Parasitoid Populations Research Articles

Banker Plant Bonuses? The Benefits and Risks of Including Brassicas in Field Margins to Promote Conservation Biocontrol of Specialist Pests in Oilseed Rape.

European agri-environment schemes include the use of flower-rich field margins to promote on-farm biodiversity, but species mixtures rarely include Brassicaceae. As pests of oilseed rape (OSR; Brassica napus) and their parasitoids are mostly brassica specialists, including brassica 'banker plants' in the mixtures would help support these important biocontrol agents and improve pest control throughout the crop rotation. We assessed the potential of six brassicaceous plants (replicated plots grown in the field) to enhance populations of parasitoids of OSR pests whilst minimising proliferation of their pest hosts. Fodder radish (Raphanus sativus) facilitated high production of parasitoids of the pollen beetle pest (Brassicogethes aeneus) but may proliferate Ceutorhynchus weevil pests due to low parasitism. Turnip rape (B. rapa) and the B. rapa hybrid 'Tyfon' showed potential to perform a trap cropping function for pests, but their early flowering phenology resulted in B. aeneus larvae escaping parasitisation, potentially assisting proliferation of this pest. Forage rape B. napus exhibited similarly high B. aeneus parasitoid production characteristics to R. sativus but did not potentiate problems with other pests, indicating that it would be a favourable banker plant option. Careful selection of plants in field margin mixtures is therefore needed to maximise their benefits and ideally the whole crop pest-beneficial complex needs to be studied, as focus on a single major pest risks unintended consequences with other pest problems.

Enhancing biocontrol potential of Trichogramma chilonis against borer pests of wheat and chickpea

Communication between plants and herbivores occur mostly through chemicals. Plants emit volatiles in response to the attack of herbivores called herbivore-induced plant volatiles (HIPVs), which are employed by the plants to attract their herbivores' natural enemies. Promising HIPVs when used in the form of controlled release formulations under field conditions can act as arrestants of released or wild population of parasitoids to spend comparatively more time in searching of various stages of herbivores; thus management of crop pests is enhanced. Gel formulation of octadecane (Saturated hydrocarbon) when applied 24h after release of Trichogramma chilonis in wheat and chickpea enhanced the foraging activity against pink stem borer (Sesamia inferens) and pod borer (Helicoverpa armigera), respectively resulting in reduced symptoms and increased grain yields. Controlled release formulations of promising plant volatile organic compounds (pVOCs) can be useful to augment and enhance foraging activity of natural enemies against crop herbivores.

Ovipositor characteristics differ between two parasitoids (Hymenoptera, Figitidae) of Drosophila suzukii (Diptera, Drosophilidae) in an adventive landscape

Different ovipositor characteristics among parasitoid species that share similar niches are associated with different wasp life histories and selective pressures. The length of wasp ovipositors, for example, can determine the accessibility of hosts that feed at different depths within food substrates. Two parasitoids, Ganaspis brasiliensis and Leptopilina japonica (Hymenoptera, Figitidae), which attack Drosophila suzukii (Diptera, Drosophilidae) in their native range, have been investigated for their suitability for the global biological control of the small fruit pest. Despite their sympatry in microhabitat, the parasitoids have differing host ranges, and D. suzukii parasitism rates by each parasitoid species appear to depend on the fruit species occupied by the host species. Adventive populations of both parasitoids have been detected in the Pacific Northwest of Canada and the United States where they can be found parasitizing D. suzukii larvae in crop and non-crop fruits. We dissected and measured the ovipositors of parasitoids reared from three species of fresh fruits at three sites in southwestern British Columbia, Canada, and investigated the influence of parasitoid species, fruit type, and collection site on ovipositor characteristics. We found that ovipositor length differed markedly between the two parasitoid species and between sites while ovipositor width, and stoutness, differed only between the two parasitoid species, but did not vary among sites or fruit hosts. We discuss how ovipositor morphology traits could be associated with differences in life history and host ranges in the two parasitoid species.

