Augmentative Biological Control Research Articles

Impact of diet composition of <I>Corcyra cephalonica</I> (Lepidoptera: Pyralidae) on the development and reproduction of <I>Trichogramma chilonis</I> (Hymenoptera: Trichogrammatidae)

Utilizing parasitoids for augmentative biological control frequently depends on the physiological state of the parasitoids and the pest population density at the time of release. Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) is commonly used as an egg parasitoid for biological insect pest control via augmentation and field release. A crucial component of mass production programmes is the host’s nutritional compatibility. So, the investigations were carried out to study the effect of diet composition of Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) on developmental and reproductive parameters of Trichogramma chilonis Ishii. The T. chilonis was reared on Corcyra cephalonica fed on different diets (D1-D7) in the laboratory at 25℃±1℃ with 75±5% RH. Based on pooled data of two generations T. chilonis had shown significantly highest parasitization of 85.80%, adult emergence percentage 75.00% and sex-ratio 1.62:1 on rice moth eggs obtained from Maize (48.5%) + Sorghum (48.5%) + Groundnut (3%) diet (D5). Trichogramma adult’s emergence was observed earlier (3.10 days) on the host’s eggs reared on the Bajra (100%) diet (D1). In case of adult longevity, the maximum longevity of 7.70 days was recorded on the host’s egg obtained from the D5 diet over the others. These findings may help to improve the developmental and reproductive performance of T. chilonis and an optimized D5 diet may be useful for mass rearing of this egg parasitoid.

Assessment of Kweilingia divina as a potential augmentative biological control agent against the gramineous weed Microstegium vimineum

Microstegium vimineum (Trin.) A. Camus, commonly called stiltgrass, is an exotic and indigenous troublesome weed in the United States and eastern Asia, respectively. Between 2020 and 2022, a damaging disease was observed on M. vimineum plants at the foot of Daluo Mountain in Wenzhou City, China, with an incidence of 90 %. Typical rust disease symptoms were prominently visible during the early monsoon season (June to July), consisting of chlorotic spots with many orange or orange-yellow uredinia on the abaxial surfaces of the M. vimineum leaves. Based on morphological and molecular characteristics, the fungus was identified as Kweilingia divina (Syd.) Buriticá. This article describes the studies carried out on one strain of the fungus (WZ-2) to ascertain its potential as a biocontrol agent of the weed. Host specificity testing on 61 plant species from 15 families proved that 25 major crops and 36 weeds were insensitive to this fungus, with only two other gramineous weed species being slightly susceptible. However, urediniospores were not observed on these slightly infected plants. Further research is required to assess the pathogenicity and safety of various plant species to K. divina, especially bamboos, which have been identified as susceptible. Temperature and dew period experiments have shown that the fungus has a relatively wide tolerance for infection between 15 and 40 °C, and with only 4 h of dew exposure some uredinia appeared on artificially infected M. vimineum plants. A field trial proved that urediniospores from the strain WZ-2 could infect naturally occurring M. vimineum plants, causing severe disease symptoms and plant death. Thus, strain WZ-2 has great potential as an augmentative biological control agent against M. vimineum. K. divina is a heteroecious rust fungus that requires an alternate host to complete its life-cycle. What the alternative hosts are, and the impact of the alternate hosts on outbreaks of the disease requires further study.

Understanding the movement and dispersal patterns of released Fopius arisanus (Hymenoptera: Braconidae) parasitoids in a papaya orchard.

