Augmentative Biocontrol Research Articles

Supplementary sugars enhance the production efficiency and parasitism performance of the egg parasitoid Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae).

Trichogramma spp. wasps are egg parasitoids with a long history of mass rearing for augmentation biocontrol programs in field crop and orchard landscapes. Supplementary nutrition can improve the longevity, fecundity, and biocontrol efficacy of parasitoids. To improve the production efficiency and parasitism performance of Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae), the present study screened and examined the potential supplementary nutrients for this biological control agent. Dietary supplementation with a 10% sucrose solution significantly increased wasp longevity and parasitism potential of T. dendrolimi on host eggs, but provision of pollen did not provide additional benefits. Laboratory and greenhouse cage tests demonstrated that wasp access to soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) honeydew, comprised primarily of melezitose and trehalose, improved T. dendrolimi longevity and parasitism. In conclusion, provision of a 10% sucrose solution to adult wasps will enhance the mass-rearing efficiency of T. dendrolimi; furthermore, field release of T. dendrolimi by plant vectors bearing honeydew-producing aphids holds promise for improving the biocontrol efficacy of T. dendrolimi.

First report of Telenomus remus Nixon (Hymenoptera: Scelionidae) on Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) in Egypt

BackgroundThe polyphagous alien invasive pest, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), invaded Africa and has so far spread across the continent, causing devastating impacts on maize production. In Egypt, the management of the pest by maize growers has been characterized by the application of broad-spectrum synthetic chemical insecticides, a strategy which is associated with various detrimental effects on the environment and human health. To mitigate the overreliance and excessive use of those synthetic chemicals, biological control using egg parasitoids species provides an ecologically friendly and sustainable management strategy. In that regard, this study had the objective of identifying the natural existing egg parasitoids, which could be effectively used in augmentative biocontrol of the pest in Egypt.ResultsFor the first time in Egypt, natural occurrence and parasitism of Telenomus remus Nixon, 1937 (Hymenoptera: Scelionidae) on S. frugiperda egg masses was recorded. Infested maize farms in Qena Governorate, Egypt, were surveyed, and S. frugiperda egg masses were collected and incubated in the laboratory. Emerging parasitoids’ wasps were grouped based on their morphological similarities. Natural parasitism of the egg parasitoids (Telenomus sp.) was computed from the parasitized field collected egg masses. In addition, to confirm the laboratory parasitism and suitability of the parasitoid, Telenomus sp. to develop on S. frugiperda, the parasitoid was reared on S. frugiperda egg masses for three generations under laboratory conditions. Moreover, both morphological and molecular identifications were conducted. The recovered parasitoid samples from the field S. frugiperda egg masses were Telenomus remus (Nixon) (Hymenoptera: Scelionidae). Moreover, the average field parasitism level by T. remus on S. frugiperda was 15.9%, while under laboratory conditions, the parasitism was 63.5%.ConclusionsThe natural occurrence of T. remus in Egypt and its association with S. frugiperda is an important finding upon which augmentative biocontrol strategy can be leveraged on to sustainably manage the pest populations.

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.

Drone-Related Agrotechnologies for Precise Plant Protection in Western Balkans: Applications, Possibilities, and Legal Framework Limitations

Modern agriculture necessitates the use of techniques and tools that pollute the environment less and improve the safety of food and feed production. In the field of plant protection, drones are attracting increasing attention due to their versatility and applicability in a variety of environmental and working conditions. Drone crop spraying techniques offer several advantages, including increased safety and cost effectiveness through autonomous and programmed operations based on specific schedules and routes. One of the main advantages of using drones for plant protection is their ability to monitor large areas of crops in a short amount of time. In addition to crop protection management, using drones for augmentative biocontrol facilitates the distribution of beneficial organisms to the exact locations where they are required, which can increase the effectiveness of biocontrol agents while reducing distribution costs. In this context, given the very limited commercial use of drones in the Western Balkans’ agri-food sector, the use of drones in the agri-food industry is a topic that needs to be elaborated on and highly promoted. Additionally, the specific legal regulations in Serbia that currently limit the use of drones in agriculture must be outlined. Conventional crop production is still significantly more prevalent in Serbia, but given the region’s continuous technological progress, there is no doubt that farmers’ education and future investments in precision agriculture will most likely increase the use of state-of-the-art technologies and drones in agriculture.

