Classical Biocontrol Programme Research Articles

Experimental assessment of the biosafety of Trissolcus japonicus in New Zealand, prior to the anticipated arrival of the invasive pest Halyomorpha halys

Despite numerous interceptions at the border, the brown marmorated stink bug (BMSB), Halyomorpha halys Stal (Hemiptera: Pentatomidae), is not yet established in New Zealand. Nevertheless, a classical biocontrol programme using the egg parasitoid Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae) has been initiated in anticipation of its likely arrival. The potential host range of the parasitoid in New Zealand was investigated by importing parasitised BMSB eggs into quarantine from Newark, DE, USA. Egg masses of seven species of Pentatomidae, including one sub-species, were individually exposed to naive mated female T. japonicus in no-choice laboratory experiments. The results showed that predatory Cermatulus nasalis nasalis, C. nasalis hudsoni and Oechalia schellenbergii, and the phytophagous Monteithiella humeralis, Dictyotus caenosus, Glaucias amyoti, and Cuspicona simplex are all within the physiological host range of T. japonicus, although not all appeared to be equally susceptible to parasitism. No development or emergence of T. japonicus from eggs of the cosmopolitan pentatomid plant pest Nezara viridula were observed. The likely ecological consequences of releasing T. japonicus in New Zealand are discussed, as is the subsequent decision of New Zealand’s Environmental Protection Authority to approve release of the parasitoid once BMSB arrives in New Zealand.

Parasitism of frozen Halyomorpha halys eggs by Trissolcus japonicus: applications for rearing and experimentation

ABSTRACTThe brown marmorated stink bug, Halyomorpha halys (Stål), has become a well-known pest to growers and homeowners since its 1996 introduction to the United States. A classical biocontrol programme is under development using the egg parasitoid Trissolcus japonicus. Widespread implementation of biocontrol requires efficient mass rearing, which is constrained by the availability of fresh H. halys eggs. In this study, parasitism rate, developmental time, sex ratio and size were compared between wasps reared on fresh versus frozen, newly laid (<1 d old) versus variably aged (0–3 d old), and frozen egg masses stored ≤4 y. Frozen eggs yielded 56–65% fewer wasps, with parasitism rate decreasing 1–3% per month stored. Parasitism rate, sex ratio and developmental time were comparable between newly laid and variably aged eggs. Freezing eggs for any duration did not affect sex ratio or weight of emerged wasps, but delayed emergence 5–6 d. To simulate deployment of sentinel eggs in the field, we incubated frozen eggs at 20°C and 30°C for 1–9 d before exposing them to T. japonicus, then evaluated parasitism trends. Trissolcus japonicus parasitism rate decreased 5–8% per day incubated, unhatched wasps increased 9% per day incubated and sex ratio was not impacted. Variably aged, frozen and longer stored eggs can be used for T. japonicus rearing and experimentation without affecting emerged wasp sex ratio or size within one generation, but have lower parasitism and slower development. Frozen sentinel eggs are effective <3–5 d, especially in hot conditions.

Foraging responses of Coccinella septempunctata, Hippodamia variegata and Chrysoperla carnea to changing in density of two aphid species

ABSTRACTThe successful use of predators in classical biocontrol programmes needs several background laboratory investigations, one of which is the evaluation of predator behavioural responses to changes in the density of their prey. The impact effect of the density of two prey species [Myzus persicae Sulzer and Aphis craccivora Koch (Hemiptera: Aphididae)] on the predation rates of third-instar Chrysoperla carnea Stephens (Chrysopidae: Neuroptera) and fourth-instar Coccinella septempunctata L. and Hippodamia variegata Goeze (Coccinellidae: Coleoptera) larvae was studied. Although prey species, predator species, prey density, and their interactions all had significant effects on the numbers of aphids consumed, the type of functional response did not vary, remaining a type II response in all treatments. However, the type II parameters differed among predator species on the same prey species, and for each predator species on the two prey species. Chrysoperla. carnea on M. persicae and H. variegata on A. craccivora were more voracious than other predators. In the context of functional response and biological control, the release of these predators, that show inverse density-dependent mortality, has to be started in early season to build up their population on low aphid densities and attack later high aphid populations.

