Monitoring of resistance to spirodiclofen and five other acaricides in Panonychus citri collected from Chinese citrus orchards

BACKGROUND: Citrus red mite, Panonychus citri (McGregor), is one of the most important pesticide‐resistant pests in China. In order better to understand its resistance status, six populations of the mite were collected from Chinese citrus orchards for monitoring of resistance to spirodiclofen and another five acaricides. RESULTS: All the samples collected in the field in 2006 were susceptible to spirodiclofen. However, the LC₅₀ values in populations sampled in 2009 ranged from 3.29 to 418.24 mg L^?1 spirodiclofen, a 127‐fold difference between the least and most sensitive populations. Compared with a susceptible strain, 50‐fold and 90.8‐fold resistance to spirodiclofen was detected in populations sampled from Pinghe and Fuzhou in 2009, as well as cross‐resistance to spirotetramat. The LC₅₀ values for abamectin, fenpropathrin, hexythiazox and pyridaben in the collected samples ranged from 0.041 to 3.52 mg L^?1, from 23.91 to 696.16 mg L^?1, from 13.94 to 334.19 mg L^?1 and from 48.90 to 609.91 mg L^?1 respectively. CONCLUSION: Great variations in resistance to the tested acaricides were observed among the sampled populations. The Pinghe population developed resistance to all the acaricides tested. The Jianning population was susceptible to most acaricides tested, except pyridaben. Resistance management strategies were conducted on the basis of these observations. Copyright © 2010 Society of Chemical Industry     

Insecticide resistance status of Bemisia tabaci Q‐biotype in south‐eastern Spain

BACKGROUND: Bemisia tabaci Gennadius Q‐biotype has readily developed resistance to numerous insecticide classes. Studies in the Mediterranean area are needed to clarify the resistance status and cross‐resistance patterns in this invasive whitefly biotype. The levels of resistance in nymphs of seven strains of B. tabaci Q‐biotype from south‐eastern Spain to representative insecticides were determined. RESULTS: Six populations had low to moderate levels of resistance to azadirachtin (0.2‐ to 7‐fold), buprofezin (11‐ to 59‐fold), imidacloprid (1‐ to 15‐fold), methomyl (3‐ to 55‐fold), pyridaben (0.9‐ to 9‐fold), pyriproxyfen (0.7‐ to 15‐fold) and spiromesifen (1‐ to 7‐fold), when compared with a contemporary Spanish Q‐biotype reference population (LC₅₀ = 2.7, 8.7, 15.2, 19.9, 0.34, 20.9 and 1.1 mg L^?1 respectively). A single population collected from a greenhouse subject to intensive insecticide use exhibited generally higher resistance levels to the same array of compounds (31‐, 1164‐, 3‐, 52‐, 9‐, 19‐ and 3‐fold respectively). Pyridaben and spiromesifen were extremely effective against nymphs of all strains, with LC₅₀ values significantly below recommended application rates. CONCLUSION: In contrast to previous reports, high rates of efficacy exist for numerous insecticide classes against B. tabaci Q‐biotype populations in these intensive agricultural regions of south‐eastern Spain. This probably reflects the recent and significant reductions in exposure that have resulted from a wider uptake of IPM technologies and strategies. However, the continued presence of resistance genes also suggests that a reversion to levels of high insecticide exposure could result in a rapid selection for resistance. Copyright © 2009 Society of Chemical Industry     

Larvicidal activity of Cnidium monnieri fruit coumarins and structurally related compounds against insecticide-susceptible and insecticide-resistant Culex pipiens pallens and Aedes aegypti

BACKGROUND: An assessment was made of the toxicity of imperatorin and osthole identified in Cnidium monnieri fruit, 11 related compounds and five insecticides to larvae from insecticide‐susceptible Culex pipiens pallens (KS‐CP strain) and Aedes aegypti and wild C.p. pallens (YS‐CP colony) using a direct‐contact mortality bioassay. Results were compared with those of the conventional larvicide temephos. RESULTS: Imperatorin (LC₅₀ = 3.14 and 2.88 mg L^?1) was 1.9‐, 3.7‐ and 4.2‐fold and 2.4‐, 4.5‐ and 4.6‐fold more toxic than isopimpinellin, isoimperatorin and osthole against susceptible C. p. pallens and A. aegypti larvae respectively. Overall, all of the compounds were less toxic than temephos (0.011 and 0.019 mg L^?1). The toxicity of these compounds was virtually identical against larvae from the two Culex strains, even though YS‐CP larvae were resistant to fenthion (resistance ratio RR = 390), deltamethrin (RR = 164), cyfluthrin (RR = 14) and temephos (RR = 14). This finding indicates that the coumarins and the insecticides do not share a common mode of action. The structure–activity relationship indicates that the chemical structure and alkoxy substitution and length of the alkoxyl side chain at the C8 position are essential for imparting toxicity. CONCLUSION: The C. monnieri fruit‐derived coumarins and the related coumarins described merit further study as potential insecticides or lead molecules for the control of insecticide‐resistant mosquito populations. Copyright © 2012 Society of Chemical Industry     

