Insect Pest Management Programs Research Articles

Virulence and Reproduction of Entomopathogenic Nematodes Isolated from a Single Mexican Locality

Abstract Entomopathogenic nematodes (EPNs) are important biological control agents of insect pests. Strains or isolates obtained in specific regions and utilized in situ might contribute to the success of EPNs, since they are adapted to local abiotic conditions. We isolated and identified three isolates each of Heterorhabditis bacteriophora Poinar and Steinernema carpocapsae (Weiser) from soils at Saltillo, Coahuila State, Mexico. These six isolates were bioassayed against larvae of Tenebrio molitor L., using six concentrations of infective juveniles (IJs) per larva (0, 10, 25, 50, 100, 200). EPN-induced mortality of the isolates ranged from 15.2% to 100%. The designated M5 isolate of S. carpocapsae caused 100% mortality after 72 h at concentrations ≥25 IJs/larva with a median lethal concentration of 4.99 IJs/larva. Comparison of mortality levels induced at the same concentration of the six EPN isolates indicated that the Steinernema isolates, in general, induced higher mortality levels than the Heterorhabditis isolates. IJ production in T. molitor larvae also was greatest with the M5 isolate of S. carpocapsae following exposure of larvae to a concentration of 100 IJs/larva with a mean of 17,320 IJs/larva. Based on induced mortality and IJ production, the S. carpocapsae M5 isolate appears to be a viable candidate for further study and possible development for use in insect pest management programs. This study indicates that naturally coexisting local nematode isolates possess different attributes critical for their use as biocontrol agents.

New Assays for Rapid Detection of Beet Leafhopper-Associated Plant Pathogens, 'Candidatus Phytoplasma trifolii', Beet Curly Top Virus, and Spiroplasma citri.

The beet leafhopper Circulifer tenellus is an important pest of agricultural crops in the United States, where it transmits beet curly top virus, beet leafhopper-transmitted virescence agent phytoplasma, and Spiroplasma citri to numerous crops, affecting yield and quality. Each of these pathogens have been linked to serious disease outbreaks within Washington State in the past century. To mitigate the risk of disease, growers target the beet leafhopper in their insect pest management programs. Knowledge of pathogen prevalence in beet leafhopper populations could help growers make better management decisions, but timely diagnostics is required. Four new assays were developed for the rapid detection of the beet leafhopper-associated pathogens. These include two assays that detect Beet leafhopper transmitted virescence agent (a PCR and a real-time PCR SYBR green assay), a duplex PCR assay that simultaneously detects beet curly top virus and Spiroplasma citri, and a multiplex real-time PCR assay for the simultaneous detection of all three pathogens. The screening of dilution series generated from plant total nucleic acid extracts with these new assays typically led to detection at levels 10- to 100-fold more sensitive than the conventional PCR assays currently used. These new tools will allow the rapid detection of beet leafhopper-associated pathogens in both plant and insect specimens and will have the potential to be used in diagnostic laboratories seeking to disseminate fast and accurate results to growers for implementation in their insect pest monitoring programs.

Characterization of insecticidal metabolite oosporein in Lecanicillium saksenae (Kushwaha) Kurihara and Sukarno, a geographically distinct isolate from Kerala, India

Lecanicillium saksenae, an indigenous isolate from Kerala, India is a potent entomopathogen against hemipteran pests. The wine-red pigmentation produced by this isolate distinguishes it from many other isolates of L. saksenae reported across the globe. This study, therefore, sought to isolate and characterize the pigment molecule. The wine-red pigment extracted through liquid - liquid partition of the fungal culture was subjected to structural characterization and identification through UV spectrometry, Fourier Transform Infrared Spectrometry (FTIR), High Resolution Liquid Chromatography, Mass Spectrometry (HR-LCMS) and Nuclear Magnetic Resonance Spectrometry (NMR). It was unambiguously identified as a dibenzoquinone compound, oosporein, a known bioactive insecticidal metabolite. The empirical formula of which was confirmed as C14H10O8 and molecular weight, m/z 306.22. The dose dependent bioefficacy of oosporein with 1000 ppm at 96 h recorded a mortality of 60.25 per cent in nymphs of brinjal mealybug, Coccidohystrix insolita, while it was still lower (51.00%) in adults. In this study, we could identify that L. saksenae reported from Kerala, India was geographically distinct. Sequence analysis based on 18srDNA and phylogenetic analysis confirmed the species identity of this indigenous isolate with that of L. saksenae documented in NCBI. This finding paves the way for the possibilities of tapping the potential of bioactive metabolites for pest management and uplifting the species as a potent bioagent in insect pest management programmes.