Population level interactions between an invasive woodwasp, an invasive nematode and a community of native parasitoids

Parasitic nematodes and hymenopteran parasitoids have been introduced and used extensively to control invasive Eurasian Sirex noctilio woodwasps in pine plantations in the Southern Hemisphere where no members of this community are native. Sirex noctilio has more recently invaded North America where Sirex-associated communities are native. Sirex noctilio and its parasitic nematode, Deladenus siricidicola, plus six native hymenopteran woodwasp parasitoids in New York and Pennsylvania, were sampled from 204 pines in 2011–2019. Sirex noctilio had become the most common woodwasp in this region and the native parasitoids associated with the native woodwasps had expanded their host ranges to use this invader. We investigated the distributions of these species among occupied trees and the interactions between S. noctilio and natural enemies as well as among the natural enemies. Sirex noctilio were strongly aggregated, with a few of the occupied trees hosting hundreds of woodwasps. Nematode parasitism was positively associated with S. noctilio density, and negatively associated with the density of rhyssine parasitoids. Parasitism by the parasitoid Ibalia leucospoides was positively associated with host (S. noctilio) density, while parasitism by the rhyssine parasitoids was negatively associated with density of S. noctilio. Thus, most S. noctilio come from a few attacked trees in a forest, and S. noctilio from those high-density trees experienced high parasitism by both the invasive nematode and the most abundant native parasitoid, I. l. ensiger. There is little evidence for direct competition between the nematodes and parasitoids. The negative association occurring between rhyssine parasitoids and I. l. ensiger suggests rhyssines may suffer from competition with I. l. ensiger which parasitize the host at an earlier life stage. In addition to direct competition with the native woodwasp Sirex nigricornis for suitable larval habitat within weakened trees, the large S. noctilio population increases the parasitoid and nematode populations, which may increase parasitism of S. nigricornis.

Divergent life histories between wild and commercially-sourced Cotesia flavipes (Hymenoptera: Braconidae) parasitizing four species of Diatraea (Lepidoptera: Crambidae)

Moths of the genus Diatraea Guilding (Lepidoptera: Crambidae) are stalk-boring pests of sugarcane throughout the neotropics. In Colombia, the economically important species are D. busckella, D. indigenella, D. saccharalis, and D. tabernella. Augmentative releases of the gregarious endoparasitoid Cotesia flavipes (Cameron) are one tactic used to manage this pest complex. We compared the laboratory performance of two C. flavipes populations, one field-collected, and one commercially-sourced, on all four host species, hypothesizing lower performance of the commercial population on host species other than D. saccharalis due to continuous rearing on this species. Parasitism success did not vary with parasitoid source, but varied among host species, being highest in D. indigenella and lowest in D. tabernella, with other species intermediate. Sex ratio was female-biased, averaging 0.635, and did not vary with parasitoid source or host species. Wild wasps developed more slowly than commercial wasps on all hosts, being slowest on D. tabernella, whereas commercial wasps were slowest on D. busckella. Both parasitoid populations produced their largest broods in D. indigenella, but commercial wasps produced smaller broods than wild wasps in D. busckella and D. tabernella, and substantially lower weight gain of host larvae post-parasitism, suggesting impaired host regulation ability. In all host species, wild wasps produced larger female progeny, based on wing area, than commercial wasps. When all metrics of parasitoid performance (fitness) were combined into a single index of host suitability, D. indigenella was the most suitable host for both parasitoid populations. Both parasitoid sources had similar performance on D. saccharalis, the host used to rear the commercial population, whereas wild wasps performed better on all other Diatraea species. The inadvertant consequences of artificial selection in mass-reared cultures of gregarious endoparasitoids are discussed, specifically the evolution of faster development and smaller body size.

Diversity of Hymenopteran Parasitoids in Coffee Plantations under Agroecological Transition and Its Impact on Coffee Leaf Miner (Leucoptera coffeella) Infestations

