Sublethal effects of NeemAzal- T/S botanical insecticide on Dutch and Serbian populations of Encarsia formosa (Hymenoptera: Aphelinidae)

Sublethal effects of an azadirachtin-based botanical insecticide (commercial product NeemAzal-T/S) on behaviour, life history traits and population growth of one commercial (Dutch strain, D) and two Serbian populations (Bujanovac, B; Negotin, N) of Encarsia formosa Gahan were evaluated in laboratory bioassays. In a two-choice test, parasitoids from all tested populations preferred to parasitise the untreated whitefly nymphs over those treated with 50, 25, 12.5, 6.25 and 3.12?mg/l of azadirachtin. All concentrations caused significant deterrent effects after 24?h, and the following deterrence indices were calculated: 9.7–60.9% (B), 5.5–57.5% (N) and 12.9–63.5% (D). The longevity of adults exposed for 48?h to residues of the botanical insecticide (applied at LC₅₀) was shorter (1.5–1.7 days) than that of control wasps. Both daily and total parasitism were significantly reduced (by 41.7, 48.3 and 60.1% for N, D and B, respectively) compared to control, as well as adult emergence in the F₁ generation. The instantaneous rate of increase (r_i) of surviving adults was also significantly reduced (by 13.2, 19. 3 and 20.5%, for populations N, B, and D, respectively). Adults from all tested populations, emerged from pupae treated with the botanical insecticide applied at LC₅₀, showed reduced parasitism, adult emergence, and r_i levels, but the reduction was significant only for adult emergence of B and r_i of B and N. Juvenile development of the parasitoid in treated pupae was significantly extended, compared to control. The implications of these results on integrated control of the greenhouse whitefly are discussed.     

Seasonal occurrence of spotted wing drosophila in various small fruits and berries in Pennsylvania and Maryland

Spotted wing drosophila (SWD) (Drosophila suzukii), a major invasive pest of small fruit crops, was first found in Pennsylvania and Maryland during the 2011 crop season, and since then, it has been established throughout the fruit growing regions of both states. A season‐long field study was conducted to find out the seasonal occurrence of SWD in several fruit crops (e.g. blueberry, tart and sweet cherry, floricane‐fruiting summer red raspberry, blackberry, primocane‐fruiting fall raspberries and table grapes) in Pennsylvania and Maryland in 2014. This is the first study determining seasonal occurrence of SWD using a standard commercial lure (Pherocon^® SWD Dual‐Lure^?)‐baited traps in this region. In both states, SWD adults were not captured prior to the month of July, and populations of SWD were found to build up in fruit crops only from mid‐July onwards. This indicates early season fruit crops or varieties are not at risk from SWD fruit injury in these two states. Such early fruit crops, for instance strawberry, sweet and tart cherry, are generally harvested before SWD populations build up in this region. In this context, implications of SWD population in various small fruit crops grown in this region and the utility of SWD Dual‐Lure ^? in season‐long monitoring of SWD population are discussed.     

The effects of non-crop habitat on spotted wing drosophila (Drosophila suzukii) abundance in fruit systems: A meta-analysis

1. Drosophila suzukii (SWD) poses a threat to soft and stone fruit globally. SWD inhabits non-crop areas adjacent to farms from where it moves into crops to cause damage. Effective IPM control strategies, considering both the crop and non-crop area, are needed to control this economically important pest.
2. We conducted a meta-analysis to quantify the impacts of different non-crop habitats around fruit farms on SWD populations, comparing abundance of SWD trapped in crop and non-crop habitats.
3. Overall, SWD abundance was greater in non-crop habitats than in cropped areas and this difference was greatest in farms adjacent to woodland, or field margins containing known SWD host plants.
4. The difference in SWD abundance between crop and non-crop habitats was not affected by crop type but was greatest in the winter months and in conventional compared to organic farms, indicating conventional approaches can reduce relative SWD abundance.
5. Drosophila suzukii overwinter in non-crop habitats which provide refuge outside the cropping season. However, certain habitats support greater relative abundance of SWD than others and this is also affected by farm management. We discuss what these findings mean for effective control of SWD.