Sublethal effects of nine insecticides on Drosophila suzukii and its major pupal parasitoid Trichopria drosophilae.

Although the pupal parasitoid Trichopria drosophilae is employed in conservative and augmentative biocontrol of Drosophila suzukii infestations, current pest management strategies mostly rely on multiple insecticide applications. In this context, the aim of the study was to investigate the baseline toxicity of nine insecticides on D. suzukii larvae and their multiple sublethal effects (LC10 ) on immature stages of the pest feeding on contaminated diet and T. drosophilae developing within the intoxicated host. Chlorpyriphos and azadirachtin showed the lowest and the highest LC10 , which values were 9.78×1013 and 1.46×103 times lower than their recommended label field rate, respectively. Among tested insecticides, imidacloprid, malathion and dimethoate were the only treatments that did not affect the juvenile development time of D. suzukii, while spinosad and the organophosphates chlorpyriphos and dimethoate did not influence fly pupal size. No sublethal effects were recorded on T. drosophilae degree of infestation (DI) and juvenile development time. On the contrary, cyazypyr and dimethoate negatively affected the success of parasitism (SP) and the number of progeny of the pupal parasitoid, in association with malathion for the first parameter and spinosad for the fertility. Compared to the untreated control, more female progeny emerged following azadirachtin exposure, while dimethoate caused the opposite effect. Imidacloprid, lambda-cyhalothrin and spinetoram decreased hind tibia length of emerged parasitoids. This study provides new insights on the (eco)toxicological profile of nine insecticides and new information needed to support the deployment of T. drosophilae in the field within the sustainable management techniques against D. suzukii. This article is protected by copyright. All rights reserved.

Integration of augmentative biocontrol with synthetic pesticides and other control methods for IPM – Challenges and prospects*

The importance of augmentative biological control and chemical control, and the need and scope for integrating these, rather than dismissing them as incompatible, so as to create a win-win situation for both are highlighted. Besides the judicious use of chemicals and periodical releases of parasitoids/predators, other options such as insect-resistant transgenic crops, host plant resistance, botanical insecticides, sex pheromones, trap crops, pest resistance management, new product development, regulatory measures, etc., should also be exploited, as appropriate to a given situation, so as to develop an Integrated Pest Management (IPM) package. The practicality of such an IPM is explained, citing Bt cotton as an example. It is reiterated that IPM is the most prudent approach for sustainable crop production and protection with the major emphasis being laid on biological control and other eco-friendly methods as indicated by the latest global trend.

Distance‐dependent attraction of the generalist aphid parasitoid Aphidius colemani towards synthetic volatile organic compounds under greenhouse conditions

AbstractManipulation of insect foraging may provide the basis for effective insect pest control strategies. Recent laboratory and small‐scale greenhouse experiments have shown that a blend of styrene and benzaldehyde is attractive to some Aphidius parasitoids, making it a good candidate for attracting and retaining these natural enemies in cropping systems. However, an appropriate dispenser type and appropriate dose for field application and its attraction range have yet to be identified. In this study, we performed experiments to determine an appropriate dispenser type – Omnilure® vs. low‐density polyethylene (LDPE) bags – and the most suitable dose to attract Aphidius colemani Viereck (Hymenoptera: Braconidae) under commercial greenhouse conditions and to determine the maximum distance of attraction. A mixture of 10 mg styrene and 100 μg benzaldehyde was the most attractive dose for A. colemani when provided by the dispensers under greenhouse conditions. The highest percentage of parasitoids was attracted when insects were released at a distance of 0.5 m from the Omnilure dispensers. Nevertheless, compared to the solvent control the blend of styrene and benzaldehyde remained attractive over a distance of up to 5 m. The potential application of these results in novel augmentation biocontrol strategies is discussed.

