Parasitoid Longevity Research Articles

The effect of flower morphology on the longevity of Diadegma semiclausum (Hymenoptera: Ichneumonidae)

Refugia plants can support the biological control of plant pests by increasing the presence and fitness of parasitoids. One of the factors that determine the suitability of refugia plants with parasitoids is the flower morphology. This study used Diadegma semiclausum, a parasitoid of cabbage pest, Plutella xylostella. This study aimed to determine the effect of refugia plants’ flower morphology on the longevity of D. semiclausum adults. Refugia plants used were Rorippa indica, Brassica rapa, Ageratum conyzoides, and Sphagneticola trilobata. Research methods consist of insect rearing and plant preparation, testing refugia flowers’ influence on parasitoid longevity, and measuring flower morphology (corolla length and aperture, and nectar location). The results showed all refugia flower treatments could increase the parasitoid longevity compared to control (1.71-3.69 times). The best effect was demonstrate by the R. indica treatment, followed by B. rapa, A. conyzoides, and S. trilobata. Correlation and regression analysis showed that the increasing corolla aperture and length positively affected parasitoid longevity. Flowers with exposed nectar positions (R. indica and B. rapa) makes the parasitoid easy to access, even though the corolla flowers were longer than A. conyzoides and S. trilobata.

Impact of Metarhizium robertsii on Adults of the Parasitoid Diachasmimorpha longicaudata and Parasitized Anastrepha ludens Larvae.

Simple SummaryThe Mexican fruit fly Anastrepha ludens is a polyphagous pest that infests at least 32 tropical and subtropical plant species of different families. A. ludens is native of Mexico, and is distributed from Northern Mexico to Central America. Integrated Pest Management (IPM) programs build upon the Sterile Insect Technique (SIT) and biological control agents (parasitoids and microbial pathogens), two eco-friendly sustainable control strategies, which are highly relevant in organic farming. In our laboratory study we evaluated the efficacy of fungal pathogens and intraguild predation (IGP) risk of one strain of Metarhizium robertsii and another of Metarhizium anisopliae, when used in conjunction with the braconid parasitoid Diachasmimorpha longicaudata. Our results show a reduced negative effect of M. robertsii on D. longicaudata adults, and a low IGP risk when D. longicaudata-parasitized larvae were exposed to Metarhizium strains. Our study is important for organic, tropical fruit growers because it shows that M. robertsii and D. longicaudata are promising biocontrol agents for organic farming in Veracruz, Mexico.Biological control of the Mexican fruit fly, Anastrepha ludens, is mainly carried out by releasing parasitoids, such as Diachasmimorpha longicaudata, and by applying entomopathogenic fungi (EPF), such as Metarhizium anisopliae, Beauveria bassiana, or Isaria fumosorosea, which can be applied to the soil or dispersed using infective devices. The combined use of two or more biocontrol agents could improve A. ludens control, but IGP between natural enemies, if it occurs, may have negative effects. We evaluated the effects of EPF on D. longicaudata. First, we determined the susceptibility of adults of D. longicaudata to strains of EPF (Metarhizium robertsii strain V3-160 and M. anisopliae strain MAAP1). We also evaluated the infection of these two fungi on A. ludens larvae parasitized by D. longicaudata. Finally, we determined sub-lethal effects on adults of D. longicaudata that emerged from larvae that had been exposed to low concentrations of M. robertsii. Both fungi caused moderate mortality to D. longicaudata adults. There were no adverse effects on the longevity of parasitoids that emerged from parasitized larvae exposed to M. robertsii. Based on these results, we argue that M. robertsii has the potential to be used for biocontrol of A. ludens, with limited risk to D. longicaudata adults.

