Cercosporoid hyphomycetes associated with Tibouchina herbacea (Melastomataceae) in Brazil

Nine species of fungi on the aquatic weed Sagittaria montevidensis (arrowhead) in southern and southeastern Brazil were collected, identified, described and illustrated in a survey for possible biological control agents against this weed. Seven of them are anamorphic fungi, Alternaria alternata, Botrytis cinerea, Cercospora apii, Cercospora sagittariae, Colletotrichum gloeosporioides, Plectosporium alismatis and Pseudocercospora arthrospora, and two smut fungi, Doassansiopsis deformans and Narasimhania alismatis. All represent new host records or new geographic localities for occurrences of the fungi. Pseudocercospora arthrospora is new to science. It differs from known species of genus Pseudocercospora mainly by its subhyaline and disarticulating conidia and host. This fungus is close to Thedgonia but can be distinguished for this genus by its conidiogenesis. Based on the description and disease symptoms Cylindrocarpon sagittariae, recorded on S. trifolia from Japan, is regarded here as a later synonym of Plectosporium alismatis. Preliminary observations of the fungi in the field and in culture suggest that four of these have potential for use as biocontrol agents against S. montevidensis, namely C. sagittariae, C. gloeosporioides, P. alismatis and P. arthrospora.

The role of dipteran predators in biological pest control programs is reviewed and discussed. Diptera encompasses a large number of potentially efficient predators for biological pest control, yet only a few species are routinary used. The families Syrphidae and Cecidomyiidae provide some of the most successful examples of biological control, but other families (e.g., Muscidae, Sarcophagidae, Sciomyzidae) also include species with that potential. Most applications of Diptera as predators involve the conservation biological control approach, while the augmentative approach has involved only a few species, almost exclusively of Syrphidae and Cecidomyiidae. In a few cases, classical biological control has been employed. Commercialization of species mainly to be used in the augmentative approach is discussed, also focusing on the critical issues linked to rearing methods. The dual services performed by Diptera (pollination as adults and biological control as larvae) have been studied in detail for Syrphidae only, but would deserve further study in other families, e.g., Sarcophagidae. This is the first review in which the use of predatory Diptera in biological control programs is investigated for all families and in all types of applications. This review recommends a multi-taxon approach in the use of Diptera in biological control since a large number of taxa have considerable potential, although this has not yet been tested in practical applications.

Prioritizing weeds for biological control development in the western USA: Results from the adaptation of the biological control target selection system

