Toxicity and pharmacokinetics of insect growth regulators and other novel insecticides on pupae of Hyposoter didmator (Hymenoptera: Ichneumonidae), a parasitoid of early larval instars of lepidopteran pests

Susceptibility of the lepidopteran parasitoid Hyposoter didymator (Thunberg) to seven modern insecticides, azadirachtin, diflubenzuron, halofenozide, methoxyfenozide, pyriproxyfen, tebufenozide, and spinosad, was tested in the laboratory. Pupae were exposed to different doses of each compound by direct topical application. At the field recommended doses, methoxyfenozide and tebufenozide had no effect on H. didymator. Halofenozide had a low effect on both adult emergence and adult survival but the progeny size and parasitism capacity were not affected. Diflubenzuron was moderately toxic to the parasitoid, while azadirachtin, pyriproxyfen and spinosad were very toxic, affecting all its life parameters. In the pyriproxyfen and spinosad treatments, no progeny was obtained. As a second approach of this study, we determined the rate of penetration through the pupal cocoon and absorption in the parasitoid body as pharmacokinetic parameters important for toxicity. Most of the radioactivity was retained in the silken cocoon, indicating a low accumulation in the parasitoid body. Among all compounds tested, diflubenzuron exhibited the highest absorption in the parasitoid body, followed by pyriproxyfen. For halofenozide, methoxyfenozide and tebufenozide, low absorption (<2%) was found. In addition, we tested for the presence of molting hormone receptors in Hyposoter tissues using a monoclonal antibody 9B9. Our data suggest that the use of diflubenzuron azadirachtin, pyriproxyfen, halofenozide, and spinosad in combination with H. didymator in integrated pest management (IPM) programs should be carefully evaluated. Methoxyfenozide and tebufenozide could be considered safe for this parasitoid.     

Effects of carbonyl sulfide, methyl iodide, and sulfuryl fluoride on fruit phytotoxicity and insect mortality

Three potential chemical fumigants: carbonyl sulfide (COS), methyl iodide (MI) and sulfuryl fluoride (SF) were tested at selected dosages on lemons against California red scale (Aonidiella aurantii) and MI and COS were tested on nectarines against codling moth (Cydia pomonella). In nectarines, COS was tested at 0, 20, 40, 60 and 80 mg litre^?1, MI at 0, 10, 15, 20 and 25 mg litre^?1. Both fumigants intensified nectarine peel color, delayed fruit softening, but did not alter overall fruit quality. COS at 80 mg litre^?1 resulted in 87% codling moth mortality, but the fumigant dosage was insufficient to reach the desired probits 9 level (99.9968%). MI gave 100% codling moth mortality at 25 mg litre^?1. Lemons were treated with MI at 0,10,20,40,60 mg litre^?1, SF at 0,10,20,40, 80 mg litre^?1 and COS at 0,20,40, 60 and 80 mg litre^?1. MI gave 100% red scale mortality at ≥40 mg litre^?1 but caused significant fruit injury. Conditioning lemons at 15°C for 3 days before MI fumigation lessened lemon phytotoxicity. Forced aeration at 3.5 standard litres per minute of lemons for 24 h following MI fumigation at 20 mg litre^?1 significantly reduced phytotoxicity compared to 2 h postfumigation aeration after MI treatment. SF at ≥40 mg litre^?1 gave 100% red scale mortality but resulted in commodity phytotoxicity. Lemons treated with the highest selected dose of 80 mg litre^?1 COS gave only 87% kill of red scale, but failed to reach the desired probit 9 level.     

Susceptibility of the predatory stinkbug <Emphasis Type="Italic">Picromerus bidens</Emphasis> to selected insecticides

