Mean Larval Mortality Research Articles

In-vitro Study to Determine the Dose of Beauveria bassiana for Management of Spodoptera frugiperda

Pest insects known as fall army worm (Spodoptera frugiperda) can feed on over 80 different types of crops. It has the potential to significantly reduce the yields of major cereal crops including oats (Avena sativa L.). The oat crop is one of the preferred hosts of this pest. This fodder crop is directly used as animal feed so, chemical control of pests is not preferable. One of the alternatives for the management of fall army worm on fodder oats is the use of microbials which have some advantages over the use of chemical insecticides, as they are highly host specific with low environmental contamination. Beauveria bassiana is a fungus and can be used to control this pest. So, the present study was undertaken to standardize the dose of Beauveria bassiana for management of fall army worm. The virulence test was conducted against third instar larvae of S. frugiperda. The larvae were treated with three doses of B. bassiana of 1×1012spore/ml concentration i.e.,1, 2, and 3ml/L, by dipping them for 30 seconds in 10 ml of suspension. In case of control, larvae were treated with distilled water containing a drop of Tween- 80 (0.02%). At 24 hours after treatment, the differences in the mean larval mortality among different doses of B. bassiana were non-significant. However, at 48 and 72 hours after treatment, the differences in the mean larval mortality among different doses of B. bassiana were significant. Highest larval mortality was recorded at 48 and 72 hours after treatment in 3 ml/L (29.39 and 86.67%, respectively).

Contribution of a groundwater-influenced hinterland drainage system to the restoration of salmonid spawning grounds at the upper river Danube

Groundwater-influenced ditches, so called hinterland drainage systems (HDS), accompany many heavily modified water bodies (HMWBs). Herein, we evaluate the usefulness of including HDS as functional habitats in river restoration approaches by assessing their role as salmonid recruitment areas in HMWBs. We tested the functionality of spawning grounds in a groundwater-influenced HDS compared to the quality of those not influenced by groundwater (OHB 1 and OHB 2), based on bioindication using brown trout eggs. Eggs were placed in each compartment of a two-layered container of 20 cm diameter and 30 cm total depth (known as the HydroEcoSedimentary Tool or HEST) pre-filled with sediment, mimicking hyporheic conditions. A total of 81 HESTs were evenly distributed across the three sites to assess egg and larvae mortality whilst exposed at two substrate depths (5–10 cm and 17–22 cm). In addition, key physico-chemical variables such as dissolved oxygen, temperature, pH, turbidity, electric conductance and substratum composition were analyzed. Mean egg mortality in the HDS was 33% lower than in both non-groundwater-influenced spawning grounds, whereas mean larval mortality was highest in the HDS (95%) compared to 74% at OHB 1 and 66% at OHB 2. The exposure depth of eggs had a significant influence on mortality, with more dead eggs and larvae in the deeper substrate layers, most likely attributed to an increase of fine sediment and a decrease of oxygen availability over time. Particularly the HDS revealed high mortality rates of larvae since it had a 17% lower mean oxygen level compared to the other spawning grounds. These findings suggest that if additional measures such as substratum restoration were undertaken to increase oxygen availability within HDS, these groundwater-dominated ditches could be incorporated as part of an efficient river restoration strategy.

Susceptibility of Pre-adult Biological Stages of Mythimna separata (Walker) (Lepidoptera: Noctuidae) to Three Entomopathogenic Fungi (Hypocreales)

Armyworms are polyphagous insect pests of agricultural crops. Their population is usually managed below threshold level using insecticides. However, a single control measure is insufficient to attain a sustainable pest management. Hence, this research was conducted to assess the three species of entomopathogenic fungi as potential biological control agents against Mythimna separata (Walker) or paddy armyworm. Dose mortality assays were conducted to determine the pathogenicity of Beauveria bassiana (Bals.) Vuill., Metarhizium anisopliae (Metschn.) Sorokin, and Metarhizium rileyi (Farlow) Kepler, S.A. Rehner and Humber against various biological stages of M. separata including egg, 1st to 6th larval instars, prepupa, and pupa. These entomopathogenic fungi did not have ovicidal activity but affected the survivorship of the resulting neonates. Exposure of eggs to B. bassiana, M. anisopliae, and M. rileyi infected 64, 60, and 70 % of the resulting neonates, respectively. Adult emergence was also reduced in fungal-treated (29% in B. bassiana, 10% in M. anisopliae, and 10% in M. rileyi) as compared with 64% in control. At 7 d after treatment, M. rileyi applied at 1 x 105 to 1 x 109 conidia/mL was the most pathogenic causing a mean larval mortality of up to 70% as compared to B. bassiana and M. anisopliae with less than 10% mortality. Among the larval instars, the 1st, 2nd, and 3rd were the most susceptible to fungal infection. Conidial concentrations (1 x 108 and 1 x 109 conidia/mL) induced the highest larval mortalities as compared to the lower conidial concentrations (1 x 105 and 1 x 107 conidia/mL) of the entomopathogenic fungi. The prepupal and pupal stages were also slightly susceptible to the entomopathogenic fungi. These findings showed the pathogenic effect of the entomopathogenic fungi particularly M. rileyi to M. separata.