Opinions about the value of biological control are often extreme. Colloquially, biological control most often refers to classical biological control, in which one species is introduced from another region to control pests such as arthropod herbivores in agricultural systems, or weeds in managed and natural systems.1 As such, biological control has the potential to be a low-cost, chemical free, means to control pests. Numerous biological control programs have been unqualified successes (Bellows 2001), such as the control of cacti in Australia with the moth Cactoblastis cactorum (Raghu and Walton 2007), of cottony-cushion scale (Icerya purchasi) in California with the vedalia lady beetle, Rodolia cardinalis (Caltagirone and Doutt 1989), and of glassy-winged sharpshooters in French Polynesia with the egg parasitoid Gonatocerus ashmeadi (Grandgirard et al. 2009). Yet, classical biological control, as with any introduction of a species into a new area, necessarily involves the unknown and therefore carries some inherent risk (Simberloff and Stiling 1996) – what will these organisms actually do in a novel ecosystem? The most unpredictable element in biological control is the extent to which the realized niche is modified in the new environment. This effect has been responsible for some disastrous outcomes of classical biological control, many of which occurred during an era when vertebrates were being introduced around the world by Europeans for a variety of reasons (e.g., introducing the birds of Shakespeare to America, Mirsky 2008), including for biological control (Howarth 1991). The introductions as biological control agents of cane toad to Australia (Crossland et al. 2000) and mongoose to Hawaii (Hays and Conant 2007) are notorious. Introductions of generalist invertebrate agents also have had dire consequences, such as the introduction of predatory snails to French Polynesia (Murray et al. 1988; Coote 2007). In retrospect, some of the unintended consequences of biological control could have been avoided with more ecological knowledge (McEvoy and Coombs 2000) or more societal appreciation for native species (which has developed with time, Henneman and Memmott 2001), but with other introductions, it would have been impossible to know ahead of time what the risks would be (e.g., gall fly agents of knapweeds providing supplementary food to mice that harbor hantavirus, Pearson and Callaway 2006). Many of the unknown outcomes of biological control are purely ecological – what is the risk that a wasp, introduced to parasitize an agricultural pest, will also be able to feed on a native insect? Other unknowns involve evolution – will a herbivore adapt over time to be able to feed on a new nontarget host or hybridize with a closely related species? This volume explores the evolutionary aspects of biological control. Although often overlooked, evolutionary considerations are critical to all stages of classical biological control, from agent selection, to quarantine, release, establishment, and ultimately success in pest control (Ehler et al. 2004). Many questions are unresolved. For example, should agents be chosen that have a long history with the host or are ‘new associations’ more likely to succeed (Hokkanen and Pimentel 1989)? Can one improve effectiveness through artificial selection (Hopper et al. 1993)? Will postcolonization adaptation of the agent increase the likelihood of success, and/or are hosts equally likely to evolve resistance over time (Roderick 1992; Holt and Hochberg 1997; Hufbauer 2001)? Are generalist consumers more likely to survive in novel environments or are specialists more effective (Murdoch et al. 1985; Waage 1990; Brodeur 2012)? More recently, concern for the environment, as well as theory examining the reasons for success of generalist predators, prompted a shift to the release of specialized consumers typically preceded by extensive testing aimed at delimiting the host range of candidate biological control agents. While this approach has clearly made biological control more predictive ecologically, research focused on host range currently lacks measures of genetic variation in host use and responses of those hosts, and thus evolutionary uncertainties remain.

The success rate of weed biological control programs is difficult to evaluate and the factors affecting it remain poorly understood. One aspect which is still unclear is whether releases of multiple, genetically distinct populations of a biological control agent increase the likelihood of success, either by independent colonization of different environmental niches or by hybridization that may increase the agent's fitness and adaptive ability. Since hybridization is often invoked to explain the success of unintentionally introduced exotic species, hybridization among biocontrol agents may be similarly important in shaping the effectiveness of biological control programs. In this study, we first evaluated intraspecific hybridization among populations of a weed biological control agent, the ragwort flea beetle, Longitarsus jacobaeae. These insects were introduced as part of a classical biological control program from Italy and Switzerland. We genotyped 204 individuals from 15 field sites collected in northwest Montana, and an additional 52 individuals that served as references for Italian and Swiss populations. Bayesian analysis of population structure assigned seven populations as pure Swiss and one population as pure Italian, while intraspecific hybrid individuals were detected in seven populations at frequencies of 5%–69%. Subsequently, we conducted a 2‐year exclusion experiment using six sites with Swiss beetles and three with hybrid beetles to evaluate the impact of biological control. We found that biological control by Swiss beetles and by hybrid beetles is effective, increasing mortality of the target plant, Jacobaea vulgaris, by 42% and 45%, and reducing fecundity of surviving plants by 44% and 72%, respectively. Beetle densities were higher and mortality of larger plants was higher at sites with hybrids present. These results suggest that hybridization of ragwort flea beetles at high‐elevation sites may improve biological control of tansy ragwort and that intraspecific hybridization of agents could benefit biological control programs.

Manipulation of the abundance and distribution of natural enemies is the fundamental basis of biological control. Whether a classical biological control or conservation-augmentation program is being conducted, the database for identifying “ideal” natural enemies is limited. A literature survey of selected host-parasite studies involving, in part, comparisons utilizing ecological indices, suggested that parasite communities are not random assortments of species but are “structured” in terms of life history attributes and habitat stability. Thus, patterns in the composition of parasite communities may provide a framework for selecting suitable biological control agents. However, the ecological indices generally considered—species richness, diversity, evenness, niche breadth, and niche overlap—may have a very limited application in the implementation of biological control. Recommendations involving autecological and synecological studies of parasite communities are presented for contributing relevant data in biological control programs.