     

Ingestible insecticides for spotted wing Drosophila control: a polyol,Erythritol, and an insect growth regulator,Lufenuron

Bioassays tested insecticidal activity of Erythritol from the nutritive sweetener, Truvia, and an insect growth regulator, Lufenuron, against life stages (eggs, larvae, pupae, adults) of Drosophila melanogaster (Meigen) and Drosophila suzukii (Matsumura), the spotted wing Drosophila (SWD). These compounds were chosen for their demonstrated acute toxicity to adult and larval Drosophila and potential use on organic fruit farms. D. melanogaster fed on standard Drosophila diet media moistened with water containing known concentrations of Erythritol. Likewise, SWD consumed standard diet media as well as thawed host fruit (blackberries and blueberries) treated with solutions of Erythritol, Lufenuron or both. During the first bioassay, Erythritol at lower concentrations between 0 and 500 mm (~61 000 ppm) in water and mixed with instant diet media increased adult survival from ~80% to 97% for D. melanogaster and SWD. However, from aqueous concentrations ranging from 1750 (~414 000 ppm) to 2000 mm (~244 000 ppm), Erythritol killed 100% of adult Drosophila in culture vials. One hundred per cent mortality for SWD and D. melanogaster occurred at ≥0.5 m (~61 000 ppm) Erythritol added to diet media or topically applied to host fruit. In a second bioassay, 0.013–1.000 ppm of aqueous Lufenuron, a chitin synthase inhibitor, when added to dry diet media prevented 90–99% of SWD from reaching the pupal stage. In another assay, ~67% of SWD eggs or neonates (early first instars) died inside blackberries pre‐treated with (dipped in) a soapy solution of 10 ppm Lufenuron. Pre‐treating blackberry fruit with an Erythritol–Lufenuron mixture reduced SWD brood survival by 99%. Likewise, during our last fruit‐based bioassay, 98% of eggs and neonates died inside blueberries similarly pre‐treated. During the last experiment, Lufenuron in diet media also rendered adult females sterile. Sterility, however, dissipated over 7 days once females began feeding on a Lufenuron‐free diet media.     

Simpler is better: fewer non‐target insects trapped with a four‐component chemical lure vs. a chemically more complex food‐type bait for Drosophila suzukii

Baits – fermented food products – are generally attractive to many types of insects, which makes it difficult to sort through non‐target insects to monitor a pest species of interest. We test the hypothesis that a chemically simpler and more defined attractant developed for a target insect is more specific and attracts fewer non‐target insects than a chemically more complex food‐type bait. A four‐component chemical lure isolated from a food bait and optimized for the spotted wing drosophila (SWD), Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), was compared to the original wine/vinegar bait to assess the relative responses of non‐target insects. In several field experiments in Washington State, USA, it was shown that numbers of pest muscid flies, cutworm and armyworm moths, and pest yellowjackets were reduced in traps baited with the chemical lure compared to the wine/vinegar bait. In other field experiments in the states of Washington, Oregon, and New York, numbers of non‐target drosophilid flies were also reduced in traps baited with the chemical lure relative to wine/vinegar bait. In Washington, numbers of Drosophila melanogaster Meigen and Drosophila obscura Fallen species groups and Drosophila immigrans Sturtevant were reduced in the chemical lure traps, whereas in New York, D. melanogaster and D. obscura species groups, D. immigrans, Drosophila putrida Sturtevant, Drosophila simulans Sturtevant, Drosophila tripunctata Loew, and Chymomyza spp. numbers were reduced. In Oregon, this same effect was observed with the D. melanogaster species group. Taken together, these results indicate that the four‐component SWD chemical lure will be more selective for SWD compared to fermentation baits, which should reduce time and cost involved in trapping in order to monitor SWD.     