The Palaearctic stinkbug Picromerus bidens L. (Heteroptera: Pentatomidae) has been considered as a potential biocontrol agent of several defoliator pests in various agricultural and forest ecosystems. It may therefore be a valuable alternative for the Nearctic pentatomid Podisus maculiventris (Say) (Heteroptera: Pentatomidae), the augmentative use of which has largely been abandoned in Europe given its possible environmental impact as an exotic polyphagous predator. However, no study has yet documented the impact of insecticides on P. bidens, which is essential to evaluate the possible combination of this predatory pentatomid with current insecticide applications in integrated pest management (IPM) programmes. This study reports on laboratory experiments investigating the susceptibility of P. bidens to five insecticides with different modes of action: the pyrethroid deltamethrin, the diacylhydrazine methoxyfenozide, the juvenile hormone mimic pyriproxyfen, the spinosyn spinosad, and the neonicotinoid imidacloprid, all of which are used to control defoliator pests. Fourth-instar nymphs and female adults of the predator were exposed to formulated materials of the insecticides by residual contact. Methoxyfenozide and spinosad did not cause significant mortality to 4th instars and female adults of P. bidens. In contrast, deltamethrin and imidacloprid were harmful to nymphs and adults of the predator, with LC₅₀ values ranging between 1.5 and 9.9 mg a.i./l. Pyriproxyfen was toxic to 4th instars with an LC₅₀ value of 13.9 mg a.i./l but did not affect female adults. Reproduction and longevity of P. bidens were not adversely affected when the predator was exposed to field concentrations of spinosad, methoxyfenozide, or pyriproxyfen, or sublethal concentrations (around LC₁₀) of deltamethrin and imidacloprid. The results from residual contact experiments suggest that methoxyfenozide, spinosad, and to a lesser extent, pyriproxyfen may be compatible with P. bidens in an IPM programme. Further experiments assessing food chain toxicity of these compounds should offer a more complete picture of their selectivity.     

Effect of imidacloprid on the sivlerleaf whitefly, Bemisia argentifolii Bellows and Perrring (Homoptera: Aleyrodidae), and whitefly parasitism

Bioassays were conducted under greenhouse conditions to determine the effect of imidacloprid on adult and nymphal stages of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring, and parasitism by Encarsia formosa (Gahan). A flowable formulation (24Oglitre^-1) of imidacloprid at six rates (0.09, 0.04 and 0.02 g a.i. litre^-1 pot volume for experiments 1 and 2; 0.009, 0.004, and 0.002 g a.i. litre^-1 pot volume for experiment 3) was evaluated. After a 48 h exposure to treated plants, high mortality of adult whitefly (>94%) was observed. Adults exposed to poinsettias treated 150 days earlier also had significantly greater mortality (>79%) than the adults on control plants. When exposed to treated plants for only 6 h, >65% of adults were killed. All three rates of imidacloprid caused >97% mortality of immature whiteflies by day 19. When treated plants were continually exposed to adult whiteflies, immature mortality was 100% for the three higher rates of imidacloprid up to and including 88 days after treatment. During the same time, emerging adults were reduced significantly. Immatures reinfested on plants treated 161 days earlier, incurred 80% mortality at the higher rate 0.09 g a.i. litre^-1 pot volume and 38% mortality at 0.02 g a.i. litre^-1 pot volume. At lower treatment rates, results varied. At 0.009 g a.i. litre^-1 of pot volume, mean percentage whitefly mortality (65%) 25 days after treatment was significantly higher than the controls; however, whitefly mortality at 0.004 and 0.002 g a.i. litre^-1 pot volume was not significantly different from controls or plants treated with the higher rate. Parasitoids could develop to the adult stage on whiteflies infesting imidacloprid treated plants. Parasitism occurred at low levels (< 10%), doe to high levels of whitefly mortality on treated plants. No phytotoxicity was observed for any treatment throughout the length of the trials that lasted through flowering.     

Toxicity of diflubenzuron, pyriproxyfen, imidacloprid and diafenthiuron to the predatory bugOrius laevigatus (Het.: Anthocoridae)

The susceptibility of the predatory bugOrius laevigatus (Fieber) to the insect growth regulators diflubenzuron, pyriproxyfen, the nitroguanidine insecticide imidacloprid and the thiourea compound diafenthiuron was investigated in the laboratory. Fifth-instar nymphs were exposed to formulated materials of each compound and adults were exposed to formulated materials of diafenthiuron and imidacloprid. In each case, exposure via ingestion and residual contact was tested. Pyriproxyfen was harmless toO. laevigatus nymphs by both ways of exposure. The respective LC₅₀-values of diflubenzuron via ingestion and residual contact were 229.9 and 391.1 mg a.i./l. Diafenthiuron did not cause significant mortality to fifth-instar nymphs and adults via ingestion but was toxic by residual contact with LC₅₀-values of 329.4 mg a.i./l and 125.9 mg a.i./l for nymphs and adults respectively. Imidacloprid proved to be the most toxic compound with LC₅₀-values of 1.1 and 0.04 mg a.i./l for nymphs and 2.1 and 0.3 mg a.i./l for adults, via ingestion and residual contact, respectively. The results suggest that use of pyriproxyfen in an integrated pest management programme will not cause any problems but that imidacloprid, and to a lesser extent, also diflubenzuron and diafenthiuron could be harmful to the predator.     