Biological control potential of an aphid parasitoid, Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) against Brevicoryne brassicae (Linnaeus) (Hemiptera: Aphididae), a pest of oilseed brassicas in India

Biological and behavioural attributes of Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) were studied on Brevicoryne brassicae (Linnaeus) (Hemiptera: Aphididae). The total developmental duration of the parasitoid was longer in younger nymphal instars compared to that in older nymphal instars of aphid. Host age affected the oviposition period and fecundity of the ovipositing parasitoid. Survival of the immatures was higher in older as compared to the younger instars. Sex ratio for the parasitoid was found to be female-biased. Adult longevity of D. rapae was longer for females compared to that of males. Mean longevity of adult female parasitoid was longer, while parasitizing nymphs of younger age groups (1–2 days) compared to that of older age groups (4–5 days). B. brassicae reared on cabbage (Brassica oleracea var. capitata) was found to be the best host for D. rapae based on high per cent parasitism and high fecundity. The parasitoid showed a higher preference towards third nymphal instar of B. brassicae both in choice and no-choice tests. The results from experiments on mutual interference revealed that per capita searching efficiency decreased significantly from 0.99 to 0.05 with an increase in parasitoid densities from 1 to 8. Logistic regression exhibited a type II functional response for D. rapae. The handling time (Th) and searching efficiency (a) values were calculated to be 1.35 ± 0.05 h and 0.025865 ± 0.001525 h, respectively. This investigation suggests that D. rapae could be an effective biocontrol agent of B. brassicae that would supplement its management options in oilseed brassicas.

Performance of Trichogramma chilonis on different host

The laboratory experiment was conducted during 2017-2018 to study the different biological attributes of Trichogramma chilonis Ishii as influenced by host eggs of different ages. Significantly maximum percent egg parasitization was noticed on eggs of Helicoverpa armigera (Hubner) with 62.39 percent which was at par with the Corcyra cephalonica (Stainton) eggs (60.36 percent). This was followed by Earias vittella Fabricius 46.31 percent. Less parasitized eggs were recorded in Leucinodes orbonalis Guenee (10.35 percent). Age of host eggs significantly affected the parasitization by T. chilonis . The maximum parasitization (58.87 percent) was noticed in fresh eggs i.e. 24 hrs old followed by 48 hrs (44.91 percent) while 72 hrs old eggs were less preferred by T. chilonis and could parasitize only 30.56 percent. Development period for parasitoid ranged between 8.66 to 9.44 days on different host eggs. The highest adult parasitoid longevity (7.22 days) was observed from the parasitized eggs of H. armigera which was at par with C. cephalonic a (7.10 days), E. vittella (6.88 days) and L. orbonalis (6.88 days). However, the different lepidopteran eggs as well as age of host eggs did not show significant differences pertaining to percent adult parasitoid emergence. Fresh host eggs of 24 hrs could produce more female progeny of T. chilonis (54.30 percent) compared to 72 hrs old eggs (42.65 percent). The sex ratio (male: female) of emerging parasitoid progeny was observed highest on 24 hrs old eggs (1:1.55) followed by 48 hrs old eggs (1:1.23) while lowest sex ratio was observed on the eggs of 72 hrs old age (1:0.95). The maximum per day fecundity of T. chiloni s was noticed on the 24 hrs old eggs (6.75) followed by 48 hrs old eggs (4.80). The lowest fecundity (2.05) of T. chilon is was observed on the 72 hrs old eggs, whereas the highest male-female ratio and fecundity was noticed on eggs of E. vittella among different hosts.

Performance of the parasitoid species Aphelinus asychis Walker (Hymenoptera: Aphelinidae), Aphidius ervi (Haliday)\xa0(Hymenoptera: Braconidae) and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae), using Myzus persicae (Sulzer) (Hemiptera: Aphididae) as host

Three parasitoid species viz. Aphelinus asychis Walker (Hymenoptera: Aphelinidae), Aphidius ervi (Haliday) (Hymenoptera: Braconidae) and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) parasitizing the aphid species Myzus persicae (Sulzer) (Hemiptera: Aphididae) in mid-hills of north India were studied. At different locations and times of the year, the parasitization by A. asychis, A. ervi, and D. rapae ranged from 7.53 to 37.58, 4.26 to 80.45, and 74.25 to 80.48%, respectively. All the 3 parasitoids successfully completed their development on different nymphal instars of the aphid host and the total developmental duration of A. asychis, A. ervi, and D. rapae ranged 10.4–14.6, 24.2–29.6, and 10.2–15.2 days, respectively. It was significantly longer on the 1st nymphal instar of the host. The longevity of the female parasitoids was significantly longer than their counterparts. Differences in host age significantly influenced the longevity of female parasitoids and it was more on 1 to 2-day-old nymphs than that on 4 to 5-day-old nymphs. Fecundity and ovipositional periods of the parasitoids on younger (1–2 days old) host age group were considerably prolonged than on the older ages of the aphid. Average total fecundity of A. asychis and D. rapae was significantly higher when parasitizing 1–2-day-old nymphs. In A. asychis, host feeding behavior was also observed by a total host feeding of 89.2 aphids (1–2 days old) and 43.4 aphids (4–5 days old) during its life span. It is concluded that A. asychis, A. ervi, and D. rapae can be mass reared using M. persicae as host and can be utilized successfully in augmentative biological control program.

