the importation and consideration was given to the establishment of Lipolexis oregmae Gahan (Hymenoptera: Aphidiidae) in a classical biological control program. Prior to introducing L. oregmae, we conducted a survey to determine the abundance of Lysiphlebus testaceipes Cresson (Hymenoptera: Aphidiidae) in T. citricida. A high-fidelity PCR analysis was conducted using Lysiphlebus- and Lipolexis-specific ITS2 rRNA primers on alcohol-preserved brown citrus aphids and the results were positive for both parasitoids. The fortuitous establishment of L. oregmae in Jamaica was surprising, and was confirmed by rearing adults from parasitized aphids and obtaining taxonomic confirmation based on morphology. In addition, its identity was confirmed molecularly by cloning and sequencing 16S, 12S, and COI sequences from the Florida colony of L. oregmae and from Jamaican specimens. The three DNA sequences were 100% identical for specimens from both sources. The phylogenetic analysis using 16S sequences indicated a close relationship of the Florida and Jamaica populations of L. oregmae with L. gracilis. During 2005, an island-wide survey of citrus in six parishes confirmed that both L. testaceipes and L. oregmae commonly parasitize T. citricida, but that L. oregmae was the more widely distributed and abundant parasitoid. The pathway by which L. oregmae might have entered Jamaica is discussed.

Impact of Introduction of <I>Bactrocera dorsalis</I> (Diptera: Tephritidae) and Classical Biological Control Releases of <I>Fopius arisanus</I> (Hymenoptera: Braconidae) on Economically Important Fruit Flies in French Polynesia

Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), was discovered on Tahiti Island in July 1996. Eradication programs were conducted from 1997 to 2001, but failed. From 1998 to 2006, B. dorsalis was recovered from 29 different host fruit from the five Society Islands: Tahiti, Moorea, Raiatea, Tahaa, and Huahine. Analysis of coinfestation patterns by B. dorsalis, Bactrocera tryoni (Froggatt), and Bactrocera kirki (Froggatt) suggested B. dorsalis had displaced these two species and become the most abundant fruit fly in coastal areas. To suppress B. dorsalis populations, a classical biological control program was initiated to introduce the natural enemy Fopius arisanus (Sonan) (Hymenoptera: Braconidae) into French Polynesia from Hawaii. Wasps were released and established on Tahiti, Moorea, Raiatea, Tahaa, and Huahine Islands. In guava, Psidium guajava L., collections for Tahiti, F. arisanus parasitism of fruit flies was 2.1, 31.8, 37.5, and 51.9% for fruit collected for 2003, 2004, 2005 and 2006, respectively. Based on guava collections in 2002 (before releases) and 2006 (after releases), there was a subsequent decrease in numbers of B. dorsalis, B. tryoni, and B. kirki fruit flies emerging (per kilogram of fruit) by 75.6, 79.3, and 97.9%, respectively. These increases in F. arisanus parasitism and decreases in infestation were similar for other host fruit. Establishment of F. arisanus is the most successful example of classical biological control of fruit flies in the Pacific area outside of Hawaii and serves as a model for introduction into South America, Africa, and China where species of the B. dorsalis complex are established.

Engineering an invasion: classical biological control of the glassy-winged sharpshooter, Homalodisca vitripennis, by the egg parasitoid Gonatocerus ashmeadi in Tahiti and Moorea, French Polynesia

The glassy-winged sharpshooter, Homalodisca vitripennis Germar (=H. coagulata Say) (Hemiptera: Cicadellidae), invaded Tahiti in 1999 and spread rapidly to the main island groups of French Polynesia becoming an important pest. It threatened agriculture, native biodiversity, and created serious social and recreational problems. Further, massive uncontrolled populations on Tahiti presented an elevated invasion threat to other South Pacific nations. In 2004, a classical biological control program against H. vitripennis was initiated in French Polynesia using the highly host-specific egg parasitoid Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae). After risk assessment studies indicated an acceptably low level of risk to non-target species, 13,786 parasitoids were released at 27 sites in Tahiti between May and October 2005. Here we present the results of G. ashmeadi and H. vitripennis population surveys during the first year of their interaction in French Polynesia (until mid-May 2006). The impact of G. ashmeadi on H. vitripennis was extremely rapid and high. Parasitism of H. vitripennis egg masses by G. ashmeadi has averaged 80–100% in Tahiti since the introduction of the parasitoid, and populations of H. vitripennis nymphs and adults have decreased by more than 90% since December 2005. Populations of H. vitripennis have been successfully maintained at this low level for more than 1 year. The same results were obtained in nearby Moorea where the parasitoid was probably spread by the unregulated transport of plants infested with parasitized H. vitripennis eggs. Population monitoring continues in order to determine if a stable equilibrium between the pest and the parasitoid has been reached.

