Functional Response of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) to Sugarcane Whitefly Aleurolobus barodensis (Maskell) in Laboratory Conditions

A functional response study of Chrysoperla carnea (Stephens) larvae to different densities of sugar cane whitefly Aleurolobus barodensis (Maskell) was conducted in test tubes at 26?±?2 °C, 65?±?5 % RH. Chrysoperla carnea showed two different types of functional response in larval instars. First instar exhibits type II. However, second and third larval instars revealed type III functional response. Based on modified Holling’s disk equation, the highest searching rates (a) of 0.82?±?0.0247 h^?1 was found for first instar larva. For second and third larval instars, the attack coefficient (b) were 0.002?±?0.030 and 0.0025?±?0.0424 respectively. The shortest handling time (T_h) per prey was observed at third instar stage (1.574?±?0.0568 h) followed by second and first instar with 1.72?±?0.0411 h and 1.919?±?0.0568 h respectively.     

Comparative bioassay of different isolates of Bacillus thuringiensis subsp. kurstaki on the third larval instars of diamondback moth,Plutella xylostella (L.) (Lep.: Plutellidae)

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, this insect has been a serious pest for cabbage fields in Tehran province. Resistance of P. xylostella to all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported up to now. According to many researchers, to eliminate the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. In line with this, the uses of microbial control agents (MCAs) are discussed. The bacterium, Bacillus thuringiensis (Bt) is one of microbial control agents of pests. It is characterised by its ability to produce proteic crystalline inclusions during sporulation. Cry1 protein has insecticidal activity and is highly specific to certain insects and not toxic to unrelated insects, plants or vertebrates. In this work, the pathogenicity of some Bt isolates, including Dipel, 20, 29, 79 and 87, was tested against P. xylostella and the lethal concentrations (LC₅₀) of their crystal proteins to P. xylostella third larval instar was determined. The experiment was designed in factorial in randomised complete design with 5 treatments (different concentrations including 10⁴, 10⁵, 10⁶, 10⁷, 10⁸ CFU/ml and 5 replications and with 10 third larval instars. Spore–crystal complex was applied to the surface of natural diets (cabbage leaves) and the mortality of P. xylostella larvae was assessed 120?h after exposure of Bt toxin in each treatment. Results showed that percentage of survival was significantly higher for control treatment. Results also showed that after 5?days, LC₅₀ for isolates of Dipel, 20, 29, 79 and 87 were equal to 1?×?10⁶, 1?×?10⁵, 5?×?10⁵, 4?×?10⁵ and 1?×?10⁴ CFU/ml, respectively. LT₅₀ were equal to 93.71, 48.04, 71, 40.49 and 75.28?h. Of and most the percentage larval mortality relate to attendance 87 and also at least percentage mortality is related to the groom Dipel.     

Effect of dose of cytoplasmic polyhedrosis virus on infection,mortality, development rate,and larval and pupal weights of the pink bollworm

Host-pathogen relationships were studied between the pink bollworm, Pectinophora gossypiella, and a cytoplasmic polyhedrosis virus (CPV). Results showed that the median effective dose (ED₅₀), the dose that infects half the test subjects, was 1.91 × 10² polyhedral inclusion bodies (PIB)/ml of diet. The median lethal dose (LD₅₀) was 1.72 × 10⁵ PIB/ml. Diagnosis for CPV infection was more reliable in adult pink bollworms than in late-instar larvae. Duration of the larval stage increased with viral dose, but duration of the pupal stage was not affected by CPV. Weights of infected male and female pupae were 23.7 and 24.0% less than those of untreated pupae, respectively. Pupal weights were not significantly influenced by increases in the viral dose. Weights of larvae of a given age decreased as dose increased. The effect of CPV on duration of the immature stages and on pupal weight was not significantly influenced by rearing temperatures between 25.0° and 32.5°C. Pupal weight of infected pink bollworms decreased as the duration of the larval stage increased.     

