Enhanced mortality of Bemisia tabaci nymphs by Isaria javanica combined with sublethal doses of chemical insecticides

The aim of this current study was to evaluate the mortality of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) nymphs by the combination between the entomopathogenic fungus Isaria javanica (Friedrichs & Bally) Samson & Hywel‐Jones and synthetic chemical insecticides. The bioefficacy of I. javanica and the insect growth regulators named spiromesifen and buprofezin was tested alone and in combination against B. tabaci nymphs under screenhouse conditions. The in vitro compatibility between these two control agents was previously assessed under laboratory conditions. The sublethal concentration (LC₂₅) of these insecticides towards second‐instar nymphs was determined and then mixed with the fungal treatments to investigate the type of interaction. All I. javanica isolates at 5 × 10⁷ conidia/ml inflicted nymphal mortality by up to 62.4%. The insecticides did not influence the germination and mycelial growth of the selected I. javanica isolate CG1282. In general, the insecticide–fungus combinations increased nymphal mortalities in comparison with their single counterparts. Combinations with the fungus and buprofezin or spiromesifen augmented nymphal mortality by 10% and 24%, respectively, in comparison with the fungus alone. Additive interaction was found with the combination of the I. javanica CG1282 at 1 × 10⁶ conidia/ml and spiromesifen at 1.56 ppm, and additive and synergistic interactions were achieved with the fungus at 5 × 10⁶ conidia/ml and spiromesifen at 3.12, 6.25 and 12.5 ppm. Additive interactions were also observed from mixtures of fungus at 5 × 10⁶ and buprofezin at 3.12 and 6.25 ppm. Only combinations of I. javanica with spiromesifen reduced to some extent the mycosis on dead nymphs. The joint action of I. javanica with sublethal doses of these insecticides may be a promising tool to assist in the integrated management system for B. tabaci.     

Detection of Bemisia tabaci remains in predator guts using a sequence-characterized amplified region marker

Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) B biotype is an invasive species (biotype) in China. In order to understand the role that native natural enemies might play in its control, techniques were developed for detecting B. tabaci DNA within the gut of predators. A species-specific DNA fragment, ca. 350 bp, was identified by random amplified polymorphic DNA analysis. This fragment was absent in other closely related or co-occurring prey species, cotton, and other select predator species. After cloning and sequencing the fragment, one pair of sequence-characterized amplified region (SCAR) primers was developed, which amplified a single band of 240 bp. Specificity tests performed with the primers showed the presence of the 240-bp band for B. tabaci in all developmental stages and both sexes, in adult Propylaea japonica (Thunberg) (Coleoptera: Coccinellidae) fed on B. tabaci nymphs in the laboratory, and in predators collected in cotton fields. Following consumption of a single red-eyed B. tabaci nymph, prey DNA was detectable in 100% of P. japonica at t = 0, decreasing to 20% after 12 h of digestion, and no B. tabaci DNA detected at t = 24 h. In total, we analyzed the gut contents of 185 field-collected predators, representing four different orders. All nine field-collected predator species (namely, P. japonica, Harmonia axyridis, Scymnus hoffmanni, Coccinella septempunctata, Orius sauteri, Chrysopa pallens, Chrysopa formosa, Erigonnidium graminicolum, and Neoscona doenitzi) contained DNA from B. tabaci and are assumed predators of this pest insect. Overall, the B. tabaci was eaten by more than 50% of field-collected predator individuals, including larvae of the coccinellids (P. japonica and H. axyridis) and lacewings (C. pallens and C. formosa) and adults of O. sauteri and the spiders (E. graminicolum and N. doenitzi). There was a trend of a higher percentage of larval than adult coccinellids and lacewings that preyed on B. tabaci in the field. This study provides a framework for the future use of molecular gut content analysis in arthropod conservation ecology and food web research, with considerable potential for quantifying threats to invasive or endemic pest species in China and elsewhere.     