Implementation of augmentative biological control requires estimates of parasitoid dispersal from the release point to determine appropriate release density, spacing, and timing. This study evaluated the movement patterns of Fopius arisanus Sonan (Hymenoptera: Braconidae) parasitoids, which have historically been used to control invasive tephritid fruit flies. The wasps were released from the central point, and dispersal was monitored over time using parasitism in sentinel fruit and trap captures at 40 points radiating out from the center (15-240 m). The releases were conducted 4 times during June, July, September, and November 2006. The data showed that there were large declines in dispersal by distance. Parasitism was greatest closest to the release point, within 30 m. Parasitism was also greatest within the first 24 h of the release. After 1 wk, parasitism decreased from 41% to 1.5% within 30 m. These data correlated strongly with trap capture data, which also showed that parasitoid movement favored the SE region of our release site, roughly corresponding to the overall prevailing winds. Wind speed, relative humidity, and temperature all affected parasitoid movement during our trial, indicating the complex environmental factors that can affect release success. This is the first report of dispersal metrics for F. arisanus. Our findings are in agreement with other similar studies on braconid movement generally and suggest that frequent, high-density releases are most effective since the dispersal of F. arisanus is limited and retention in the environment is low. We discuss our results in the context of international augmentative biological control release programs.

To move or not to move: Dispersal of Orius insidiosus in strawberry plants

AbstractSpatial and temporal distribution of food resources influences predatory insects' foraging and dispersal behavior. Orius insidiosus (Say) (Hemiptera: Anthocoridae) is a good biological control agent of western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), in the strawberry crop and consumes two‐spotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae), and pollen as well. Augmentative biological control programs may fail if, following release, predators disperse from the crop. We studied the dispersal of O. insidiosus as a function of pollen availability, density of their main prey WFT, and the presence of the alternative prey TSSM, within and between strawberry plants. We found that O. insidiosus remained on the flowers during the 24 h of the assay. The dispersal of predators to a neighboring flower with thrips was approximately six times greater from a flower without pollen than from a flower with pollen. When TSSM was the only prey available, O. insidiosus colonized the leaves, and its dispersal within the plant was greater. At the plot scale, the predator dispersal from the release plant to other plants also depended on the presence of flowering plants and prey. Our results highlight the importance of flowering plants and pollen availability in enhancing the persistence of O. insidiosus in strawberry plants. Releases of this predator in the strawberry crop should be after the beginning of flowering, even at low WFT densities.

Bridging boundaries: Six years of community engagement with biological control implementation and monitoring of water hyacinth on Hartbeespoort Dam, South Africa

Water hyacinth has been present on Hartbeespoort Dam since the 1960s. Historical weed management consisted of herbicide and mechanical/manual removal. However, due to funding constraints, biological control was implemented as a cost-effective and environmentally friendly alternative. The impoundment receives excessive phosphorus and nitrogen due to its location downstream from densely populated cities, which includes one of the capital cities of South Africa, Pretoria. Considering that Hartbeespoort Dam is in a temperate region, with cool winters, we embarked on an augmentative biological control approach. To increase our biological control efforts, we had to bridge the research-implementation gap. We fostered a community of practice, by creating a space for the affected community to actively participate in the programme. This would give us the opportunity to share scientific knowledge to affected stakeholders, gauge the public perception, and align potential goals. Social media, in-person meetings and training sessions were used to engage with the public. To increase the availability of the water hyacinth biological control agent, Megamelus scutellaris, community members (i.e. private stakeholders) were offered the opportunity to manage satellite rearing stations. Between 2018 and 2023, nearly half a million Megamelus scutellaris individuals, sourced from both the Centre for Biological Control’s mass-rearing facility and satellite rearing stations around Hartbeespoort Dam, have been released into the dam. Water hyacinth cover on the dam drastically declined every year following a build-up of Megamelus scutellaris. Over the course of the programme, private stakeholders that were actively involved grew from two (2018) to 16 (2023). Analysing the participation of private stakeholders using a framework that looks at the level of value gained from our interactions, two partners reached a value chain phase that led to an expansion of biological control implementation. Longer-term private stakeholders generated increased interest for biological control implementation in their community, which resulted in recruitment of new private stakeholders. We also evaluated the knowledge of the affected community in 2023 through an online questionnaire. Out of 132 respondents, 51 % had knowledge of what biological control entails, with 56 % acknowledging that biological control has had a positive impact on the management of water hyacinth. Bridging the research-implementation boundary has strengthened biological control efforts, enabling a more sustainable approach to the management of water hyacinth on Hartbeespoort Dam. However, continued community engagement is necessary to increase the public’s knowledge about the practice of biological control.