Pathogenicity of Beauveria bassiana isolated from Moroccan Argan forests soil against larvae of Ceratitis capitata (Diptera: Tephritidae) in laboratory conditions

The Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), is the major tephritid pest in Morocco. This pest survives in Moroccan forests Argania spinosa and continually invades the nearest agricultural areas. Entomopathogenic fungi are an interesting tool for fruit fly control and hold a useful alternative to conventional insecticides. However, primary selection of effective pathogens should be taken in laboratory condition prior to applying them in the field. Here, we used third late instar larvae of C. capitata to investigate the effectiveness of 15 local Beauveria bassiana isolates. Results showed that all isolates were able to infect the larval stage, producing a large mortality rate in puparia ranging from 65 to 95 % and caused significant reduction in adult emergence. The fungal treatments revealed that the mycosis occurred also in adults escaping infection as pupariating larvae. The percentage of mycosed puparia was highest in strain TAM6.2 (95 %) followed by ERS4.16 (90 %), therefore they were the most virulent. Median lethal concentration (LC₅₀) was studied for five isolates at four concentrations ranging from 10⁵ to 10⁸ conidia ml^?1. The results showed that the slopes of regression lines for B. bassiana ERS4.16 (slope = 0.386) and TAM6.2 (slope = 0.41) were the most important and had the lowest LC₅₀ values (2.85 × 10³ and 3.16 × 10³ conidia ml^?1 respectively). This investigation suggests that the soil of Argan forests contains pathogenic B. bassiana isolates and highlights for the first time their potential as biological control toward C. capitata larval stage in Morocco.     

Life table of Gaeolaelaps aculeifer (Acari: Laelapidae) feeding on larvae of Lycoriella auripila (Diptera: Sciaridae) with stage-specific estimates of consumption

Gaeolaelaps aculeifer (Canestrini, 1883) is a soil-dwelling predatory mite with potential for use as a biological control agent of fungus gnats (Diptera: Sciaridae) in mushroom production. The life table, predation rate and population growth rate of G. aculeifer on a diet of larvae of the sciarid fly, Lycoriella auripila, at 23?±?1°C, 60?±?5% RH and a photoperiod of 0:24 (L:D)?h was investigated. The results revealed that the duration of egg, larva, protonymph, deutonymph, females and males of G. aculeifer were 3.8?±?0.1, 1.4?±?0.1, 3.9?±?0.1, 4.1?±?0.1, 67.7?±?2.8 and 60.3?±?3.1 days, respectively. Net reproductive rate (R₀) was 54.8?±?7.1 offspring, intrinsic rate of increase (r) was 0.12?±?0.01 offspring day^?1, finite rate of increase (λ) was 1.13?±?0.01 day^?1and mean generation time (T) was 32.3?±?0.6 days. The predator consumed a mean of 0.08?±?0.05, 1.73?±?0.18, 3.16?±?0.28 and 75.9?±?7.1 third instar L. auripila larvae during the larval (1.3?±?0.1 days), protonymph (3.9?±?0.1 days), deutonymph (4.1?±?0.1 days) and adult (52.6?±?2.2 days) stages. Population parameters and consumption rates suggest that G. aculeifer has good potential as a biological control agent of L. auripila in mushroom production.     

Pine processionary moth (Thaumetopoea pityocampa,Lepidoptera: Thaumetopoeidae) larvae are highly susceptible to the entomopathogenic fungi Metarhizium brunneum and Beauveria bassiana

The larvae of the pine processionary moth (PPM), Thaumetopoea pityocampa, feed on the needles of pine and cedar. The urticating hairs of older instars pose a threat to human and animal health. Strains of the entomopathogenic fungi, Metarhizium brunneum (V275, ARSEF 4556) and Beauveria bassiana (KTU-24), were assayed against first to fourth instar T. pityocampa using doses ranging from 1?×?10⁵ to 1?×?10⁸ conidia mL^?1. The three strains differed slightly in their virulence but caused 100% mortality of all instars at the highest dose. The newly emerged or first instar larvae were extremely susceptible with 100% mortality being achieved 2–4 days post inoculation with V275 at all but the lowest dose. The fourth instar larvae appeared to be less susceptible than earlier instars. There was good horizontal transmission of conidia from treated to un-inoculated larvae. However, mortality was higher in third and fourth instars and where the ratio of inoculated versus untreated larvae was high. This we presume is due to spores being more readily trapped by the urticating hairs found on third and older instar larvae. Injection of the nests offers a simple and environmentally friendly way of controlling the pest with reduced risk to operators.     