Effects of temperature on the growth and reproduction characteristics of Bemisia tabaci B‐biotype and Trialeurodes vaporariorum

The development period, survival rate, longevity and fecundity of two whiteflies, Bemisia tabaci B‐biotype and Trialeurodes vaporariorum (Homoptera: Aleyrodidae) were compared under different temperature laboratory conditions (15°C, 18°C, 21°C and 24°C). Egg development of B. tabaci B‐biotype was significantly longer compared with that of T. vaporariorum at 15°C, 18°C and 24°C. Significantly longer pseudo‐pupae development and lower survival rate were found in B. tabaci B‐biotype at 15°C compared with those at 18°C, 21°C and 24°C. Significantly higher fecundity was found in B. tabaci B‐biotype at 24°C compared with that at 15°C, 18°C and 21°C. However, the fecundity of T. vaporariorum was significantly lower at 24°C relative to that at 15°C, 18°C and 21°C. Significantly shorter 1st instar larval development was found in T. vaporariorum compared with that of B. tabaci at 15°C and 18°C. Significantly longer 2nd instar larval development was found in B. tabaci and T. vaporariorum at 15°C compared with that at 18°C, 21°C and 24°C. However, significantly shorter 3rd instar larval development was found in T. vaporariorum compared with that of B. tabaci at 15°C, 18°C and 24°C. The adaptive divergence of tolerance to relatively low temperature may be an important factor that results in the interspecific differentiation between the seasonal dynamics of these two whiteflies in China.     

Time-dose-mortality modelling and virulence indices for six strains of Verticillium lecanii against sweetpotato whitefly, Bemisia tabaci (Gennadius)

Bioassays of six strains of Verticillium lecanii (Zimmermann) Viégas were conducted with the sweet potato whitefly, Bemisia tabaci. For inoculation, batches of third‐instar whitefly nymphs on sweetpotato seedlings were immersed in conidial suspensions of five dosages at concentrations from 10³ to 10⁷ conidia/ml. Each dosage was used to inoculate 150–250 nymphs. The nymphs were maintained at 25°C, under 95% RH, photo phase of 16 : 8 (L : D) and observed daily for mortality. The resulting data were analysed over 8 days by a complementary log‐log (CLL) time‐dose‐mortality model, based on the Hosmer–Lemeshow test, analysing the time‐dose trends for five concentrations of six strains of V. lecanii simultaneously. The parameters from the model were used to estimate the virulence indices (the values of LC₅₀) of six strains against B. tabaci. Based on the time‐dose‐mortality relationships fitted and the virulence indices, the virulence of the six strains of V. lecanii for B. tabai was compared. Results indicated that the strain Vl6063 imported from Canada and the domestic strains V3450 and Vp28 derived from B. tabaci and a scale insect, respectively, were more virulent than the others with LC₅₀ values of 2.57 × 10⁵, 6.03 × 10⁵ and 6.03 × 10⁵, respectively.     

Local genetic adaptation generates latitude‐specific effects of warming on predator–prey interactions

Temperature effects on predator–prey interactions are fundamental to better understand the effects of global warming. Previous studies never considered local adaptation of both predators and prey at different latitudes, and ignored the novel population combinations of the same predator–prey species system that may arise because of northward dispersal. We set up a common garden warming experiment to study predator–prey interactions between Ischnura elegans damselfly predators and Daphnia magna zooplankton prey from three source latitudes spanning >1500 km. Damselfly foraging rates showed thermal plasticity and strong latitudinal differences consistent with adaptation to local time constraints. Relative survival was higher at 24 °C than at 20 °C in southern Daphnia and higher at 20 °C than at 24 °C, in northern Daphnia indicating local thermal adaptation of the Daphnia prey. Yet, this thermal advantage disappeared when they were confronted with the damselfly predators of the same latitude, reflecting also a signal of local thermal adaptation in the damselfly predators. Our results further suggest the invasion success of northward moving predators as well as prey to be latitude‐specific. We advocate the novel common garden experimental approach using predators and prey obtained from natural temperature gradients spanning the predicted temperature increase in the northern populations as a powerful approach to gain mechanistic insights into how community modules will be affected by global warming. It can be used as a space‐for‐time substitution to inform how predator–prey interaction may gradually evolve to long‐term warming.     