Influence of host egg age on parasitic potential of the entomophagous, Telenomusremus Nixon (Hymenoptera: Scelionidae) against the Fall armyworm, Spodopterafrugiperda (J.E. Smith) (Lepidoptera: Noctuidae) and investigations on the developmental biology and ultrastructure of egg parasitoid immature stages

BackgroundBiological control through augmentative release of egg parasitoids is a potential tool in integrated management of field crop pests. The egg parasitoid, Telenomusremus Nixon (1937) (Hymenoptera: Scelionidae), is found promising against the fall armyworm, Spodopterafrugiperda (Smith) (Lepidoptera: Noctuidae) in different parts of the world. However, fundamental information on the parasitic capabilities with reference to the host eggs of progressing ages is very limited. The investigations reported herein focused on the influence of host egg age on the parasitic potential, developmental biology and morphological features of the sexes of T.remus that could aid in decisions on their field release. The laboratory experiments were carried out with FAW egg masses of different ages (24, 48 and 72 h old). Host eggs glued to paper strips (3 × 5 cm) were offered to T.remus for parasitization at the parasitoid: host ratio 1:40 under standard laboratory conditions. Developmental biology of immature stages of T.remus and the adult sexual dimorphism were studied through stereomicroscopic and scanning electron microscopic examinations on 24 h old FAW egg masses parasitized by T.remus.ResultParasitic potential of T.remus on FAW eggs of different ages indicated the highest level of parasitization on 24 h old eggs with 98.2% parasitization, followed by 48 h old eggs and 72 h old eggs of the host were avoided by the parasitoid female and hence no parasitism occurred. The developmental duration of T.remus on 24 h old FAW eggs was recorded as 9.61 days and 48 h old eggs as 9.52 days, respectively. Microscopic examinations revealed the presence of six immature bio-stages viz., egg (1 day), two larval instars (each 1 day), pre-pupal (1 day), pupal (5 days) and adult stage with a total developmental duration of 9 days. T.remus adults can be differentiated by the morphology, type and number of antennal segments. The scape or the basal antennal segment was slender and longer in males, whereas shorter in females. T.remus female has a club typed antenna with 11 segments, while male has geniculate antenna with 12 segments.ConclusionsThe parasitoid exhibited selective preference for fresh stages of eggs than the matured ones indicating requirement of early field interventions coinciding with fresh brood emergence of FAW. Among the six stages of development, the pupal duration was found to be the longest in the study indicating that in augmentative biocontrol, host eggs with fully developed parasitoid stages, especially the pupal stage could be the appropriate one for field deployment.

Effects of abiotic factors on the immature development, adult performance, and field parasitism of mass-reared Anastatus parasitoids (Hymenoptera: Eupelmidae)

ABSTRACT Anastatus japonicus Ashmead, A. fulloi Sheng, and Wang, and A. dexingensis Sheng and Wang are vital biocontrol agents for the univoltine litchi stink bug Tessaratoma papillosa (Drury) in Taiwan as well as other invasive hemipteran and lepidopteran pests worldwide. An effective augmentative biocontrol programme was established with Anastatus parasitoids produced using eggs of the ailanthus silkmoth (Samia cynthia (Drury)) as factitious hosts. The study’s objective was to evaluate the immature development and adult performance of three Anastatus parasitoid species at 20, 25, and 30°C. The highest numbers of female and total progeny were produced by A. japonicus at 25°C and by A. dexingensis and A. fulloi at 20°C and 30°C, respectively. Anastatus japonicus had higher parasitism rates than A. dexingensis and A. fulloi at all three temperatures. The female ratios increased from 24.9% at 20°C to 70.4% at 30°C. The highest female ratios were recorded during the first two weeks of reproduction, and male progeny’s proportion gradually increased with female age. Anastatus japonicus was selected as the biocontrol agent for mass production based on its high fecundity and female progeny production rates. The field parasitism from the three release sites showed 30–40% of field parasitism during the first nine days of release. A significant reduction of field parasitism occurred after rainfall. The A. japonicus production system developed herein using the eggs of the factitious ailanthus silkmoth host could be commercialised to provide biocontrol against other hemipteran and lepidopteran pests species.