Toxicity of Chemically Spiked Sediment to the Carpet Shell Clam Ruditapes decussatus Embryos and Larvae

The objective of this research was to assess the toxicity of sediment contaminated with cadmium, DDT, chlorpyrifos, and fluoranthene to embryos and larvae of the European clam Ruditapes decussatus, exposed to two sediment fractions, the whole sediment and elutriate. The percentages of abnormal D-shaped larvae and larval mortality have been investigated. The median effective concentration (EC50) values, reducing 50% of the percentage of D-shaped larvae, in whole sediments and elutriates were, respectively, 1.17 mg/kg and 417.1 μgl^?1 (3.71 μM) for cadmium, 1.66 mg/kg and 97.8 μgl^?1 (0.48 μM) for fluoranthene, 1.71 mg/kg and 384.8 μgl^?1 (1.08 μM) for DDT, and 0.96 mg/kg and 339.5 μgl^?1 (0.96 μM) for chlorpyrifos. The 96h-median lethal concentrations (LC50) reducing larval survival by 50% were 4.04 mg/kg 654.3 μgl^?1 (5.82 μM) for cadmium, 17.41 mg/kg 8666.6 μgl^?1 (42.84 μM) for fluoranthene, 3.93 mg/kg and 457.4 μgl^?1 (1.29 μM) for DDT, and 2.53 mg/kg and 308.06 μgl^?1 (0.87 μM) for chlorpyrifos. Based on EC₅₀ and LC₅₀ comparisons to toxicity data for other marine species, these findings suggest that the R. decussatus embryotoxicity and larvae mortality bioassay were among the most sensitive tools for sediment quality assessment.     

Insecticidal efficacy of two isolates of Beauveria bassiana (Bals.) (Vuill.), on the second larval stage of Leptinotarsa decemlineata (Say) (Col.: Chrysomelidae)

Leptinotarsa decemlineata is a serious potato pest throughout the world that has developed resistance to many insecticides. This study investigated the virulence of two indigenous isolates of Beauveria bassiana, consisting of DEBI007 and IR1217C. Five different concentrations of each isolate, 1 × 10⁷, 3.1 × 10⁷, 1 × 10⁸, 3.1 × 10⁸ and 1 × 10⁹ conidia ml^?1, were applied in bioassay using dipping method on second instar larvae. Control insects were treated with distilled water containing 0.01% Tween-80 (Sigma, Germany) as surfactant. The results showed that mortality percentages due to DEBI007 and IR1217C isolates in the highest concentration were 60% and 57.77%, respectively. There was a significant difference between efficacies of different conidial concentrations; therefore, with rise in conidial concentration, the mortality percentage was increased. The DEBI007 isolate that was previously isolated from the soil was more effective than IR1217C isolate. Calculated LC₅₀ for this effective isolate was 1.4 × 10⁷ conidia ml^?1, which, respectively, is the highest concentration.     

Evaluation of a granular formulation containing Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) microsclerotia in controlling eggs of Aedes aegypti (Diptera: Culicidae)