Risk posed to honeybees (Apis mellifera L,Hymenoptera) by an imidacloprid seed dressing of sunflowers

In a greenhouse metabolism study, sunflowers were seed‐treated with radiolabelled imidacloprid in a 700 g kg^?1 WS formulation (Gaucho® WS 70) at 0.7 mg AI per seed, and the nature of the resulting residues in nectar and pollen was determined. Only the parent compound and no metabolites were detected in nectar and pollen of these seed‐treated sunflower plants (limit of detection <0.001 mg kg^?1). In standard LD₅₀ laboratory tests, imidacloprid showed high oral toxicity to honeybees (Apis mellifera), with LD₅₀ values between 3.7 and 40.9 ng per bee, corresponding to a lethal food concentration between 0.14 and 1.57 mg kg^?1. The residue level of imidacloprid in nectar and pollen of seed‐treated sunflower plants in the field was negligible. Under field‐growing conditions no residues were detected (limit of detection: 0.0015 mg kg^?1) in either nectar or pollen. There were also no detectable residues in nectar and pollen of sunflowers planted as a succeeding crop in soils which previously had been cropped with imidacloprid seed‐treated plants. Chronic feeding experiments with sunflower honey fortified with 0.002, 0.005, 0.010 and 0.020 mg kg^?1 imidacloprid were conducted to assess potential long‐term adverse effects on honeybee colonies. Testing end‐points in this 39‐day feeding study were mortality, feeding activity, wax/comb production, breeding performance and colony vitality. Even at the highest test concentration, imidacloprid showed no adverse effects on the development of the exposed bee colonies. This no‐adverse‐effect concentration of 0.020 mg kg^?1 compares with a field residue level of less than 0.0015 mg kg^?1 ( = limit of detection in the field residue studies) which clearly shows that a sunflower seed dressing with imidacloprid poses no risk to honeybees. This conclusion is confirmed by observations made in more than 10 field studies and several tunnel tests. © 2001 Society of Chemical Industry     

Determination of baseline susceptibility of European populations of Tuta absoluta (Meyrick) to indoxacarb and chlorantraniliprole using a novel dip bioassay method

BACKGROUND: Tuta absoluta(Meyrick) is one of the most serious pests of tomato recently introduced in the Mediterranean region. A novel bioassay method designed for the accurate determination of insecticide toxicity on T. absoluta (IRAC method No. 022) was validated by three different laboratories [Greece (NAGREF), Italy (UC) and Spain (UPCT)] on European populations. RESULTS: The insecticides indoxacarb and chlorantraniliprole were used as reference products. The IRAC leaf dip method is easy to perform, producing repeatable, homogeneous responses. LC₅₀ values for indoxacarb ranged between 1.8 and 17.9 mg L^?1 (NAGREF), 0.93 and 10.8 mg L^?1 (UC) and 0.20 and 0.70 mg L^?1 (UPCT), resulting in a tenfold, 12‐fold and fourfold difference between the least and most susceptible populations at each laboratory respectively. For chlorantraniliprole, LC₅₀ values ranged between 0.10 and 0.56 mg L^?1 (NAGREF), 0.23 and 1.34 mg L^?1 (UC) and 0.04 and 0.24 mg L^?1 (UPCT), resulting in a sixfold difference in all three cases. Overall, UPCT reported lower mean LC₅₀ to indoxacarb, while UC reported higher LC₅₀ to chlorantraniliprole. CONCLUSIONS: The new bioassay is reliable, providing a useful tool in the design of IRM strategies. Within each country/lab, the variability observed in the results for both indoxacarb and chlorantraniliprole can be attributed to natural variation. Future research is necessary to determine the extent to which it is possible to compare results among laboratories. Copyright © 2012 Society of Chemical Industry     

Shift in the level of susceptibility and relative resistance of brinjal shoot and fruit borer <Emphasis Type="Italic">Leucinodes orbonalis</Emphasis> (Guen) to diamide insecticides