Seasonal Variations of Spodoptera frugiperda Host Plant Diversity and Parasitoid Complex in Southern and Central Benin.

Simple SummaryThe detection of fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) in 2016 attacking maize fields in central and west Africa indicated the need to increase the knowledge on the pest host plants and natural enemies adapting to it. A field survey was conducted for two years (from June 2018 to January 2020) to determine host plant and parasitoid records variations across seasons (maize growing and off-seasons) in selected sites in southern and central Benin. A total of eleven new host plant species were reported for the first time, including grasses. The survey revealed seven parasitoid species belonging to four families, namely Platygastridae, Braconidae, Ichneumonidae and Tachinidae, associated with FAW on maize and alternative host plants. The most abundant parasitoid species found was the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). The study provides crucial information for understanding the bioecology of the pest and for its long-term management using natural enemies.Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) was recorded for the first time in 2016 attacking maize fields in central and west Africa. Soon after, several other regions and countries have reported the pest in almost the entire sub-Saharan Africa. In the present study, we assumed that (i) a variety of alternative plant species host FAW, especially during maize off-season, (ii) a wide range of local parasitoids have adapted to FAW and (iii) parasitoid species composition and abundance vary across seasons. During a two-year survey (from June 2018 to January 2020), parasitoids and alternative host plants were identified from maize and vegetable production sites, along streams and lowlands, on garbage dumps and old maize fields in southern and partly in the central part of Benin during both maize growing- and off-season. A total of eleven new host plant species were reported for the first time, including Cymbopogon citratus (de Candolle) Stapf (cultivated lemon grass), Bulbostylis coleotricha (A. Richard) Clarke and Pennisetum macrourum von Trinius (wild). The survey revealed seven parasitoid species belonging to four families, namely Platygastridae, Braconidae, Ichneumonidae, and Tachinidae associated with FAW on maize and alternative host plants. The most abundant parasitoid species across seasons was the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). These findings demonstrate FAW capability to be active during the maize off-season in the selected agro-ecologies and provide baseline information for classical and augmentative biocontrol efforts.

Shipping augmentative biocontrol agents.

The majority of worldwide trading in live arthropods is done by specialised companies that produce and distribute beneficial insects, mites and nematodes for augmentative biological control of pests on crops. These beneficial arthropods, predators or parasitoids of crop pests and some nuisance species, which are harmless to humans, plants and other animals, are mass-reared, transported and released in the target environment as a viable alternative to chemical pesticides. As such, they play a major role in achieving a more sustainable and regenerative agriculture. Thousands of international air shipments are performed yearly by up to 30 major companies. Over the decades that this industry has been active, no significant transport problems have arisen. This is due to stringent standards that the industry has generated, including designated departments to deal with quality control and logistics, as well as guides for each species concerning packaging, storage and transport conditions. In addition, transporters always adhere to the regulatory standards of the importing and exporting countries, which is attested to by the documents included by the companies with each shipment. Two major issues arise when shipping live arthropods: first, the need to maintain stable environmental conditions within the shipping units (maintaining a cool chain) and, second, minimising transport time (preventing delays). This paper discusses the procedures implemented by the companies to assure quality, the documents required and provided currently, and the challenges to the safe transportation of beneficial organisms.

Transcriptional Regulation of Reproductive Diapause in the Convergent Lady Beetle, Hippodamia convergens.