We evaluated the potential of a granular formulation of Metarhizium brunneum F52 containing microsclerotia (MbMSc granules) for control of Aedes aegypti by targeting eggs. MbMSc granules produced infective conidia within 14 days after application to 2.5?g moist potting soil, producing 5.9?×?10⁵, 2.08?×?10⁶ and 6.85?×?10⁶ conidia from 1, 5 and 25?mg MbMSc granules, respectively. Application of MbMSc triggered premature eclosion of eggs (EC_50?=?12?mg) with percentages as high as 31?±?2.9% and 67?±?4.3% of the eggs treated with 5 and 25?mg MbMSc granules, respectively, after 14 days on moist filter paper. Premature eclosion of eggs started at 3 days subsequent to MbMSc granule application and survival of larvae was significantly reduced for granule treated eggs (74?±?2.2%, 39?±?2.0% and 23?±?4.9% larvae survived for 1, 5 and 25?mg granule treatments, respectively, EC₅₀?=?4.9?mg). When MbMSc granules were applied in moist potting soil with mosquito eggs, rates of 1, 5 and 25?mg of MbMSc granules significantly reduced adult emergence with only 81?±?2.1%, 47?±?1.9%, and 34?±?2.1% emergence, respectively (EC₅₀?=?7?mg). Eggs treated with increasing concentrations of fungal conidia enhanced premature eclosion of eggs with an EC₅₀?=?1.6?×?10⁶ conidia/mL. Our results demonstrate that MbMSc granules are a promising candidate for control of A. aegypti and that fermentative production of Mb F52 microsclerotia as the active propagule has the potential for use for mosquito control.     

Host-age-dependent parasitism and reproductive success of Apanteles stantoni (Hymenoptera: Braconidae), a larval parasitoid of Diaphania indica (Lepidoptera: Pyralidae)

The relative suitability of five instars of Diaphania indica (Saunders) (Lepidoptera: Pyralidae) as a substrate for the development of a larval parasitoid, Apanteles stantoni Ashmead (Hymenoptera: Braconidae), was investigated. Maximum parasitism (22.25?±?1.21%) under laboratory conditions was observed in the early larval instars. The highest parasitoid emergence was recorded from the second (86.07?±?0.70%) and third (98.93?±?0.72%) instar larvae of D. indica, and that from the first larvae was 71.43?±?1.18%. The number of cocoons in each cluster, length and width of single cocoons, percentage emergence, sex ratio and adult longevity of A. stantoni collected from different instars of D. indica were also recorded. These results indicated that the life stage of the host when the parasitoid larvae complete their final instar is particularly important for their development. Therefore, considering the efficiency of parasitism and reproduction, the second-instar larvae of D. indica is the most suitable stage for mass rearing A. stantoni in the laboratory.     

Larval metamorphosis of the mussel Mytilus galloprovincialis Lamarck, 1819 in response to neurotransmitter blockers and tetraethylammonium

The metamorphic response of pediveliger larvae of Mytilus galloprovincialis to the neurotransmitter blockers chlorpromazine, amitriptyline, rauwolscine, idazoxan, atenolol and butoxamine, and to tetraethylammonium chloride (TEA) was investigated through a series of bioassays. Chlorpromazine, amitriptyline and idazoxin inhibited larval metamorphosis induced by 10^?4 M epinephrine. The concentration that inhibited metamorphosis by 50% (IC₅₀) for chlorpromazine and amitriptyline was 1.6 × 10^?6 M and 6.6 × 10^?5 M, respectively. Idazoxan was less effective with an IC₅₀ of 4.4 × 10¹³ M. Moreover, these three inhibitors showed no toxicity at any of the concentrations tested. The larval metamorphic response to K⁺ was not inhibited by 10^?3 M tetraethylammonium chloride after 96 h. Thus, the neurotransmitter blockers chlorpromazine and amitriptyline are inhibitors of larval metamorphosis, and will be useful tools for antifouling studies.     

Biological activity of Hyposidra talaca nucleopolyhedrovirus against all instar stages of a destructive tea pest Hyposidra talaca (Lepidoptera: Geometridae) in India

Hyposidra talaca (Walker) (Lepidoptera: Geometridae) is the most harmful pest of northeastern tea hub of India that devastates the tea production by feasting on the tea leaves. Hyposidra talaca nucleopolyhedrovirus (HytaNPV) is a natural enemy of the aforesaid pest, as it poses great obstruction in the multiplication of the pest by causing significant larval mortality. The study was undertaken to screen the virus activity against first to fifth instar H. talaca larvae. Early instar stages are found more susceptible than the late stages as they tend to reflect highest LC₅₀ value for fifth instar as 4.3 × 10⁷ POB/ml and lowest LC₅₀ value for first instar as 7 × 10⁴ POB/ml within seven days of inoculation. LT₅₀ values vary between 2.47 and 8.45 days for neonates to fifth instar. The high record of virulence of HytaNPV indicates its bright prospect as a useful microbial biopesticide.     