IMPACTS OF REPEATED APPLICATIONS OF BACILLUS THURINGIENSIS VAR. ISRAELENSIS DE BARJAC AND TEMEPHOS,USED IN BLACKFLY (DIPTERA: SIMULIIDAE) CONTROL,ON MACROINVERTEBRATES IN THE MIDDLE ORANGE RIVER,SOUTH AFRICA

Summary

The impacts of five consecutive treatments of blackfly larvicides on macroinvertebrates in the middle Orange River were assessed. The abundance of the midge Xenochironomus sp. and the limpet Burnupia sp. was lower at sites treated with Bacillus thuringiensis var. israelensis (B.t.i.) compared to control sites (P<0.05). There was no medium-term impact on the abundance of two B.t.i.-sensitive taxa: Simulium spp. and the midge Rheotanytarsus fuscus. Repeated applications of the organophosphate temephos (Abate^R 200EC) significantly reduced the abundance of 25% of the invertebrate taxa in the stones-in-current biotope (P<0.1). The most affected taxa were R. fuscus, certain Baetis spp. mayflies and Coenagrionidae damselflies. Ordination of the species/sample matrix using detrended correspondence analysis showed that changes in invertebrate abundance and composition caused by either larvicide were well within the range of natural seasonal and spatial variation. However, the control programme may be detrimental to non-pest blackfly species, particularly the South African endemic Simulium gariepense, which may be endangered because of river regulation. It is concluded that the medium-term impacts of operational dosages of B.t.i. and temephos are safe provided that the recommended dosages of temephos are adhered to, and provided certain sections of river are left untreated as refugia for sensitive taxa.     

Intraguild interactions between the predator Macrolophus pygmaeus and the parasitoid Eretmocerus mundus,natural enemies of Bemisia tabaci

The native parasitoid Eretmocerus mundus Mercet and the predator Macrolophus pygmaeus Rambur are widely used to control Bemisia tabaci (Gennadius) in Mediterranean tomato greenhouses. An optimal biological control strategy for B. tabaci should take into account intraguild interactions between these natural enemies. In this study, predator's prey preferences and prey consumption were studied when offered different parasitoid and whitefly stages. The effect of the host plant on the adults of both natural enemies was also examined. M. pygmaeus preferred to consume B. tabaci over E. mundus when immature stages and adults of B. tabaci and E. mundus were offered. They consumed a larger amount of healthy B. tabaci nymphs and adults than of parasitised nymphs or E. mundus adults. The predator M. pygmaeus interfered with the reproduction of E. mundus females on cotton but not on tomato. However, B. tabaci nymphal mortality on tomato associated with parasitoid host feeding was also lower when the adult parasitoids coexisted with the predators. The joint release of M. pygmaeus and E. mundus adults did not increase the control of the whitefly B. tabaci.     

Pesticide‐mediated disruption of spotted wing Drosophila flight response to raspberries

The disruption of chemical communication between insects and host plants may take place due to an interference with the signal‐emitting host plant, or the signal‐receiving insect, compromising the signal production and emission, or its reception and processing. Anthropogenic compounds, in general, and pesticides, in particular, may impair the chemical communication that mediates host location by insects. Five different pesticides (the insecticides malathion, pyrethrins and spinetoram, and the fungicides fenhexamid and pyrimethanil) were applied at their field rates to raspberry fruits, or Petri dishes enclosing adult spotted wing Drosophila (SWD; Drosophila suzukii), and the attraction to fruit volatiles was evaluated in a series of two‐choice flight bioassays. The application of raspberry fruit with pesticides did not statistically affect attraction of unexposed adults, with exceptions being the spinetoram treatment, which led to mild insect avoidance, and the pyrethrin treatment, which resulted in slightly preferential attraction. In contrast, adults sublethally exposed to the pesticides had their flight take‐off impaired by the insecticides, but not by the fungicides. Furthermore, all pesticides, and particularly the insecticides, compromised the upwind capture of adults. Thus, the treatment with pesticides may indeed interfere with the flight response of SWD to host volatiles, particularly when the insects were previously exposed to pesticides. These findings are suggestive of the potential for sublethal insecticidal exposures to aid pest control and also provide evidence that pesticide use may compromise sampling/trapping strategies for this pest species that are based on attraction to host volatiles.     