Simple SummaryDiapause is a dormant period typically controlled by daylength that ensures an insect’s survival through harsh environmental conditions. The convergent lady beetle, Hippodamia convergens, undergoes a reproductive diapause in winter, where female ovaries remain immature and no eggs are laid. This species is an important biological control agent, but during diapause, beetles are less likely to eat pest insects. Thus, knowledge of diapause mechanisms may facilitate manipulation thereof to improve biological control. Further, molecular studies of adult diapause and diapause in Coleoptera are relatively lacking. Here, we assembled and annotated a transcriptome for this species and quantified transcript expression changes during diapause. Female beetles were sampled at three times in diapause (early, mid, and late diapause), which allowed us to characterize the molecular processes occurring at distinct transitions throughout diapause. We found that transcripts involved in flight were consistently upregulated during diapause, which is consistent with dispersal flights at this stage, while transcripts involved in ovarian development were downregulated, which is consistent with the shutdown of reproduction in diapausing females. These findings identify key regulators of diapause in H. convergens and contribute to a growing body of literature on the molecular mechanisms of diapause across the insect phylogeny.Diapause is an alternate development program that synchronizes an insect’s life cycle with seasonally abundant resources and ensures survival in unfavorable conditions. The physiological basis of diapause has been well characterized, but the molecular mechanisms regulating it are still being elucidated. Here, we present a de novo transcriptome and quantify transcript expression during diapause in the convergent lady beetle Hippodamia convergens. H. convergens is used as an augmentative biocontrol agent, and adult females undergo reproductive diapause that is regulated by photoperiod. We sampled females at three stages (early, mid, and late diapause) and compared transcript expression to non-diapausing individuals. Based on principle component analysis, the transcriptomes of diapausing beetles were distinct from non-diapausing beetles, and the three diapausing points tended to cluster together. However, there were still classes of transcripts that differed in expression across distinct phases of diapause. In general, transcripts involved in muscle function and flight were upregulated during diapause, likely to support dispersal flights that occur during diapause, while transcripts involved in ovarian development were downregulated. This information could be used to improve biological control by manipulating diapause. Additionally, our data contribute to a growing understanding of the genetic regulation of diapause across diverse insects.

A Catalogue of Natural Enemies of Invasive Alien Plants in South Africa: Classical Biological Control Agents Considered, Released and Established, Exotic Natural Enemies Present in the Field, and Bioherbicides

A catalogue of natural enemies considered and released as biological control (biocontrol) agents against invasive alien plants in South Africa has been maintained for many years, and is updated here to include the period 2011-2020. The current catalogue reorders and separates data for exotic natural enemies that have been approved as classical biocontrol agents, from those on exotic natural enemies that have been considered but not released, exotic natural enemies that have been inadvertently introduced into South Africa with host plants that include target weed species, and locally sourced natural enemies that have been considered as bioherbicides. Ninety weed species have been targeted for biocontrol, with 310 exotic natural enemies considered, 136 classified as de jure or de facto classical biocontrol agents, and 92 established in the field on 66 target weeds. Ten of these species were found to have established independently of being released while research on them was in progress. An additional six exotic species have been found established on target weeds, and 11 locally sourced natural enemies have been considered for inundative or augmentative biocontrol, of which two have been developed commercially. Of the exotic natural enemies deliberately established, 35% inflict extensive damage to their host plants. Insects make up the majority of biocontrol agents (90%), with the balance of 8% being fungi and 2%, mites. Both establishment rates and damage levels vary between taxa. Five biocontrol agents previously considered established, have not been found in the field for several years and their persistence is in doubt. Outcomes of biocontrol at a plant population level are indicated for 54 target weeds on which agents have been established for over a decade. The increase in numbers of target weeds considered, as well as biocontrol agents released, over the past decade, has been enabled by continued generous funding and an efficient release-approval process.

Optimizing Photoperiod, Exposure Time, and Host-to-Parasitoid Ratio for Mass-Rearing of Telenomus remus, an Egg Parasitoid of Spodoptera frugiperda, on Spodoptera litura Eggs.