Psyttalia ponerophaga (Hymenoptera: Braconidae) as a potential biological control agent of olive fruit fly Bactrocera oleae (Diptera: Tephritidae) in California

The olive fruit fly, Bactrocera oleae (Rossi), is a newly invasive, significant threat to California's olive industry. As part of a classical biological control programme, Psyttalia ponerophaga (Silvestri) was imported to California from Pakistan and evaluated in quarantine. Biological parameters that would improve rearing and field-release protocols and permit comparisons to other olive fruit fly biological control agents were measured. Potential barriers to the successful establishment of P. ponerophaga, including the geographic origins of parasitoid and pest populations and constraints imposed by fruit size, were also evaluated as part of this investigation. Under insectary conditions, all larval stages except neonates were acceptable hosts. Provided a choice of host ages, the parasitoids' host-searching and oviposition preferences were a positive function of host age, with most offspring reared from hosts attacked as third instars. Immature developmental time was a negative function of tested temperatures, ranging from 25.5 to 12.4 days at 22 and 30 degrees C, respectively. Evaluation of adult longevity, at constant temperatures ranging from 15 to 34 degrees C, showed that P. ponerophaga had a broad tolerance of temperature, living from 3 to 34 days at 34 and 15 degrees C, respectively. Lifetime fecundity was 18.7 +/- 2.8 adult offspring per female, with most eggs deposited within 12 days after adult eclosion. Olive size affected parasitoid performance, with lower parasitism levels on hosts feeding in larger olives. The implications of these findings are discussed with respect to field manipulation and selection of parasitoid species for olive fruit fly biological control in California and worldwide.

Thermal requirements of Fidiobia dominica (Hymenoptera: Platygastridae) and Haeckeliania sperata (Hymenoptera: Trichogrammatidae), two exotic egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Diaprepes abbreviatus is an exotic root weevil occurring in southern US. It is a highly polyphagous species which can complete its entire life cycle on citrus and several woody ornamental plants. The lack of native egg parasitoids for this weevil in citrus orchards has triggered efforts to evaluate candidate egg parasitoids from the Caribbean Region into Florida. The egg parasitoids Fidiobia dominica and Haeckeliania sperata are two exotic natural enemies of D. abbreviatus recently introduced in the US in a classical biological control program. The thermal requirements of both parasitoids were studied in the laboratory. The upper development threshold (UDT) of F. dominica was 30.0°C, its maximal development rate (MDR) occurred at 27.6°C, its lower development threshold (LDT) was 9.6°C and its thermal constant (K) for development from egg to adult was 293.1 DD. For H. sperata, UDT was 35.0°C, MDR occurred at 31.0°C, LDT was around 15°C and K was 188.1 DD. Based on these results, both species would be able to complete 17 to 18 generations annually in southern Florida. However, host availability during critical periods could severely impair the ability of these egg parasitoids to establish and successfully control D. abbreviatus in areas where winter temperatures fluctuate around 12°C, the LDT for this pest.

Host specificity testing of Gonatocerus spp. egg-parasitoids used in a classical biological control program against Homalodisca vitripennis: A retrospective analysis for non-target impacts in southern California

Classical arthropod biological control programs lack a universally adopted, broadly utilitarian, and standardized risk assessment testing strategy for precisely estimating physiological and ecological host range of potential biological control agents. We implemented a rigorous host specificity testing protocol for estimating potential physiological and ecological risk to non-target species posed by exotic parasitoids utilized in a classical biological control program and subsequently evaluated it in terms of efficacy at estimating realized risk. This testing strategy was evaluated at two environmental scales, micro-scale Petri dish studies and macro-scale cage studies, with choice and no-choice host options presented on multiple plant species to two related egg parasitoids with dissimilar life history strategies. The solitary Gonatocerus ashmeadi Girault and gregarious G. fasciatus Girault (Hymenoptera: Mymaridae) are non-native egg-parasitoids of the exotic Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), and were introduced as part of a classical biological control program in southern California, USA. The parasitoids’ physiological and ecological host ranges were estimated on three non-target indigenous sharpshooters and results were compared with observed non-target impacts in the field. Laboratory tests with G. ashmeadi revealed Homalodisca liturata Ball (Hemiptera: Cicadellidae) eggs were a physiologically and ecologically acceptable host; Graphocephala atropunctata (Signoret) and Draeculacephala minerva Ball (Hemiptera: Cicadellidae) eggs were not acceptable hosts. Tests with G. fasciatus revealed both H. liturata and D. minerva, but not G. atropunctata eggs, were a physiologically acceptable host. Only H. liturata eggs were determined to be an ecologically acceptable host for G. fasciatus. Non-target parasitism of H. liturata eggs by G. ashmeadi in southern California habitats was determined. Field surveys reported here failed to reveal parasitism of G. atropunctata or D. minerva eggs by either G. ashmeadi or G. fasciatus in the respective native habitats in southern California.