Rapid on-site identification of the biocontrol agent of the Asian chestnut gall wasp

ABSTRACTIn classical biocontrol programmes, a rapid and correct identification of the introduced antagonist is a key issue during both the release and establishment monitoring phases. It is often difficult to distinguish morphologically cryptic species or immature stages. An accurate diagnosis can now be provided by molecular diagnostic methods. Among the conventional and real-time PCR-based methods, loop-mediated isothermal amplification (LAMP) is a particularly suitable technique as it allows a rapid amplification of target DNA directly in the field. During the programme implemented in Italy against the Asian chestnut gall wasp (ACGW) Dryocosmus kuriphilus, we developed a real-time LAMP assay, combined with a simple DNA extraction method, for rapid in-field identification of larvae, pupae, and adults of the biocontrol agent, the parasitoid Torymus sinensis. Validation of the assay comprised adults as well as preimaginal stages of parasitoids obtained from ACGW galls collected from different localities. Results confirmed the effectiveness of the LAMP assay to rapidly and specifically identify the target parasitoid in the field. This assay will be a valuable tool for quick on-site checking of the parasitism rate.

Selection of non‐target tephritids for risk evaluation in classical biocontrol programmes against the olive fruit fly

AbstractThe olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is the key pest of olives (Olea europaea L.). Classical biological control against this insect was previously attempted in Spain with Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae), with very limited success. Other parasitoids are now available for new classical biological control programmes. Before release of exotic parasitoids, an assessment of their potential impact on non‐target species is required. Surveys were conducted in different olive groves in south‐eastern Madrid to study wild tephritids associated with Asteraceae plants. We recorded plant species and their abundance and collected flower heads to identify and quantify tephritid species. Fruits from Rosa canina L. were also collected. After a multicriteria analysis (MCA), we propose Urophora hispanica Strobl, U. stylata (Fabricius) and Carpomya schineri (Loew) as candidates for further risk assessment experiments. Additional information on new associations between tephritid flies and Asteraceae plants and on autochthonous Hymenoptera parasitizing tephritids is provided.

Classical biological control of Fallopia japonica in the United Kingdom – lessons for Europe

Shaw RH, Tanner R, Djeddour D &amp; Cortat G (2011). Classical biological control of Fallopia japonica in the United Kingdom – lessons for Europe. Weed Research51, 552–558.SummaryThe programme for the biological control of Fallopia japonica in the United Kingdom has provided some valuable insights into the practicalities of delivering a classical biological control programme against a weed in the European Union. In the absence of tailored legislation, the licensing process was complex but not prohibitive. It involved the production of a pest risk analysis (PRA; based on the EPPO template), an application through national legislation (the UK Wildlife and Countryside Act), the production of peer‐reviewed publications, expert committee consideration, further commissioned peer review and public consultations prior to final Ministerial judgement, which was granted in March 2010. Although there is room for some streamlining in the process, this approach has proved to be effective and robust and should be applicable to similar programmes in Europe. This is important, because classical biological control has considerable potential for the management of F. japonica and other weed targets throughout Europe, especially those impacting habitats where chemical use is all but impossible. The lessons learned from the knotweed biocontrol programme are discussed, and current weed biocontrol activities in Europe are briefly summarised. A classical biocontrol programme needs to deliver more than just pure science, because effective communication and negotiations in the public and political arena can provide more challenges than the traditional scientific ones.

Using parasitoids to infer a native range for the obscure mealybug, Pseudococcus viburni, in South America

The co-evolutionary relationships between mealybug hosts (Hemiptera: Coccoidea) and Encyrtidae (Hymenoptera) appear to be particularly strong, and many successful classical biological control programmes against mealybugs have been carried out using these parasitoids. It is a puzzle, then, that the obscure mealybug, Pseudococcus viburni (Signoret) (Hemiptera: Pseudococcidae), is considered to be an American species but is not attacked by native parasitoids in the USA, whereas it is controlled in Europe by Acerophagus maculipennis (Mercet) (Encyrtidae) which was described from the Canary Islands (as Pseudophycus maculipennis). An examination of the biogeographical origins of both the Pseudococcus maritimus complex (to which P. viburni clearly belongs) and the genus Acerophagus Smith, coupled with historical trade records, supports the hypothesis that P. viburni and A. maculipennis are co-evolved Neotropical species, and that both were transported from S. America (probably Chile) to Europe via the Canary Islands on host plants such as potato, possibly as early as the sixteenth century. Invasion of P. viburni into the USA (and elsewhere around the world) occurred later, but without A. maculipennis (or other natural enemies). This explains why P. viburni in the USA is not attacked by native North American parasitoids and why A. maculipennis is not known to attack any mealybugs of Palaearctic origin. The hypothesis adds confidence that well conducted classical biocontrol programmes involving these taxa pose a low environmental risk to native, non-target fauna.