Telenomus remus (Nixon) is a dominant egg parasitoid of the destructive agricultural pest Spodoptera frugiperda (J. E. Smith), and so is used in augmentative biocontrol programs in several countries. An optimized mass-rearing system is essential to produce biological control products in a timely and cost-effective manner. In this study, the photoperiod, host egg:parasitoid ratio, and exposure time were evaluated to identify the optimal rearing conditions for T. remus on the alternative host Spodoptera litura (Fabricius) eggs. Results showed that increasing photoperiod above 12L:12D remarkably improved parasitoid progeny yield and life table parameters. Overlong photoperiods shortened female longevity, but within acceptable limits. There was a significant negative correlation between parasitism rate and host egg:parasitoid ratio under exposure times of 12 and 36 h, but not 24 h. Percentage of female progeny increased significantly along with increasing the host egg:parasitoid ratio. A significant negative relationship between the number of emerged adults per egg and the host egg:parasitoid ratio was observed at an exposure time of 36 h. It was concluded that T. remus may be mass-reared most efficiently on S. litura eggs using a photoperiod of more than 12L:12D, a 14-20:1 host egg:parasitoid ratio, and an exposure time of 24 h. These findings can be used to produce T. remus more efficiently and at lower costs.

Optimum density of <i>Eocanthecona furcellata</i> (Wolff) (Hemiptera:Heteroptera: Pentatomidae) to be considered for mass production under laboratory conditions

<p><em>Eocanthecona furcellata</em> (Wolff) is a potential native predator of lepidopteran larvae that can be easily reared under laboratory conditions and released in augmentative biocontrol for management of pests in various crops. For successful mass production of any predator cannibalism under crowded rearing conditions is the major limiting factor. In the present study, attempts were made to know the ideal population considered for group rearing with minimal or no cannibalism. It was recorded that the predator population of 5 to 25 on <em>Corcyra cephalonica</em> (S.) and <em>Galleria mellonella</em> L. and 5 to 30 on <em>Samia cynthia ricini</em> Boisd. and <em>Spodoptera litura</em> F. was feasible for group rearing with higher percent survival rate when reared in different group arenas. The survival percent was higher on hosts, <em>C. cephalonica</em>, <em>G. mellonella</em>, <em>S. litura</em> and recorded lower on <em>S. cynthia ricini</em> under group rearing condition. </p>

Effect of Temperature on the Development and Survival of Feltiella Acarisuga (Vallot) (Diptera: Cecidomyiidae) Preying on Tetranychus Urticae (Koch) (Acari: Tetranychidae).

Simple SummaryThe predatory gall midge is one of the most effective natural enemies of the two-spotted spider mite, which is an economic pest causing a severe impact on a wide variety of plants worldwide. In general biocontrol programs, midges have been reared in insectaries and released into agriculture fields or greenhouses. In this study, we tested the effect of temperature on the development and survival of the predatory gall midge. The results showed that temperature played a crucial role in determining the emergence time and survival rate at each development stage. We described the responses to temperatures using several equations and estimated the values for explaining the observed biological patterns. The developed equations suggested that 23.3–28.7 °C temperatures were suitable for the total immature stage. In contrast, conditions around 8 °C and 35 °C should be avoided due to the high mortality. These results can help to determine the effective temperatures for both rearing and releasing, and ultimately contribute to the successful biological control of the spider mite.The predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae), is an acarivorous species that mainly feeds on spider mites (Acarina: Tetranychidae). Because of its cosmopolitan distribution and predation efficacy, it is considered an important natural enemy available as a biological agent for augmentative biocontrol. However, despite its practical use, the thermal development and survival response to temperature have not yet been fully studied. In this study, we investigated the stage-specific development and survival of F. acarisuga at seven temperatures (11.5, 15.7, 19.8, 23.4, 27.7, 31.9, and 35.4 °C) to examine the effect of temperature on its lifecycle. All developmental stages could develop at 11.5–31.9 °C, but the performance was different according to the temperature. From the linear development rate models, the lower development threshold and thermal constant of the total immature stage were estimated at 8.2 °C and 200 DD, respectively. The potential optimal and upper threshold temperatures for the total immature stage were estimated as 29.3 and 35.1 °C using a non-linear development model. The operative thermal ranges for development and survival at 80% of the maximum rate were 24.5–32.3 and 14.7–28.7 °C, respectively. Thus, it was suggested that 24.5–28.7 °C was suitable for the total immature stage. In contrast, conditions around 8 °C and 35 °C should be avoided due to the lower development rate and high mortality. Our findings provide fundamental information for an effective mass-rearing and releasing program of F. acarisuga in an augmentative biocontrol program and help to predict phenology.