Potency of Bacillus thuringiensis and Bacillus subtilis against the cotton leafworm,Spodoptera littoralis (Bosid.) Larvae

The biological activities of two species of bacteria isolated from soil of cotton fields identified as Bacillus subtilis strain NRC313 (BS NRC313) and Bacillus thuringiensis strain NRC335 (BT NRC335) were evaluated against the third larval instar of the cotton leafworm, Spodoptera littoralis (Boisd.). The different entomopathogenic bacteria of BS NRC313and BT NRC335 contained 10 × 10⁸ cell/ml, and caused mortality of 100 and 97.3% for the above mentioned strains, respectively. Concentrations of 2.5 × 10⁸ to 10 × 10⁸ cell/ml of strains BS NRC313 and BT NRC335 were applied to the larvae: LC₅₀ were 3.3 × 10⁸ and 3.9 × 10⁸ cell/ml respectively. The influence of exposure to toxin concentrations manifested in terms of decreasing the adult emergence and prolongation of the generation period. The percentage of larvae that survived and succeeded to pupate increased by decreasing the concentration. The longevity of adult emergence that resulted from larvae treated with Bacillus subtilis were 6.0 ± 0.51 and 9.0 ± 0.63 days at 5 × 10⁸ and 2.5 × 10⁸ cell/ml, respectively compared with 9.8 ± 0.47 in control. The results indicated that Bacillus subtilis was more potent than Bacillus thuringiensis. Field applications of B. thuringiensis, B. subtilis and Reldan achieved 55.6, 67.4 and 89.4% reduction of the cotton leafworm larvae Spodoptera littoralis in clover plants under field conditions.     

Studies on the application of a nuclear polyhedrosis virus to control populations of the Egyptian cottonworm, Spodoptera littoralis

Variations in the resistance to nuclear polyhedrosis virus (NPV) were found in three populations of Spodoptera littoralis. The LD₅₀ for the most resistant population was 1.07 × 10⁴ PIB/5th instar larva as compared to 8.4 × 10² and 5.8 × 10² PIB/larva in the other two populations. The effect of NPV persisted in larvae which survived and pupated. Some of the pupae died, and those which survived produced normally shaped adults. While fecundity was sharply reduced in the less resistant populations, the effect on the most tolerant population was less pronounced. A 3-year-old inoculum, stored unprotected from daylight and without cooling, was much less effective even against the most sensitive larval population as compared to a relatively fresh and refrigerated batch. Larvae in their 6th instar proved to be approximately 10-fold more resistant to the NPV than 5th instar ones, while the difference in weight was only about twice. These variations in resistance to NPV are also discussed from the point of view of applying S. littoralis NPV in pest control schemes.     

Induction of metamorphosis of pediveliger larvae of the mussel Mytilus galloprovincialis Lamarck, 1819 using neuroactive compounds,KCl, NH4Cl and organic solvents

Pediveliger larvae of Mytilus galloprovincialis were subjected to a series of bioassays to investigate the induction of metamorphosis using neuroactive compounds, K⁺, NH₄ ⁺ and organic solvents. Growth and survival of post-larvae obtained using ethanol and methanol were also observed. Epinephrine, phenylephrine, clonidine and metanephrine induced larval metamorphosis at 10^?6 to 10^?4 M in both 24-h and continuous exposure assays. In 24-h exposure assays, α-methyldopa at 5×10^?5 M and methoxyphenamine at 5×10^?5?10^?4 M induced 55?94% metamorphosis. Similarly, excess K⁺ at 3×10^?2 M induced 39% metamorphosis and NH₄ ⁺ at 1?5×10^?2 M induced 63–78% metamorphosis. The EC50s of seven organic solvents ranged from 0.04 to 0.82 M. Post-larvae that metamorphosed using ethanol and methanol survived as juveniles and grew at the same rate as those from microbial biofilm. Thus, the above compounds can be useful inducers of metamorphosis for antifouling studies using larvae and juveniles of M. galloprovincialis.     