Chemiluminescence method for the determination of piroxicam by the enhancement of the tris‐(4,7‐diphenyl‐1,10‐phenanthrolinedisulphonic acid) ruthenium(II) (RuBPS)–cerium(IV) system and its application

A simple, rapid chemiluminescence (CL) method was described for the determination of piroxicam, a commonly used analgesic agent drug. A strong CL signal was detected when cerium(IV) sulphate was injected into tris‐(4,7‐diphenyl‐1,10‐phenanthrolinedisulphonic acid) ruthenium(II) (RuBPS)–piroxicam solution. The CL signal was proportional to the concentration of piroxicam in the range 2.8 × 10^–8–1.2 × 10^–5 mol/L. The detection limit was 2 × 10^–8 mol/L and the relative standard deviation (RSD) was 3.7% (c = 7.0 × 10^–7 mol/L piroxicam; n = 11). The proposed method was applied to the determination of piroxicam in pharmaceutical preparations in capsules, spiked serum and urine samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.     

Impacts of elevated CO2 on Bemisia tabaci infesting Bt cotton and its parasitoid Encarsia formosa

Atmospheric carbon dioxide concentration is expected to rise in the coming decades. Rising atmospheric CO₂ levels may alter plant‐insect‐parasitoid associations due to the indirect effects of CO₂ enrichment on phytochemicals important for herbivore and parasitoid nutrition. Tritrophic effects of elevated CO₂ on Bt cotton (GK‐12) and non‐transgenic (Simian‐3, or S3) cotton [Gossypium hirsutum L. (Malvaceae)], Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae), and its parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae), were examined in open‐top chambers. Significantly, longer egg‐adult developmental duration and higher mortality of nymphs were observed under elevated CO₂ concentrations on both cotton cultivars during three successive generations. However, no significant differences were found in adult longevity, offspring sex ratio, and the number of eggs laid per female adult of B. tabaci fed on transgenic (GK‐12) or non‐transgenic cotton (S3) grown under elevated CO₂. Abundance of B. tabaci adults increased from 10 to 120 per plant and then decreased to 40 per plant through the growing season, but no significant differences in density occurred between CO₂ treatments and between cultivar treatments. Similarly, no significant differences were found in the developmental duration, parasitization rate, and adult emergence rate of E. formosa after parasitizing B. tabaci for three successive generations. Our results showed that the effects of transgenic Bt cotton did not significantly affect the development, survivorship, life span, or fecundity of B. tabaci and its parasitoids. Moreover, interactions between B. tabaci and E. formosa were not significantly affected by elevated CO₂. These results suggest that the biological control of B. tabaci by E. formosa would not be influenced by transgenic Bt cotton and/or elevated CO₂, indicating that the current risk management strategy regarding B. tabaci outbreaks and biocontrol by E. formosa will remain effective if the atmospheric CO₂ level continues to rise.     

Effects of Tomato chlorosis virus on the performance of its key vector,Bemisia tabaci,in China

Tomato chlorosis virus (ToCV), which is a newly emerged and rapidly spreading plant virus in China, has seriously reduced tomato production and quality over the past several years. In this study, the effect of ToCV on the demography of the whitefly, Bemisia tabaci biotype Q (Hemiptera: Aleyrodidae), fed on infected and healthy tomato plants was evaluated using the age‐stage, two‐sex life table. When reared on ToCV‐infected tomato plants, the fecundity, length of oviposition period and female adult longevity of B. tabaci biotype Q decreased significantly, while the pre‐adult duration significantly increased compared to controls reared on healthy tomatoes. Consequently, the intrinsic rate of increase (r) and finite of increase (λ) of B. tabaci biotype Q on ToCV‐infected tomato plants significantly decreased compared to those on healthy tomatoes. Population projection predicted that a population of B. tabaci biotype Q fed on ToCV‐infected tomatoes increases slower than on healthy plants. These findings demonstrated that ToCV infection decreased the performance of B. tabaci biotype Q on tomato plants.     

No signs of Na+/K+‐ATPase adaptations to an invasive exotic toxic prey in native squamate predators

Invasions by exotic toxic prey, like the release of the South American cane toad (Bufo (Rhinella) marinus) to the toad‐free Australian continent in 1935, have been shown to result in massive declines in native predator numbers. Due to minor nucleotide mutations of the Na⁺/K⁺‐ATPase gene most Australian squamate predators are highly susceptible to cane toad toxin. However, in spite of this, predators like yellow‐spotted goannas (Varanus panoptes) and red‐bellied black snakes (Pseudechis porhyriacus) still persist in parts of Queensland where they, in some areas, have co‐existed with cane toads for more than 70 years. Here, we show that the amino acids of the Na⁺/K⁺‐ATPase enzyme in the two species do not provide toad toxin resistance, and hence the two Queensland predators are still highly susceptible to cane toad toxin. Both yellow‐spotted goannas and lace monitors (Varanus varius) have, however, been recorded avoiding feeding on cane toads in areas where they co‐exist with this toxic amphibian. Moreover, both varanids have also been shown to learn to avoid feeding on toads when first subjected to conditioned taste aversion. Such behavioural shifts may therefore explain why yellow‐spotted goannas and red‐bellied black snakes still exist in cane toad infested areas of Queensland. The process appears, however, to be unable to rapidly restore varanid populations to pre‐toad population numbers as even after 10 years of co‐existence with cane toads in the Northern Territory, we see no signs of an increase in yellow‐spotted goanna numbers.     