Aphid Honeydew Enhances Parasitoid Longevity to the Same Extent as a High-Quality Floral Resource: Implications for Conservation Biological Control of the Wheat Stem Sawfly (Hymenoptera: Cephidae).

Providing sugar resources for parasitoids is an important component of habitat management approaches to bolster biological control. We screened three flowering cover crop species, and one aphid species, for their potential to increase the longevity of the parasitoid wasp, Bracon cephi (Gahan) (Hymenoptera: Braconidae), an important biological control agent of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae). We found that buckwheat and honeydew from the cereal aphid, Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae), increased longevity of B. cephi females by over threefold, while longevity on sunflower and coriander was not significantly different from controls on wheat. The results suggest that incorporating buckwheat into cover crop mixes could enhance parasitoid performance. However, the finding that honeydew associated with a common aphid in wheat provides a suitable resource suggests that a better understanding of the varying quality, and spatial and temporal availability, of aphid honeydew will be a critical consideration in evaluating the potential benefits of managing floral resources for parasitoid conservation in this system.

Alyssum (Lobularia maritima) selectively attracts and enhances the performance of Cotesia vestalis, a parasitoid of Plutella xylostella

The use of nectar-providing plants to nourish natural enemies of pest species has become a widely-used approach in conservation biological control to reduce pest damage without the indiscriminate use of insecticides. Choice of plant species is crucial to maximize benefits, but suitable species are yet to be identified for many important crop-pest systems. Here we explored the suitability of three candidate nectar plants for use in brassica vegetables to suppress the globally significant pest, Plutella xylostella L. (Lepidoptera: Plutellidae), using the widely-distributed parasitoid, Cotesia vestalis (Haliday) (Hymenoptera: Braconidae). Volatiles of alyssum (Lobularia maritima (L.) Desv) (Brassicaceae) were attractive to the parasitoid and access to flowering shoots increased adult longevity and realized fecundity of C. vestalis. Moreover, adult diamondback moth derived no benefit from this flower. In contrast, buckwheat (Fagopyrum esculentum Moench) (Polygonaceae), a species widely used in conservation biological control in other systems, increased the longevity and fecundity of both pest and parasitoid, rendering it less suitable. A third plant, heronsbill (Portulaca grandiflora Hook.) (Portulacaceae) denied benefit to the pest and promoted longevity of the parasitoid under no-choice conditions but did not improve fecundity and was repellent to female parasitoids under choice conditions. The contrasting effects of this set of plants illustrate the need to test multiple response variables and effects on both pest and natural enemy when seeking optimal nectar plants for use in a novel conservation biological control system.

Negative Life History Impacts for Habrobracon hebetor (Hymneoptera: Braconidae) that Develop in Bollworm Larvae Inoculated with Helicoverpa armigera Nucleopolyhedrovirus.

Cotton bollworm, Helicoverpa armigera Hubner, is a cosmopolitan polyphagous pest of many crops. Habrobracon hebetor Say and Helicoverpa armigera nucleopolyhedrovirus (HearNPV) are two important biocontrol agents used to manage this pest, sometimes in combination. We evaluated the sublethal effects of HearNPV on H. hebetor life table parameters under laboratory conditions when its host (second instar H. armigera) was treated with HearNPV, and tested H. hebetor females for their ability to discriminate against inoculated hosts. Emergence of adults reared as solitary larvae was reduced by half on LC30-inoculated larvae compared to controls, but not on LC5 or LC15-inoculated hosts. Low concentrations (LC5, LC15, and LC30) of HearNPV had no effects on overall parasitoid developmental time, but longevity and lifetime fecundity was reduced for females emerging from hosts receiving the LC30 treatment. Net reproductive rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ) were all decreased in a concentration-dependent manner in the LC15 and LC30 treatments, as were female life expectancy, age-specific survivorship (lx), and age-specific fecundity (mx), whereas population doubling time (DT) increased. Parasitoids did not discriminate against LC15-inoculated larvae in choice or no-choice tests, but parasitized more LC50-inoculated hosts than controls in the choice test, with no significant differences in total numbers of eggs laid in either case. Although parasitoids suffered some loss of fitness in HearNPV-inoculated hosts under these laboratory conditions, these agents still appear compatible for joint application against H. armigera under field conditions, provided parasitoid releases are made 2 d after NPV application.