Uji Efektivitas Larvasida Ekstrak Daun Pegagan (Centella asiatica L. Urban) Terhadap Larva Culex quinquefasciatus

Culex quinquefasciatus is a vector of filariasis (elephantiasis) and Japanese encephalitis. Filariasis is still an unresolved disease in Indonesia. The use of temephos as a chemical larvicide repeatedly causes environmental pollution and is difficult to decompose, so the World Health Organization recommends looking for alternative effects. Gotu kola leaf extract contains metabolic substances such as steroids,saponins, flavonoids, phenolics that can be used as larvicides. This study aimed to determine the effectiveness of the larvicide extract of pegagan (Centella asiatica L. Urban) on the mortality of Culex quinquefasciatus larvae. This study used an experimental research design with a posttest only control group design using 4 concentration groups and 2 control groups, consisting of 4 repetitions in each, namely concentrations of 125 ppm, 250 ppm, 500 ppm, 1000 ppm, abate positive control and aquadest negative control. with the mean larval mortality was 31%, 65%, 81%, 98% which was observed for 48 hours. The number of larval deaths was analyzed using the Kruskall-Wallis test and logit analysis. The results of the analysis showed that pegagan leaf extract had an effect on the mortality of Culex quinquefasciatus larvae with a significant value (p < 0.05), then the results of logit regression analysis showed the LC50 value of 206.71 ppm. The conclusion of this study was that the leaf extract of pegagan (Centella asiatica L. Urban) was effective against the mortality of Culex quinquefasciatus larvae.

Uji Efektivitas Larvasida Ekstrak Daun Pegagan (Centella asiatica L. Urban) Terhadap Larva Culex quinquefasciatus

Culex quinquefasciatus is a vector of filariasis (elephantiasis) and Japanese encephalitis. Filariasis is still an unresolved disease in Indonesia. The use of temephos as a chemical larvicide repeatedly causes environmental pollution and is difficult to decompose, so the World Health Organization recommends looking for alternative effects. Gotu kola leaf extract contains metabolic substances such as steroids,saponins, flavonoids, phenolics that can be used as larvicides. This study aimed to determine the effectiveness of the larvicide extract of pegagan (Centella asiatica L. Urban) on the mortality of Culex quinquefasciatus larvae. This study used an experimental research design with a posttest only control group design using 4 concentration groups and 2 control groups, consisting of 4 repetitions in each, namely concentrations of 125 ppm, 250 ppm, 500 ppm, 1000 ppm, abate positive control and aquadest negative control. with the mean larval mortality was 31%, 65%, 81%, 98% which was observed for 48 hours. The number of larval deaths was analyzed using the Kruskall-Wallis test and logit analysis. The results of the analysis showed that pegagan leaf extract had an effect on the mortality of Culex quinquefasciatus larvae with a significant value (p < 0.05), then the results of logit regression analysis showed the LC50 value of 206.71 ppm. The conclusion of this study was that the leaf extract of pegagan (Centella asiatica L. Urban) was effective against the mortality of Culex quinquefasciatus larvae.

