Potential biocontrol agents for biofouling on artificial structures

The accumulation of biofouling on coastal structures can lead to operational impacts and may harbour problematic organisms, including non-indigenous species. Benthic predators and grazers that can supress biofouling, and which are able to be artificially enhanced, have potential value as augmentative biocontrol agents. The ability of New Zealand native invertebrates to control biofouling on marina pontoons and wharf piles was tested. Caging experiments evaluated the ability of biocontrol to mitigate established biofouling, and to prevent fouling accumulation on defouled surfaces. On pontoons, the gastropods Haliotis iris and Cookia sulcata reduced established biofouling cover by >55% and largely prevented the accumulation of new biofouling over three months. On wharf piles C. sulcata removed 65% of biofouling biomass and reduced its cover by 73%. C. sulcata also had better retention and survival rates than other agents. Augmentative biocontrol has the potential to be an effective method to mitigate biofouling on marine structures.     

Native and introduced range surveys for egg parasitoids of Agrilus auroguttatus,an invasive pest of native oaks in California

The invasive goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), has caused extensive mortality to indigenous oaks in southern California. This woodborer is native to southern Arizona where low population densities may, in part, be due to the presence of co-evolved natural enemies. Surveys were conducted in Arizona and California from June to August 2013 by deploying sentinel egg masses in an attempt to attract, collect and identify potential egg parasitoids of this beetle that could be used for a classical biological control programme in California. In total, 18,052 A. auroguttatus eggs were deployed throughout the native and introduced range. Parasitoids did not attack any eggs deployed in Arizona or California. The inability to detect egg parasitoids could be explained by the following: (1) host-specific egg parasitoids of A. auroguttatus do not exist, (2) surveying time did not coincide with peak activity of egg parasitoids or (3) surveying methods were insufficient at detecting egg parasitoids.     

A review on the genus Metarhizium as an entomopathogenic microbial biocontrol agent with emphasis on its use and utility in Mexico

Metarhizium is a genus of entomopathogenic fungi that was initially classified into three species and varieties. More recently, DNA sequencing has improved the phylogenetic resolution of Metarhizium which now includes 30 species. The insect host ranges vary within the genus and some species such as M. robertsii have broad host ranges, while others such as M. acridum show a narrow host range and are restricted to the order Orthoptera. Metarhizium spp. are ubiquitous naturally occurring soil inhabiting fungi, and some are rhizosphere colonisers and their diversity has been attributed to various selective factors (habitat type, climatic conditions, specific associations with plants and insect hosts). Metarhizium have been used for the biological control of insect pests that affect economically important agricultural crops and have been tested under laboratory and field conditions for the control of insect vectors of human disease, showing the effectiveness of the fungus against the target pest. In Mexico, Metarhizium species have been used for the control of insect pests such as the spittlebug (Hemiptera: Cercopidae), and locusts (Orthoptera) that affect crops such as corn, bean and sugarcane. Biosafety studies, such as dermal and intragastric tests in mammalian models have also been carried out to ensure safety to humans and other animals. Metarhizium shows great promise as an alternative to chemical insecticides that has relatively low impact on human health and the environment. Key features of Metarhizium for biocontrol of insects are outlined with special reference to their utility in Mexico.     

Evaluation of fungal culture filtrate containing chitinase as a biocontrol agent against Helicoverpa armigera

AIMS: To evaluate the biocontrol efficacy of culture filtrate containing chitinase from Trichoderma harzianum against Heliothis. METHODS AND RESULTS: T. harzianum was cultured by submerged fermentation using colloidal chitin as sole carbon source. The ability of the culture filtrate to hydrolyse colloidal chitin indicated the presence of chitinase as one of its components. Biocontrol assay on Heliothis showed that the culture filtrate is a potent antifeedant as it reduced the feeding rate and body weight of the larvae. It reduced the successful pupation and increased larval and pupal mortality in a dosage-dependent manner when applied topically. The highest mortalities (70%) were recorded for groups treated with 2000 U ml(-1) chitinase activity. The percentage of adult emergence was zero for the highest chitinase concentration (2000 U ml(-1)) tried. CONCLUSIONS: The studies showed that the culture filtrate containing chitinase from T. harzianum is capable of negatively affecting the growth and metamorphosis of Heliothis larvae. SIGNIFICANCE AND IMPACT OF THE STUDY: In view of the need for safer and environmentally friendly pest management tools, the present study could help in the development of enzyme-based biopesticides against Heliothis.     