Do Ready-Mix Insecticides Cause Lethal and Sublethal Effects on Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) Pupa?

The use of selective insecticides aids farmers in maintaining pest populations below the economic threshold level. The integrated use of biological and chemical control is only possible if the effects of insecticides on natural enemies are studied. Although the IOBC/WPRS standards allow us to compare these studies worldwide, the methods used are sometimes inconsistent. This study determined the effects of ready-mix insecticides applied on pupae of Trichogramma pretiosum (Riley, 1879) (Hymenoptera: Trichogrammatidae) and compared the effects on emergence of two different methods of exposing T. pretiosum pupae to insecticides: immersed or sprayed using a Potter tower. Both methods gave the same results, indicating that they can be compared. Moreover, it is important to go beyond IOBC/WPRS classification and study the effects of pesticides on different biological parameters of natural enemies. This additional step may increase the likelihood of successful integration of biological and chemical control. Based on the emergence reduction, Chlorantraniliprole + lambda-cyhalothrin, abamectin + chlorantraniliprole, and alpha-cypermethrin + teflubenzuron were classified as innocuous (class 1). Cypermethrin + profenofos and cyproconazole + thiamethoxam were classified as slightly harmful (class 2). Methanol + methomyl and lufenuron + profenofos were classified as harmful (class 4). Abamectin + chlorantraniliprole, although classified as innocuous, reduced the parasitism, longevity, and flight capability of the adult parasitoids. None of these insecticides altered the emergence and sex ratio of the second generation.

Relevance of the ecological traits of parasitoid wasps and nectariferous plants for conservation biological control: a hybrid meta-analysis.

Ecosystem services are key to human survival. In agriculture, they offer potential to intensify production while reducing reliance on hazardous inputs, including pesticides. Nectar plants can nourish natural enemies of pests and thereby promote the ecosystem service of biological control. To date, however, the selection of optimal plants has been reliant on laborious testing of multiple candidate species for use in each new agroecosystem. We report a hybrid meta-analysis of published literature, employing Bayesian network analysis. The hybrid meta-analysis identified the particular plant and parasitoid traits that were most predictive of promoted or suppressed parasitoid longevity. Integrating trait effects identified a combination of plant-parasitoid traits that had the highest impact on parasitoid longevity: compound umbel or raceme inflorescence form and shallow corolla, together with high potential fecundity of the parasitoid. Unlike earlier analyses focusing on taxonomic categories, we analyzed effect sizes in relation to the ecological traits of parasitoids and plants. This generated the first generalizable guidelines for selecting nectar plants as well as appropriate parasitoid targets for the enhancement of biological control. Within the guidelines, optimal outcomes resulted when plants with compound umbel or raceme inflorescences and shallow corollas were combined with fecund parasitoids. More widely, this type of ecological trait-based meta-analysis opens a new avenue for optimizing the delivery of other types of ecosystem services. © 2019 Society of Chemical Industry.

Side effects of Bacillus thuringiensis on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae).