Host plant influences pathogenicity of Beauveria bassiana to Bemisia tabaci and its sporulation on cadavers

Laboratory bioassays were conducted to determine host plant effect on pathogenicity of the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill. (Ascomycota: Hypocreales) to the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). Fourth instar B. tabaci reared on cucumber, tomato, melon, green pepper, potato, eggplant, marrow, cabbage, bean or cotton, were treated with 1 × 10⁷ conidia/ml B. bassiana EABb 93/14-Tp isolate. Mortality caused by B. bassiana significantly increased with time and it was significantly affected by the host plant on which the nymphs were reared. Mean mortality of nymphs 8 days after inoculation ranged between 52.3±7.3 for nymphs reared on cotton and 91.8±5.8 for nymphs reared on cucumber. Average survival times of nymphs treated with the fungal suspensions were also significantly influenced by the host plant, with a mean of 4.7±0.1 days for nymphs reared on cucumber, 6.6±0.2 days for cotton and 6.9±0.1 days for green pepper. The production of newly formed conidia was also affected by host plant and varied from 111000±8600 conidia/cadaver for nymphs reared on cotton to 597000±28000 conidia/cadaver for those reared on melon.     

Inactivation of Bacillus cereus by Na‐chlorophyllin‐based photosensitization on the surface of packaging

Aims: This study was focused on the possibility to inactivate food‐borne pathogen Bacillus cereus by Na‐chlorophyllin (Na‐Chl)‐based photosensitization in vitro and after attachment to the surface of packaging material. Methods and Results: Bacillus cereus in vitro or attached to the packaging was incubated with Na‐Chl (7·5 × 10^?8 to 7·5 × 10^?5 mol l^?1) for 2–60 min in phosphate buffer saline. Photosensitization was performed by illuminating cells under a light with a λ of 400 nm and an energy density of 20 mW cm^?2. The illumination time varied 0–5 min and subsequently the total energy dose was 0–6 J cm^?2. The results show that B. cereus vegetative cells in vitro or attached to the surface of packaging after incubation with 7·5 × 10^?7 mol l^?1 Na‐Chl and following illumination were inactivated by 7 log. The photoinactivation of B. cereus spores in vitro by 4 log required higher (7·5 × 10^?6 mol l^?1) Na‐Chl concentration. Decontamination of packaging material from attached spores by photosensitization reached 5 log at 7·5 × 10^?5 mol l^?1 Na‐Chl concentration. Comparative analysis of different packaging decontamination treatments indicates that washing with water can diminish pathogen population on the surface by <1 log, 100 ppm Na‐hypochlorite reduces the pathogens about 1·7 log and 200 ppm Na‐hypochlorite by 2·2 log. Meanwhile, Na‐Chl‐based photosensitization reduces bacteria on the surface by 4·2 orders of magnitude. Conclusions: Food‐borne pathogen B. cereus could be effectively inactivated (7 log) by Na‐Chl‐based photosensitization in vitro and on the surface of packaging material. Spores are more resistant than vegetative cells to photosensitization‐based inactivation. Comparison of different surface decontamination treatments indicates that Na‐Chl‐based photosensitization is much more effective antibacterial tool than washing with water or 200 ppm Na‐hypochlorite. Significance and Impact of the Study: Our data support the idea that Na‐Chl‐based photosensitization has great potential for future application as an environment‐friendly, nonthermal surface decontamination technique.     