Impact of the nicotinic acetylcholine receptor mutation R81T on the response of European Myzus persicae populations to imidacloprid and sulfoxaflor in laboratory and in the field

Sulfoxaflor (Isoclast™ active) is a sulfoximine insecticide that is active on a broad range of sap-feeding insects, including species that exhibit reduced susceptibility to currently available insecticides. Colonies of Myzus persicae (green peach aphid) were established from aphids collected in the field from peach (Prunus persica) and nectarine (Prunus persica var. nucipersica) orchards in France, Italy and Spain. The presence of the nicotinic acetylcholine receptor (nAChR) point mutation R81T was determined for all the colonies. Eight of the 35 colonies collected were susceptible relative to R81T (i.e., R81T absent), three of the colonies were found to be homozygous for R81T while 24 colonies had R81T present in some proportion (heterozygous). Sulfoxaflor and imidacloprid were tested in the laboratory against these M. persicae field colonies, which exhibited a wide range of susceptibilities (sulfoxaflor RR = 0.6 to 61, imidacloprid RR = 0.7 to 986) (resistance ratios, RR) to both insecticides. Although sulfoxaflor was consistently more active than imidacloprid against these field collected M. persicae, there was a statistically significant correlation across all colonies between the RRs for imidacloprid and sulfoxaflor (Pearson's r = 0.939, p < 0.0001). However, when a larger group of the colonies from Spain possessing R81T were analyzed, there was no correlation observed for the RRs between imidacloprid and sulfoxaflor (r = 0.2901, p = 0.3604). Thus, consistent with prior studies, the presence of R81T by itself is not well correlated with altered susceptibility to sulfoxaflor. In field trials, sulfoxaflor (24 and 36 gai/ha) was highly effective (~avg. 88–96% control) against M. persicae, demonstrating similar levels of efficacy as flonicamid (60–70 gai/ha) and spirotetramat (100–180 gai/ha) at 13–15 days after application, in contrast to imidacloprid (110–190 gai/ha) and acetamiprid (50–75 gai/ha) with lower levels of efficacy (~avg. 62–67% control). Consequently, sulfoxaflor is an effective tool for use in insect pest management programs for M. persicae. However, it is recommended that sulfoxaflor be used in the context of an insecticide resistance management program as advocated by the Insecticide Resistance Action Committee involving rotation with insecticides possessing other modes of action (i.e., avoiding rotation with other Group 4 insecticides) to minimize the chances for resistance development and to extend its future utility.

Interrelation between Surface Wax Alkanes from Red Kidney Bean (Phaseolus vulgaris L.) Seeds and Adzuki Bean Weevil [Callosobruchus chinensis (F.)] (Coleoptera: Bruchidae)

Background: Callosobruchus chinensis (Fabricius) (Coleoptera: Bruchidae) is one of the major insect pests of Phaseolus vulgaris L. grains, commonly known as rajma seeds, in Europe and Asia including India. Infestations of these insects destroy majority of legume seeds including rajma which causes a great economic loss. Hence, a proper sustainable pest management measures are necessary for storage of rajma seeds. For this, the study aims to identify and quantify the n-alkane profile from the surface waxes of rajma seeds and their role as olfactory cue in C. chinensis. Individual synthetic alkane followed by the synthetic blends mimicking rajma seed surface wax n-alkanes as olfactory cue was also evaluated.Methods: Collected rajma seeds were solvent extracted to isolate surface waxes. The extract then fractioned by thin-layer chromatography and followed by gas chromatography-mass spectrometry analyses to purify, quantify and identify n-alkanes.Result: Rajma seeds’ surface waxes analysis revealed 18 n-alkanes between n-C15 and n-C33. The predominant alkanes were n-octacosane and n-hexadecane. n-Octadecane was the least abundant alkane in seeds. Total alkane content was 3502.67±12.82µg from 100 g (number 200 ± 5.13) seeds. Adult female C. chinensis elicited attraction towards the surface wax alkanes at concentrations of 0.5, 1, 2, 4 and 6 seed(s) equivalent of rajma seed(s) in the Y-tube olfactometer bioassay, but the highest attraction was observed at 6 seeds equivalent. Hence, a synthetic alkane blend resembling of 6 seeds equivalent, present in seeds’ surface wax alkane or a combination of nine (which elicited positive response) synthetic alkane blend resembling 6 seeds equivalent could be used as lures in developing baited trap in insect pest management programme.