Brinjal shoot and fruit borer Leucinodes orbonalis Guen. is a major pest of brinjal in India. The field collected larvae of L.orbonalis were tested for their susceptibility to three diamide insecticides by fruit dip bioassay technique. Cyantraniliprole and chlorantraniliprole were 5.23 and 2.80 times more toxic to L. orbonalis as compared to flubendiamide. Large variation in the susceptibility of L. orbonalis to cyantraniliprole, chlorantraniliprole, flubendiamide was observed and the LC₅₀ values were 0.084, 0.157 and 0.439 mg a.i. L^?1, respectively. In span of two years there was a significant increase in the LC₅₀ values of cyantraniliprole (0.062 to 0.085 mg a.i. L^?1), chlorantraniliprole (0.097 to 0.157 mg a.i. L^?1), flubendiamide (0.284 to 0.439 mg a.i. L^?1) to population of L. orbonalis, which showed 1.35, 1.62 and 1.55 fold resistance, respectively indicating faster development of resistance to diamide insecticides.     

Insecticide toxic effects on Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)

BACKGROUND: The parasitoid Trichogramma ostriniae (Pang and Chen) is a major natural enemy of many lepidopterans, but only a few studies have been conducted on the compatibility of biological and chemical controls. In this study, the selectivity of 30 insecticides to T. ostriniae adults was evaluated. RESULTS: Among the seven classes of chemicals tested, organophosphates and carbamates had the highest intrinsic toxicity to the wasp, with LC₅₀ values ranging from 0.032 (0.029–0.038) to 2.38 (1.91–3.15) mg AI L^?1. They are followed by phenylpyrazoles, avermectins, neonicotinoids and pyrethroids, which induce variable toxicity responses, with LC₅₀ values ranging from 0.14 (0.11–0.21) to 56.67 (48.94–67.24) mg AI L^?1, from 2.57 (1.85–4.28) to 4.48 (3.34–6.83) mg AI L^?1, from 2.48 (1.80–4.03) to 503.6 (457.6–557.5) mg AI L^?1 and from 5.44 (3.95–8.84) to 104.2 (92.48–119.7) mg AI L^?1 respectively. The insect growth regulators (IGRs) exhibited least toxicity to the parasitoid. CONCLUSION: Risk quotient analysis classifies neonicotinoids, avermectins, pyrethroids, IGRs and phenylpyrazoles (with the exception of butane‐fipronil and fipronil) as safe agents to the parasitoid, but categorises organophosphates and carbamates as slightly to moderately toxic or dangerous to T. ostriniae. Copyright © 2012 Society of Chemical Industry     

Selection for imidacloprid resistance in silverleaf whiteflies from the Imperial Valley and development of a hydroponic bioassay for resistance monitoring

A field-collected population of the silverleaf whitefly, Bemisia argentifolii, was selected with the nicotinyl compound, imidacloprid, over 32 generations to determine if resistance would develop when maintained under continuous selection pressure in a greenhouse. Resistance was slow to increase at first with low to moderate levels of resistance (RR from 6- to 17-fold) in the first 15 generations of selection. Further selection steadily led to higher levels of resistance, with the greatest resistance ratio at 82-fold, the gradual rise suggesting the involvement of a polygenic system. At the end of the selection, slopes of probit regressions were substantially steeper than earlier, indicating increased homogeneity of imidacloprid resistance in this strain. A hydroponic bioassay featuring systemic uptake of imidacloprid through roots was developed to monitor the changes in resistance to imidacloprid in the selected whitefly strain and in seven field-collected strains from Imperial Valley, California. Six out of seven field-collected strains exhibited low LC₅₀ values (0·002 to 0·512 mg ml^-1) compared to the selected resistant strain, with one exception where the LC₅₀ was 0·926 mg ml^-1 (RR=15·0). Variation in responses to imidacloprid in the field strains suggest that this technique is sufficiently sensitive to detect differences in susceptibilities of whitefly populations. The imidacloprid-resistant strain showed no cross-resistance to endosulfan, chlorpyrifos or methomyl (RR ranging from 0·4- to 1·5-fold). A low level of cross-resistance was observed to bifenthrin in the IM-R strain at 7-fold. The success of selection for resistance to imidacloprid has serious implications for whitefly control programs that rely heavily on imidacloprid. ©1997 SCI     

Bioactivity of short-chain aliphatic ketones against adults of the granary weevil, Sitophilus granarius (L.)