Ratio-dependent competitions between a Wolbachia-uninfected bisexual strain and Wolbachia-infected thelytokous strain of the egg parasitoid, Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae)

BackgroundWolbachia-infected thelytokous Trichogramma wasps have been considered as potential effective biocontrol agents against lepidopteran pests in agriculture and forests. However, intra-specific competition may arise when Wolbachia-infected thelytokous Trichogramma coexist with their uninfected bisexual counterparts in fields or during mass-rearing procedures. This competition could potentially impact the efficacy of Trichogramma females in biological control programs.ResultsThis study examined the parasitic capacities of bisexual (TdB) and Wolbachia-infected thelytokous (TdT) strains of Trichogramma dendrolimi as influenced by host density (ranging from 5 to 70 host eggs) and wasp density (two, four, and six females per arena). The experiments involved inter-strain competition between TdB and TdT strains (Inter-Td) as well as intra-strain competition within the TdT (Intra-TdT) or TdB (Intra-TdB) strains. Results revealed that females in the Inter-Td group exhibited a higher attack rate compared to those in the Intra-TdT and Intra-TdB groups, irrespective of wasp density. Specifically, when six females were present, the Inter-Td group showed significantly shorter host handling times than the Intra-TdT group. Within intra-strain cohorts, TdT females displayed a lower attack rate than TdB females when four or six females were present, and longer host handling times when six females were present. Mutual interference between individuals was not affected by competition types. Females of the Inter-Td group exhibited a higher probability of superparasitism than those of the Intra-TdB group or Inter-Td group. When both strains coexisted, the proportion of TdT offspring with six females was higher than that with two females or four females. Male ratios of bisexual offspring in Inter-Td groups were higher than those in Intra-TdB groups. The male ratio of bisexual offspring in the Inter-Td group increased with wasp density.ConclusionsOur study highlights the negative impact of Wolbachia on parasitic capacity of Trichogramma females, increasing the likelihood of superparasitism. The coexistence of both strains enhances total parasitic efficacy, albeit resulting in a higher proportion of male offspring compared to scenarios with only uninfected females. The results will provide the reference for the usage of Wolbachia-infected thelytokous strain of T. dendrolimi in augmentative biological control programs.

Testing the Effects of Prey Type on the Life History and Population-Level Parameters of Chrysoperla externa (Neuroptera: Chrysopidae).

Green lacewings are valuable predators, utilized in augmentative biological control against various agricultural pests. However, further studies are required to comprehend the performance of these predators when consuming natural prey. We investigated the capacity of Chrysoperla externa (Hagen) to utilize the following three distinct prey types: the pupae of the coffee leaf miner Leucoptera coffeella (Guérin-Mèneville & Perrottet), the eggs of the sugarcane borer Diatraea saccharalis (F.), and the eggs of the Mediterranean flour moth Ephestia kuehniella (Zeller). The first two of these species are naturally occurring prey found in field crops, while the last serves as a factitious prey species for the mass rearing of natural enemies. We hypothesized that the type of prey would differentially affect the life history and population-level parameters of C. externa. Laboratory experiments were conducted to compare the pre-imaginal survival and developmental times, adult longevity and reproduction, and population growth of C. externa when larvae were provided with each of the three prey items. Results indicated that C. externa utilized the two natural prey items, L. coffeella pupae and D. saccharalis eggs, for its development, reproduction, and population growth. However, larvae developed significantly faster and females exhibited higher reproductive parameters, including fecundity and daily oviposition, when consuming the factitious prey, E. kuehniella eggs. This resulted in a higher intrinsic rate of population increase, as well as shorter times for the population to double in size. Understanding the population dynamics of C. externa when consuming different prey items is crucial for optimizing their utilization in augmentative biological control programs.