Characterization and Pathogenicity Test of Entomopathogenic Nematode Steinernema Species-Kalro

Entomopathogenic nematodes (EPNs) are worldwide soil-dwelling insect parasitic nematodes. They are potential pest bio-control agents a key component of Integrated Pest Management (IPM) programs. This study aimed to characterize and evaluate the pathogenicity of an EPN isolate from Kenya. The nematode was isolated from soils using insect bait technique and both morphological and molecular identification was performed. Efficacy of the isolate was evaluated against Tomato leafminer larvae (Tuta absoluta Meyrick.) using dose-based treatments of 0-control, 100, 150, 200, and 250 infective juveniles (IJs/ml). Morphological analysis revealed body length (L) of 835(659-987) µm and 1781 (1297-2097) µm from fresh IJs and males respectively. Males lacked a mucron. The isolate was characterized by the partial sequence length of 877 bp of the ITS region. Blastn results indicated the EPN isolate had a similarity match of 81-92% with Afro-tropical Steinernema species. It matched with Steinernema sp. (AY230186.1) from Kenya at 92% and Sri Lanka (AY230184.1). Phylogenetic analysis placed the isolate together with Steinernema sp. (AY230186.1) and (AY230184.1) with a bootstrap value of 100%. Maximum mean larval mortality (80%; 96%) was achieved 24 and 48 h post-treatment at concentration 150 IJs/ml. All nematode concentrations achieved over 50% mean mortality after 24 h period. There was a significant difference (P = 0.001) between doses 150 and 200 IJs/ml. From the study, it was concluded that the nematode isolate was Steinernema sp now referred to as Steinernema sp. Kalro (Genebank Accession MW151701). The EPN has the potential for development as a biological control agent against T. absoluta.

EVALUATION OF A NEW TRUCK-MOUNTED ULV SPRAYING MACHINE WITH BACILLUS THURINGIENSIS VAR. ISRAELENSIS AGAINST LARVAL CULEX QUINQUEFASCIATUS

A field study about the effectiveness of a new truck-mounted ultra-low-volume (ULV) machine against larval Culex quinquefasciatus Say was conducted at Anastasia Mosquito Control District of St. Johns County, St. Augustine, FL, during the summer of 2017. Cx. quinquefasciatus larvae were treated using a ground application at different concentrations of Bti using a new truck-mounted ULV sprayer with a horizontal nozzle. Mortality of larvae was recorded after 24 h, and droplet sizes were measured. Overall, Bti sprayed by the new truck-mounted ULV spraying machine at a concentration of 2.625 mg/L resulted in the highest mortality of mosquito larvae. The results indicate that the Bti concentrations of 0.875 mg/L and 0.065 mg/L resulted in a significant difference in mean larval mortality between each distance from the spray line (P < 0.05), while the mortality by the other 3 concentrations (0.477 mg/L, 2.625 mg/L, and 5.25 mg/L) tested did not. The LC50 and LC90 of Bti against larvae were 0.261 mg/L (0.239~0.286) and 1.687 mg/L (1.481~1.922), respectively. The coverage (swath) of the spray by the new ULV machine showed that the Bti could be sprayed at least 33 meters away with a 20 meter width. Therefore, the new truck-mounted ULV spraying machine with liquid Bti could be used to treat a large area effectively and efficiently and as an additional tool for the control of mosquito larvae.

Impact of conventional insecticides on two bollworms and their indirect effects on the ectoparasitoid, Bracon brevicornis (Wesmael) (Hymenoptera: Braconidae)

BackgroundCotton bollworms such as Pectinophora gossypiella and Earias insulana are serious pests which destroy the cotton plant, and Bracon brevicornis is a parasitoid which attacked the larvae of bollworms.ResultsIn this study, experiments were performed to investigate and evaluate the toxicity of etofenprox and chlorpyrifos insecticides against newly hatched larvae of Pectinophora gossypiella and Earias insulana. Some biological aspects of compound effects on larval and pupal duration, percentage of mortality, and percentage of adult emergence which resulted from treated newly hatched larvae were studied. The results revealed that LC50 was 0.7 and 0.87 ppm when P. gossypiella was treated with etofenprox and chlorpyrifos, respectively, while LC50 was 0.09 and 0.73 ppm when E. insulana was treated with etofenprox and chlorpyrifos, respectively. The obtained results showed that the percentage of mean larval mortality was 65.0 and 63.0% for treated P. gossypiella, while it was 71.0 and 66.0% for treated E. insulana. The corresponding figure for pupal percentage mortality was 8.0 and 10.0% for treated P. gossypiella, but it was 5.0 and 2.0% for treated E. insulana, with etofenprox and chlorpyrifos, and a prolongation effect in larval and pupal development (total immature stage) resulted from treated both bollworms as follows: 35.5 and 32.4 days for treated P. gossypiella compared with 21.9 days in control and 34.7 and 23.2 days for treated E. insulana compared with 23.1 days in control. The indirect effect of etofenprox and chlorpyrifos on the total immature stage of Bracon brevicornis was 18.2 and 19.5 days compared with 14.3 days in control when B. brevicornis parasitized on P. gossypiella larvae while it was 19.8 and 20.6 days compared with 15.2 days when B. brevicornis parasitized on E. insulana larvae.ConclusionThe life cycle of B. brevicornis after parasitism on P. gossypiella and E. insulana larvae treated with etofenprox and chlorpyrifos were increased than the control larvae.