Limited protection of the parasitoid Pachycrepoideus vindemiae from Drosophila suzukii host‐directed spinosad suppression

Laboratory trials were conducted to determine whether the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), puparium can provide an effective physical barrier to protect immature stages of the pupal parasitoid Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) from spinosad treatments. Spinosad insecticides are currently an important suppression strategy for D. suzukii in organically managed fruit orchards although they are well known to cause mortality in hymenopteran parasitoids. High adult P. vindemiae female mortality (83%) occurred within 24 h of exposure to D. suzukii pupae treated with 10 mg a.i. l^?1 spinosad and female parasitoids did not avoid the pupae treated with similar low levels of spinosad in choice tests that included untreated pupae. Pachycrepoideus vindemiae develops as an idiobiont ectoparasitoid on host fly pupa within the sclerotized host puparium. Significant P. vindemiae survival and emergence was recorded when parasitized D. suzukii puparia were exposed to field treatment levels of spinosad; however, the parasitoid survival was dependent on the time of the spinosad treatment of the host post‐parasitization. Significant parasitoid survival occurred when the host puparia were treated at 2 weeks when the parasitoid was in the pupal stage but did not occur when the host puparia were treated at 1 week post‐parasitization, when the parasitoids were still in a larval stage. The parasitoid adults consumed or otherwise came in contact with residual degrading spinosad when they exited the treated host, and consequently high and low adult parasitoid mortality occurred when the adults emerged from puparia treated at 2 and 1 week(s), respectively. Our study indicates that generally the integration of P. vindemiae parasitism into a sustainable D. suzukii management program is not compatible with spinosad treatments, although P. vindemiae in the pupal stage inside sclerotized host puparia appear to be minimally impacted by spinosad treatments, provided that the spinosad degrades before parasitoid emergence.     

Compatibility of Spinosad, Tebufenozide and Azadirachtin with Eggs and Pupae of the Predator Chrysoperla carnea (Stephens) Under Laboratory Conditions

Under laboratory conditions, the toxicity of three novel insecticides, spinosad (Tracer ® ), tebufenozide (Mimic ® ) and azadirachtin (Align ® ), was tested against eggs and pupae of the predator Chrysoperla carnea (Stephens). In a first series of assays, eggs were dipped in an aqueous concentration and no ovicidal activity was scored for the three insecticides. In the second, when females were ovipositing on treated substrate for 24 h, fecundity and hatching percentages were similar as compared to controls and the offspring developed normally until the adult stage. However, spinosad, at the highest concentrations tested, caused a slight, significant reduction in the adult life span and fecundity. In a third series of experiments, pupae developed into normal adults after topical treatment for the three insecticides. Herewith, a pharmacokinetic study indicated low accumulation in the body after pupal cuticle penetration when administrating 14 C-labelled insecticide. Fourthly, pupation of last-instar larvae in treated substrate was normal for spinosad and tebufenozide. Only azadirachtin caused a slight reduction in the number of pupae and adults; however, fecundity and fertility of surviving adults was normal. In conclusion, the current results indicate that the three insecticides are not toxic to eggs and pupae of C. carnea .     

Feeding deterrent effect of carvone, a compound from caraway seeds, on the slug Arion lusitanicus

The feeding deterrent effect of carvone on the slug Arion lusitanicus was investigated. Carvone, a natural compound from caraway seeds, was incorporated into mulch to reduce its inherent volatility. In a laboratory choice experiment, boxes were filled on one side with carvone‐treated mulch and on the other side with untreated mulch. At carvone concentrations ranging from 0.03–0.75 ml litre^?1 mulch, slugs ate significantly more lettuce on the untreated side. In a laboratory based no‐choice experiment, carvone concentrations of 0.25 and 0.75 ml litre^?1 mulch significantly reduced slug feeding in comparison with the untreated control. Moreover at the highest concentration of carvone (0.75 ml litre^?1 mulch) 50% mortality was recorded over a period of 5 days, indicating a clear molluscicidal effect. Due to its volatility carvone did not decrease plant defoliation by A. lusitanicus when applied directly onto lettuce. Subsequent field evaluation showed 0.75 ml litre^?1 mulch to partially reduce slug feeding damage. However, this effect was not sufficient to significantly increase lettuce yield. The incorporation of a higher carvone concentration into mulch is still to be tested to confirm whether carvone‐treated mulch can be recommended as an effective alternative approach to chemical slug control.     