Are predatory mites effective as biological control agents to suppress Oligonychus ilicis (Acari: Tetranychidae) in blueberry plantings?

Southern red mite, Oligonychus ilicis McGregor (Acari: Tetranychidae), is an important polyphagous spider mite pest that causes economic damage to many ornamentals, coffee, and fruit crops. Blueberry growers in the Southeastern United States, including Florida and Georgia, have experienced severe losses due to outbreaks of O. ilicis. Predatory mites are an important management tool used for controlling spider mites; however, predators have not been studied and successfully evaluated in blueberry systems. Amblyseius swirskii Athias-Henriot, Phytoseiulus persimilis Athias-Henriot, and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) are among the most economically important arthropod agents used in augmentative biological control worldwide. To evaluate the potential of these 3 commercially available predatory mites for use in blueberry plantings, we conducted experiments under controlled laboratory conditions and in the greenhouse. In preliminary laboratory experiments, P. persimilis and N. californicus significantly reduced the number of O. ilicis motile stages below those found in the untreated control, indicating the potential for these 2 predatory mite species to suppress O. ilicis populations. Amblyseius swirskii did not perform well controlling O. ilicis motiles in the laboratory. Under greenhouse conditions, N. californicus and P. persimilis significantly reduced the number of eggs after 7 days of release and the number of motile stages after 14 days of release. This is the first report of using phytoseiid mites to suppress O. ilicis in blueberry systems in the United States. Further studies on predator behavior, feeding preferences, and acaricide compatibility with predators are required to investigate the possibility of using P. persimilis, and N. californicus as biological control agents of O. ilicis in blueberry systems.

Optimizing the releasing strategy used for the biological control of the sugarcane borer Diatraea saccharalis by Trichogramma galloi with computer modeling and simulation

One of the challenges in augmentative biological control programs is the definition of releasing strategy for natural enemies, especially when macro-organisms are involved. Important information about the density of insects to be released and frequency of releases usually requires a great number of experiments, which implies time and space that are not always readily available. In order to provide science-based responses for these questions, computational models offer an in silico option to simulate different biocontrol agent releasing scenarios. This allows decision-makers to focus their efforts to more feasible options. The major insect pest in sugarcane crops is the sugarcane borer Diatraea saccharalis, which can be managed using the egg parasitoid Trichogramma galloi. The current strategy consists in releasing 50,000 insects per hectare for each release, in three weekly releases. Here, we present a simulation model to check whether this releasing strategy is optimal against the sugarcane borer. A sensitive analysis revealed that the population of the pest is more affected by the number of releases rather than by the density of parasitoids released. Only the number of releases demonstrated an ability to drive the population curve of the pest towards a negative growth. For example, releasing a total of 600,000 insects per hectare in three releases led to a lower pest control efficacy that releasing only 250,000 insects per hectare in five releases. A higher number of releases covers a wider range of time, increasing the likelihood of releasing parasitoids at the correct time given that the egg stage is short. Based on these results, it is suggested that, if modifications to the releasing strategy are desired, increasing the number of releases from 3 to 5 at weekly intervals is most likely preferable.

Management of aphids on winter high tunnel crops

High tunnels offer several benefits to specialty crop growers including crop protection and season extension. Although crops are actively grown in high tunnels during the winter, few management recommendations exist for winter pests that are actively feeding and reproducing in this protected environment. This study evaluated the efficacy of three commercially available predators used for the augmentative biological control of aphids, Adalia bipunctata, Orius insidiosus, and Chrysoperla carnea, in combination with OMRI-approved pesticides labeled for aphids on spinach and strawberry. Pesticides included PyGanic (pyrethrin), Neemix (azadirachtin), and Sil-MATRIX (Potassium silicate). Laboratory and field experiments indicate high survival of biocontrol agents under row covers in high tunnels, and preventative and/or curative management of aphids. Spray trials had varied results, but spinach marketability was highest in plots that received PyGanic while strawberry marketability was lowest in this treatment. We also observed high compatibility of predators with each spray product, with one exception being A. bipunctata that was susceptible to PyGanic in one experiment. Strawberry yield (weight per plant) and spinach marketability was negatively correlated with accumulated aphid days in our study, indicating a need for aphid management in these crops during winter.