Bio-efficacy of Heterorhabditis bacteriophora (Rhabditida: Heterorhabditidae) against serpentine leafminer, Liriomyza trifolii Burgess (Diptera: Agromyzidae) in oilseed crops

Virulence and efficacy of Entomopathogenic Nematode (EPN), Heterorhabditis bacteriophora was tested against late instar larva of serpentine leafminer , Liriomyza trifoli i, under laboratory conditions. Five different Infective Juvenile (IJs) concentrations (10, 30, 50, 70 and 100 IJ larva -1 ) were used. The highest mortality rate caused by H. bacteriophora is 65.1% at 24 hours and 73.8% at 48 hours post inoculation at an inoculation concentration of 100 IJ larva -1 . The minimum concentration of 30 IJs per larva shown 37.1% and 52.2% mean larval mortality at 24 and 48 hours post inoculation, respectively. The virulence of H. bacteriophora (LC 50 ) was established at 54 IJs at 24 hours and 37.8 IJs at 48 hours for killing 50% of the larvae tested. The results of this study revealed the potential and scope of EPNs for their utilization in management of L. trifolii in oilseed crops.

Essential oil in management of coconut rhinoceros beetle Oryctes rhinoceros L.

Plant derived essential oil is used as a component in management of coconut rhinoceros beetle Oryctes rhinoceros L. (Coleoptera: Scarabaeidae). A study was undertaken to evaluate the bioefficacy of essential oil from Ocimum basilicum, Eucalyptus citriodora, Trachyspermum ammi and their major constituent thymolin for management of O. rhinoceros. These essential oils derived from plant parts were characterized and their physiological response and biocidal activity was determined. Basil, citriodora, ajowan oil and thymol caused electrophysiological response in the antennae of O. rhinoceros adults. Behavioural response of beetles was tested in‘Y’ tube olfactometer having a choice between odour arm containing essential oil and control arm having zero air. Orientation of beetles to essential oil laden arm ranged from 15–30%. Over 70–85% of the beetles moved towards the control arm. Citriodora and basil oil inhibited hatching of 70% of eggs and also caused larval mortality. The mean larval mortality ranged from 61–66%. The repellence, ovicidal and growth regulating effect of essential oil offers an ecofriendly option in management of coconut rhinoceros beetle.

Potential of entomopathogenic nematodes of the genus Heterorhabditis for the control of Stomoxys calcitrans (Diptera: Muscidae).

The present study verified the pathogenic potential of entomopathogenic nematodes (EPNs) of the genus Heterorhabditis (Heterorhabditis bacteriophora, isolate HP88 and Heterorhabditis baujardi isolate LPP7) to immature stages of Stomoxys calcitrans in the laboratory. All EPN concentrations of the H. bacteriophora HP88 strain caused mean larval mortality greater than 90% after four days. Higher concentrations of the H. baujardi LPP7 isolate (≥50 EPNs/larva) eliminated more than 70% of larvae after six days with the concentration 200 EPNs/larva reaching mortality levels of 93.3%. The larval mortality at all concentrations of EPNs (25, 50, 100, 150, and 200 EPNs/larva) for both strains was significant (p<0.05) when compared to the respective control groups. Concentrations of H. bacteriophora HP88 yielded an LC50 of 0.36 EPN/larva and LC90 of 29.1; while H. baujardi LPP7 yielded an LC50 of 39.85 and LC90 of 239.18. H. bacteriophora HP88 provided greater inhibition of the emergence of adults when compared to the response obtained with H. baujardi LPP7. EPNs did not cause considerable mortality when applied directly to pupae. The set of observed results suggests that the EPNs of the genus Heterorhabditis, isolates HP88 and LPP7, are a promising alternative in the control of the stable fly.