Natural enemies of bridal creeper &lt;i&gt;Asparagus asparagoides&lt;/i&gt; in New Zealand

Bridal creeper is a weed of natural and productive areas in the northern North Island of New Zealand A classical biocontrol programme was initiated in 20052007 with a survey of invertebrate fauna and pathogens associated with the weed in New Zealand Although bridal creeper was attacked by a wide range of generalist invertebrates their overall damage affected

Trichogramma bournieri Pintureau & Babault (Hymenoptera: Trichogrammatidae) and Chilo sacchariphagus Bojer (Lepidoptera: Crambidae) in sugarcane in Mozambique: A new association

Chilo sacchariphagus Bojer (Lepidoptera: Crambidae), a sugarcane stalk borer indigenous to South East Asia, and the nearby Indonesian Islands, was identified from African sugarcane in Mozambique in 1999. Prior to a classical biocontrol programme being implemented against it, intensive pre-release surveys for the presence of any indigenous natural enemies on life stages of the borer were completed. Negligible parasitism of larval and pupal stages was recorded. In contrast, egg batches found were heavily parasitised. Parasitoid adults emerging from the eggs were found to be only the indigenous Trichogramma bournieri Pintureau & Babault (Hymenoptera: Trichogrammatidae). Aspects of the impact of T. bournieri on C. sacchariphagus eggs in Mozambican sugarcane are presented, and the potential of using this egg parasitoid against C. sacchariphagus in an augmentation biocontrol programme is discussed.

Introduction of a parasitoid for mealybug biocontrol a case study under new environmental legislation

Pseudaphycus maculipennis is one of the few known encyrtid parasitoids of the obscure mealybug (Pseudococcus viburni) It was released in New Zealand on 14 February 2001 The importation process under changing environmental legislation over an 8 year period is detailed and the implications of the new legislation for future classical biocontrol programmes is discussed

Optimal release strategies for biological control agents: an application of stochastic dynamic programming to population management

Summary 1. Establishing biological control agents in the field is a major step in any classical biocontrol programme, yet there are few general guidelines to help the practitioner decide what factors might enhance the establishment of such agents. 2. A stochastic dynamic programming (SDP) approach, linked to a metapopulation model, was used to find optimal release strategies (number and size of releases), given constraints on time and the number of biocontrol agents available. By modelling within a decision‐making framework we derived rules of thumb that will enable biocontrol workers to choose between management options, depending on the current state of the system. 3. When there are few well‐established sites, making a few large releases is the optimal strategy. For other states of the system, the optimal strategy ranges from a few large releases, through a mixed strategy (a variety of release sizes), to many small releases, as the probability of establishment of smaller inocula increases. 4. Given that the probability of establishment is rarely a known entity, we also strongly recommend a mixed strategy in the early stages of a release programme, to accelerate learning and improve the chances of finding the optimal approach.

First record of Cercospora pistiae causing leaf spot of water lettuce (Pistia stratioites) in Brazil, with particular reference to weed biocontrol.

Pistia stratioites, the water lettuce, is an important pantropical aquatic weed. It has been the target of successful classical biocontrol programmes utilizing an insect natural enemy collected in Brazil and introduced into Australia, Papua New Guinea and South Africa. Little attention was given to the fungal pathogens associated with this weed as potential biocontrol agents. An 11-month field survey in the state of Rio de Janeiro involving repeated visits to 12 sites, and a 2-month survey in the Amazonas Basin (Amazonas state) in Brazil, yielded only one pathogenic fungus on P. stratioites. This was identified as Cercospora pistiae. No previous record of this species has been made in Brazil nor in the New World. The fungus is described and its taxonomy and biocontrol potential discussed herein. C. pistiae is a damaging pathogen of water lettuce. Its distribution was restricted to two interconnected sites in Rio de Janeiro. A literature and herbaria survey yielded few fungi associated to water lettuce (8 species), probably reflecting a lack of adequate collection in the centre of origin of the plant.

The potential for control of bracken in the UK using introduced herbivorous insects

AbstractBracken (Pteridium aquilinum (L.) Kuhn) is an invasive native weed in the UK causing problems in upland agriculture and in land of amenity and conservation value; it may represent a risk to human health. Existing control methods such as cutting or herbicide use are subject to practical, economic or environmental constraints in many areas of the UK. Classical biological control of bracken would involve the introduction of specialist bracken‐feeding herbivores from other parts of the world. Classical biological weed control has a reasonable record of success in other parts of the world and an exemplary safety record, but remains untried in the UK. The typical development of a classical weed biocontrol programme is presented using the UK bracken programme as an example. Finally the current position of this classical biocontrol programme is reviewed with an assessment of the prospects for the future. With appropriate funding, a full field release of at least one species of South African bracken‐feeding moth should be achieved during the mid‐1990s.