Entomopathogens and their role in insect pest management

Agricultural production faces significant challenges due to the loss of crop yields, highlighting the need for improvements in pest management methods to enhance productivity. Crop growers are increasingly pressured to minimize the use of chemical pesticides without compromising yields. However, managing pests has become more challenging due to pesticide resistance and limited product availability. Consequently, there is an urgent requirement for alternative approaches. Entomopathogens such as fungi, bacteria, viruses, and nematodes emerge as promising alternatives to broad-spectrum chemical insecticides. They have been widely employed to control insect pests in cultivated crops, employing successful strategies such as augmentation and classical biological control. These methods involve applying or introducing bacteria, baculoviruses, fungi, and nematodes. Utilizing entomopathogens offers numerous benefits beyond their effectiveness. These advantages encompass the capacity to treat expansive areas with a sole application, ensuring safety for both humans and non-target organisms. Additionally, their use leads to decreased pesticide residues in food, the conservation of natural enemies, and a boost in biodiversity within managed ecosystems. Entomopathogens present a viable solution by offering effective pest control while addressing environmental, human health, and ecosystem sustainability concerns. The primary emphasis of this review is on the present condition of bio-formulations, the pathogenicity associated with entomopathogens, their mode of action, and the possible implementation of diverse microbial formulations aimed at achieving sustainable pest management.

Effects of cold storage temperature, host status, and larval stage on the biological characteristics of Cotesia chilonis

AbstractShelf life is an important determinant of the quality of parasitoids used as natural enemies in augmentation biological control. Cotesia chilonis (Munakata) (Hymenoptera: Braconidae), an obligate endoparasitoid of Chilo suppressalis (Walker) (Lepidoptera: Crambidae), has potential for use through augmentation biological control in China. Here, the effects of cold storage temperature, host status, and larval stage on the biological characteristics of C. chilonis were investigated to extend the agent's shelf life. Results showed that the number of healthy C. chilonis adults obtained was reduced by 3.5% and 47.7% when C. suppressalis larvae in either natural or induced diapause were used as hosts compared to nondiapausing control larvae. Both parasitism and cold storage significantly reduced the supercooling point of nondiapausing C. suppressalis larvae, whereas the opposite result was observed in those of natural diapause. In order to improve the long‐term storage of C. chilonis, nondiapausing C. suppressalis larvae were parasitized for 1, 3, 5, and 7 days to allow C. chilonis to develop into different larval stages before being transferred into cold storage for 30 days at 4 or 10°C. Compared to the control, the C. chilonis cocoon formation and emergence rates of the 1‐day‐old egg treatment group held at 10°C were reduced by 15% and 17%, respectively. The results also showed that the duration of the larval stage of C. chilonis was prolonged fourfold after storage at 4 and 10°C. Individuals held at 10°C had a significantly longer cocoon and adult stage compared to those held at 4°C. The biological parameters and life history of the F1 generation of C. chilonis returned to normal levels under laboratory conditions. In conclusion, C. suppressalis larvae were successfully used to extend the shelf life of C. chilonis for use in augmentative biocontrol programs.

Optimizing the Release Pattern of Telenomus podisi for Effective Biological Control of Euschistus heros in Soybean.