Population spread of the introduced red imported fire ant parasitoid, Pseudacteon tricuspis Borgmeier (Diptera: Phoridae), in Louisiana

Abstract Predicting the spread of introduced species, such as natural enemies used in classical biological control programs, requires quantitative data on the rates of spread. Here, the pattern of spread of Pseudacteon tricuspis Borgmeier (Diptera: Phoridae), a parasitoid of the red imported fire ant ( Solenopsis invicta Buren; Hymenoptera: Formicidae), was monitored at two widely separated release sites in Louisiana, USA. At both sites, P. tricuspis range expansion (measured as the mean radius of the range from four cardinal directions) was accelerating during the first four years post-release. This pattern contrasts with a linear pattern expected with simple diffusion. This suggests that population spread involved both a neighborhood diffusion and long-distance dispersal component. This is known as stratified or jump dispersal. Annual rates of spread were low in the first two years post-release (possibly owing to an Allee effect), increased rapidly in years 3–4, and slowed down or leveled off by years 5–6. Annual spread rates reached a peak of 15–25 km/yr, with the northward spread being about 40% greater than the spread in the other cardinal directions. High rates of spread in the latter years and directional bias in the spread of P. tricuspis may have been driven by prevailing winds and two northward-moving hurricanes. Spread of introduced species offers insight into factors affecting spread that is more difficult to evaluate for native species.

Host specificity of Anagrus epos: a potential biological control agent of Homalodisca vitripennis

Anagrus epos Girault (Hymenoptera: Mymaridae) is a candidate for a classical biological control program targeting the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Because mass production of GWSS is expensive and labor-intensive, a factitious host that is more economical to produce is desirable to mass produce A. epos for colonization and augmentation efforts. Here, we report the results of host specificity tests and potential rearing techniques for A. epos under laboratory conditions. Females discriminated and oviposited into eggs of seven cicadellid species: H. vitripennis, Circulifer tenellus (Baker), Erythroneura variabilis Beamer, Amblysellus grex (Oman), Graphocephala atropunctata (Signoret), Macrosteles severini Hamilton, and H. liturata Ball, and two cerambycid species: Phoracantha recurva Newman and P. semipunctata (F.). Anagrus epos successfully completed development in the eggs of H. vitripennis, C. tenellus, E. variabilis, A. grex, G. atropunctata, M. severini, and H. liturata. The use of a factitious host and potential nontarget effects of this generalist parasitoid are discussed.

TOOLS FOR EVALUATING LIPOLEXIS OREGMAE (HYMENOPTERA: APHIDIIDAE) IN THE FIELD: EFFECTS OF HOST APHID AND HOST PLANT ON MUMMY LOCATION AND COLOR PLUS IMPROVED METHODS FOR OBTAINING ADULTS

Abstract Lipolexis oregmae Gahan was introduced into Florida in a classical biological control program directed against the brown citrus aphid, Toxoptera citricida (Kirkaldy), on citrus. Prior to evaluating distribution, host range, and potential nontarget effects of L. oregmae in Florida, we evaluated the role of other potential host aphids and host plants on mummy production and location. Under laboratory conditions, this parasitoid produced the most progeny on the target pest, the brown citrus aphid on citrus. This parasitoid, unlike the majority of aphidiids, did not produce mummies on any of the host plants tested when reared in black citrus aphid T. aurantii (Boyer de Fonscolombe) on grapefruit, spirea aphid Aphis spiraecola Patch on grapefruit and pittosporum, cowpea aphid A. craccivora Koch on grapefruit and cowpeas, or melon aphid A. gossypii Glover on grapefruit and cucumber. Thus, sampling for L. oregmae mummies of these host aphids and host plants must involve holding foliage in the laboratory...