A population genetic signature of human releases in an invasive ladybeetle

Biological invasions have been accelerated by a variety of human activities. Propagule pressure, the number of introduced individuals and independent introductions, is probably to be influenced by these human activities and may be an important factor for successful range expansion in new environments. We tested whether the current distribution of the predatory ladybeetle Coccinella septempunctata in the introduced range (USA) is the result of multiple historical human introductions or natural range expansion from the first established populations in the USA. To test this hypothesis, we compared historical records of propagule size, propagule number, specific introduction locations and the date of each introduction, with estimates of genetic variation in mitochondrial DNA (cytochrome oxidase I). Our results indicated that genetic diversity in the introduced range was positively correlated with historical records of propagule size and number and negatively correlated with distance to nearest introduction point, suggesting that multiple human releases were successful. Higher genetic diversity in populations found near introduction points suggest that initial founder effects were limited, but lower genetic diversity found farther from introduction points is probably the result of serial founder effects during secondary range expansion. These results suggest that the current distribution of C. septempunctata in the introduced range is the result of a combination of human releases and short‐range expansion from multiple established populations in the introduced range.     

Parasitoid diversity and impact on populations of the diamondback moth Plutella xylostella (L.) on Brassica crops in central México

Three experimental plots were established and maintained during one year at two sites in the state of Querétaro, México, in order to identify species of parasitoids attacking the diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae), and to gather information concerning their relative importance and patterns of population fluctuation. At both sites, the plots were planted with broccoli, cabbage and cauliflower during three cropping seasons. Parasitoid species identified were: Diadegma insulare Cresson, Diadromus (= Thyraeella) collaris Gravenhorst (Hymenoptera: Ichneumonidae); Habrobracon sp. (Hymenoptera: Braconidae); Oomyzus (= Tetrastichus) sokolowoskii Kurdjumov (Hymenoptera: Eulophidae); and Spilochalcis (= Conura) sp. (Hymenoptera: Chalcididae). This last species is a hyperparasitoid of D. insulare. The most abundant and frequently occurring species was D. insulare, it occurred in both localities during all three cropping seasons. The highest levels of parasitism caused by D. insulare on DBM were registered in the spring-summer season of 1996 at `La Soledad' farm with averages of 42.7, 45.0 and 44.5% on cabbage, broccoli, and cauliflower, respectively. Because D. insulare was detected attacking the pest at very low population densities during the initial stages of the crop cycle, it is assumed that the parasitoid has a high searching capacity. Correlation (r) between DBM and D. insulare population numbers was positive and significant. The other species identified occurred sporadically and had little impact on pest populations. The identification of D. collaris represents the first record of this species in North America.     

Potential of an antagonistic bacterium isolate obtained fromLentinus lepideus basidiospores as a biocontrol agent

TheBurkholderia sp. isolate 87-11 obtained from basidiospores ofLentinus lepideus was antagonistic against severalPythium andRhizoctonia isolates. The bacterium was tested against soilborne diseases of five plants caused byP. aphanidermatum andR. solani by soil and seed application, and its potential as a biocontrol agent is discussed.     

Niche-based modelling as a tool for predicting the risk of alien plant invasions at a global scale

Predicting the probability of successful establishment of plant species by matching climatic variables has considerable potential for incorporation in early warning systems for the management of biological invasions. We select South Africa as a model source area of invasions worldwide because it is an important exporter of plant species to other parts of the world because of the huge international demand for indigenous flora from this biodiversity hotspot. We first mapped the five ecoregions that occur both in South Africa and other parts of the world, but the very coarse definition of the ecoregions led to unreliable results in terms of predicting invasible areas. We then determined the bioclimatic features of South Africa's major terrestrial biomes and projected the potential distribution of analogous areas throughout the world. This approach is much more powerful, but depends strongly on how particular biomes are defined in donor countries. Finally, we developed bioclimatic niche models for 96 plant taxa (species and subspecies) endemic to South Africa and invasive elsewhere, and projected these globally after successfully evaluating model projections specifically for three well‐known invasive species (Carpobrotus edulis, Senecio glastifolius, Vellereophyton dealbatum) in different target areas. Cumulative probabilities of climatic suitability show that high‐risk regions are spatially limited globally but that these closely match hotspots of plant biodiversity. These probabilities are significantly correlated with the number of recorded invasive species from South Africa in natural areas, emphasizing the pivotal role of climate in defining invasion potential. Accounting for potential transfer vectors (trade and tourism) significantly adds to the explanatory power of climate suitability as an index of invasibility. The close match that we found between the climatic component of the ecological habitat suitability and the current pattern of occurrence of South Africa alien species in other parts of the world is encouraging. If species' distribution data in the donor country are available, climatic niche modelling offers a powerful tool for efficient and unbiased first‐step screening. Given that eradication of an established invasive species is extremely difficult and expensive, areas identified as potential new sites should be monitored and quarantine measures should be adopted.     