Agroecological basis for the design of biotechnological traps based on Isaria fumosorosea for the biological control of Bemisia tabaci in strawberry crops

Isaria fumosorosea is an entomopathogenic fungus that is used as a control alternative for nymphs and adults of Bemisia tabaci. Currently there are some commercial products, however, in greenhouse or field, these do not reach the levels of control as in the laboratory because the viability of the spores decreases as a result of the conditions of application of these products in situ. The objective of this work is to implement, through agroecological data, a system of biotechnological traps based on I. fumosorosea to increase the control efficiency mainly of adults of B. tabaci in strawberry greenhouses. One way to quantify the degree of infestation of a crop is the use of yellow traps, likewise to determine the spatial distribution of adults. The Taylor method [(1984). Assessing and interpreting the spatial distributions of insect populations. Annual Reviews of Entomology, 29, 321–357) was used in five different strawberry cultivation models, finding aggregate and regular distributions. Finally, once the crop model with the highest degree of infestation was selected, the designed traps were tested and mortalities were obtained between 50% and 90% in both the laboratory and the greenhouse. The biotechnological traps based on I. fumosorosea both in the laboratory and in the greenhouse had statistically the same effect as those used under the traditional method used in the field that is aspersion; therefore, this alternative method of application can be a tool important for the biological control of this pest.     

Oviposition and development potential of the spotted‐wing drosophila,Drosophila suzukii (Diptera: Drosophilidae), on uninjured Campbell Early grape

The spotted‐wing drosophila (SWD), Drosophila suzukii (Diptera: Drosophilidae), originally distributed across a few Asian countries including South Korea, has invaded North America and Europe but is absent from Australia. In order to export the South Korean grape cultivar Campbell Early to Australia, its potential to serve as an oviposition and development medium for SWD must first be determined. In this study, we determined the oviposition and development potential of SWD on Campbell Early, after elucidating the SWD life cycle and establishing an artificial diet‐based mass‐culturing system. An investigation of the life cycle under five temperature regimes (16, 19, 22, 25 and 28°C) showed that the durations of the egg, larval and adult stages were shortened when temperature was increased from 16, 19, 22, 25 and 28°C, but pupal duration was shortest at 25°C and extended again at 28°C. A test of oviposition and development potential of SWD on Campbell Early grape clusters showed oviposition of 30.8 ± 6.8 eggs per cluster of injured grapes and 157.7 ± 16.2 eggs on a culture dish of artificial diet. However, in a similar experiment using uninjured grape clusters, only a single egg was deposited on the grape skin, which soon dried. In light of these results, newly harvested grapes left at vineyards during daily harvests are unlikely to serve as an oviposition and development medium for SWD, as long as the grapes remain uninjured.     

Circadian Phase,Sleepiness, and Light Exposure Assessment in Night Workers With and Without Shift Work Disorder

Most night workers are unable to adjust their circadian rhythms to the atypical hours of sleep and wake. Between 10% and 30% of shiftworkers report symptoms of excessive sleepiness and/or insomnia consistent with a diagnosis of shift work disorder (SWD). Difficulties in attaining appropriate shifts in circadian phase, in response to night work, may explain why some individuals develop SWD. In the present study, it was hypothesized that disturbances of sleep and wakefulness in shiftworkers are related to the degree of mismatch between their endogenous circadian rhythms and the night-work schedule of sleep during the day and wake activities at night. Five asymptomatic night workers (ANWs) (3 females; [mean?±?SD] age: 39.2?±?12.5 yrs; mean yrs on shift?=?9.3) and five night workers meeting diagnostic criteria (International Classification of Sleep Disorders [ICSD]-2) for SWD (3 females; age: 35.6?±?8.6 yrs; mean years on shift?=?8.4) participated. All participants were admitted to the sleep center at 16:00?h, where they stayed in a dim light (<10 lux) private room for the study period of 25 consecutive hours. Saliva samples for melatonin assessment were collected at 30-min intervals. Circadian phase was determined from circadian rhythms of salivary melatonin onset (dim light melatonin onset, DLMO) calculated for each individual melatonin profile. Objective sleepiness was assessed using the multiple sleep latency test (MSLT; 13 trials, 2-h intervals starting at 17:00?h). A Mann-Whitney U test was used for evaluation of differences between groups. The DLMO in ANW group was 04:42?±?3.25?h, whereas in the SWD group it was 20:42?±?2.21?h (z = 2.4; p?<?.05). Sleep did not differ between groups, except the SWD group showed an earlier bedtime on off days from work relative to that in ANW group. The MSLT corresponding to night work time (01:00–09:00?h) was significantly shorter (3.6?±?.90?min: [M?±?SEM]) in the SWD group compared with that in ANW group (6.8?±?.93?min). DLMO was significantly correlated with insomnia severity (r = ?.68; p < .03), indicating that the workers with more severe insomnia symptoms had an earlier timing of DLMO. Finally, SWD subjects were exposed to more morning light (between 05:00 and 11:00?h) as than ANW ones (798 vs. 180 lux [M?±?SD], respectively z?=??1.7; p?<?.05). These data provide evidence of an internal physiological delay of the circadian pacemaker in asymptomatic night-shift workers. In contrast, individuals with SWD maintain a circadian phase position similar to day workers, leading to a mismatch/conflict between their endogenous rhythms and their sleep-wake schedule. (Author correspondence: vgumeny1@hfhs.org)     