A newly described species of Pseudocercospora from Ficus microcarpa differs from other Pseudocercospora species on Ficus spp. (Moraceae) by small fascicles of branched conidiophores hidden in the suprastomatal chamber and by the absence of leaf spots, of stromata and of external hyphae. Newly recorded fungi on other ornamental plants in Taiwan are Cercospora apii s. lat. (C. pistiae) on Pistia stratiotes, C. flagellaris, Passalora bougainvilleae, Pseudocercospora pancratii, Ps. violamaculans, and Ps. wedeliae.

In Zimbabwe, the structure and integrity of various ecosystems is rapidly deteriorating, in part due to invasive alien plants. While there is recognition of the challenges posed by invasive alien plants and the complexity surrounding their successful management, very little has been done, documented or evaluated in the country recently, including classical weed biological control activities. We review the current status of invasive alien plants and classical weed biological control in Zimbabwe especially their management and legislation governing this management. We record the presence and distribution of weed biological control agents currently in Zimbabwe. The Biological Control Target Selection (BCTS) system was used to identify invasive plant species in Zimbabwe that could benefit from on-going or new classical biological control programmes. While biological control has been implemented in the country since the 1960s, and significant control has been achieved on floating aquatic macrophytes, no biological agent has been released on a terrestrial weed since 1961. However, 10 agents released in neighbouring South Africa have spread naturally into the country on contiguous plant populations and some are providing gratuitous control of some of the weeds. We identified 19 invasive alien plants that could be successfully managed through classical weed biological control, and for 12 of these, this could be achieved at minimal cost, as agents are available within the region. Zimbabwe, perhaps with the help of international aid organisations investing in the region, could: a) conduct extensive surveys of established biological control agents already present in the country; b) redistribute these agents into areas of the country where they are not already present and foster those spreading north in South Africa and likely to arrive eventually through natural spread, and; c) initiate new weed biological control programmes against new targets by importing new agents available from South Africa or Australia.

Next generation biological control – an introduction

Potential for negative interactions between successful arthropod and weed biological control programs: A case study with Lilioceris species

Biological control has a long and rich history in Ukraine which is closely linked with other countries of the Former Soviet Union, and some relevant studies from these countries are also included in this review. The use of natural enemies against Ukrainian insect pests demonstrates that biological control approaches have enjoyed a degree of success. The release of Aphelinus mali in a classical biological control programme against the woolly apple aphid, Eriosoma lanigerum , was successful. In contrast, the release of the hemipterans, Perillus bioculatus and Podisus maculiventris , against the Colorado potato beetle, Leptinotarsa decemlineata , was not successful, and studies in the use of these hemipterans as biological control agents continue. Conservation biological control is practised in apple and cereal cropping systems resulting in a number of predators and parasitoids being preserved. Augmentation of natural enemies, especially predatory mites against the spider mite Tetranychus urticae in greenhouse cucumber and tomato production, has provided suppression of this pest. Various strains of Bacillus thuringiensis are being used inundatively against Lepidopteran, coleopteran and mosquito pests. A granulovirus has been studied for use against the codling moth ( Cydia pomonella ), and the fungus, Beauveria bassiana , is being evaluated against several insect pests. Entomopathogenic nematodes have generated some interest for future use in Ukraine as potential biological control agents against soil-inhabiting pests. Although biological control programmes have been practised for many years, the agricultural sector in Ukraine is moving from a command to a market economy. The latter economy is profit-driven and relies more on chemical pesticide usage. The challenge is to integrate biological control programmes into the market economy.