南方小花蝽液体人工饲料的饲养效果评价

为评价一种液体人工饲料的饲养效果,以棉蚜饲养南方小花蝽作对照,用液体人工饲料连续两代饲养南方小花蝽若虫和成虫,对南方小花蝽各生长阶段的生长和发育指标进行调查。结果显示：用人工饲料饲养的南方小花蝽若虫历期（22～23天）与对照组（21天）之间不存在显著差异,说明液体人工饲料可以很好的满足南方小花蝽若虫生长的营养要求。然而,用棉蚜饲养的对照组南方小花蝽成虫获得率可达到63%,而人工饲料组连续两代的成虫获得率分别仅为45% 和43%。取食人工饲料的南方小花蝽成虫,在产卵前期、产卵量及寿命方面与对照组都没有显著差异,仅在产卵期方面有着显著差异,人工饲料组小花蝽的产卵期为13～16天,而对照组小花蝽的产卵期可达20天,说明液体人工饲料也可以很好的满足南方小花蝽成虫生殖发育的营养要求。     

A laboratory evaluation of the microsporidian Vavraia culicis as an agent for mosquito control

The susceptibility of the mosquitoes Aedes aegypti, Aedes taeniorhynchus, Anopheles albimanus, Culex pipiens quinquefasciatus, Culex salinarius, and Culex tarsalis to infection by the microsporidian Vavraia culicis was determined. Using 18-hr exposures to 5 × 10³, 1 × 10⁴, 5 × 10⁴, and 1 × 10⁵ spores/ml, C. salinarius, C. tarsalis, and A. albimanus were found to be significantly more susceptible than A. aegypti. The most severe infections were observed in C. salinarius and C. tarsalis, although heavy infections of approximately 1 million spores per adult were recorded at the higher dosages in all species tested except A. aegypti. Production trials indicated that up to 5.4 × 10⁸ spores could be routinely produced in individual corn earworms, Heliothis zea. Inactivation of the spores by sunlight was measured by observing the subsequent incidence of infection and spore production in A. albimanus. These two measurements provided an LT₉₀ of 5.5 and 3.3 hr, respectively.     

斑翅肩花蝽布丁人工饲料的饲养效果评价

斑翅肩花蝽 Tetraphleps galchanoides Ghauri是铁杉球蚜 Adelges tsugae (Annand) (hemlock woolly adelgid)的重要天敌。为开展斑翅肩花蝽的人工繁殖, 我们自主研制了一种主要成分为蛋白质、 脂肪、 碳水化合物的原料配制布丁人工饲料, 所配制人工饲料产率为74.5%, 含水率为8.6%, 感官评定得分为81.7分。为评价斑翅肩花蝽布丁人工饲料的饲养效果, 在实验室以铁杉球蚜作对照, 用布丁人工饲料饲养斑翅肩花蝽, 测定了斑翅肩花蝽若虫发育历期、 存活率及成虫繁殖力, 并调查了若虫和成虫林间捕食量。结果表明： 用布丁人工饲料饲养的斑翅肩花蝽若虫发育历期（103.2±6.5 d）与对照的若虫发育历期（105.7±8.4 d）不存在显著差异（P>0.05）; 用布丁人工饲料饲养的斑翅肩花蝽若虫存活率（73.2%）略低于对照的若虫存活率（77.4%）, 而且第1, 2和3代成虫获得率相近; 取食布丁人工饲料的斑翅肩花蝽成虫, 在产卵前期、 产卵期、 产卵量与对照组均无显著差异, 但孵化率、 成虫寿命存在显著差异, 取食布丁人工饲料的卵孵化率为85.8%, 成虫寿命为51.9±4.0 d, 而对照组的卵孵化率仅为71.4%, 成虫寿命仅为37.4±2.6 d。林间释放用布丁人工饲料饲养的斑翅肩花蝽, 若虫和成虫均有效捕食铁杉球蚜。因此, 此种布丁人工饲料可用于大量饲养繁殖斑翅肩花蝽, 满足大面积生物防治铁杉球蚜的需要。     

Identification of the parasitoid community associated with an outbreaking gall wasp,Zapatella davisae,and their relative abundances in New England and Long Island,New York