Cytochalasin B inhibition of brain glucose transport and the influence of blood components on inhibitor concentration

The effect of cytochalasin B on cerebral glucose transport and metabolism was investigated in 19 isolated perfused dog brain preparations. Cytochalasin B is a potent, non-competitive inhibitor of glucose transport at the blood-brain interface. Both glucose transport into (K_i = 6.6 ± 1.9 μM) and out of the capillary endothelial cell are inhibited. The inhibition is readily reversible by perfusion with blood containing no cytochalasin B. After 2 min of exposure to 30 μM cytochalasin B, the cerebral oxygen consumption decreased by 31% probably due to decreased availability of glucose for oxidative metabolism. About one-half of the cytochalasin B that is dissolved in blood is bound to erythrocytes and other blood components while the remainder is free.     

Sublethal effects of a Beauveria bassiana-based mycopesticide on Dutch and Serbian populations of Encarsia formosa (Hymenoptera: Aphelinidae)

ABSTRACT

The effects of a Beauveria bassiana-based product (trade name Naturalis-L; strain ATCC 74040) on the behaviour, life history traits and population growth of one commercial Dutch strain and two local Serbian populations (Bujanovac and Negotin) of Encarsia formosa Gahan (Hymen.: Aphelinidae) were evaluated in laboratory bioassays. In a two-choice test, parasitoids from all tested populations preferred to parasitise untreated whitefly nymphs over those treated with 1, 0.5, 0.25, 0.125 and 0.0625?ml/l of the mycopesticide. The longevity of adults of population Bujanovac exposed for 48?h to residues of the mycoinsecticide applied at the LC₅₀ concentration was 1.4 days shorter than that of control wasps. Total parasitism was significantly reduced (by 17.5, 26.2 and 31.4% for the Negotin, Dutch and Bujanovac populations, respectively) compared to control, as well as adult emergence in the F₁ generation (reductions of 20.3 and 26.7%, for the Dutch and Bujanovac populations, respectively). The instantaneous rate of increase (r_i) of surviving adults was also significantly reduced by mycopesticide treatment by 6.3, 13.8 and 15.1%, for the Negotin, Bujanovac, and Dutch populations, respectively. Adult parasioids emerged from pupae treated with the LC₅₀ concentration of the mycopesticide showed slower juvenile development, longevity, parasitism, adult emergence, and r_i values, but the reduction in r_i was significant only for the Bujanovac and Dutch populations (4.2 and 8.3%, respectively). The implications of these results on integrated control of the greenhouse whitefly Trialeurodes vaporariorum Westwood (Hem.: Aleyrodidae) are discussed in terms of adjusting the timing of Naturalis-L applications and parasitoid release.     

A method for estimating natural survival rate and mean fecundity of an adult insect population by dissecting the female reproductive organs

Several problems were discussed in relation toMacDonald' s method (MacDonald , 1957) for estimating the survival rate of a natural population of adults with varying survival rates and unstable age structure.