The biodiversity of natural competitors is vital to key ecosystem services and agroecosystems’ benefits to society. The abundance and richness of hymenopteran parasitoid communities, and subsequently their services, are dependent on the variety of habitats in the different agroecological landscapes. Here, we monitored the fluctuation of predatory wasps and hymenopteran parasitoid populations and their impacts on coffee leaf miner infestations under different coffee plantation landscapes. Thus, 24 sampling plots were arranged in four cultivation systems: conventional (CONV), in transition to organic shaded (T.OSH), in transition to organic full-sun (T.OFS), and without pesticide (T.WOP). In each plot, leaves with intact mines were collected randomly once a month over a period of 23 months. Parasitoid species, coffee leaf miner infestation, predation, and parasitism were assessed based on the emerged parasitoids and wasps’ activity signs in the mines. The data on parasitoids revealed the presence of 621 hymenopteran parasitoids, of which, 420 were Braconids and 201 were Eulophids. Overall, the abundance of braconid specimens (67.6%) was greater, but the species richness was higher in Eulophids. The highest species richness of L. coffeella parasitoids was in T.OSH and T.OFS. Furthermore, in the coffee plants evaluated, the coffee leaf miner population is well established and does not cause economic damage, as the spontaneous action of predatory wasps and parasitoids, in addition to climatic factors, contributes to regulating these pest infestations. Of these parasitoids, the braconid Orgilus niger and Stiropius reticulatus were found to be promising and well-adapted control provider species.

Non-target attack of the native stink bug, Podisus maculiventris by Trissolcus japonicus, comes with fitness costs and trade-offs

Accidentally introduced parasitoids can provide biological control of the invasive pest they followed but could also pose a threat to native species if they are not specialists. Attack of native species could reduce the effectiveness of adventive natural enemies if it is accompanied by reduced fitness, and it may increase acceptance of non-target species. We tested how intermittent host shift and prolonged exposure to a non-target, native species Podisus maculiventris (Say) (Hemiptera: Pentatomidae) may affect the fitness and host acceptance of the egg parasitoid, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) that was co-introduced with the invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). In the first experiment, replicate parasitoid populations were reared either with or without a history of host switching over a 10-generation period between the native and the invasive stink bug that was followed by three generations of continuous reproduction on either host. In the second experiment, replicated populations were exposed for three continuous generations to either the native or invasive host. Occasional or prolonged reproduction on the native host did not increase acceptance and developmental success on the non-target species. Emergence rate of T. japonicus was consistently lower when it reproduced on the native stink bug. There was also a trade-off for the parasitoid, in terms of reduced emergence rate, when switching back to H. halys from the native host. These results suggest that host shifts to native species could reduce the effectiveness of T. japonicus at attacking H. halys, but the fitness costs may prevent significant non-target effects in nature.

Complex dynamical behavior and control of a discrete ecological model

Cyclic types of ecological dynamics have been found in several biological species of forest Lepidoptera. There are several possible reasons for this, for example, interactions with consumers, predators, plant quality index, and interactions of density-dependent type. Furthermore, interaction with consumers and plant quality index is regarded as key ingredients to alter the dynamics for the parasitoid population. Consequently, the quality of food resources fluctuates due to the level of herbs. Such changes have been observed in different systems of forest pests. Lepidoptera (larch budmoth) is a destructive worm that affects high-altitude trees around the world and is rapidly declining and becoming extinct in large areas of the forest. Considering the interaction between the budmoth and plant quality index for larch trees in the mountain range in Switzerland (Swiss Alps), we discuss the dynamics of a discrete-time system. Ivlev type functional response regarding plant quality index is used for the formulation of discrete-time model concerning the interaction between the index of plant quality and budmoth. Moreover, the existence of steady-states, their local behaviors, and the boundedness of solutions are carried out for the discrete-time model under consideration. It is investigated that the model undergoes flip bifurcation about coexistence by applying the theory of normal forms and the center manifold theorem. Furthermore, the direction and the existence of Hopf bifurcation are explored for the model around its coexistence. Various methods of controlling chaos have been introduced to avoid system fluctuations and bifurcating attitudes. Validation of the analytical findings is illustrated through numerical simulations. Finally, the analytical results are validated by experimental and actual field data.

Coexistence conditions in generalized discrete-time models of insect population dynamics