An augmentative biological control program using the egg parasitoid Telenomus podisi Ashmead (Hymenoptera: Platygastridae) is a promising tool for the management of the brown stink bug, Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) in soybeans. The T. podisi are released as adults or pupae within lab-reared E. heros eggs. Because of the small size of the parasitoid and potentially limited dispersal ability, determining the optimal release pattern is critical for biological control of the target pest. This study used sentinel E. heros eggs to investigate T. podisi dispersal within soybean crops during two distinct phenological stages: the beginning of flowering (Vn-R1) and the grain-filling phase (R5-R6). Data were analyzed using semi-variograms and kriging maps. The results indicate significant differences in parasitism rates between the two plant growth stages and among different matrices. The maximum dispersal range for T. podisi was calculated at 39.0 m in the Vn-R1 stage with a maximum parasitism rate of 42%, while in the R5-R6 stage, the maximum dispersal range was calculated to be 30.9 m with a maximum parasitism of 73%. Therefore, it is recommended that release points for T. podisi be spaced no further than 30 m apart. These results provide valuable insights for future research and applications in biological control strategies, including adjustment of the logistics and release technique depending upon the crop phenological stage.

Status and trends of biological control research, extension, and education in the United States

Abstract The number of public-sector biological control scientists and practitioners in the United States was determined by a survey conducted in 2019. A total of 344 personnel were identified in 49 states and Washington DC; 218 employed by universities, 86 by the federal government and 36 by state departments of agriculture. There were 10-34 personnel in eight states, 6-9 in 11, and 0-5 in 31, overall averaging less than 50% of their combined effort on biological control. Applications for biological control agents included about 30% for row crops and vegetables; 12% each for orchards, urban landscapes, outdoor ornamentals, and forests; and 22% for the remainder. The federal government provided an average of 42% of the funding for university, federal, and state biological control research and extension. The states contributed 29-35%, commodity groups supplied 19-24%, and the remaining funds were from private sources. Of 54 universities in the United States, 18 conducted in-person classroom education and training in biological control, with seven offering courses via distance. However, another 18 universities had discontinued their comprehensive courses. Biological control instruction was incorporated into courses and workshops on integrated pest management and sustainable agriculture at 50 universities. Correspondingly, during the past 24 years, biological control has gradually developed from primarily an independent discipline to increasingly being part of integrated pest management. Classical, augmentative and conservation biological control have nevertheless remained distinguishable high priority subdisciplines. Funding continues to be essential for advancing biological control, requiring societal understanding and acceptance. Advancement of biological control in the United States will require increased investment in personnel and their education and training, along with delivery of effective pest management technologies.

Insight into the host-specificity of a native and a newly introduced parasitoid of Tuta absoluta and prospect for biological control

New strategies are urgently needed to control Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), one of the most destructive pests of tomato crops. Originating from South America, it is spreading rapidly and has evolved resistance to most common insecticides making it highly challenging to control. Regarding biological control, the parasitoid Necremnus tutae Ribes & Bernardo (Hymenoptera: Eulophidae) is widely present around the Mediterranean basin and has adapted to the invader playing a substantial role in its control. In addition, the neotropical parasitoid Dolichogenidea gelechiidivoris Marsh (Hymenoptera: Braconidae) has established accidentally following its host in Spain and Algeria and a classical biological control program using this species is ongoing in Sub-Saharan Africa. Understanding the trophic connections between D.gelechiidivoris, N.tutae, the targeted host T.absoluta and potential non-target hosts is essential to assess their value as augmentative or classical biological control agents and to promote their establishment in conservation biocontrol. We conducted host-specificity tests in the laboratory using four European leafminer species to evaluate the specificity of these two parasitoids to T.absoluta. We then assessed their affinity for T.absoluta by exposing sentinel plants with the alternative host Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) inside and around greenhouses and measuring each parasitoid species' field parasitism rate. Our results show that of the four non-target species tested in the laboratory, N.tutae attacked three, while D.gelechiidivoris attacked only P. operculella. In the greenhouse, N.tutae did not prefer P.operculella or T.absoluta, whereas D.gelechiidivoris preferred the latter. The mean parasitism rate of T.absoluta over the three-month monitoring period in the greenhouses reached 27% for N.tutae and 35% for D.gelechiidivoris. We discuss the importance of host affinity for understanding potential non-target effects and the value a natural enemy can have as biological control.