The endoparasitoid wasp Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) is used to control defoliating lepidopteran pests. Chemical insecticides are not compatible with natural enemies, but bioinsecticides, such as Bacillus thuringiensis Berliner (Bt), have great potential for use in integrated pest management. However, interactions between Bt and P. elaeisis still need to be investigated. This study aimed to evaluate the effects of Bt on parental and first-generation P. elaeisis parasitizing Bt-susceptible and -resistant Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). An additional aim was to determine the toxicity of Bt to susceptible third-instar S. frugiperda larvae. Larvae were exposed to lethal concentrations (LC50 and LC90) of Bt and then allowed to be parasitized by P. elaeisis. Parasitoid longevity, immature production, reproductive performance, and behavioral responses were evaluated. Bt repelled P. elaeisis and reduced immature production. Parental and first filial generation parasitoids of both sexes emerged from Bt-treated larvae showed lower survivorship than controls. Parasitoids had poorer reproductive performance in Bt-susceptible and -resistant pupae than in untreated pupae. Palmistichus elaeisis emerged from Bt-susceptible and -resistant S. frugiperda showed altered host-searching behavior and reproductive parameters, which indicates low compatibility between the bioinsecticide agent and the parasitoid wasp.

Some Aspects of the Biology of Trichopria anastrephae (Hymenoptera: Diapriidae), a Resident Parasitoid Attacking Drosophila suzukii (Diptera: Drosophilidae) in Brazil.

Spotted-wing Drosophila, Drosophila suzukii (Matsumura, 1931), is an economic pest of thin-skinned fruit crops. Its control has commonly been carried out through chemical methods. However, given the need to develop safer and environmentally friendly management alternatives, the pupal endoparasitoid Trichopria anastrephae Lima stands out as a potential biological control agent. However, the lack of information on the mass rearing of this parasitoid limits its use. Thus, the objective of our study was to provide information that is useful for rearing T. anastrephae using D. suzukii as a host. The effects of pupal age, exposure time, and pupal density on the parasitism rate were examined, as was the effect of honey provision for extending adult parasitoid longevity. Exposing 15 12-h-old pupae per female for 24 h resulted in higher parasitism rates and a greater number of emerged parasitoids. Males and females of T. anastrephae fed with pure honey (100%) or honey diluted to 50% in water lived longer compared to those fed 10% honey, no food, or only water.

Quality of aphid honeydew for a parasitoid varies as a function of both aphid species and host plant

Honeydew i.e., the sugar-rich excretion of phloem-sap feeders, is the most available sugar source in agroecosystems which enables parasitoids to increase their fitness. For the parasitoids of honeydew-producing insects, honeydew is associated with host presence, suggesting that parasitoids can find carbohydrate sources and hosts at the same place. Hence, these parasitoids may have evolved to efficiently use the honeydew produced by their main hosts as a carbohydrate source. In this context, we assessed the relationship between the adult fitness (in terms of longevity and fecundity) of the aphid parasitoid Aphelinus abdominalis (which prefer attack aphid species belonging to the Macrosiphini tribe), fed on honeydew produced by 19 different plant-aphid combinations, and parasitoid preference (i.e., the choice of female to oviposit) and ability to produce offspring in these combinations. Honeydew quality was modulated by both the plant and aphid host species. The honeydew produced by eight aphid species (e.g., Macrosiphum euphorbiae and Aphis craccivora) resulted in high parasitoid longevity (same longevity as the honey-fed positive control) and an increase in egg load between 24 and 48 h, compared to the negative control (fed only water). In contrast, nine aphid species (e.g., Brevicoryne brassicae and Aphis nerii) excreted low-quality honeydew that did not increase parasitoid longevity or egg load (similar to the negative control water-fed parasitoids). There was no relationship between A. abdominalis adult fitness when fed various honeydews and its preference as well as its ability to produce offspring in the hosts producing these honeydews. Several hypotheses that may explain this lack of relationship are discussed.

Effects of toxic baits and food-based attractants for fruit flies on the parasitoid Fopius arisanus (Sonan) (Hymenoptera: Braconidae).

This study aimed to evaluate the effects of toxic baits and attractants for fruit flies on the biology of its parasitoid Fopius arisanus. We tested two food-based attractants; hydrolysed corn protein (Biofruit® 3%) and sugarcane molasses (7%), their mixtures with spinosad and malathion-based insecticides, and a ready-to-use commercial bait (Success 0.02 CB®). Malathion-based lures were used as references for mortality (i.e., positive control), while negative control was honey. The formulations Biofruit® + malathion (T1), molasses + malathion (T2), and spinosad + molasses (T3) were toxic to F. arisanus, being classified as harmful (class 4). In addition, toxic baits composed of Biofruit + spinosad (T4) reduced parasitism by 97.99%, being rated as moderately harmful (class 3). Yet, Success 0.02 CB® (T7) was considered slightly toxic (class 2), causing a 64.55% reduction in parasitism. Regarding the biological parameters of F. arisanus, offspring number and parasitoid longevity were significantly reduced by using hydrolysed protein attractants when compared to the control (honey). However, sugarcane molasses improved parasitoid reproduction and longevity, as did the honey. Lastly, ingestion tests showed the major role of attractants in toxic-bait formulations against F. arisanus.