Natural Enemies of Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) in Different Agro-Ecologies.

Simple SummaryFall armyworm (FAW), Spodoptera frugiperda, was reported in Cameroon for the first time in 2017 and by the end of 2018; the pest was found all over the country. Cameroon is among the first countries in Africa where the southern armyworm (SAW), Spodoptera eridania, another economical important armyworm was reported. The African governments adopted emergency actions around chemical insecticides despite the range of economic and health risks associated with chemical control. This work aims at identifying parasitoids (natural enemies) of armyworms and test their acceptability, suitability, and host range on Spodoptera spp., that can play a significant role in the sustainable management of these spodopterans. Field surveys conducted lead to the identification of two egg and four larval parasitoids. The fall armyworm was the predominant spodopteran. Laboratory studies were conducted to assess the performance of parasitoids associated with both pests in Cameroon. T. remus showed significantly higher parasitism on FAW than SAW, with significantly shorter development time on FAW, while inducing significant non-reproductive mortality on FAW. Laboratory performance of larval parasitoid was not compared between the two spodopterans identified but the developmental parameters showed that C. icipe has a shorter development time compared to other larval parasitoids.Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) and southern armyworm (SAW) Spodoptera eridania (Stoll) have become major threats to crops in Africa since 2016. African governments adopted emergency actions around chemical insecticides, with limited efforts to assess the richness or roles of indigenous natural enemies. Field surveys and laboratory studies were conducted to identify and assess the performance of parasitoids associated with spodopterans in Cameroon. FAW was the most abundant spodopteran pest. Telenomus remus (Nixon), Trichogramma chilonis (Ishi), Charops sp. (Szépligeti), Coccygidium luteum (Cameron), Cotesia icipe (Fernandez & Fiaboe), and Cotesia sesamiae (Cameron) are the first records in the country on spodopterans. Telenomus remus, T. chilonis, C. icipe, and Charops sp. were obtained from both FAW and SAW; C. luteum and C. sesamiae from FAW. The distribution of spodopterans, their endoparasitoids, and parasitism rates varied with host, season and location. In the laboratory, T. remus showed significantly higher parasitism on FAW than SAW, and significant differences in the development parameters between the two host eggs, with shorter development time on FAW. It induced significant non-reproductive mortality on FAW but not on SAW. Developmental parameters showed that C. icipe has a shorter development time compared to other larval parasitoids. Implications for conservative and augmentative biocontrol are discussed.

Egg Parasitoids of Cabbage Caterpillars in Sri Lanka: A Search for Biocontrol Agents

Purpose : Management of cabbage caterpillar complex through augmentative release of egg parasitoids has been suggested considering the current issues in insecticide application, mainly the effect on human health, non-target effects and environmental pollution. Use of local egg parasitoid species is preferred considering the environmental risk associated with the use of exotic species; therefore, this study was conducted to examine the egg parasitoid guild of cabbage caterpillars in Sri Lanka. Research Method : Field survey was conducted during January 2012 to May 2013 in major cabbage growing areas in the mid-country. Eggs of cabbage caterpillars were collected and reared them until the emergence of host larvae or adult parasitoids. Emerged parasitoids were preserved in 70% ethanol, and prepared the microscopic slides upon the dissection of male genitalia. Parasitoids were identified by using taxonomic keys and Trichogramma literature as per the protocol suggested by Natural History museum, London and the identities were confirmed by the taxonomist in Natural history museum in London. Findings : Trichoplusia ni, Spodoptera litura, Crocidolomia pavonana and Plutella xylostella were found as the members of cabbage caterpillar complex. Two egg parasitoid species: Trichogramma chilonis Ishi and Trichogramma achaeae Nagaraja and Nagarkatti were found attacking eggs of cabbage caterpillars. Trichogramma chilonis has been reported previously in Sri Lanka but Trichogramma achaeae is the first country report. T. chilonis was widely distributed and caused for higher level of parasitism than T. achaeae. The highest level of parasitism (67%) by both species was found in Trichoplusia ni eggs which was significantly different from other species. Level of parasitism of caterpillar eggs was significantly varied between pesticide free fields (16.8%) and conventional fields (13.1%). Research Limitation : The study of behavioral characters of these parasitoids is required to assess the suitability as biocontrol agents; as an initial step for augmentative biocontrol, the locally available egg parasitoids were reported in this study. Originality/ Value : These findings would be contributing Sri Lankan agriculture sector to develop the augmentative biocontrol approach to manage the cabbage caterpillar complex and to produce pesticide residues free crop produce.