Leveraging computational intelligence to identify and map suitable sites for scaling up augmentative biological control of cereal crop pests

Fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith) is a major pest affecting cereal production in Africa. Biological control (BC) technologies are being promoted as a sustainable alternative to chemical control, which can lead to health risks and environmental hazards. However, effective deployment of these technologies requires site-specific recommendations. In this study, we use a step-by-step modelling approach to map suitable sites for BC technologies, focusing on the parasitoid Cotesia icipe using the FAW level of infestation, the ecological niche of the parasitoid, and the FAW host crop. The level of pest infestation was estimated using an evolutionary adaptive Neuro-Fuzzy inference system (R2 > 0.89) while the pest ecological niche was obtained using the maximum entropy algorithm (area under curve, AUC > 0.9). A fuzzy operator was used to combine all fuzzified variables into a single layer that represents the landscape's overall suitability for C. icipe in maize farms. Our computational findings indicate that C. icipe holds substantial promise as a BC agent in maize farms, with suitability levels consistently surpassing 90% throughout maize cropping seasons. The findings demonstrate that the utilization of artificial intelligence, combined with data science and knowledge representation, serves as an effective advisory tool for guiding the deployment of BC agents, such as parasitoids, for the sustainable management of FAW. This approach enables informed decision-making and enhances the efficacy of FAW management strategies by providing valuable insights and recommendations based on data-driven and computer intelligence analyses.

Aecial and Telial Host Specificity of Puccinia coronata var. coronata, a Eurasian Crown Rust Fungus of Two Highly Invasive Wetland Species in North America.

The Eurasian crown rust fungus Puccinia coronata var. coronata (Pcc) was recently reported in North America and is widespread across the Midwest and Northeast United States. Pcc is a close relative of major pathogens of oats, barley, and turfgrasses. It infects two highly invasive wetland plants, glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea), and could be useful as an augmentative biological control agent. We conducted large greenhouse trials to assess the host specificity of Pcc and determine any threat to cultivated cereals, turfgrasses, or native North American species. A total of 1,830 accessions of cereal crop species and 783 accessions of 110 other gramineous species were evaluated. Young plants were first inoculated with a composite uredinial inoculum derived from aecia. Accessions showing sporulation were further tested with pure urediniospore isolates. Sixteen potential aecial hosts in the families Rhamnaceae and Elaeagnaceae were tested for susceptibility through inoculation with germinating teliospores. Thirteen grass species within five genera in the tribe Poeae (Apera, Calamagrostis, Lamarckia, Phalaris, and Puccinellia) and four species in Rhamnaceae (Frangula alnus, F. californica, F. caroliniana, and Rhamnus lanceolata) were found to be susceptible to Pcc, with some species native to North America. All assessed crop species and turfgrasses were resistant. Limited sporulation, however, was observed on some resistant species within Poeae and four other tribes: Brachypodieae, Bromeae, Meliceae, and Triticeae. Among these species are oats, barley, and Brachypodium distachyon, suggesting the possible use of Pcc in studies of nonhost resistance.

Influence of fall armyworm Spodoptera frugiperda egg mass scales and layers on the performance of three species of egg parasitoid Trichogramma with different ovipositor lengths