A steroidal lactone, withaferin A acts as a potential insect growth regulator against polyphagous pest, Spodoptera litura (Lepidoptera: Noctuidae)

Administration of a steroidal lactone, withaferin A to last larval instar of a polyphagous pest, Spodoptera litura caused severe impairment of development resulting into a significant delay in larval–pupal and pupal–adult ecdysis, larval mortality, ecdysial stasis, formation of larval–pupal and pupal–adult intermediates, suppression of pupation and adult emergence and formation of abnormal pupae and adultoids. The LC50 value in topical administration of withaferin A was 180.3 µg·µL−1 against freshly moulted sixth instar larvae of S. litura. This suggests that a bioactive ingredient withaferin A, found in the parts of the medicinal plant, Withania somnifera interferes with the neuroendocrine system of the insects resulting into disruption of moulting and metamorphosis. The active ingredient, withaferin A from W. somnifera may be safely and judiciously employed for the control of S. litura under field conditions along with other bio-rational approaches for insect pest management programs.

Morphological characterization of antennal sensilla of Earias vittella (Fabricius) (Lepidoptera: Nolidae)

The shoot and fruit borer, Earias vittella Fab. (Lepidoptera: Nolidae) is an important and most devastating insect pest on okra and cotton. The pest mainly responsible for causing significant direct damage to tender shoots and fruits of okra, flowers and green bolls of cotton causing net yield loss in both crops. Many non-chemical control strategies have been developed under the insect pest management program, A complete knowledge on the antennal morphology of E. vitella is essential for future electrophysiological and behavioural studies. In the present study, the antennal morphology and types of sensilla on the antennae of both sexes of E. vitella were examined using light and scanning electron microscopy. Nine distinct types of sensilla were identified on the antennae of both sexes: sensilla trichodea, sensilla basiconica, sensilla coeloconica, sensilla auricillica (multiporous), sensilla chaetica, uniporous peg sensilla (uniporous), sensilla styloconica, sensilla squamiformia and bohm bristles (aporous). Among all sensilla, the most widespread are multiporous sensilla trichodea with 42.90 ± 1.77/flagellomere in male and 37.38 ± 1.38/flagellomere in female. Sensilla basiconica were the second most common sensillum type in male antennae with 15.67 ± 1.92/flagellomere. Other multiporous sensilla such as auricillica (11.90 ± 0.99) and coeloconica (4.57 ± 0.25) were significantly more abundant in female than in male antennae. Results of the study provide morphological evidence that E. vitella antennae possess microscopic cuticular structures that can play a role in perception of pheromones, plant odours and other chemical stimulants. This will open up opportunities to assess the possibility of using pheromones and plant-derived compounds for the monitoring or management of E. vittella moths in the agricultural landscapes.

Sulfoxaflor efficacy in the laboratory against imidacloprid-resistant and susceptible populations of the green peach aphid, Myzus persicae: Impact of the R81T mutation in the nicotinic acetylcholine receptor