ESTABLISHMENT OF LIPOLEXIS OREGMAE (HYMENOPTERA: APHIDIIDAE) IN A CLASSICAL BIOLOGICAL CONTROL PROGRAM DIRECTED AGAINST THE BROWN CITRUS APHID (HOMOPTERA: APHIDIDAE) IN FLORIDA

Abstract The parasitoid Lipolexis oregmae Gahan (introduced as L. scutellaris Mackauer) was imported from Guam, evaluated in quarantine, mass reared, and released into citrus groves in Florida in a classical biological control program directed against the brown citrus aphid, Toxoptera citricida Kirkaldy. Releases of 20,200, 12,100, and 1,260 adults of L. oregmae were made throughout Florida during 2000, 2001, and 2002, respectively. To determine if L. oregmae had successfully established, surveys were conducted throughout the state beginning in the summer of 2001 and continuing through the summer of 2003. Parasitism during 2001 and 2002 was evaluated by holding brown citrus aphids in the laboratory until parasitoid adults emerged. Lipolexis oregmae was found in 10 sites in 7 counties and 4 sites in 3 counties with parasitism rates ranging from 0.7 to 3.3% in 2001 and 2002, respectively. Laboratory tests indicated that high rates of mortality occurred if field-collected parasitized aphids were held in plas...

INVERTEBRATE FAUNA ASSOCIATED WITH TORPEDOGRASS, PANICUM REPENS (CYPERALES: POACEAE), IN LAKE OKEECHOBEE, FLORIDA, AND PROSPECTS FOR BIOLOGICAL CONTROL

Abstract Torpedograss, Panicum repens L., is an adventive, rhizomatous grass species that has become an invasive weed of terrestrial, wetland, and aquatic environments in tropical and subtropical regions worldwide. Until recently, strategies for controlling torpedograss in the USA have focused almost exclusively on mechanical and chemical methods, either alone or in combination, with varied results. A survey of the arthropods and nematodes currently associated with the plant in Lake Okeechobee, Florida, was conducted as part of a feasibility study to determine whether torpedograss is an appropriate target for a classical biological control program. Overall, approximately 4,000 arthropods and 400 nematode specimens were collected. Sweep, clipped vegetation, and soil core samples were dominated by representatives of the arthropod orders Hemiptera, Hymenoptera, Diptera, and Acari. Lesion nematodes of the genus Pratylenchus were commonly associated with the roots of torpedograss. None of the organisms collect...

Classical biological control of the cabbage root fly, Delia radicum , in Canadian canola: an analysis of research needs.

Abstract The cabbage root fly (=cabbage maggot), Delia radicum , has increased in importance over the past two decades as a pest of canola (oilseed rape) in Canada. Although D. radicum has been a part of the North American insect fauna for some time, it is not native, so the introduction of natural enemy species from Europe is being considered for integration with existing management strategies. The biology of D. radicum , the injuries it causes to the crop, and strategies already available for its control are briefly reviewed, followed by the process by which Aleochara bipustulata , a predator and parasitoid of D. radicum , was identified as the most promising candidate for introduction in a classical biological control programme. The literature on A. bipustulata and other species in the same genus is then brought together to illustrate the importance of studies to evaluate the potential of A. bipustulata to provide control, and its effects on non-target species.

A review of introductions of pathogens and nematodes for classical biological control of insects and mites

Compared with parasitoids and predators, classical biological control programs targeting arthropod pests have used pathogens and nematodes very little. However, some pathogens and nematodes that have been introduced have become established and provided excellent control and have been introduced in increasing numbers of areas over decades, often after distributions of pests have increased. We summarize 131 introductions, the majority of which have occurred since 1950. The most commonly introduced microorganisms have been fungi, viruses and nematodes, although microsporidia, bacteria and oomycetes have also been introduced; among these groups, viruses were the most successful in establishing followed by nematodes, fungi and microsporidia. All major orders of insects and prostigmatid mites have been targeted and in 63.6% of the programs the pests being targeted were invasive species and not native. Pathogens and nematodes yielded excellent success in establishment against sawflies and wood wasps (100% of programs) and 40–48% establishment among other host orders. Classical biological control has been used for long-term control of arthropod pests on islands almost as much as in mainland areas. It has been used most frequently in perennial systems and highest rates of establishment of arthropod pathogens and insect parasitic nematodes were documented from forests (63.0%) and tree crops (66.7%). One explanation for the low number of releases of arthropod pathogens and insect parasitic nematodes has been confusing and difficult regulations but recent changes and institution of the FAO’s Code of Conduct is expected to improve scientists’ ability to introduce microbial natural enemies for classical biological control.