Gall wasps (Hymenoptera: Cynipidae) are phytophagous insects that often go unnoticed; however, when they are introduced to a new area or released from their natural enemies, they have the capacity to outbreak and cause extensive foliar damage. One such outbreaking pest, Zapatella davisae (Cynipidae: Cynipini), causes significant damage and mortality to black oak, Quercus velutina, in the northeastern United States. In this study, we aimed to identify the parasitoid community associated with Z. davisae, compare differences in percent parasitism of Z. davisae in Cape Cod and Long Island, and determine which parasitoid species contribute most to parasitism in each region. From both locations, we reared parasitoids, identified morphological groups, analyzed percent parasitism rates for each group, and used DNA barcoding to provide species‐level identifications. On Long Island, there was nearly 100% parasitism in 2015 followed by a near total collapse of the population in 2016. In contrast, parasitism rates were lower and remained consistent on Cape Cod between 2015 and 2016, which may explain the greater canopy damage observed in that region. Species of Sycophila were the dominant parasitoids, with one species Sycophila nr. novascotiae representing ~65% of reared parasitoids from Long Island, and two species of Sycophila (S. nr. novascotiae and S. foliatae) with near equal representations on Cape Cod. In order to manage an insect pest, it is important to understand factors that influence its mortality and survival. An understanding of how these infestations progress overtime can help predict the impact that newer infestations in Nantucket, MA, and coastal Rhode Island will have on black oak populations and will aid in the management of this rapidly spreading gall wasp pest.     

Predicting the number of ecologically harmful exotic species in an aquatic system

Most introduced species apparently have little impact on native biodiversity, but the proliferation of human vectors that transport species worldwide increases the probability of a region being affected by high-impact invaders – i.e. those that cause severe declines in native species populations. Our study determined whether the number of high-impact invaders can be predicted from the total number of invaders in an area, after controlling for species–area effects. These two variables are positively correlated in a set of 16 invaded freshwater and marine systems from around the world. The relationship is a simple linear function; there is no evidence of synergistic or antagonistic effects of invaders across systems. A similar relationship is found for introduced freshwater fishes across 149 regions. In both data sets, high-impact invaders comprise approximately 10% of the total number of invaders. Although the mechanism driving this correlation is likely a sampling effect, it is not simply the proportional sampling of a constant number of repeat-offenders; in most cases, an invader is not reported to have strong impacts on native species in the majority of regions it invades. These findings link vector activity and the negative impacts of introduced species on biodiversity, and thus justify management efforts to reduce invasion rates even where numerous invasions have already occurred.     

Acceptance and suitability of Cacyreus marshalli (Lepidoptera: Lycaenidae) as host for three indigenous parasitoids

Laboratory tests were conducted in Italy to evaluate the acceptance and suitability of the alien butterfly Cacyreus marshalli Butler as host for three indigenous parasitoids, Trichogramma brassicae (Bezdenko), Exorista larvarum (L.) and Brachymeria tibialis (Walker). Only E. larvarum and B. tibialis showed potential to adapt to C. marshalli. Their contribution to biological control appeared to be especially related to host mortality due to incomplete parasitoid development.     

A century of the ornamental plant trade and its impact on invasion success

We identify a significant relationship between domestic market-based propagule pressure, as measured both in presence in the British horticultural market and in seed prices of ornamental plant species, with success in invasion. We employ a multispecies temporal approach and use a Generalized Estimation Equation model comparing ornamental non-native species introduced into Britain which started to invade with species introduced but not known outside cultivation. Historical nursery catalogues gave information on the availability and prices of seeds of 506 ornamental species in the British horticultural market every 20 years from 1885 to 1985. Higher market frequency and cheap prices of seeds were more significant and had a greater impact on the invading probability 20 years later than at the date of listing in a nursery catalogue. Our results suggest that national economic factors are an important part of the explanation for the invasiveness of ornamental plant species, and hence for the development of potential solutions.     