Motivated by the annual life histories of insects residing in the temperate-regions of the world, there is a rich tradition of modeling their population dynamics using a discrete-time formalism. Here, we consider an antagonistic interaction between two insect species – a parasitoid wasp that lays an egg within its host insect species. The egg hatches into juvenile parasitoid that develops within the body of the host by using it as resource and this ultimately results in host death. The parasitoid emerges from the host as a free-living insect that goes on to attack other hosts. Such interaction are ubiquitous with over 65,000 known species of parasitoid wasps and such wasps have potential in biologic control of pest insect species. We introduce a general class of discrete-time models for capturing the population dynamics of two competing parasitoid species that attack the same vulnerable stage of the host species. These models are characterized by two density-dependent functions: an escape response defined by the fraction of hosts escaping parasitism; and a competition response defined by the fraction of parasitized hosts that develop into adult parasitoids of either species. Model analysis reveals remarkably simple stability conditions for the coexistence of competing parasitoids. Coexistence occurs, if and only if, the adult host population increases with host reproduction rate, and the log sensitivity of the competition response is less than half. The latter condition implies that any increase in the adult parasitoid population will result in a sufficiently slow increase in the fraction of parasitized hosts that develop into parasitoids of that type. We also consider a semi-discrete formulation of a competing species model that incorporates host density-dependence in the attack rate. This model expands the class of models for which the analytical results apply, and we systematically compare the numerical results of this model to the established coexistence conditions

The effect of integrated pest management on Scirpophaga innotata population and natural enemies on rice field in South Sulawesi, Indonesia

Abstract. Rahmawasiah, Abadi AL, Mudjiono G, Rizali A. 2022. The effect of integrated pest management on Scirpophaga innotata population and natural enemies on rice field in South Sulawesi, Indonesia. Biodiversitas 23: 4510-4516. White rice stem borer, Scirpophaga innotata, is an important pest on rice plants that needs attention because the population is quite large in Luwu Raya. This pest attacks rice plants at all growth stages and can result in yield losses in rice production. Synthetic insecticides are a common control technique used by farmers to control these pests. The continuous use of pesticides will certainly have a negative impact. Therefore, pursuing effective control strategies and maintaining environmental sustainability is necessary. This study aimed to determine the white rice stem borer population and its natural enemies on rainfed land, and permanent irrigated lands managed conventionally and integrated pest management. The research was carried out using insect sampling techniques and calculating the white rice stem borer population and natural enemies in rice cultivation. In rainfed and irrigated rice fields, rice cultivation was carried out using conventional methods and integrated pest management (in the form of planting refugia and regulating the use of synthetic pesticides). The sampling was carried out on plants from the vegetative phase to the generative phase. The type of insect taken was the white rice stem borer in the form of collecting groups of eggs and larvae. Imago was observed visually and using a farmcop. In addition, the collection of natural enemy insects on the plantation was also carried out. The results showed that the application of the integrated pest management system caused no significant effect on the decline of the white rice stem borer population in both rainfed and permanently irrigated lands in Luwu Raya. The white rice stem borer population was more commonly found in rainfed land than permanently irrigated land. The parasitoids found were Telenomus rowani, Tetrastichus schoenobii and Trichogramma japonicum. The population of Telenomus rowani was more numerous than other types of parasitoids. On average, the parasitoid population was more in the land managed by integrated pest management (IPM) application than the conventionally managed land. The predators found on the land were Oxyopes javanus, Agriocnemis femina, Conocephalus longipennis, Menochilus sexmaculata, Ophionea nigrofasciata, Micraspis lineata, and Paederus fuscipes. Predator populations were more on land managed with the application of IPM than on land managed conventionally.

Filth Fly Parasitoid (Hymenoptera: Pteromalidae) Monitoring Techniques and Species Composition in Poultry Layer Facilities.

Muscid flies, especially house flies (Musca domestica L.) (Diptera: Muscidae), are a major pest of poultry layer facilities. Augmentative biological control of muscid flies with pteromalid wasps has gained increased attention in recent years. Knowing which pteromalid species are present in a specific area could produce more effective filth fly control. The purpose of this project was to survey parasitoid populations in poultry layer facilities in central and southeastern Pennsylvania from June through September. Two genera of parasitoids, Spalangia and Trichomalopsis, were collected over the course of the survey. Overall, out of 3,724 parasitized pupae the species collected in order of most to least common were Spalangia cameroni Perkins, Spalangia nigroaenea Curtis, Trichomalopsis spp., and Spalangia endius Walker. House fly parasitism overall and by each parasitoid species varied by location and over the four study months. A second objective was to evaluate a new parasitoid trap for surveying parasitoid wasp populations. This device uses a combination of house fly third instars and development media. This was compared to a more traditional method, the sentinel bag, which uses only fly pupae. A higher proportion of Spalangia spp. emerged from the new trap design and more Trichomalopsis spp. emerged from the sentinel bag. This suggests that using this new device alongside the traditional collection method may result in more accurate sampling of pteromalid populations.