A key to effective insect pest management and insecticide resistance management is to provide growers with a range of new tools as potential alternatives to existing compounds or approaches. Sulfoxaflor (Isoclast™ active) is a new sulfoximine insecticide which is active on a broad range of sap-feeding insects, including species that have reduced susceptibility to currently used insecticides, such as imidacloprid from the neonicotinoid class. Sulfoxaflor (SFX) and imidacloprid (IMI) were tested in laboratory bioassays to compare the susceptibility of field populations of green peach aphid, Myzus persicae (Sulzer), exhibiting varying degrees of resistance involving an alteration (R81T) to the insect nicotinic acetylcholine receptor. The LC50 values for M. persicae exposed to SFX ranged from 0.09 to 1.31 (mg litre−1), whereas when the same populations were exposed to IMI the LC50 values ranged from 0.6 to 76.2 (mg litre−1). M. persicae were significantly more sensitive to SFX as compared to IMI for nine of the 13 populations tested. For M. persicae populations confirmed to be homozygous susceptible (ss) or heterozygous rs) for the R81T point mutation, there was no significant differences in the observed LC50 values for either SFX or IMI relative to the susceptible reference population (15LP1). However, in all M persicae populations that were homozygous (rr) for the R81T point mutation, susceptibility was significantly less to IMI as compared to the reference population with resistance ratios ranging from 22.1 to 63.5-fold. In contrast, only one homozygous resistant population (15MP9) exhibited a statistically significant change in susceptibility (RR = 10-fold) to SFX as compared to the reference population, which was far less than the 56-fold observed for imidacloprid in that same population. Thus, this study indicates there is no specific correlation between the laboratory efficacy of SFX and IMI in field collected populations in Spain displaying varying degrees of resistance to IMI. Furthermore, the presence of target site resistance in M. persicae to IMI, in the form of the R81T mutation, does not a priori translate to a reduction in sensitivity to sulfoxaflor. Consequently, SFX can be an effective tool for use in insect pest management programs for green peach aphid. These data also serve as a baseline reference for green peach aphid sensitivity to SFX prior to commercial uses in Spain.

Irradiation dose response under hypoxia for the application of the sterile insect technique inDrosophila suzukii.

Treating insects with a lower oxygen atmosphere before and during exposure to radiation can mitigate some of the negative physiological effects due to the irradiation. The irradiation of pupae under oxygen-reduced environment such as hypoxia or anoxia is routinely used in the sterile insect technique (SIT) of some tephritid species as it provides radiological protection. This treatment allows to have the sterile pupae already in sealed containers facilitating the shipment. SIT is an environment friendly control tactic that could be used to manage populations of Drosophila suzukii in confined areas such as greenhouses. The objectives of this study were to assess the effect of irradiation on the reproductive sterility in D. suzukii males and females under low-oxygen atmosphere (hypoxia) and atmosphere conditions (normoxia). Additionally, we assessed the differences in radiological sensitivity of pupae treated under hypoxia and normoxia conditions. Finally, the effect on emergence rate and flight ability of the irradiated D. suzukii adults exposed to doses that induced >99% of sterility were assessed. Pupae needed a 220 Gy irradiation dose to achieve >99% of egg hatch sterility in males irrespective of the atmosphere condition. For females the same level of sterility was achieved already at 75 Gy and 90 Gy for the normoxia and hypoxia treatments, respectively. Radiation exposure at 170 and 220 Gy under the two atmosphere treatments did not have any effect on the emergence rate and flight ability of D. suzukii males and females. Therefore, hypoxia conditions can be used as part of an area-wide insect pest management program applying SIT to facilitate the protocols of packing, irradiation and shipment of sterile D. suzukii pupae.

Qualitative Determination, Quantitative Evaluation and Comparative Insecticidal Potential of Ruta Graveolens Essential Oil and Its Major Constituents in the Management of Two Stored Pests Sitophilus Zeamais (Coleoptera: Curculionidae) And Corcyra Cephalon

Eco-chemical control based on essential oil mediated plant-insect interactions is an alternative method to the unsystematic use of insecticides, due to advanced structural diversity and allelopathic potential of essential oils. In this sense, present work was aimed at qualitative and quantitative investigation of chemical composition and the evaluation of insecticidal activities of Ruta graveolens essential oil and its major constituents against Sitophilus zeamais and Corcyra cephalonica in stored maize. Fresh leaves were subjected to hydrodistillaton and the chemical composition of oil was studied. Essential oil and its major constituents were then assessed for their allelopathic activity on test insects. Fifty components were identified, where long chain aliphatic 2-methyl ketones predominated the oil as major constituents. Results revealed strong concentration-, insect species- and time-dependent toxicities, in which oil caused 100 % mortalities at concentrations of 1.52 and 0.46 µL/cm2 against S. zeamais and C. cephalonica respectively after 24 hours of exposure. In aliphatic 2-methyl ketone series, respective congeners having odd and even number of carbon atoms were more effective on S. zeamais and C. cephalonica. These findings provide a scientific basis for the eco-potential of using essential oil of R. graveolens and its major constituents in integrated insect pest management programs.