Studies on biological control for the sustainable management of weeds that exert serious ecological, economic, and human health problems are attracting increasing attention. Detection of potential biological control agents (pests, pathogens, etc.) on target weed species is the first step in the biological control program. This study aimed to determine the microfungi species found on noxious weed species in the Yüksekova basin situated in Hakkari province, Türkiye. Continued traditional agricultural practices, minimum or no use of pesticides and fertilizers, and better protection of natural flora/fauna compared to other parts of Türkiye were reasons for the selection of the basin in the current study. Field surveys were carried out in different periods during 2020 and 2021. A total of 101 microfungi species were recorded on 79 weed species belonging to 29 families in the basin. The most common fungi species in the basin were in genera Puccinia (29 species), Alternaria (18 species), Uromyces (14 species), and Curvularia (4 species). Weed hosts of the above-mentioned fungi species mostly belonged to Asteraceae (20 species), Fabaceae (7 species), Poaceae (7 species), and Lamiaceae (6 species) families. While 84 microfungi species were recorded on a single host, and the remaining 17 were found on more than one weed species. It has been observed that Puccinia cyani (Schleich.) Pass., Puccinia chondrillina Bub & Syd., and Uromyces polygoni-aviculariae (Pers.) P. Karsten significantly inhibited the growth and development of their host weed species (Centaurea spp., Chondrilla juncea L., and Polygonum aviculare L.) and were able to suppress the populations of the weeds in the fields. The results revealed that it would be beneficial to review the recorded pathogens in terms of biological activity and to carry out detailed field studies in the region.

Introduction: The endoparasitoid Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae) can be reared with the alternative host Tenebrio molitor (Linnaeus, 1758) (Coleoptera: Tenebrionidae). Host storage at low temperatures can regulate parasitoid production and demand in biological control programs. Material and Methods: The life-cycle (egg-adult), parasitism and emergence percentage, number of parasitoids emerged per host pupae, sex ratio and longevity of the T. howardi offspring per T. molitor pupa were evaluated after low temperature storage of this host for different periods and its immature (pupae) in T. molitor pupae for five periods at 10.3 ºC. Tenebrio molitor pupae stored at 0.5 ± 0.09 °C and 2.7 ± 0.11 °C for 10 and 20 days, respectively, were adequate to produce T. howardi. Results: The biological characteristics of this parasitoid were better with T. molitor pupae stored at 0.5 ± 0.09 °C and 2.7 ± 0.11 °C for 10 and 20 days. Tetrastichus howardi immature (pupae) can be stored in T. molitor pupae for 10, 20, 30, 60 and 90 days at 10.3 ºC, preferably in pupae of this host for 10 days to produce these adults of this parasitoid for biological control programs. Discussion: These results contribute to overcoming one of the difficulties encountered in the massive production of parasitoids which is to obtain large numbers of suitable hosts when they are needed. Therefore, the possibility of conserving T. molitor pupae to rear T. howardi will be useful to use this natural enemy in biological pest control programs. Keywords: Biological control, Cold storage, Parasitoids, Progeny.

Biological control programmes have varied in the extent of ecological studies carried out on potential agents and target organisms. At one extreme, studies were limited to surveys for potential biological control agents, which were then shipped to the target country. The biological control programme against Scotch broom (Cytisus scoparius) is at the other extreme: we list 29 significant studies on the ecology of broom in its native and introduced ranges, probably representing at least 100 years of work by scientific personnel. These studies have proved useful for predicting the success and safety of the biological control programme against broom as an alien weed. Three studies highlight the significance of insect herbivores reducing broom longevity and seed production: an 11-year insecticide exclusion experiment in the UK; replicated experiments examining recruitment of broom as a native plant in the UK/France and as an alien weed in New Zealand/Australia; and simulation modelling of broom abundance. However, predicting the contribution of each biological control agent to broom suppression is difficult, and may be required for risk-benefit analyses under new regulations. The safety of broom agents to non-target plant species has been addressed using normal host range testing procedures, and extensive field surveys of broom and related plants in Europe. There are concerns over adverse, indirect effects that released biological control agents may have on non-target organisms. For insect herbivores released against weeds, adverse indirect effects could occur because the agent acts as a new food source, competitor or disease vector in existing food webs; or because there are adverse effects on existing biota via a reduction in the abundance of the target weed (or non-target plant). Ecological studies of broom enable us to identify some of these potential effects, but predicting their magnitude prior to release of an agent is a major ecological challenge. Equally important to emphasize are the potential benefits to indigenous species from suppression of alien weeds. A balance is needed, because the time and resources required to make accurate ecological predictions of potential adverse effects from released agents could impede biological control of key environmental weeds, resulting in worse net impacts on indigenous species.

Biological Control as Biotechnological Amelioration and Ecosystem Intensification in Managed Ecosystems