Searching of Underground Host Patches by a Pupal Parasitoid.

When hosts are distributed in discrete patches, ways in which parasitoids search and move between patches affect variability in parasitism risk among hosts and host-parasitoid population dynamics. This study examined the patch searching behavior of the solitary pupal parasitoid Dirhinus giffardii (Silvestri) (Hymenoptera: Chalcididae) on its host Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) which pupates underground. In a series of two laboratory experiments, host patches were created by burying pupae in peat moss, and the foraging behavior of the parasitoid was recorded. If D. giffardii can detect underground patches, the parasitoid would preferentially exploit high quality patches where the quality of a patch is represented by the number of unparasitized hosts in the patch. The first experiment investigated the effect of patch size (i.e., number of hosts) and host status (whether hosts are parasitized or unparasitized) on patch searching behavior. Results showed parasitoids were more likely to exploit a large patch than a small patch regardless of host status. The second experiment examined the effect of relative locations of patches by establishing three patches (one large patch and two small patches with unequal inter-patch distances from the large patch). The probability of parasitism was lower for the small patch close to the large patch than the small patch far from the large patch. The parasitism patterns described in the experiments have important implications on the distribution of parasitism risk among hosts and population dynamics.

Behaviour drives contemporary evolution in a failing insect-parasitoid importation biological control programme

Biological control of pests continues to become more important in agriculture as pesticides are being withdrawn. However, successful control can be compromised by contemporary evolution. Recent work in New Zealand has shown that the once-successful biological control programme of the sexually reproducing grassland weevil pest Listronotus bonariensis by the asexual parasitoid Microctonus hyperodae has now failed. To explain the mechanisms associated with this, weevil parasitism rates were intensively monitored between 1994 and 2019. Frequent sampling took place at widely dispersed New Zealand sites spanning the warmer northern regions to the cooler south. Based on elapsed heat accumulation above the parasitoid’s development temperature threshold of 10.2°C degree-day (DD), the results over c. 25 years indicated that the extent of parasitism decline at a given location was directly related to the accumulated DD. The latter, in turn, was taken to be indicative of parasitoid activity and selection pressure. Accordingly, laboratory microcosm experiments measuring the response of weevils collected from the North–South distribution to a common population of parasitoids showed that the weevils from the warmer northern region showed higher rates of avoidance of the searching parasitoids than those from the cooler south. This strongly supported the hypothesis that the weevil resistance mechanism is related to levels of parasitoid avoidance behaviour arising from long-term parasitoid selection pressure. This study of the behaviourally based acquisition of resistance to a biological control agent illustrates a general need to consider the potential capability of an exotic target host to develop resistance to imported biological control agents. This includes identifying existing host adaptations that selection pressure could potentially act upon that may compromise otherwise successful biological control programmes. Such a requirement points to the need for long-term monitoring of biological control systems and understanding of parasitoid/host dynamics.

Flowering agricultural landscapes enhance parasitoid biological control to Bemisia tabaci on tomato in south China.

Agricultural landscape pattern may enhance biocontrol services by supporting parasitoid populations, including parasitoids of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae). In this study, we selected four landscape types in Yunnan province, in south China, which were characterized by flower fields, mountain, river, and urban areas as their main elements. We then carried out systematic surveys in tomato fields found within each landscape type, to determine the diversity, occurrence, and parasitism rate of parasitoids. We found that parasitoids from the genus Encarsia and Eretmocerus were the main natural enemies present, and the most abundant species were recorded in the flower and the mountain landscapes. Also, Encarsia formosa (Hymenoptera: Chalcidoidea) formed the highest relative abundance regardless of the landscape type. We also found that the population density of B. tabaci in flower landscapes was the lowest than that in other landscape types. During the main activity period of B. tabaci, the parasitism rate in the flower landscape was higher than that in other landscape types. Our findings showed that the occurrence of B. tabaci was relatively mild in the flower landscapes. The landscape type was also beneficial to parasitoids as it enhanced their parasitism rate. Therefore, agriculture environmental schemes should consider increasing the size of flower fields in the surrounding landscape to enhance the sustainable control of B. tabaci by the natural agricultural ecosystem.

The Spatial and Temporal Variations in the Superparasitism ofDiachasmimorpha longicaudataPopulation Lines on Different Hosts After Field Release.