Predation and reproductive output of the ladybird beetle <Emphasis Type="Italic">Stethorus tridens</Emphasis> preying on tomato red spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis>

Predatory behaviour and reproductive output of the ladybird beetle Stethorus tridens Gordon as function of the tomato red spider mite (TRSM), Tetranychus evansi Baker & Pritchard, densities was investigated in the laboratory. Adult female of S. tridens were isolated in cylindrical plastic arenas, containing a leaf disc of Solanum americanum Mill. with 5, 20, 40, 60, 80 or 100 T. evansi nymphs. The number of prey consumed and eggs laid were evaluated daily for ten consecutive days, starting at the oviposition. Oviposition of S. tridens was positively correlated with prey consumption and lower threshold prey consumption for S. tridens laying eggs was 16.3 mites per day. The instantaneous rate of attack (ca. discovery area) and the handling time were 0.0062 h⁻¹ and 0.83 h, and 0.00254 h⁻¹ and 0.78 h, respectively, for predators at the 1st- and 10th-oviposition day. The predator exhibited a type II functional response at 1st- and 10th-oviposition day with a maximum consumption per predator of 33 T. evansi nymphs per day at the highest prey density. The ladybird beetle S. tridens is often collected associated with red spider mite colonies on solanaceous wild plants and the results suggest the potential of this ladybird beetle to control T. evansi in tomatoes crops. Handling editor: Eric Lucas.     

Confirming therapeutic target of protopine using immobilized β2‐adrenoceptor coupled with site‐directed molecular docking and the target‐drug interaction by frontal analysis and injection amount–dependent method

Drug‐protein interaction analysis is pregnant in designing new leads during drug discovery. We prepared the stationary phase containing immobilized β₂‐adrenoceptor (β ₂‐ AR) by linkage of the receptor on macroporous silica gel surface through N ,N ′‐carbonyldiimidazole method. The stationary phase was applied in identifying antiasthmatic target of protopine guided by the prediction of site‐directed molecular docking. Subsequent application of immobilized β ₂‐ AR in exploring the binding of protopine to the receptor was realized by frontal analysis and injection amount–dependent method. The association constants of protopine to β ₂‐ AR by the 2 methods were (1.00 ± 0.06) × 10⁵M⁻¹ and (1.52 ± 0.14) × 10⁴M⁻¹. The numbers of binding sites were (1.23 ± 0.07) × 10⁻⁷M and (9.09 ± 0.06) × 10⁻⁷M, respectively. These results indicated that β ₂‐ AR is the specific target for therapeutic action of protopine in vivo. The target‐drug binding occurred on Ser¹⁶⁹ in crystal structure of the receptor. Compared with frontal analysis, injection amount–dependent method is advantageous to drug saving, improvement of sampling efficiency, and performing speed. It has grave potential in high‐throughput drug‐receptor interaction analysis.     

Population suppression of Bemisia tabaci (Hemiptera: Aleyrodidae) using yellow sticky traps and Eretmocerus nr. rajasthanicus (Hymenoptera: Aphelinidae) on tomato plants in greenhouses

We conducted three experiments for management of Bemisia tabaci (Gennadius) biotype ‘B’ on tomatoes under greenhouse conditions: (i) vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3‐m row; (ii) releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m² in the high whitefly density greenhouses (> 10 adults/plant), or twice at 15 adults/m² at a 5‐day interval in the low whitefly density greenhouses (< 10 adults/plant); and (iii) using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m² in high whitefly density greenhouses or twice at 15/m² at a 5‐day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m² in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m² in low whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs of B. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m² in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m² at a 5‐day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.     

Evaluation of the pathogenicity of Aschersonia aleyrodis on Bemisia tabaci in the laboratory and greenhouse

The entomopathogenic fungus Aschersonia aleyrodis (Webber) is a promising fungal species against whiteflies. In this work, the pathogenicity of A. aleyrodis isolate Aa005 against MEAM1 Bemisia tabaci (Gennadius) was evaluated under laboratory and greenhouse conditions. The bioassay results indicated that the percentage of larval mortalities was concentration and age dependent. A. aleyrodis showed high pathogenicity against second and third instars and pupae with LC₅₀ values of 7.93?×?10⁶, 1.08?×?10⁷, and 1.56?×?10^7?conidia?mL^?1, respectively. The median lethal time (LT₅₀) was lower (4.60 days) for second instars and was the highest (6.17 days) for pupae when inoculated with a concentration of 1?×?10^7?conidia?mL^?1. Weekly sampling of immatures showed that the per cent mortality caused by A. aleyrodis at a conidial concentration of 1?×?10^7?conidia?mL^?1 was 71.21% in small nymphs, 69.31% in large nymphs and 53.36% in pupae. The dispersion index (DI) and Lloyd’s Index of Patchiness (LIP) values indicated that the infected immatures had a tendency to aggregate. The study demonstrated that A. aleyrodis isolate A005 is an effective biocontrol agent for B. tabaci control under laboratory and greenhouse conditions.     