Effect of insecticides on Trichogramma exiguum (Trichogrammatidae: Hymenoptera) preimaginal development and adult survival

The effect of insecticides on Trichogramma exiguum Pinto & Platner emergence, adult survival, and fitness parameters was investigated. Insecticides tested were lambda cyhalothrin, cypermethrin, thiodicarb, profenophos, spinosad, methoxyfenozide, and tebufenozide. All insecticides, with the exception of methoxyfenozide and tebufenozide, adversely affected Trichogramma emergence from Helicoverpa zea (Boddie) host eggs when exposed at different preimaginal stages of development (larval, prepupal, or pupal). Regardless of the developmental stage treated, none of the insecticides tested had a significant effect on the sex ratio or frequency of brachyptery of emerged females. However, the mean life span of emerged T. exiguum females significantly varied among insecticide treatments, and was significantly affected by the developmental stage of parasitoid when treated. Based on LC50 values, spinosad and prophenofos were the most toxic compounds to female T. exiguum adults, followed by lambda cyhalothrin, cypermethrin, and thiodicarb. Insecticides field-weathered for four to 6 d on cotton leaves showed no activity against female T. exiguum adults.     

Post-harvest age-induced seed dormancy of Acer ginnala and its alleviation by growth regulator and low temperature treatments

One-month-old fruits of Acer ginnala with winged pericarp attached gave 44% germination and this was not increased by cold treatment at 4°C for 0, 10, 20, or 30 days, gibberellic acid treatment at 0, 1, 10, 100 or 1000 mg litre^-1, or ethephon treatment at 0, 2, 20, 200 or 2000 mg litre^-1. After 6 months of storage at 20–25 °C, germination of untreated fruits fell to 5% but could be restored to that of 1-month-old fruits by incubation at 4 °C for 30 days. After 9 months storage, no germination occurred in untreated fruits. Cold treatment (30 days at 4 °C partially restored germination (26%). Treatment with either gibberellic acid (1000 mg litre^-1) and 30 days at 4 °C (40%) or ethephon (100 mg litre^-] and 30 days at 4 °C improved germination (69%). The combination of all three treatments, i.e. 100 mg litre^-1 gibberellic acid, 100 mg litre^-1 ethephon and 30 days at 4 °C, optimised germination (86%). Thus, dormancy of A. ginnala developed during storage but could be reversed by a combination of treatment with low temperature and growth regulators. The highest germination (86%) was achieved after low temperature and growth regulator treatment of stored fruit.     

在玻璃表面上短时接触硅藻土和多杀菌素对四纹豆象的致死效应和亚致死效应（英文）

四纹豆象Callosobruchus maculatus (F.)是伊朗豇豆种子上的主要贮藏害虫。控制这一害虫时, 用生物杀虫剂比用常规杀虫剂更为合适。本研究评价了室内条件下在玻璃表面上硅藻土和多杀菌素对四纹豆象成虫的致死效应和亚致死效应。结果表明： 硅藻土处理24 h和48 h后, 对四纹豆象成虫的LC50 值分别为 1.47和0.2 g/m²; 多杀菌素处理24 h和48 h后, 对四纹豆象成虫的LC50 值分别为102.9 和68.8 mg ai/L, 说明两种化合物都对四纹豆象成虫具有较高的急性毒性。通过检测生物学参数, 研究了LC₂₀浓度的硅藻土和多杀菌素对四纹豆象的亚致死效应。LC₂₀浓度的硅藻土和多杀菌素使四纹豆象成虫的繁殖力分别比对照降低了71.5%和17.2%, 卵孵化率降低了57.5%和27.8%, 成虫寿命缩短了74.7%和17.1%。接触LC₂₀浓度的硅藻土和多杀菌素使这一害虫的蛹期分别比对照延长了4.8%和2.3%。亚致死效应研究表明, 硅藻土和多杀菌素对四纹豆象的生命参数均产生了负面影响。总之, 致死效应和亚致死效应综合显示, 硅藻土在防治四纹豆象上具有较大的潜力。     

Effect of spinosad and predatory mites on control of Frankliniella occidentalis in three strawberry cultivars

Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a major pest of strawberry, Fragaria × ananassa Duchesne (Rosaceae). Spinosad is highly efficacious against F. occidentalis, and spinosad is believed to be compatible in an integrated pest management program. This study determined whether F. occidentalis could be controlled with predatory mites [Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) (both Acari: Phytoseiidae), and Hypoaspis miles (Berlese) (Acari: Laelapidae)] and spinosad in strawberry. In the glasshouse, three strawberry cultivars (Camarosa, Camino Real, and Albion) were sprayed once with spinosad at the recommended rate (80 ml 100 l^?1 rate, 0.096 g a.i. l^?1) or with water (control). Thrips adults were released onto plants 24 h after spraying and predatory mites released 6 days later. Spinosad significantly reduced thrips numbers compared with water. All three mite species reduced F. occidentalis numbers, and spinosad had no effect on predatory mites. Though H. miles could not be counted, the numbers of thrips in treatments with H. miles were lower than those in treatments without the mite. Thrips numbers were lowest on Camino Real and highest on Camarosa. These results suggest that the use of Camino Real with spinosad applications followed by releases of predatory mites can significantly reduce thrips numbers.     

Direct and indirect effects of simulated calcareous dredge material on eggs and larvae of pink snapper Pagrus auratus

The direct and indirect effects of a simulated, calcarenite‐based dredge material on eggs and larvae of pink snapper Pagrus auratus were assessed. Direct effects were assessed by measuring hatch rate or survival of eggs and pre‐feeding larvae, respectively, over a range of concentrations and exposure durations. Exposure of eggs to suspended solid concentrations up to 10 000 mg l^?1 for 24 h did not affect egg buoyancy or hatch rate, despite sediment adherence occurring at the two highest concentrations tested. Newly hatched larvae, whose mouths were still closed, were relatively tolerant of suspended solids, with a 12 h lethal concentration resulting in 50% mortality, LC₅₀, of 2020 mg l^?1 and a first observable effect concentration of 150 mg l^?1. Once the larvae's mouths opened, tolerance was significantly reduced, with a 12 h LC₅₀ of 157 mg l^?1 and a first observable effect concentration of 4 mg l^?1. Tolerance of larvae to suspended solids was negatively correlated with suspended solids concentration and exposure time, with exposure durations of ≤6 h being significantly less detrimental than those of 9 h or more. Indirect effects to larvae were assessed by measuring ingestion of copepod nauplii by 10 and 15 days post‐hatch (dph) larvae at sediment concentrations from 0 to 200 mg l^?1 in 50 mg l^?1 increments over 4 h. Ingestion was not significantly affected by sediment for 10 dph larvae, but by 15 dph, sediment had a far greater impact on ingestion, with larvae in all sediment treatments eating significantly fewer copepods than those in the control.     

Effects of selected insecticides on Cotesia plutellae, endoparasitoid of Plutella xylostella

Effects of field dosages ofselected insecticides to Cotesiaplutellae (Kurdjumov) (Hymenoptera: Braconidae), a larval endoparasitoidof Plutella xylostella L. (Lepidoptera: Plutellidae), wereinvestigated under laboratory conditions.Emergence of adult C. plutellae frominsecticide-treated pupae was not significantlydifferent from the control treatment. Contacttoxicity to C. plutellae adults variedgreatly among the insecticides in a paperresidue contact bioassay. Threeazadirachtin-based insecticides, Agroneem(4.8 mg a.i.liter^–1), Neemix (20 mga.i.liter^–1) and Ecozin (20 mgai.liter^–1) caused 11.1, 16.7 and 5.6%adult mortality, respectively. Of fourcommercial Bacillus thuringiensis (Bt)insecticides examined (all at 1.2 mga.i.liter^–1), Crymax and Xentari had noeffect on adult parasitoids, whereas Mattchcaused 5.6% mortality, and Dipel caused 11.1%mortality. Indoxacarb (53 mg a.i.liter^–1),-cyhalothrin (28 mg a.i.liter^–1) andspinosad (53 mg a.i.liter^–1) caused 100,88.5 and 50% adult mortalities, respectively.Low adult mortality (0–5.6%) was recorded fromingestion of azadirachtin-based, Btinsecticides and indoxacarb, compared with100% adult mortality in treatments of spinosador -cyhalothrin. Compared with the watercontrol, ingestion of azadirachtin-basedinsecticides significantly reduced parasitismby 50–57%, and Bt insecticides by 8–25%.However, ingestion of these insecticides didnot affect longevity of male and femaleparasitoid adults with one exception; femalelongevity was significantly reduced in theindoxacarb treatment. Insecticide residuescaused considerable mortality of C.plutellae adults, 39 and 44% mortality causedby 10 d old indoxacarb and -cyhalothrin,respectively, and 24 and 0% mortality causedby 7 and 10 d old residues of spinosad,respectively.     