Evaluating the behavior of the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) in the field allows improving strategies for its release. Thus, the aim of this study was to evaluate spatial and temporal variations in the superparasitism of two populations of D. longicaudata on two fruit fly hosts after releasing them in a guava (Psidium guajava L.; cultivar 'Paluma') orchard. The two parasitoid populations used were CS and AS, which were reared on Ceratitis capitata (Wiedemann) and Anastrepha fraterculus (Wiedemann), respectively. Four releases were carried out without host choice. Host larvae were offered to the parasitoids in sentinel traps attached at varying heights on the plant, and in plants located at eight different directions and seven distances (7.0, 21.0, 35.0, 49.0, 59.4, 63.0, and 69.3m) from the center of the parasitoid release point. The traps remained in the orchard for 24, 48, and 168h after release. After removing the traps, they were taken to the laboratory for scar counting. The percentages of parasitism, superparasitism, mortality, and emergence of parasitoids were determined. Data were analyzed using the generalized linear mixed-effect model (GLMM). The AS females were more active, as they exerted higher parasitism and superparasitism at the first distance and 48h after release, leaving a higher number of oviposition scars on the host A. fraterculus. Additionally, higher host mortality was observed in A. fraterculus at the closest points and the first 48h. The highest percentage of parasitoid emergence was observed in C. capitata parasitized by AS females.

The effects of a naturalized weed, Lepidium virginicum, on the development and behaviors of the diamondback moth and its natural enemies in Hawaii

Weeds can play numerous important roles in pest suppression in agroecosystems. These include influencing the host searching behaviors of herbivorous pests and their natural enemies and providing shelter and alternative food sources for predators and parasitoids. Virginia pepperweed, Lepidium virginicum, is a widespread naturalized weed in Hawaii and can often be found in and around agricultural fields. It is a member of the Brassicaceae family and is a known host plant of the diamondback moth (DBM), Plutella xylostella. In this study, we found that DBM preferentially oviposit on L. virginicum (vegetative stage) when presented with a choice of cabbage. Using laboratory and semi-field trials, we investigated the responses of the natural enemies of DBM to the vegetative stage of L. virginicum and cabbage infested with DBM larvae. When DBM-infested plants were placed in the field for 48 h, more spiders and parasitized DBM larvae were recovered from the L. virginicum than from cabbage. In laboratory choice experiments, we demonstrated that the dominant DBM parasitoid species in Hawaii (Cotesia vestalis) oviposited in more host larvae on L. virginicum compared to cabbage, though this had no particular benefit for parasitoid development (adult size and sex ratio). Our findings suggest that the presence of L. virginicum in cabbage agroecosystems could be beneficial by serving to divert DBM oviposition away from cabbage and promoting predator and parasitoid populations.

Fluctuation Patterns Spodoptera frugiperda and Its Natural Enemies on Maize Plants With IPM and Conventional Practice in Malang Regency

Spodoptera frugiperda (Lepidoptera: Noctuidae) is a pest that originated in the United States and then migrated to Indonesia. This pest reportedly attacked corn in West Pasaman, West Sumatra Province, in 2019. This study aimed to determine the effect of cultivation practice on fluctuations in natural enemies and S. frugiperda. The research was conducted in Pandan Rejo Village, Pagak, Malang Regency. Data from observations of pest populations' natural enemies were then analyzed using simple quantitative analysis. The population and intensity of Spodoptera frugiperda attacks on IPM practices were always lower than those on conventional practices. During observation, there were 2 species of natural enemies, Braconidae and Scelionidae. The parasitoid population in IPM is always higher than in conventional practice. The lower parasitoid population at conventional practice failed to suppress the S. frugiperda population. Farming business analysis calculated using the R/C ratio showed that IPM practice had a value of 1.03 while conventional was only 0.55. IPM practice is feasible and more ecologically friendly than conventional practice.