Laboratory culture and evaluation of the tubeworm Ficopomatus enigmaticus for biofouling studies

Ficopomatus enigmaticus, a euryhaline tube-building polychaete worm with a subtropical to temperate distribution, is an increasingly problematic fouling organism. In this study, laboratory protocols for maintaining adult broodstock, destructive spawning, larval culture and a settlement bioassay were developed. The method routinely yielded approximately 200 larvae per spawning adult. The mean number of eggs released by females was 1517 and the mean number of spermatozoids per male was 4.425?×?10⁶. Fertilisation success, using an initial concentration of 2.5?×?10⁶ spermatozoids and 45?eggs?ml^?1, was 76% after a contact time of 60?min. The first cleavage occurred after 20?min and the trocophore larval stage was attained by 18?h. Metatrochophores were observed 4?d post-fertilisation and were competent to settle 1?day later. The proportion of larvae that settled after 48?h was surface-dependent: 10.24% on glass, 1.39% on polystyrene and 11.07% on a poly(dimethylsiloxane) elastomer. The presence of a biofilm on glass increased the rate of settlement 7-fold compared to clean glass.     

Virulence potential of some fungal isolates and their control-promise against the Egyptian cotton leaf worm,Spodoptera littoralis

A preliminary virulence test of four fungal isolates, Beauveria bassiana IMI 382302, Beauveria bassiana IMI 386701, Trichoderma harzianum T24 and Aspergillus flavus Link against larvae of Spodoptera littoralis was performed. The most effective isolates against larvae of S. littoralis were B. bassiana 302 and T. harzianum T24, which also showed the lower percentage of pupation compared with the other two isolates under the same conditions of treatments. Three concentrations (1 × 10⁶, 1 × 10⁷ and 1 × 10⁸ ml^?1) of the aqueous conidial suspension of the four tested isolates were carried out against both larval and pupal stages of S. littoralis within five days post-treatment. T. harzianum T24 showed 80% larval mortality only when applied at the highest conidial concentration, while A. flavus showed 100% pupal mortality only, at all of its conidial concentrations. However, B. bassiana IMI 382302 showed relatively high dose-dependant larval and pupal mortalities, while strain IMI 386701 of B. bassiana showed a very weak mortality against pupae at higher concentrations, and no virulence against larvae was recorded. Enzymatic and antibiosis bioassays of the four fungal isolates showed relatively high activities against Fusarium spp. for most of the tested isolates. Clear zone of enzyme activity on agar plates proportionally increased with increasing the concentration of enzyme substrate and prolongation of the incubation period. Mtabolites produced in the agar culture inhibited the growth of Fusarium spp. and the productivity differed greatly among isolates or strains of the same isolate. Volatile and non-volatile compounds produced by A. flavus Link showed a higher inhibition activity against Fusarium spp. compared with the other fungal isolates. The humoral antifungal response of insect host is relatively high compared to the anti-bacterial one. Injection of larvae with the immune sensitive bacteria Micrococcus luteus (5 × 10³ bacteria/larva) showed a detectable humoral response by 2 h, peaked around 12 h and became hardly detectable by 24 h post-injection. Injection of larvae with conidial suspension (5 × 10³ conidia/larva) from each of the fungal isolates showed humoral antifungal activity against B. bassiana IMI 386701 and A. flavus only. This activity was detectable by 12 h, peaked around 36 h and became hardly detectable by 48 h post-injection. Although the humoral antifungal response was started slowly compared to the antibacterial one, it lasted for longer and enabled larvae to withstand the infection with these immune-sensitive fungal strains. No humoral activity was detected against B. bassiana IMI 382302, although however, weak activity was detected against T. harzianum T24 only at the low conidial concentration but not at the higher one (1 × 10⁸ ml^?1). Thus, this study concludes that larvae of S. littoralis showed immune-dependant sensitivity to T. harzianum T24 and B. bassiana IMI 382302. Therefore, this study may recommend these two fungal isolates as mycoinsecticides in the battle against cotton leaf worm in Egypt. Hence, they have been selected for future comprehensive bioassays in the laboratory under conditions similar to that in the field. This, in fact, may help for developing effective mycoinsecticides against this pest. Penetration mechanims of insect cuticle by entomopathogenic fungi will be discussed.     