Influence of spinosad on immature and adult stages of <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> (Stephens) (Neuroptera: Chrysopidae)

Toxicity of spinosad to immature stages of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and its effect on the reproduction and survival of adult stages after direct spray and ingestion treatments were evaluated. Spinosad was harmless to C. carnea eggs and pupae irrespective of concentrations or method of treatments. Direct spray of spinosad to first instar caused significant reduction in rate of pupation and L1-adult survival, but did not affect the rate of adult emergence. Third-instar bioassay revealed significant difference in L3-adult survival. When C. carnea first instars were fed upon spinosad-treated-Brevicoryne brassicae (L.), significant differences in investigated parameters were not observed among different treatments. The weight of third instar and pupae were comparable regardless of tested spinosad concentrations. Also, feeding on spinosad treated-B. brassicae had no negative impact on fecundity and fertility. Furthermore, ingestion of spinosad contaminated-B. brassicae significantly prolonged larval and larval + pupal periods. The larval feeding capacity of C. carnea did not differ significantly between larvae fed on spinosad-treated and untreated aphids with the exception of first instar. When C. carnea adults were allowed to oviposit on spinosad treated-substrate, total number of eggs laid, percent of eggs laid on the treated substrate and egg hatching did not differ from those of control. However, when adults were fed on spinosad-treated artificial diet, negative effects on adult survival and fecundity were observed.

Oviposition and feeding behavior of the maize borer,Chilo partellus,in response to eight essential oil allelochemicals

Eight essential oil compounds were evaluated against the maize borer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), to determine their influence on oviposition and feeding behavior. Thymol was the most active compound against C. partellus when evaluated as an oviposition deterrent (ODI₅₀ = 1.36 mg ml^?1), an ovicide (LC₅₀ = 2.06 mg ml^?1), or a feeding deterrent (FI₅₀ = 141.8 μg cm^?2) in laboratory experiments. The results corroborated with greenhouse experiments, in which egg laying on maize plants was inhibited significantly when the treatment was 15 times the concentration used in the laboratory experiments. However, there was neither any correlation between oviposition deterrence and feeding inhibition, nor between oviposition deterrence and ovicidal action. Apparently, toxicity per se or ovicidal action does not play any role in choice of oviposition in C. partellus. This was more obvious when the efficacy of compounds was compared in greenhouse experiments where ODI values and number of eggs laid on the treated leaves did not differ significantly in choice and no‐choice situations. Apparently, toxicity plays an important role in predicting host plant choice, but behavioral response in terms of oviposition preference is independent of toxic action, particularly for non‐host toxins. Thus, the same compounds affecting oviposition behavior on the one hand and having ovicidal or feeding deterrent properties on the other could be useful in field situations in any area‐wide integrated pest management model.     

Effect of insecticides on the diamondback moth (Lepidoptera: Plutellidae) and its parasitoid Diadegma insulare (Hymenoptera: Ichneumonidae)

Studies were conducted to evaluate the toxicity of insecticides to adult Diadegma insulare (Cresson) and its host the diamondback moth, Plutella xylostella (L.). Leaf-dip and direct-dip bioassays for diamondback moth larvae and residual bioassays for adults of diamondback moth and D. insulare were used to assess mortalities. Larval mortalities at field rates were significantly higher with carbaryl, permethrin, spinosad, and tebufenozide when compared with Bacillus thuringiensis, or imidacloprid in the larval-dip bioassay 72 h after treatment. In the leaf-dip and residual bioassays, both permethrin and spinosad caused 100% mortalities to diamondback moth larvae and adults, respectively, 72 h after treatment. Of all the materials tested, only B. thuringiensis and tebufenozide were not toxic to D. insulare 24 h after treatment. Spinosad was not toxic to D. insulare 30 min after treatment. However, 100% mortality was observed 8 h after treatment.     