Inventory insects of sorghum plantation in Northern Sumatera, Indonesia

The purpose of this research was to invent types and abundance insects in sorghum plantation in Lalang Village, Rambutan District, Tebing Tinggi from July to August 2021, with an area of 12 m × 12 m. Insects were collected using sweep traps, pit fall traps, light traps and yellow sticky traps. The collected insects were collected and then were identified. Data analysis was carried out by descriptive quantitative with Purposive Random Sampling (PRS), which identified in the Pest labouratory-USU. The results research identified was four insects Orders (Coleoptera, Diptera, Hemiptera and Lepidoptera) with 9 families (Chrysomelidae, Scarabaeidae, Cecidomyiidae, Muscidae, Aphidae, Dephiciodae, Pentatomidae, Noctuidae, Pyraliidae) and 16 species. The highest insect pest population was at the time of the sixth sampling as many as 634 individuals/plot, the predator population was 248 individuals/plot, and the parasitoid population was 118 individuals. Calculation of richness index R1yst=8.49: R1sn=7.65, eveness index (Eyst=0.59; Esn=0.48) and insects diversity Shannon-Wiener index (H’yst=2.56; H’n=2.13). Then the parameter environmental measure of temperature (30.3-36.2°C), humidity (82-90%) were carried out during the sorghum plantation period.

Tanggap Parasitoid Braconidae (Hymenoptera) Terhadap Hama Invasif Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) pada Tanaman Sayuran dan Hias di Bali

Response of Braconid Parasitoid Against Invasive Pest, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) on Vegetable and Ornamental Crops in Bali. Research on the respopnse of Braconid parasitoids to the invasive pest, Liriomyza trifolii that attacks ornamental plants and vegetables in Bali, was carried out from September 2020 to March 2021. This study aimed to determine the type and abundance of parasitoid populations that responded to Liriomyza trifolii on host plants in the field. In addition, this study also aims to evaluate the level of parasitization of each parasitoid against L. trifolii. This study used a purposive sampling method by taking leaf samples that showed active symptoms of Liriomyza larvae in the leaves of plants. The research focused on vegetables and ornamental plants cultivated in lowlands <500 meters above sea level (masl), mediumlands 500-1000 meters above sea level and highlands> 1000 meters above sea level. The results showed that there were two species of Braconid parasitoids that responded to Liriomyza trifolii in the field, namely Opius dissitus and Opius cromatomiyae. The relative abundance and degree of parasitization of the two parasitoids showed variation between host plant species and altitude. The relative abundance of O. dissituse was high in chrysanthemum (10.81%) at an altitude of >1000 masl and low in long beans (0.53%) at an altitude of <500 masl. The highest relative abundance of O. cromatomiyae was in marigold flowers (51.18%) at an altitude of <500 masl and the lowest was in chrysanthemum (44.83%) at an altitude of > 1000 masl. The highest level of parasitization of O. dissitus was found in pakcoy plants (50.00%) at an altitude of >1000 masl and the lowest was in mustard plants (6.06%) at an altitude of <500 masl. The highest level of parasitization of O. cromatomiyae was in celery (33.33%) at an altitude <500 masl and the lowest was in tomato plants (25.00%) at an altitude> 1000 masl. Both species of Braconid parasitoids have high potential as biological control agents for L. trifolii as indicated by their relative abundance and high levels of parasitization against these invasive pests.

Mortality of Emerald Ash Borer Larvae in Small Regenerating Ash in New York Forests

Despite a robust biocontrol program against emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), parasitoid populations cannot build quickly enough to save mature ash trees. The future of ash as a viable component of North American forests depends on survival of immature ash that were too small to be attacked during the initial outbreak. This study was designed to quantify impacts of established introduced parasitoids and native woodpeckers on the population growth of emerald ash borer infesting regenerating ash saplings in white ash forests. Most emerald ash borer larvae were killed by Tetrastichus planipennisi Yang and woodpeckers in the fourth instar. Life-table analyses revealed that the estimated net reproductive rate of emerald ash borer was R0 = 4.2 in eastern New York and R0 = 0.0 in western New York. Without mortality from parasitoids and woodpeckers, R0 values would have been 16.4 and 7.9 in eastern and western New York, respectively. We monitored the health of mature and sapling ash trees from 2012 to 2017 and found that large trees were significantly more likely to be infested with emerald ash borer and to die than smaller trees. Fifty-four percent to 81% of ash saplings contained no living emerald ash borer, and the density of emerald ash borer at all sites was very low (< 4/m2). This study adds to the growing body of evidence that emerald ash borer biocontrol is contributing to population control and can help promote survival of young ash trees as forests recover from emerald ash borer outbreaks.