Control of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> and <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis> in cucumber by <Emphasis Type="Italic">Amblyseius swirskii</Emphasis>

Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) and Frankliniella occidentalis (Thysanoptera: Thripidae) are major pests in greenhouse grown cucumber crops. Recently, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was shown an effective biological control agent of both pests. Hence, perhaps both pests can be controlled simultaneously by this predator. However, with simultaneous infestation of both pests, synergistic effects, or interference could affect biological control and perhaps require changes in release rates of the predator. Thus, the aim of the present study was to evaluate different release rates of A. swirskii to control both pests under a worst case scenario of rapid immigration into a cucumber greenhouse. Two experiments were conducted, one simulating the influx of whiteflies alone (whitefly experiment) and the other immigration of whiteflies and thrips together (whitefly plus thrips experiment). Three treatments were compared in the whitefly experiment: (1) B. tabaci alone, (2) B. tabaci + 25 A. swirskii m⁻² and (3) B. tabaci + 75 A. swirskii m⁻². The high release rate was more effective than the low rate in controlling B. tabaci alone. The high rate was subsequently tested against B. tabaci and F. occidentalis for the whitefly and thrips experiment in which five treatments were compared: (1) B. tabaci alone, (2) F. occidentalis alone, (3) B. tabaci + 75 A. swirskii m⁻², (4) F. occidentalis + 75 A. swirskii m⁻² and (5) B. tabaci + F. occidentalis + 75 A. swirskii m⁻². This rate of A. swirskii controlled whiteflies and thrips either alone or together. Therefore, 75 A. swirskii m⁻² should be an adequate rate for controlling both pests either alone or simultaneously in cucumber greenhouses.     

Cardenolide‐defended milkweed bugs do not evoke learning in Nephila senegalensis spiders

Antipredator defense of herbivorous insects often relies on the potential toxicity of defensive chemicals sequestered from their host plants. The colorful Lygaeinae (Heteroptera: Lygaeidae) store a concentrated mixture of toxic cardenolides (cardiac glycosides) in specialized storage compartments of the bugs' integument, from which they are released upon attack. Larvae and adults of the large milkweed bug Oncopeltus fasciatus (Heteroptera: Lygaeinae) are specialized to feed on cardenolide‐containing milkweeds in the plant genus Asclepias and display a conspicuous red and black colorations. To investigate whether O. fasciatus gained improved protection by feeding on a toxic host plant (Asclepias syriaca), compared to a nontoxic alternative (sunflower seeds), we fed nymphs and adults of O. fasciatus to the golden orb‐weaver Nephila senegalensis. While visually oriented vertebrates, such as avian predators, have been intensively investigated for their reaction to defensive compounds and aposematic coloration, less attention has been paid to invertebrate predators. Their different perceptual abilities can provide important opportunities for testing hypotheses on warning coloration and chemical defenses. The predation trials showed that the bugs fed on Asclepias were significantly less likely to be killed than the bugs reared on a cardenolide‐free diet. This suggests that sequestered cardenolides in O. fasciatus nymphs and adults represent a significant fitness advantage on an individual level against this invertebrate predator. Yet, when testing for avoidance learning in the spiders, negative experience did not change the way how similar prey was attacked at the next encounter. In this case, visual or chemical aposematism thus does not seem to matter for predator learning.     