Effects of neem and spinosad on Ceratothripoides claratris (Thysanoptera: Thripidae), an important vegetable pest in Thailand, under laboratory and greenhouse conditions

Toxicity of three biopesticides, i.e., two neem products and spinosad, was determined on foliage-dwelling life stages of Ceratothripoides claratris (Shumsher) (Thysanoptera: Thripidae), a major thrips pest on tomatoes, Lycopersicon spp., in central Thailand. Direct and residual contact toxicities of NeemAzal-TS (1% azadirachtin) and systemic activity of NeemAzal-MD 5 (5% azadirachtin) affected the survival of first larval stage (L1) in a concentration-dependent manner. However, neither second larval stage (L2) nor adult survival was influenced by both neem products. On the contrary, spinosad caused 100% mortality in both larval stages and adults of C. claratris regardless of the concentrations tested. No strong ovicidal effects were detected in three different age groups of eggs (i.e., 1, 2, and 3 d old) topically treated with both NeemAzal-TS and spinosad. Residual toxicity was highest with fresh residues of NeemAzal-TS compared with 1-, 3-, 5-, and 7-d-old residues and in general was higher under laboratory than greenhouse conditions. Irrespective of the age of the spray residues, spinosad always caused 100% mortality in larvae and adults. Strongest systemic effects were observed in L1 larvae 1 d after soil drenching with NeemAzal-MD 5 at the highest concentration tested. Foliar and soil applications of NeemAzal-TS and NeemAzal-MD 5, respectively, did not cause any oviposition deterrent effects.     

Significance of penetration,excretion, and transovarial uptake to toxicity of three insect growth regulators in predatory lacewing adults

Topical treatment of the predatory lacewing adults, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) before and after the onset of oviposition with diflubenzuron (DFB) at doses based on the maximum field recommended concentration resulted in a total inhibition of egg hatch due to death of the embryo. In contrast, pyriproxyfen (PYR) and tebufenozide (TEB) did not affect fecundity and egg fertility. To explain these differences in toxicity, the patterns of penetration through the cuticle, distribution inside the insect body, and excretion were studied using [(14)C]-labeled isotopes of each insect growth regulator (IGR). Penetration of DFB and TEB reached about 16 and 26% in 7 days, whereas 88% of PYR had penetrated in 24 h. However, the rate of excretion for PYR was very high, compared to that of DFB and TEB. Low amounts of absorbed radioactivity were recovered from the female body with the exception of DFB, the ovaries and the eggs deposited during a week. DFB and PYR concentration reached a peak in the eggs deposited at the fourth and second day after treatment, respectively. The current data indicate the importance of penetration through the insect cuticle. However, other mechanisms are likely to be involved in the selectivity of the current IGRs towards this beneficial insect.     

Efficacy of pesticides on the functional response on larval ectoparasitoid,Habrobracon hebetor Say (Hymenoptera: Braconidae)

Exposing to sub-lethal and low lethal doses of pesticides may cause changes in natural enemy behavioural, such as functional, response. In this study, the effects of chlorpyrifos, carbaryl, abamectin and spinosad were evaluated on the functional response of the Habrobracon hebetor to different densities of last instar larvae of Anagasta kuehniella Zeller. Young adult females of the parasitoid were exposed to LC₃₀ of chlorpyrifos, carbaryl, abamectin and spinosad that were 0.32, 4.03, 3.05 and 17.51?mg a.i./l for 24?h, respectively. Host densities of 2, 4, 8, 16, 32 and 64 were offered to treated young females for 2?h in 10-cm Petri dishes and then the parasitism data were recorded. Experiments were conducted in eight replications. Functional response type was determined using logistic regression and the parameters were appraised by non-linear regression using statistical analysis software. Functional response was type Ш in control and insecticide treatments. Searching efficiency in control, chlorpyrifos-, carbaryl-, abamectin- and spinosad-treated wasps were 0.008?±?0.002, 0.002?±?0.0009, 0.0034?±?0.0013, 0.0076?±?0.002 and 0.0073?±?0.002?h^?1and handling times were 1.38?±?0.1, 7.64?±?1.01, 3.3?±?0.315, 1.55?±?0.1 and 1.46?±?0.11?h, respectively. Chlorpyrifos and carbaryl had the highest effect on searching efficiency of H. hebetor. Spinosad and abamectin showed less adverse effect on the functional response parameters. Finally, after conducting the advanced field studies, spinosad and abamectin may be used as a compatible chemical material with biological control agent in integrated pest management programmes.