1. Random samplings with a fixed sampling ratio and an appropriate census interval is pre-requisite during the occurrence of the adults.
2. At each sampling, female adults are dissected to know the ratio, p_i, of nulliparous females in ith sample (i=0, 1, 2, 3, …,). The Σn_ip_i/Σn_i gives an estimate of the ratio, Fα/F, of nulliparous females in the population where n_i refers to the population size on ith census date. If a constant daily survival rate is assumed, the daily survival rate is estimated from equation (4′). When the survival rate is not constant over the period of adult occurrence, e. g. before and after the initiation of oviposition, the survival rate during pre-ovipositional period is estimated by equation (4″).
3. Decision of an economic census interval to obtain a reliable estimate of the ratio, Fα/F, is depending on the form of emergence curve, particularly on its duration and the length of pre-ovipositional period. If the normal distribution can be assumed for the emergence curve, an interval less than one third of the emergence period is recommended. Concerning with insects having a long pre-ovipositional period, a census interval which exceeds one third of the emergence period still gives a good estimate of Fα/F.
4. The mean realized fecundity of some kind of insects can be estimated by equation (5′ or 5″) using the estimates obtained by the present method.

     

SHORT-TERM IMPACTS OF FORMULATIONS OF BACILLUS THURINGIENSIS VAR. ISRAELENSIS DE BARJAC AND THE ORGANOPHOSPHATE TEMEPHOS,USED IN BLACKFLY (DIPTERA: SIMULIIDAE) CONTROL,ON RHEOPHILIC BENTHIC MACROINVERTEBRATES IN THE MIDDLE ORANGE RIVER,SOUTH AFRICA

Summary

The impacts of larvicides used in the control of blackflies (Diptera: Simuliidae) on macroinvertebrates in the stones-in-current biotope were assessed during 8 field trials in the middle Orange River, South Africa. Two Bacillus thuringiensis var. israelensis (B.t.i.) products (Vectobac^R 12AS and Teknar^R HP-D) and the organophosphate temephos (Abate^R 200EC) were applied at recommended and high dosages to simulate “operational” and “worst-possible” scenario's respectively. Mortality was evaluated either by direct counting of invertebrates on stones before and after application, or by ranking invertebrates on a 4-point relative abundance scale before and after application. In addition, the re-appearance of benthic invertebrate population densities after temephos application was examined.

At the recommended dosage (1.2 ppm/10 min), B.t.i. significantly reduced blackfly larval numbers (P<0.001) and those of the chironomid Rheotanytarsus fuscus Freeman (P<0.05). At high dosage (20 ppm/10 min), numbers of the filter-feeding mayfly Tricorythus discolor (Burmeister) (P<0.01) and the chironomid Cardiocladius sp. (P<0.05) were also significantly reduced. No Simulium predators were directly affected by B.t.i., but there were indications of food shortage amongst Hydropsychidae and Hirudinea.

Temephos caused significant reductions in the relative abundance of 5 taxa at 0.05 ppm, 3 to 6 taxa at 0.1 ppm, and 9 taxa at 1.0 ppm (P<0.05). “Non-target” organisms which were most affected included the chironomid R. fuscus, the mayflies Baetis glaucus Agnew and Choroterpes elegans Barnard, and the caddisflies Cheumatopsyche thomasseti Ulmer and Amphipsyche scottae Kimmins. The mayfly T. discolor was tolerant of temephos, even at high dosage (1.0 ppm/10 min). In winter, most taxa re-appeared within 19 days, and population densities were back to pre-treatment levels within 35 days.

It is concluded that good reduction of blackfly populations may be obtained with minimal direct impact on the “non-target” fauna, provided recommended dosages of temephos are not exceeded. Overdosing with temephos may result in high mortality of “non-target” organisms, including blackfly predators, and should be avoided.     