Spissistilus festinus (Hemiptera: Membracidae) susceptibility to six generalist predators.

Spissistilus festinus (Say) (Hemiptera: Membracidae) was shown to transmit Grapevine red blotch virus (GRBV) in a greenhouse study. Grapevines infected with GRBV exhibit reduced sugar accumulation, altered secondary metabolite production and delayed berry maturation that negatively impacts wine quality and economics. Augmentative biocontrol may be a useful integrated pest management (IPM) tool for suppressing S. festinus populations in vineyards, but minimal research has been conducted on testing potential predators against the different life stages of S. festinus. The susceptibility of S. festinus adults and nymphs (1st through 5th instar) to predation by six commercially available biocontrol agents in petri dish and bell bean plant arenas was determined under greenhouse conditions. No significant mortality of S. festinus nymphs or adults occurred when exposed to Cryptolaemus montrouzieri adults, C. montrouzieri larvae and Sympherobius barberi adults in petri dish or bell bean plant arenas. Significant mortality of 1st and 2nd instar nymphs of S. festinus in the presence of Zelus renardii nymphs was observed in petri dish but not in bell bean arenas. Hippodamia convergens adults and Chrysoperla rufilabris larvae both consumed a significant number of S. festinus nymphs in petri dish and bell bean arenas. No significant predation of S. festinus adults was documented in this experiment. Results of this study aid in identifying predators that may be suitable candidates for additional field testing to determine their potential efficacy as biocontrol agents of S. festinus in a vineyard setting.

Genetic improvement of Orius laevigatus for better fitness feeding on pollen

In many protected crops, augmentative biological control heavily relies on generalist predators, which continuous presence on the crop allows an early response to pest immigration and outbreaks. Persistence is possible by their ability to feed on alternative food, such as pollen, plant-provided or artificially supplemented. However, fitness is decreased when feeding on alternative foods, hindering performance. We present a new approach to face this challenge: genetic improvement for better fitness feeding on suboptimal food. Orius laevigatus is one of the main biological control agents used in greenhouse vegetable crops. A breeding process was carried out on the basis of a broad intraspecific variability exploration for 10-day fecundity feeding on pollen (14.2–37.9 eggs/female for 30 wild and commercial populations). Life history traits were finally compared between our two selected strains and three commercial, wild and acclimated-to-pollen unselected populations, both on rich (Ephestia eggs) and suboptimal (dry honeybee pollen) diets. Selected lines showed considerably improved values for longevity (1.5-fold), early (1.3-fold) and lifetime fecundity (1.9-fold), nymphal survival (3.5-fold), intrinsic rate of natural increase (rm) (7.3-fold) and net reproductive rate (R0) (6.7-fold) as compared to reference unselected strains when they were fed on pollen, although still lower than on the optimal diet. Selection feeding on plant material resulted in no trade-offs when feeding on the factitious prey. This improvement was due to genetic gain rather than to phenotypic plasticity to tolerate nutritious restriction. Finally, some potential contributions of these improved lines not only for augmentative biocontrol but also for artificial rearing are provided.