Susceptibility of the tobacco whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae) biotype Q to entomopathogenic fungi

Recently, the Q biotype of tobacco whitefly has been recognized as the most hazardous strain of Bemisia tabaci worldwide because of increased resistance to some insecticide groups requiring alternative strategies for its control. We studied the susceptibility of this biotype of B. tabaci to 21 isolates of Beauveria bassiana, three isolates of Isaria fumosorosea, one isolate of I. cateni, three isolates of Lecanicillium lecanii, one isolate of L. attenuatum, and one isolate of Aschersonia aleyrodis. These isolates were evaluated on pruned eggplant seedlings, at a concentration of 10⁸ conidia/mL (deposited at 6000±586 conidia mm^?2). The mortality based on mycosis varied from 18 to 97% after 6 days. Isaria fumosorosea isolate Pf04, B. bassiana isolates Bb06, Bb12, and L. lecanii L14 were found the most effective. Furthermore, five isolates were chosen for concentration–mortality response assays and compared to B. bassiana GHA as a standard. The numbers of nymphs infected by fungi were correlated with the spore concentration. L. lecanii L14 and I. fumosorosea Pf04 had the shortest LT₅₀ at 3.5 and 3.3 days at 6000±586 conidia mm^?2. Mortality declined and LT₅₀ values were longer as the concentration of conidia was reduced. The LD₅₀ values were calculated as 87, 147, 191, 263, and 269 conidia mm^?2 for isolates L14, GHA, AS1260, Bb13, and Pf04, respectively. These results indicated that the Q biotype of sweetpotato whitefly was susceptible to the five isolates of entomopathogenic fungi and these isolates have potential to be developed as microbial pesticides for whitefly control.     

Predation,oviposition and conversion rates of the predacious mite,Neoseiulus californicus (McGregor) consuming different densities of Tetranychus urticae Koch,Bemisia tabaci (Genn.) and Thrips tabaci Lind.

Rates of prey consumption, egg production and prey conversion by the predacious mite, Neoseiulus californicus (McGregor) were estimated at different densities of Tetranychus urticae Koch, Bemisia tabaci (Genn.) and Thrips tabaci Lind. in the laboratory. N. californicus females functionally and numerically responded to the increasing densities of T. urticae nymphs, B. tabaci nymphs and T. tabaci larvae showing Holling’s type II. The maximum mean predation and oviposition rates by the predator females devouring T. urticae, B. tabaci and T. tabaci occurred at 15, 10 and 10 prey individuals/day, respectively, followed by the plateau levels at higher prey densities. N. californicus females exhibited the highest feeding and oviposition on T. urticae nymphs, followed by T. tabaci larvae and B. tabaci nymphs. The predator females showed the highest efficiency in converting the prey into egg progeny at 5 individuals/day of the previous prey species, respectively. T. urticae was the most favourable for N. californicus females, followed by T. tabaci and B. tabaci.     

Nucleopolyhedrovirus infection and/or parasitism by Microplitis pallidipes affected haemolymph titre of 20‐hydroxyecdysone in Spodoptera exigua larvae

This study examined the physiological effects of joint and separate parasitism and infection by the endoparasitoid Microplitis pallidipes Szépligeti and the nucleopolyhedrovirus (NPV), respectively, on haemolymph 20‐hydroxyecdysone (20‐E) titre in Spodoptera exigua (Hübner) larvae. The results indicated that in parasitized larvae, virus‐infected larvae (5.7 × 10³ and 5.7 × 10⁵ OB/ml) and parasitized larvae infected with virus at 5.7 × 10⁵ OB/ml, compared to healthy larvae, the 20‐E all declined during the first 3 days but began to increase from day 4 after treatment, while in jointly parasitized and infected larvae (5.7 × 10³ OB/ml), the 20‐E declined during the first 4 days but began to increase on day 5 after treatment. Meanwhile, compared to parasitized larvae, the 20‐E declined during the first 4 days but significantly increased on day 5 in jointly parasitized and infected larvae (5.7 × 10³ OB/ml), while significantly increased during the first 2 days but began to decrease from day 3 after treatment in jointly parasitized and infected larvae (5.7 × 10⁵ OB/ml). Finally, in larvae that were both parasitized and virus infected (5.7 × 10³ OB/ml), compared to just virus‐infected larvae (5.7 × 10³ OB/ml), the 20‐E was lower on days 3 and 4 but higher on other days after treatment; in larvae that were both parasitized and virus infected (5.7 × 10⁵ OB/ml), compared to just virus‐infected larvae (5.7 × 10⁵ OB/ml), the 20‐E was significantly higher at the first 2 days but lower from day 3 after treatment. Our results revealed that 2nd instar larval M. pallidipes in host bodies may release 20‐E into the haemolymph of S. exigua larvae and that NPV infection may stimulate S. exigua to release more 20‐E during its third to fourth instar larval moulting. We found that this stimulatory effect was greater with higher virus concentrations.