Spatial synchrony in Drosophila suzukii population dynamics along elevational gradients

1. Spotted wing drosophila (SWD; Drosophila suzukii Matsumura, 1931) is a polyphagous invasive crop pest native of Southeast Asia able to attack a wide array of host plant species in both cultivated and natural habitats. SWD is now widespread in several mountain regions, but it is still unclear how the species moves to different elevations across the seasons, and how this depends on environmental conditions and food resources. 2. The temporal dynamics of several SWD populations were studied along elevational gradients in the Alps using a synchrony analysis. Twelve transects were selected, covering an overall elevational gradient of 2100 m. SWD abundance was monitored every 2 weeks during the growing season (from June to November 2015) when cultivated and wild hosts are potentially susceptible (i.e. fruits are ripe). 3. Spotted wing drosophila were widely distributed along all the tested elevations, revealing synchrony in population dynamics across ranges in elevation and geographic distance. Synchronised populations were observed at distances of up to 100 km at sites with similar temperatures. The high dispersal potential of the pest together with the seasonal variation in temperature are likely to be the dominant mechanisms causing the observed spatial synchrony. A factor that seemed to reduce synchrony is the large concentration of host plants (i.e. crop) in lowland agricultural landscapes. 4. The spatial synchrony in pest abundance at large spatial scale indicates that the risk of SWD outbreaks is highly dependent on drivers beyond the control of traditional field‐scale management. These findings could help in developing monitoring and predictive models of SWD population dynamics.     

Insights into the susceptibility of raspberries to Drosophila suzukii oviposition

The spotted wing drosophila (SWD) causes massive losses in red raspberry (Rubus idaeus L.) cultivation by direct oviposition leading to damages of the soft skin fruits. Knowledge of the fly's host preference could help farmers in managing the pest. We used a laboratory-based oviposition assay for screening the germplasm of Rubus to ascertain whether the spotted wing drosophila prefers certain cultivars to others for oviposition and if preference is based on citric acid and Brix content or firmness. Correlation analyses of evaluated characters with no-choice tests results in 3 years obtained no correlation between citric acid, Brix content and oviposition. Primocane raspberries were lower affected by SWD than floricane raspberries. The Rubus hybrid cultivar “Dorman Red” and the primocane cultivar “Pokusa” showed the lowest oviposition rate compared to the other 58 evaluated genotypes. We found that oviposition correlates to firmness of the investigated cultivars, which strongly indicates that host preference is partly connected to that character in raspberries. The results are discussed regarding the use of Rubus genetic resources in breeding and integrated pest management to control spotted wing drosophila in the field.     

Microbial control of cotton pests: use of the naturally occurring entomopathogenic fungus Aspergillus sp. (BC 639) in the management of Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) and beneficial insects on transgenic cotton crops

The commercial adoption of transgenic Bacillus thuringiensis (Bt) cotton (Bollgard II®) reduced the use of insecticides to control Helicoverpa spp. However, the ineffectiveness of the Bt toxin against sucking pests such as silverleaf whiteflies (Bemisia tabaci) resulted in a marked increase in B. tabaci populations and in the use of insecticides to control this pest. The effect of the entomopathogenic fungus Aspergillus sp. BC 639 on B. tabaci and beneficial insects (predominantly predatory insects) was studied in commercial cotton field trials. The results showed that oil-based extracts of the entomopathogenic fungus BC 639 control the number of B. tabaci adults and nymphs in commercial transgenic cotton crops. The BC 639 fungus caused 60.0%, 67.2%, and 68.8% mortality in adults, and 54.6%, 62.3%, and 51.7% in nymphs at 7, 14, and 21 days after treatment, respectively, relative to the unsprayed controls. The effect of BC 639 at concentrations of 125, 250, and 500?ml/ha on low-density B. tabaci (～10 nymphs/leaf) did not differ significantly from that of the commercial insecticide (pyriproxifen). However, at higher densities (>50 nymphs per leaf), low concentrations of BC 639 (125 and 250?ml/ha) were not as effective as 500?ml/ha BC 639 in successfully controlling the pest. A simple graphic analysis suggested that the more B. tabaci nymphs per leaf, the fewer adults per leaf, and that once the number of nymphs increased to ～70 per leaf, a negative feedback regulatory effect reduced the survivorship of the nymphs and adults and/or caused the emigration of the adults from the contaminated leaves in search of new resources. Therefore, the ability of BC 639 to control B. tabaci adults and nymphs with minimal effects on predatory insects indicates its potential utility in supplementing integrated pest management programmes for cotton crops.     