A rapid knockdown effect of Penicillium citrinum for control of the mosquito Culex quinquefasciatus in Thailand

Twenty local isolates of entomopathogenic fungi were determined for control of the larvae and adults of Culex quinquefasciatus. In a laboratory experiment, a Penicillium sp. CM-010 caused 100 % mortality of third-instar larvae within 2 h using a conidial suspension of 1 × 10⁶ conidia ml^?1. Its LC₅₀ was 3 × 10⁵ conidia ml^?1, and the lethal time (LT₅₀) was 1.06 h. Cloning and sequencing of its internal transcribed spacer region indicated that this Penicillium species is Penicillium citrinum (100 % identity in 434 bp). Mortality of the adult was highest with Aspergillus flavus CM-011 followed with Metarhizium anisopliae CKM-048 from 1 × 10⁹ conidia ml^?1. P. citrinum CM-010 at 1 × 10⁶ conidia ml^?1 killed 100 % larvae within 2 h while Bacillus thuringiensis var. israelensis at 5 ITU ml^?1 required 24 h. This P. citrinum CM-010 also greatly reduced survival of C. quinquefasciatus larvae in an unreplicated field test. Light and transmission electron micrographs showed that the fungal conidia were ingested by the larvae and deposited in the gut. The metabolite patulin was produced by P. citrinum CM-010 instead of citrinin.     

Analysis of molting and metamorphosis in the ecdysteroid-deficient mutant L(3)3DTS of Drosophila melanogaster

The dominant temperature-sensitive mutation L(3)3^DTS (DTS-3) in Drosophila melanogaster causes lethality of heterozygotes during the third larval instar at the restrictive temperature (29°C). Temperature-shift experiments revealed two distinct temperature-sensitive periods, with lethal phases during the third larval instar (which may persist for 4 weeks) and during the late pupal stage. At 29°C mutant imaginal discs are unable to evert in situ, but did evert normally if cultured in the presence of exogenous ecdysterone or when implanted into wild-type larval hosts. The only morphologically abnormal tissue present in the lethal larvae is the ring gland, the prothoracic gland being greatly hypertrophied in third instar DTS-3 larvae. Injection of a single wild-type ring gland rescued these mutant larvae, indicating that the mutant gland is functionally, as well as morphologically, abnormal. Finally, the mutant larvae were shown to have less than 10% of the wild-type ecdysteroid levels. These results are all consistent with a proposed lesion in ecdysteroid hormone production in DTS-3 larvae. A comparison with the phenotypes of other “ecdysone-less” mutants is presented.     

Laboratory studies on the fungus Verticillium lecanii, a larval pathogen of the large elm bark beetle (Scolytus scolytus)

From 1972 to 1974, estimates of the natural larval mortality (> second instar) of elm bark beetles caused by pathogenic organisms were always below 7'5 % of the beetle population. The pathogenic fungus Verticillium lecanii was frequently isolated from field-collected dead larvae, and in the laboratory all larvae were killed in 5 days when exposed to spore concentrations of 4·5 × 10⁶ spores/ml. V. lecanii begins to lose its pathogenicity after prolonged culture on artificial media. The time taken for V. lecanii to kill Scolytus scolytus larvae when exposed to a logarithmic series of spore dilutions from 9·1 × 10⁷/ml to 9·1 × 10³/ml increased with decreasing amounts of inoculum. Even at spore concentrations as low as 9·1 × 10³/ml the mortality of treated larvae was greater than that of untreated individuals. At 100% r.h. all treated larvae were killed over a temperature range of 5–30 °C; those maintained at 25 °C were killed most rapidly and those kept at 5 °C the slowest.