Impact of certain bio-pesticides on larval mortality of Helicoverpa armigera hübner (Noctuidae: Lepidoptera) in chickpea

Impact of certain bio-pesticides and insecticide on larval mortality of Helicoverpa armigera were evaluated under chickpea field conditions during 2010-11 and 2011-12. In all experiments, observations were undertaken on larval mortality of the pest after 1st, 3rd, 5th, 7th, and 14th days of pesticide application. Thereafter, it was concluded that after 3rd to 14th days, all treatments were found superior over the untreated control (0.0%). Under independent and interactive studies, data received after 14th days of treatments revealed that Btk (1.25 kg), HaNPV (350 LE), HaNPV (125 LE) + Btk (0.5 kg), Btk (0.5 kg) + Quinalphos (0.02%) were observed with the highest mean larval mortality as 93.33%. Btk (1.25 kg) proved its highest efficacy with similar potency (93.33%) in both the years. Whereas, Azadirachtin (0.05%) was registered with the lowest mean larval mortality as 33.33%.

Determination of Optimum Eri Silkworm Larvae Population Density in Feeding Tray using Shelf Rearing Technique

Population density during the different stages of larval growth and development is one of the crucial issues for successful commercial cocoon crop of silkworms. Using appropriate population density ensures the hygiene of silkworms in order to protect from disease infection and to ensure them good feeding appetite. Different stages of silkworm larvae require different population density or bed space during their growing period in the rearing bed. As worms increase in size, there is overcrowding and overlapping each other that leads to underfeeding, creating a microclimate for disease spread and could also lead to suffocation. Hence, appropriate bed spacing is essential to silkworm larvae, to keep them healthy and productive. The treatments used for examining the appropriate population density of young and medium aged silkworm larvae were 1200, 1000, 800, 600, 400 and 200 per feeding tray (60cm X 90cm size). Another arrangement of population density used for examining the mature aged silkworm larvae were 600, 500, 400, 300, 200 and 100 per feeding tray (60cm X 90cm size) using silkworm shelf rearing technique to evaluate the effects of population density on different larval stages eri silkworm strains. 1 st and 2 nd larval instars/stages as young age, 3 rd and 4 th larval instars as medium age, 5 th larval instar as mature age were considered in the study. Observations on larval mortality, single larval weight, single shell weight, and silk ratio from different eri silkworm strains were carefully noted for each treatment and replications. Three replications were used for each treatment. Statistically significant variation in mean larval mortality rate among population densities was observed in young, medium and mature silkworm larval stages of silkworm strains. Larval mortality rate was significantly reduced when young, medium and mature larval stages of castor feeding eri silkworm strains (Indian eri and Vietnamese eri) reared in a group of 400 to 800 worms, 400 to 600 worms and 300 to 400 worms respectively in a 60 cm X 90 cm feeding tray of shelf rearing method. Bigger Larval weight, bigger shell weight and higher percentage of silk ratio are important cocoon yield quality parameters for silkworm strains. Significant (P < 0.05) variations were observed among population densities for these important variables in all the tested eri silkworm strains. Keywords : Population density, silkworm strains, feeding tray, larval instars, larval mortality, shell weight, silk ratio

Quantitative genetic analysis of Cry1Ab tolerance in Ostrinia nubilalis Spanish populations

Tolerance to Bacillus thuringiensis Cry1Ab toxin in Spanish Ostrinia nubilalis populations was analyzed by quantitative genetic techniques, using isolines established from field-derived insects. F1 offspring was tested for susceptibility to trypsin activated Cry1Ab using a concentration that caused a mean larval mortality of 87% (±17% SD). The progeny of the most tolerant isolines (that had shown mortalities lower than 60%) was crossed to obtain the F2 generation that was exposed to the same Cry1Ab concentration. A clear reduction in mortality (62±17% SD) was observed. The upper limit for heritability was estimated to range between 0.82 and 0.90, suggesting that a high part of phenotypic variation in tolerance to Cry1Ab was attributable to genetic differences. An estimate of the minimum number of segregating factors indicated that the loci involved in tolerance to Cry1Ab were at least two. The role of the cadherin gene, which is a B. thuringiensis resistance gene in Lepidoptera, was assessed in the most tolerant isolines by using an EPIC-PCR marker specifically developed for this study. Association between cadherin and tolerance was obtained in one tolerant isoline; however it could be not confirmed by segregation analysis in the F2 progeny because F2 offspring was not viable. Our results indicate that the tolerance trait is common in Spanish field populations. Quantitative genetic techniques may be helpful for estimating the influence of genetic factors to Cry1Ab tolerance in O. nubilalis.