Weed floral resources and commonly used insectary plants to increase the efficacy of a whitefly parasitoid

Weed floral resources are often overlooked in biological control manipulations, yet common species in this group can contribute to enhanced biological control efficacy. Weed floral resources may not be examined as frequently as certain insectary species (buckwheat). Furthermore, they may require less maintenance and are adapted to grow in the planted area. Here, we investigated the effects of weed and other non-crop floral resources on Eretmocerus mundus, a parasitoid of the whitefly, Bemisia tabaci, in the laboratory. The two common weeds evaluated were shepherd’s purse (Capsella bursa-pastoris) and white rocket (Diplotaxis erucoides). These were compared with buckwheat (Fagopyrum esculentum) and alyssum (Lobularia maritima). Adults of the above parasitoid were exposed to flowers of the selected plants and survived six times longer with buckwheat than those in the control (water only) and 2.8, 3.1 and four times longer with shepherd’s purse, rocket and alyssum, respectively. All plant species significantly increased parasitoid longevity, egg load and fecundity compared to the control. Buckwheat had the greatest effect on these parameters. Parasitism rate of the pest increased by up to 72.1%. This work illustrates that the selected non-buckwheat species could have value where buckwheat germination rate and phenology may be limiting such as in arid climates, for which this work was targeted.

Effects of floral resources on the efficacy of a primary parasitoid and a facultative hyperparasitoid

AbstractResources added to agroecosystems to enhance biological control are potentially available to multiple members of the resident insect community—not only the biological control agents for which the resources are intended. Many studies have examined the effects of sugar feeding on the efficacy of biological control agents. However, such information is lacking for other, interacting species such as facultative hyperparasitoids, which may contribute to pest suppression but can also interfere with introduced biological control agents. Under greenhouse conditions, we tested the direct effects of sugar and nectar provisioning on the longevity, host‐killing impact and offspring production of two pupal parasitoids associated with leek moth, Acrolepiopsis assectella: the introduced biological control agent, Diadromus pulchellus, and the native facultative hyperparasitoid, Conura albifrons. Adding sucrose, buckwheat or a combination of buckwheat and common vetch to a sugar‐deprived system (potted leek plants in cages) increased parasitoid longevity and resulted in higher leek moth parasitism and mortality compared to water or common vetch treatments. However, the two parasitoid species exhibited a distinct temporal response to the treatments, likely influenced by differences in their life histories. This study provides insight into how integrating conservation biological control techniques could affect the success of a classical biological control programme.

Effects of Constant and Fluctuating Temperatures on Development Rates and Longevity of Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae).

The effects of fluctuating and constant temperatures on the development and longevity of Diaphorencyrtus aligarhensis (Shafee, Alam, and Argarwal) (Hymenoptera: Encyrtidae), a parasitoid sourced from Pakistan and released in California for the classical biological control of Diaphorina citri Kuwayama (Hemiptera: Liviidae), were examined. The influence of six fluctuating temperatures that averaged 15, 20, 25, 30, 32, and 35°C, over 24 h on the development times and longevity of male and female D. aligarhensis were quantified and compared to six constant temperatures set at the same average temperatures. The development rates of immature stages of D. aligarhensis as a function of temperature were modeled using one linear and four nonlinear models. Fluctuating temperatures had significant effects on parasitoid development times and longevity which differed across experimental temperatures. Degree-days required for completion of cumulative development of D. aligarhensis were significantly different being 21% lower under fluctuating temperature regimens when compared with constant temperatures. The lower temperature threshold estimates above which development occurred were estimated to be lower under constant than fluctuating temperatures. The estimated values of upper and optimum temperature limits were similar for individuals reared under constant and fluctuating temperatures. Diaphorencyrtus aligarhensis lived longer at constant intermediate temperatures and for shorter times at constant lower temperature extremes when compared with their fluctuating temperature counterparts. Daily thermal fluctuations significantly influenced life history parameters of D. aligarhensis and should be considered when assessing likelihoods of establishment and impacts of this parasitoid on D. citri across diverse citrus-growing climates.