Rate constants of acetylcholine receptor internalization and degradation in mouse muscles

The rate constants for internalization and subsequent extrusion of acetylcholine receptors (AChRs) during degradation in adult innervated and denervated mouse diaphragm muscles were determined using proteinase K (PK) digestion. This procedure separated ¹²⁵I-α-bungarotoxin (Bgt)-labeled AChRs into PK-sensitive and PK-resistant compartments. The time course of the residual radioactivity in these two compartments suggested that they represented surface membrane and internalized compartments, respectively. The data were compatible with a mathematical model based on the assumption that during degradation of AChRs a surface compartment, A, fed an internal compartment, B, with an internalization rate constant (k_i), and that B is drained from the cell with an extrusion rate constant (k_o). Using the mathematical model, we were able to determine that k_i and k_o were, respectively, 0.068 (t_1/2 ∼ 10.2 days) and 0.69–0.55 (t_1/2 ∼ 1.0– 1.25 days) for innervated muscle and were, respectively, 0.69 (t_1/2 ∼ 1.0 day) and 6.93 (t_1/2 ∼ 0.1day) for denervated muscle. Thus, the rate for internalization was about 8–10 times slower than that for extrusion from the cell for both the slowly degrading innervated (Rs) AChRs and for the rapidly degrading denervated (Rr) AChRs. This inequality betweeen k_i and k_o therefore allows the combined quantity of A(t) + B(t) , usually measured in AChR degradation studies, to approximate a single exponential. J. Cell. Physiol. 181:107–112, 1999. © 1999 Wiley-Liss, Inc.     

Quarantine host range of Bikasha collaris,a potential biological control agent of Chinese tallowtree (Triadica sebifera) in North America

Chinese tallowtree, Triadica sebifera (L.) Small (Euphorbiaceae), is one of the worst invasive weeds of the southeastern USA impacting coastal wetlands, forests, and natural areas. Traditional mechanical and chemical controls have been unable to limit the spread, and this invasive species continues to expand its range. A proposed biological control candidate, the flea beetle Bikasha collaris (Baly) (Coleoptera: Chrysomelidae), shows high specificity for the target weed Chinese tallowtree. Results from a series of no‐choice and choice feeding tests of B. collaris adults and larvae indicated that this flea beetle was highly specific to Chinese tallowtree. The larvae of B. collaris feed by tunneling in the roots, whereas the adults feed on the leaves of Chinese tallowtree. A total of 77 plant taxa, primarily from members of the tallow plant family Euphorbiaceae, were tested in numerous test designs. Larval no‐choice tests indicated that larvae completed development only on two of the non‐target taxa. Of 80 B. collaris larvae fed roots of Hippomane mancinella L. and 50 larvae fed roots of Ricinus communis L., two and three larvae completed development, respectively. The emerging adults of these five larvae died within 3 days without reproducing. Larval choice tests also indicated little use of these non‐target taxa. Adult no‐choice tests indicated little leaf damage by B. collaris on the non‐targets except for Ditrysinia fruticosa (Bartram) Govaerts & Frodin and Gymnanthes lucida Sw. When given a choice, however, B. collaris adults consumed much less of the non‐targets D. fruticosa (7.4%) and G. lucida (6.1%) compared with the control leaves. Finally, no‐choice oviposition tests indicated that no eggs were produced when adults were fed all non‐target taxa, except those fed G. lucida. These B. collaris adults fed G. lucida leaves produced an average of 4.6 eggs compared with 115.0 eggs per female when fed Chinese tallowtree. The eggs produced from adults fed G. lucida were either inviable or the emerging larvae died within 1 day. These results indicate that the flea beetle B. collaris was unable to complete its life cycle on any of the non‐target taxa tested. If approved for field release, B. collaris will be the first biological control agent deployed against Chinese tallowtree in the USA. This flea beetle may play an important role in suppressing Chinese tallowtree and contribute to the integrated control of this invasive weed.