Aerosol concentration, deposition, particle size, and exposure interval as mortality factors Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

A series of trials was conducted for an experiment. In the first trial, adults of Tribolium confusum Jacquelin du Val, the confused flour beetle, were exposed on concrete arenas and treated with a combination aerosol of pyrethrin + methoprene dispensed for 5, 10, and 20 min at particle sizes of 4, 8, 12, and 16 μm, inside an aerosol exposure chamber. Nearly all adult T. confusum were knocked down when immediately removed from the chamber. Among all the exposure time and particle size combinations, recovery increased as the post-exposure holding period increased from one to seven days and when adults were transferred to untreated dishes with flour. A second experiment evaluated the residual effect of the aerosol on concrete arenas at 1, 3, and 6 weeks using 3-4-week-old larvae of T. confusum. Adult emergence of exposed larvae decreased with increasing particle size and exposure time. A biological index that assessed development of exposed larvae to the pupal and adult stages was also related to particle size and exposure interval, and this index was correlated with adult emergence. A third set of experiments investigated effects of particle size on adult fecundity for the 10-min exposure time. Male and female adults were cross-mated: exposed female with exposed male, exposed female with unexposed male, exposed male with unexposed female, and unexposed female and unexposed male. Progeny production was reduced as particle size increased, and there were indications that females were affected more than males by the aerosol treatment. This research could be used to improve insect pest management programs by adjusting application equipment to dispense aerosols at particle sizes that give optimum control of exposed adults and residual control of immatures and would also benefit pest management programs.

Limited variations in susceptibility to an insecticidal double-stranded RNA (dsvATPaseE) among a laboratory strain and seven genetically differentiated field populations of Tribolium castaneum

There has been a considerable growth in interest to use RNA interference (RNAi) as a novel insect pest management strategy in the past 10 years. However, there has been virtually no information on insect population variations in response to double-stranded RNA (dsRNA) molecules. The objective of this study was to generate baseline susceptibilities of the red flour beetle (Tribolium castaneum) to an insecticidal dsRNA targeting vacuolar H+-ATPase subunit E gene (dsvATPaseE), and correlate the susceptibility data with sequence and expression variations of the target gene (vATPaseE), expression variations of the RNAi core genes, and overall genetic differences among a laboratory strain and seven geographical field populations of T. castaneum collected in China. Our results showed limited variations in the LD50 values of dsvATPaseE, which ranged from 0.10 to 0.29 ng/larva among the laboratory strain and the seven field populations. Considering the overlapping of the 95% confidence intervals of their LD50 values, there were no significant differences among the laboratory strain and field populations. We also found limited sequence polymorphisms and low frequencies of the polymorphisms of vATPaseE, and limited variations (<2-fold) of the endogenous expression of vATPaseE among the laboratory strain and field populations. However, we found considerable genetic variations among the individuals within each field population for most of eight loci and moderate to large genetic variations among the field populations. These results demonstrated that although the genetic variabilities were considerable among these field populations, the efficiency of RNAi targeting vATPaseE was highly consistent in T. castaneum. Our study provides work frames of resistance risk assessment for RNAi-based insect pest management programs.

Toxic effects of Nigella sativa against Rhyzopertha dominica (Coleoptera: Bostrichidae).

This study was conducted at the Institute of Plant and Environmental Protection, Insect Pest Management Program (IPMP), Stored Grain Management laboratory (NARC) Islamabad in 2018. The Insecticidal effects of essential oil i.e. Nigella sativa at the concentration of 10, 4, 2 and 1 percent showed insecticidal effect (as high as 44.44%) at concentration (10%) after 1 week. Highest mortality (44.44%) at concentration (10%) was observed on N. sativa.