Studies on the influence of temperature and humidity on biological traits of silkworm ( Bombyx mori L.; Bombycidae)

Impact of variations in temperature and humidity on pupation, hatchability and larval mortality of eleven inbred silkworm lines M-101, M-103, M-104, M-107, Pak-1, Pak-2, Pak-3, Pak-4, PFI-I, PFI-II and S-1 was investigated during autumn and spring, 2007-2008 at Sericulture Research Laboratory, Lahore. The experiment was laid out in factorial design with replications and the data was pooled over season. The larvae of 4 th and 5 th instar were exposed to three temperature regimes (25, 30 and 35 ± 1°C). Significant variations in hatchability, pupation and mortality were noticed due to the effect of temperature and relative humidity on 4 th and 5 th instar larvae of inbred silkworm lines. The maximum mean values of hatchability (93.15), pupation (93.12) and the lowest mean larval mortality (2.60) was observed at 25°C and 70-80% RH. Lower RH of (55 and 65%) even at 25°C lowered the hatchability and pupation of the silkworm lines and contributed significantly in higher larval mortality. The lowest mean value of hatchability (68.96) and pupation (76.55) was recorded at 35°C and 55% RH while highest larval mortality (11.92) was noticed at 35°C with 55% RH. The results indicate that the mean performance of inbred silkworm lines under various conditions of temperature and humidity was significantly different from each other at various temperature and humidity exposures during 4th and 5th instar. At 25°C with 75% RH, the performance of silkworm lines remained consistent but variations in temperature or humidity for three hours significantly affected all three parameters (hatchability, pupation and larval mortality). The results illustrate that hatchability percentage of M-101(84.98), Pak-2 (84.52), Pak-3 (84.32) and Pak-4 (84.05) and pupation rate of Pak-4 (86.60), Pak-2 (86.08), PFI-I (85.33) and M-101(84.88) was significantly better as compared to other silkworm lines. The mean values of larval mortality observed in Pak-2 (5.56), Pak-3 (5.76), PFI-I (6.03) and M-107 (6.20) showed significantly lower mortality. The lower relative humidity level (less than 65%) is not conducive for seed cocoon production even at the optimum temperature of 25°C. The study clearly underlines the importance of optimization of environmental conditions during larval rearing in relation to seed cocoon production. The investigations strongly recommend that temperature and relative humidity in the range of 25-26°C and 70-80% respectively are mandatory for excellent results of egg hatchability, pupation and survival rate (low larval mortality). The results also emphasize that Pak-2, Pak-3, Pak-4, PFI-I, M-101 and M-107 showed better potential for seed production and commercial exploitation. Key words: Sericulture Pakistan, silkworm rearing.

Assessment of plant extracts fortified with Bacillus thuringiensis (Bacillales: Bacillaceae) for management of Spodoptera litura (Lepidoptera: Noctuidae)

Combinations of Bacillus thuringiensis subsp. kurstaki (Btk) and some plant extracts, namely Acacia arabica (Lam.) Willd., Annona squamosa L., Datura stramonium L., Eucalyptus globulus (Labille), Ipomoea carnea Jacq., Lantana camara L., Nicotiana tabacum L. and Pongamia pinnata (L.) Pierre, were studied for their efficacy and synergistic activity against Spodoptera litura (Fab.) larvae. D. stramonium seed extract fortified with Btk recorded highest mean larval mortality of 74.7%, followed by 61% with A. arabica seed extract, 54.4% with N. tabacum leaf extract and 53% with A. squamosa seed extract. Combination of A. arabica seed extract at 25% concentration and Btk resulted in considerable mortality within 24 h. All Btk fortified extracts caused higher larval mortality than with Btk alone, indicating synergistic action except for the A. arabica leaf extract and Btk combination, which showed antagonistic effect.

Laboratory Colonization of &lt;I&gt;Anopheles aquasalis&lt;/I&gt; (Diptera: Culicidae) in Belém, Pará, Brazil

Anopheles aquasalis Curry, a coastal malaria vector with a Neotropical distribution, was collected from Belém, Pará state, Brazil, and 500 adults per cage were maintained at the Instituto Evandro Chagas insectary at 26 -30 degrees C and 80 -90% RH, where they fed on a 10% domestic sugar solution and blood from white mice. Oviposition of the parental generation (P) occurred in fresh water in dark cups introduced into mosquito cages. After eclosion, 100 larvae per pan were reared in artesian well water (salinity 0.04 g liter(-10) and fed ground fish food until pupation. After force mating in the F1 generation, the eight subsequent generations were free mating. Mean larval mortality was < 1%, and the mean developmental time from eclosion to emergence was 7.7 d (F1), 7.6 d (F2), 8 d (F3), and 7.5 d (F4). The maximum daily production of pupae (from the fourth generation on) occurred on day 6 postoviposition.