BackgroundThe fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a highly polyphagous and destructive pest of maize and other cereal crops. Biological control is a potential alternative to chemical insecticides used for the management of FAW in maize. Egg parasitoids are promising biocontrol agents as they kill the insect pest at their egg stage before it hatches, thus preventing the damaging larval stage. Trichogramma is widely used in augmentative biological control of FAW in native and invaded regions. However, FAW lay egg masses in layer by layer and eggs are covered with egg scales, this may affect the performance of Trichogramma parasitoids. Therefore, the parasitism potential of three Trichogramma species was studied on eggs with or without scales and layered eggs of FAW, further the impact of parasitoids ovipositor length on parasitism was also determined. This helps to understand the parasitism potential of parasitoids on different egg type for better implementation of biological control programs against FAW.ResultsThe effect of FAW egg mass with or without scales and layered eggs on the performance of Trichogramma chilonis, T. pretiosum and T. mwanzai was studied and results indicated that egg mass scales and the layered eggs were significantly affected the parasitism potential of Trichogramma species, but did not affect the parasitoid emergence. In general, T. chilonis parasitized a higher percentage of eggs with or without scales and layered eggs of FAW than the other two species. T. chilonis and T. mwanzai had a greater ovipositor length than T. pretiosum.ConclusionThe performance of evaluated Trichogramma species on FAW eggs with or without scales and layered eggs affected the parasitism success. The parasitism success of T. chilonis was comparably higher than other tested species. Hence, the scales on egg masses and layered eggs of FAW should be taken into account while selecting the Trichogramma species in the biological control of FAW.

Assessing Natural Incidence of Resident Pupal Parasitoids on the Drosophila suzukii (Diptera: Drosophilidae) Population in Non-crop Fruits.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), world-renowned as spotted-wing drosophila, is an invasive pest mainly affecting healthy, soft and stone fruit crops throughout Argentinian fruit-growing regions. Natural environments overgrown by exotic feral host plants apparently favour D. suzukii proliferation. This is common in the subtropical northwestern Argentina's berry-producing region. An assemblage of resident parasitoid species has been associated with D. suzukii in crop and non-crop areas of Tucumán, the Argentina's leading berries producer and exporter. Consequently, the hypothesis that the combined action of two pupal parasitoid species, Pachycrepoideus vindemiae Rondani (Hymenoptera: Pteromalidae) and Trichopria anastrephae Lima (Hymenoptera: Diapriidae), occurring in non-crop fruit areas, has a significant impact on D. suzukii natural regulation in such invaded habitats was tested. A survey of D. suzukii puparia from both feral peach [Prunus persica (L.) Batsch] (Rosaceae) and guava (Psydium guajava L.) (Myrtaceae) fallen fruits and soil surrounding them was performed in a wilderness area of Tucumán. Abundance of D. suzukii and associated parasitoids, and parasitism levels were assessed. Whole of 3437 D. suzukii puparia were recovered; 78% and 22% were surveyed from fruits and soil underneath the fruit, respectively. Tested fruits are important D. suzukii multiplying hosts. Both P. vindemiae and T. anastrephae accounted for 99.8% of total parasitoid individuals. Pupal parasitoids contribute to the D. suzukii natural mortality, as they killed a quarter of all puparia. Mostly T. anastrephae foraged on host puparia located in the fruit and P. vindemiae in both microhabitats. This information supports an augmentative biological control strategy in non-crop areas.

Hadronotus pennsylvanicus (Hymenoptera: Scelionidae): a biological control agent for pestiferous leaffooted bugs (Hemiptera: Coreidae)

Abstract In recent decades, the egg parasitoid Hadronotus pennsylvanicus (Ashmead) has gained substantial attention as an important natural enemy of pestiferous leaffooted bug species in the genera Anasa Amyot and Serville and Leptoglossus Guérin-Méneville. Throughout its native range of North America, H. pennsylvanicus parasitizes Anasa and Leptoglossus eggs in various vegetable and orchard systems. The overreliance on broad-spectrum insecticides in these systems and the demand for effective and sustainable coreid pest management strategies have motivated researchers to consider H. pennsylvanicus as an augmentative biological control agent. The potential use of H. pennsylvanicus as a classical biological control agent has also been studied in Europe in response to the rapid spread of Leptoglossus occidentalis Heidemann, an invasive pest causing significant economic losses to the European pine nut industry. Improved understanding of H. pennsylvanicus taxonomy, life history, host range, parasitoid–host ecology, laboratory rearing, and field deployment techniques have created a robust scaffold on which to build future biological control programs. This natural enemy profile reviews the current advances in the aforementioned areas of H. pennsylvanicus research and outlines the parasitoid’s prospects as a biological control agent.