Biological Control of Insect Pests of Agricultural Crops through Habitat Management Was Discussed

Biological control through habitat management leads to sustainable insect pest control. Different types of land composition such as multiple landscapes, patchiness of landscapes enhance the natural enemies which ultimately lead to control of insect pest. Plant characteristics such as flower shape, flower color and blooming period ensures excess food for natural enemies like nectar and pollen. Moreover, some agricultural practices such as tillage, crop rotation, and intercropping influence the natural enemies especially parasitoid and preda-tors. Consequently, they increase longevity and fecundity of parasitoid and predator that help to control insect pest. One of the most important recently used methods is push-pull which consists of semiochemicals called Herbi-vore-Induced Plant Volatiles (HIPVs). This compound has been used to pre-vent pest and attract natural enemies.

Host utilization, reproductive biology, and development of the larval parasitoid Tetrastichus planipennisi as influenced by temperature: Implications for biological control of the emerald ash borer in North America

The success of classical biological control programs depends in part on understanding climate effects on introduced agents. Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), a larval endoparasitoid of emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is being introduced to EAB-invaded regions of the United States (USA) and Canada for biological control. To optimize regional release strategies and increase efficiency of the EAB-biocontrol program, we determined the effects of five constant temperatures from 15 °C to 35 °C on T. planipennisi parasitism rate, development, adult longevity, and fecundity in EAB. Results showed a decrease in parasitoid development time from 139.8 days at 15 °C to 26.3 days at 30 °C, while no parasitoid eggs hatched at 35 °C. Parasitism rates, provisioned with an excess of host larvae throughout their life, increased from 1.4% at 15 °C to 28% at 30 °C then declined to 0.5% at 35 °C. Adult parasitoid longevity declined from 24 weeks at 15 °C to <2 weeks at 35 °C. Fertility table analyses revealed T. planipennisi net reproductive rate was highest at 25 °C, and intrinsic and finite rates of increase were highest at 30 °C, suggesting 25–30 °C as optimal rearing temperatures for this parasitoid. Combining these results with temperature data from climate zones of 3–7 in the USA, we predicted T. planipennisi can complete more than one generation in all locations in these climatic zones, with more generations in warmer climates. Moreover, our findings also suggest that despite the availability of suitable EAB larval stages for parasitism, releases of T. planipennisi in early spring or late fall in cold climate zones may be suboptimal due to low temperatures, as may mid-summer releases in hot climate zones due to high temperatures.

Factors shaping life history traits of two proovigenic parasitoids.

What shapes the relative investment in reproduction versus survival of organisms is among the key questions in life history. Proovigenic insects mature all their eggs prior to emergence and are short lived, providing a unique opportunity to quantify their lifetime investments in the different functions. We investigated the initial eggloads and longevity of 2 proovigenic parasitoid wasps: Anagrus erythroneurae and Anagrus daanei, (Hymenoptera: Mymaridae) that develop within leafhopper eggs in both agricultural vineyards and natural riparian habitats in Northern California. We collected Vitis spp. leaves containing developing parasitoids from 3 natural sites (Knight Landing, American River and Putah Creek) and 3 agricultural vineyards (Solano Farm, Davis Campus and Village Homes). We recorded eggloads at parasitoid emergence and female parasitoid longevity with or without honey-feeding. Theory predicts that parasitoids from vineyards (where hosts are abundant) would have higher initial eggloads and lower longevity compared with parasitoids from riparian habitats (where hosts are scarce). Although host density and parasitoid eggloads were, indeed, higher in vineyards than in riparian habitats, parasitoid longevity did not follow the predicted pattern. Longevity without feeding differed among field sites, but it was not affected by habitat type (natural vs agricultural), whereas longevity with feeding was not significantly affected by any of the examined factors. Moreover, longevity was positively, rather than negatively, correlated with eggloads at the individual level, even after correcting for parasitoid body size. The combined results suggest a more complex allocation mechanism than initially predicted, and the possibility of variation in host quality that is independent of size.