Prioritisation of potential agents for the biological control of the invasive alien weed,Pereskia aculeata (Cactaceae), in South Africa

Pereskia aculeata Miller (Cactaceae) is an invasive alien species in South Africa that is native in Central and South America. In South Africa, P. aculeata outcompetes native plant species leading to a reduction in biodiversity at infested sites. Herbicidal and mechanical control of the plant is ineffective and unsustainable, so biological control is considered the only potential solution. Climatic matching and genotype matching indicated that the most appropriate regions in which to collect biological control agents were Santa Catarina and Rio de Janeiro provinces in Southern Brazil. Surveys throughout the native distribution resulted in 15 natural enemy species that were associated with the plant. Field host range data, as well as previous host plant records, were used to prioritise which of the species were most likely to be suitably host specific for release in South Africa. The mode of damage was used to determine which species were most likely to be damaging and effective if released. The most promising species prioritised for further study, including host specificity and impact studies, were the stem-wilter Catorhintha schaffneri Brailovsky & Garcia (Coreidae); the stem boring species Acanthodoxus machacalis Martins & Monné (Cerambycidae), Cryptorhynchus sp. (Curculionidae) and Maracayia chlorisalis (Walker) (Crambidae) and the fruit galler Asphondylia sp. (Cecidomyiidae). By prioritising the potential biological control agents that are most likely to be host-specific and damaging, the risk of conducting host specificity testing on unsuitable or ineffective biological control agents is reduced.     

Survival of Beauveria brongniartii in the soil after application as a biocontrol agent against the European cockchafer Melolontha melolontha

The survival of the entomopathogenic fungusBeauveria brongniartii and its efficacyagainst the European cockchafer, Melolontha melolontha, was examined over 16months after application as a biologicalcontrol agent in different soil types inSwitzerland. In the absence of M. melolontha,the reduction of the number of the CFU in thesoil was nearly 90%. In soils with highorganic content and increased catalase activitythe decline in the CFU density of B.brongniartii was more pronounced. At siteswhere M. melolontha was present, thesurvival was significantly longer. Theapplication of B. brongniartii resultedin a maximal infection rate of 75% in the M. melolontha population. The number of CFU ofB. brongniartii in the soil started todecrease only when the M. melolonthapopulation was reduced during the epizootic(reduction of 46% on average). The rapiddecrease of the fungus in the absence of thehost gives further evidence of the highspecificity of the fungus and that asaprophytic multiplication without the host isunlikely. The fungus was isolated on aselective medium as well as by baiting withGalleria mellonella. The latter methoddid not reveal the significant differencesmentioned above, which leads to the assumptionthat the two methods may select for differentfungal strains.     

Flower strips increase the control of rosy apple aphids after parasitoid releases in an apple orchard

Mass releases of two parasitoid species, Aphidius matricariae and Ephedrus cerasicola, may provide an alternative measure to pesticides to control the rosy apple aphid Dysaphis plantaginea in organic apple orchards. As an exploratory study, we tested if the presence of flower strips between apple tree rows could improve the action of three early parasitoid releases––and of other naturally present aphid enemies––on the control of aphid colonies and the number of aphids per tree. Apple trees located at various distances from parasitoid release points were monitored in plots with and without flower strips in an organic apple orchard over two years, along the season of aphid infestation (March to July). Our case study demonstrated that the presence of flowering plant mixes in the alleyways of the apple orchard reduced the presence of D. plantaginea by 33.4%, compared to plots without flower strips, at the infestation peak date. We also showed a negative effect of increasing the distance to parasitoid release points on aphid control. However, our results at the infestation peak date suggest that the presence of flower strips could marginally compensate for the detrimental effect of increasing distance to the release point, probably by improving the persistence and dispersal capacities of natural enemies. Despite high variations in aphid population dynamics between years, we conclude that combining flower strips with early parasitoid releases in apple orchards is promising for biological control of the rosy apple aphid, although the method merits to be further refined.     

Interactions between host attributes and wasp size: a laboratory evaluation of Trichogramma platneri as an augmentative biological control agent for two avocado pests

We compared egg parasitization of two sporadic pests of avocado, Persea americana Miller, by Trichogramma platneri Nagarkatti reared on Sitotroga cerealella (Oliver) (=smaller parasitoids) with those reared on Trichoplusia ni (Hübner) (= larger parasitoids) in the laboratory. Large T. platneri females invested less time than smaller parasitoids in obtaining offspring from eggs of either Amorbia cuneana Walsingham or Sabulodes aegrotata (Gueneé). Furthermore, large T. platneri invested substantially more time (ca. 3-fold) in obtaining offspring from S. aegrotata than A. cuneana eggs. These investment times positively correlated with percentage egg-load retained by a female after it had ceased exploiting a host species. This occurred even though the offspring produced by a parasitoid from either host species manifested the same size and fecundity (= quality). Host species utilization in the laboratory mirrored that observed in the avocado groves of southern California following augmentative release of commercially produced T. platneri (Oatman & Platner, 1985). Explanations for these differences in host utilization are discussed along with their implications for augmentative biological control.