Laboratory Colonization of Anopheles aquasalis (Diptera: Culicidae) in Belém, Pará, Brazil

Anopheles aquasalis Curry, a coastal malaria vector with a Neotropical distribution, was collected from Belém, Pará state, Brazil, and 500 adults per cage were maintained at the Instituto Evandro Chagas insectary at 26–30°C and 80–90% RH, where they fed on a 10% domestic sugar solution and blood from white mice. Oviposition of the parental generation (P) occurred in fresh water in dark cups introduced into mosquito cages. After eclosion, 100 larvae per pan were reared in artesian well water (salinity 0.04 g liter-1) and fed ground fish food until pupation. After force mating in the F1 generation, the eight subsequent generations were free mating. Mean larval mortality was <1%, and the mean developmental time from eclosion to emergence was 7.7 d (F1), 7.6 d (F2), 8 d (F3), and 7.5 d (F4). The maximum daily production of pupae (from the fourth generation on) occurred on day 6 postoviposition.

Influence of Production and Bioassay Methods on Infectivity of Two Ambush Foragers (Nematoda: Steinernematidae)

The influence of production and bioassay methods on infectivity of two ambush foragers,Steinernema carpocapsaeandSteinernema scapterisci,was evaluated. Both species were mass-producedin vitroin liquid culture andin vivousing live insects:S. carpocapsaein last instar wax mothGalleria mellonellalarvae andS. scapterisciin adult house cricketsAcheta domesticus.Infectivity was assessed at 28°C against last-instarG. mellonellalarvae using a filter-paper bioassay and a newly developed “sand-well” bioassay. The infectivity ofS. carpocapsaewas not influenced by the method of production or bioassay, whereas the infectivity ofS. scapterisciwas influenced by both factors. Bothin vivoandin vitroproducedS. carpocapsaecaused >60% larval mortality at one nematode per larva (1:1) in the filter-paper bioassay, butS. scapteriscielicited less than 10% mortality. At 50 nematodes per larva,in vitro S. scapteriscicaused 41.7% mean larval mortality in the filter-paper bioassay, whereasin vivo S. scapteriscielicited only 28.5% mortality. The replacement of filter paper with a 2.5-mm-deep layer of sand (termed sand well) resulted in 2.5-fold increase in infectivity ofS. scapterisci.In the new sand-well procedure, 15S. scapterisciper larva (15:1) caused an overall mean larval mortality of 47.5% and the pattern of mortality showed a normal distribution. The infectivity ofS. carpocapsaewas not different in the 1:1 filter paper or 1:1 sand-well bioassay. These results demonstrate that nematode infectivity could be strongly influenced by both the production and bioassay methods, and there are no universal assays even when nematodes have similar foraging strategies.

Effects of Entomopathogenic Nematode Species, Rate, Soil Moisture, and Bacteria on Control of Japanese Beetle (Coleoptera: Scarabaeidae) Larvae in the Laboratory

Several strains or species of entomopathogenic nematodes, Steinernema Carpocapsae Weiser (All and Mexican strains), S. feltiae (=bibionis) (Filipjev) (Biosys #27), S. glaseri (Steiner) (Biosys #2), and Heterorhabditis bacteriophora (= heliothidis) Poinar (HP88 and Cl strains) were tested in the laboratory for their effect on larvae of Japanese beetle, Popillia japonica Newman. Mean larval mortality ranged from 17.8 to 99.4% depending upon nematode strain and rate of application. S. glaseri caused a greater percentage of mortality of P. japonica larvae than any other species or strain of nematode tested. No interactions between nematode strains, application rates, and soil moisture were significant. Larval mortality generally increased with increased nematode rates. In separate experiments, nematode symbiotic bacteria, Xenorhabdus luminescens Thomas & Poinar, X. nematophilus (Poinar & Thomas), and X. poinarii (Akhurst) were injected into Galleria mellonella (L.) and P. japonica larvae to determine pathogenicity. X. luminescens was the most pathogenic bacterium to both species, followed closely by X. nematophilus. X. poinarii demonstrated low pathogenicity to both insect species.