Comparative assessment of insect pests population densities of three selected cucurbit crops

Comparative assessment of insect pests population densities of three selected cucurbit crops

Scorpion venom: pharmacological analysis and its applications

Scorpions belong to class: Arachnida, order: Scorpionida represented now by approximately 1500 species. These are one of the most ancient group of the animals on the earth conserving their morphology almost unaltered and are the most successful inhabitants of the earth. Scorpions when stimulated secrete venom which is a cocktail of variable concentration of neurotoxins, cardiotoxins, nephrotoxins, hemolytic toxins, phosphodiesterases, phospholipases, hyaluronidase, glucosaminoglycans, histamine, seratonin, tryptophan and cytokine releasers. According to an estimate, frequency of deaths caused by scorpion sting is higher in comparison to that of caused by snake-bite. Almost all of these lethal scorpions except Hemiscorpious species belong to scorpion family Buthidae comprising 500 species. Scorpion venoms show variable reactions in envenomated patients. However, closer the phylogenic relationship among the scorpions, more similar the immunological properties. Furthermore, various constituents of venom may act directly or indirectly and individually or synergistically to exert their effects. Scorpion stings cause a wide range of conditions from severe local skin reactions to neurologic, respiratory and cardiovascular collapse. Lethal members of Buthidae family include Buthus , Parabuthus , Mesobuthus , Tityus , Leiurus , Androctonus and Centruroides . Besides their lethal properties, scorpion venoms have some unique properties beneficial to mankind. These contain anti-insect, antimicrobial and anticancer properties and thus, can play a key role in the insect pest management programmes, treatment of microbial infection and in the treatment of various cancer types.

Attractiveness of male azuki bean beetle to the synthetic blends of 2E- and 2Z-homofarnesals

Use of synthetic pheromones is biologically and economically effective approach in insect pest management programs. The female adults of azuki bean beetle (Callosobruchus chinensis L.), a worldwide oligophagous pest of legumes including azuki beans, produce sex pheromone components known as homofarnesals with two isomer compounds; (2Z,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2Z-homofarnesal) and (2E,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2E-homofarnesal). We used Z-selective method to synthesize 6:4 blend of 2E- and 2Z-homofarnesal and compared its attractiveness with two other blends; 9:1 and 1:9 using Y-olfactometry in laboratory and rocket traps in the field. Both laboratory and field experiments ascertained the higher attractiveness of synthetic homofarnesal with higher proportion of 2Z-homofarnesal. Among the tested blends of 9:1, 6:4 and 1:9 of 2E- and 2Z-homofarnesal in Y-olfactometry, the attractiveness pattern was found as 1:9≥6:4>9:1 blend. Under field condition also, the 6:4 blend was more attractive with the recapturing efficiency of 31.4±2.6% as compared to 13.6±0.4% of 9:1 blend of 2E-:2Z-homofarnesal. The result of this experiment provides an opportunity to synthesize pheromone rich in 2Z-homofarnesals with less sophisticated and economically feasible Z-selective method to incorporate it in eco-friendly alternative of azuki bean beetle management.

Genetic Basis of Cry1F-Resistance in a Laboratory Selected Asian Corn Borer Strain and Its Cross-Resistance to Other Bacillus thuringiensis Toxins.

The Asian corn borer (ACB), Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae), is the most destructive insect pest of corn in China. Susceptibility to the Cry1F toxin derived from Bacillus thuringiensis has been demonstrated for ACB, suggesting the potential for Cry1F inclusion as part of an insect pest management program. Insects can develop resistance to Cry toxins, which threatens the development and use of Bt formulations and Bt crops in the field. To determine possible resistance mechanisms to Cry1F, a Cry1F-resistant colony of ACB (ACB-FR) that exhibited more than 1700-fold resistance was established through selection experiments after 49 generations of selection under laboratory conditions. The ACB-FR strain showed moderate cross-resistance to Cry1Ab and Cry1Ac of 22.8- and 26.9-fold, respectively, marginally cross-resistance to Cry1Ah (3.7-fold), and no cross-resistance to Cry1Ie (0.6-fold). The bioassay responses of progeny from reciprocal F1 crosses to different Cry1 toxin concentrations indicated that the resistance trait to Cry1Ab, Cry1Ac and Cry1F has autosomal inheritance with no maternal effect or sex linked. The effective dominance (h) of F1 offspring was calculated at different concentrations of Cry1F, showing that h decreased as concentration of Cry1F increased. Finally, the analysis of actual and expected mortality of the progeny from a backcross (F1 × resistant strain) indicated that the inheritance of the resistance to Cry1F in ACB-FR was due to more than one locus. The present study provides an understanding of the genetic basis of Cry1F resistance in ACB-FR and also shows that pyramiding Cry1F with Cry1Ah or Cry1Ie could be used as a strategy to delay the development of ACB resistance to Bt proteins.

DIETARY SILVER NANOPARTICLES REDUCE FITNESS IN A BENEFICIAL, BUT NOT PEST, INSECT SPECIES.

Silver nanoparticles (AgNPs) have antimicrobial and insecticidal properties and they have been considered for their potential use as insecticides. While they do, indeed, kill some insects, two broader issues have not been considered in a critical way. First, reports of insect-lethal AgNPs are often based on simplistic methods that yield nanoparticles of nonuniform shapes and sizes, leaving questions about the precise treatments test insects experienced. Second, we do not know how AgNPs influence beneficial insects. This work addresses these issues. We assessed the influence of AgNPs on life history parameters of two agricultural pest insect species, Heliothis virescens (tobacco budworm) and Trichoplusia ni (cabbage looper) and a beneficial predatory insect species, Podisus maculiventris (spined soldier bug), all of which act in agroecosystems. Rearing the two pest species on standard media amended with AgNPs led to negligible influence on developmental times, pupal weights, and adult emergence, however, they led to retarded development, reductions in adult weight and fecundity, and increased mortality in the predator. These negative effects on the beneficial species, if also true for other beneficial insect species, would have substantial negative implications for continued development of AgNPs for insect pest management programs.

Control of Codling Moth (Cydia pomonella) (Lepidoptera: Tortricidae) in South Africa with Special Emphasis on Using Entomopathogenic Nematodes

In the Western Cape province of South Africa, codling moth (Cydia pomonella) is the most important lepidopteran pest of apples and pears. Currently an integrated pest management (IPM) strategy is followed. However, chemical control still plays an important role in the control of this pest. Entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae have been successfully utilized as biological control agents in classical, conservation, and augmentative insect pest management programmes. In this review different biological control options for control of codling moth are considered, with special emphasis on research being done on the biological control of codling moth using EPNs. To integrate nematodes into an IPM system, it is important to conduct research under local environmental conditions for a specific crop. Application of EPNs against codling moth will target the diapausing larval overwintering population above-ground. Especially for commercial application, the unique environmental conditions in the various production areas need to be assessed to allow for the effective use of various EPN species. Orchard application, onto trees poses its own unique challenges with regard to the inundative application of EPNs. Research on the use of EPNs to control codling moth and obstacles encountered in the success of codling moth control are discussed.

An Eco-friendly Approach to Reduce Reproductive Attributes in the Housefly, Musca domestica L. using Crude Plant Extracts

As an alternative to chemical insecticides, plant extracts showing insecticidal properties are being increasingly used nowadays in insect pest management programs. With a view to an eco-friendly approach, here we report some bioactive properties of whole-plant boiled extracts of three indigenous plant species viz., Calotropis procera (Aiton), Piper longum L. and Polygonum hydropiper L., in a housefly model. Efficacies of the whole-plant aqueous extracts of three indigenous plant species viz., Calotropis procera (Aiton), Piper longum L. and Polygonum hydropiper L., have been assayed for control of the common housefly, Musca domestica L. Using bioassays against the 2nd instar larvae, the estimated LC50 values for the three plant extracts were 557.89μL, 981.02μL and 773.27μL, respectively, suggesting C. procera as the most effective plant under study. Data on vital reproductive attributes of the experimental flies revealed that the egg-laying and egg-hatch (P 0.05). Interestingly, C. procera extracts at higher concentrations yielded 21.54% deformed pupae and 11.76% deformed adults which failed to survive. Implications of these findings in terms of developing a plant-based bio-insecticide for M. domestica having eco-friendly, safer and economic benefits have been discussed.