BACKGROUND: The granary weevil, Sitophilus granarius (L.), is one of the most damaging pests of stored grains, causing severe quantitative and qualitative losses. Sustainable control means, alternative to the commonly used fumigants and broad‐spectrum contact insecticides, are urgently needed owing to legislative limits, the development of resistant insect strains and increasing consumer demand for safe food. Short‐chain aliphatic ketones, known to be emitted by cereal grains and previously identified as repellents to adult granary weevils, were evaluated for their ability to disrupt insect orientation towards wheat grains and as possible natural fumigants. RESULTS: In behavioural bioassays, 2‐pentanone, 2‐hexanone, 2‐heptanone and 2,3‐butanedione significantly reduced insect orientation towards odours of wheat grains, with 2‐hexanone and 2‐heptanone being the most active. In fumigation tests, all compounds were effective in killing weevil adults, but they performed differently according to chemical structure, speed of action and presence of wheat grains. In the presence of grains, the highest fumigant toxicity was shown by 2‐pentanone (LC₅₀ = 8.4 ± 1.0 mg L^?1) after 24 h exposure, and by 2‐pentanone (LC₅₀ = 4.5 ± 0.3 mg L^?1), 2‐heptanone (LC₅₀ = 7.1 ± 0.3 mg L^?1) and 2‐hexanone (LC₅₀ = 8.1 ± 0.6 mg L^?1) 1 week after the treatment end. CONCLUSION: Short‐chain aliphatic ketones have potential for applications in IPM programmes for the granary weevil because of their behaviour‐altering activity and fumigant toxicity. Copyright © 2011 Society of Chemical Industry     

Inheritance mode and realized heritability of resistance to imidacloprid in the brown planthopper,Nilaparvata lugens (Stål) (Homoptera: Delphacidae)

BACKGROUND: The brown planthopper, Nilaparvata lugens (Stål), is a serious pest that causes enormous losses to the rice crop in Asia. The genetic basis of imidacloprid resistance was investigated in N. lugens. RESULTS: The resistant strain, selected for imidacloprid resistance from a field population of N. lugens collected from Nanjing, Jiangsu Province, China, showed a 964‐fold resistance compared with the laboratory strain. Progenies of reciprocal crosses (F₁ and F₁′) showed similar dose–mortality responses (LC₅₀) to imidacloprid, and also exhibited a similar degree of dominance (D), 0.58 for F₁ and 0.63 for F₁′. Chi‐square analyses of self‐bred and backcross progenies (F₂, F₂′ and BC respectively) rejected the hypothesis for a single gene control of the resistance. The estimated realized heritability (h²) of imidacloprid resistance was 0.1141 in the resistant strain of N. lugens. CONCLUSION: The results showed that imidacloprid resistance in N. lugens was autosomal and was expressed as an incompletely dominant trait, probably controlled by multiple genes. Copyright © 2009 Society of Chemical Industry     

Contact and fumigant toxicity of plant essential oils and efficacy of spray formulations containing the oils against B‐ and Q‐biotypes of Bemisia tabaci

BACKGROUND: The contact + fumigant toxicity of 92 plant essential oils and control efficacy of 18 experimental spray formulations containing nine selected essential oils (0.5 and 0.1% sprays) and six commercial insecticides to females from B‐ and Q‐biotypes of Bemisia tabaci were evaluated using vapour‐phase mortality and spray bioassays. RESULTS: Garlic and oregano (LC₅₀, 0.15 mL cm^?3) were the most toxic oils against B‐ and Q‐biotype females. Strong fumigant toxicity to both biotype females was also obtained from catnip, cinnamon bark, clove bud, clove leaf, davana, savory and vetiver Haiti oils (LC₅₀, 0.17–0.48 mL cm^?3). The 0.5% sprays of these oils (except for thyme red oil) resulted in 90–100% mortality against both biotype females. Only garlic applied as 0.1% spray provided 100% mortality. Spinosad 100 g L^?1 suspension concentrate (SC) treatment resulted in 92 and 95% mortality against both biotype females, whereas acetamiprid 80 g L^?1 wettable powder (WP), imidacloprid 80 g L^?1 SC, thiamethoxam 100 g L^?1 water‐dispersible granule (WDG) and pyridaben 200 g L^?1 WP treatments resulted in 89–100% mortality against B‐biotype females only. CONCLUSION: In the light of global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment, the essential oils described, particularly garlic, cinnamon bark and vetiver Haiti, merit further study as potential insecticides for the control of B. tabaci populations as fumigants with contact action. Copyright © 2011 Society of Chemical Industry     

Dicofol resistance in Tetranychus cinnabarinus: resistance and stability of resistance in populations from Antalya, Turkey

Resistance against dicofol was investigated in the carmine spider mite, Tetranychus cinnabarinus. Higher resistance levels were detected by leaf residual bioassays than by topical bioassays, both done using a Potter spray tower, in almost all populations of T cinnabarinus examined from Antalya, Turkey. For instance, the resistance level at LC₉₅ was 17.5‐fold in topical bioassays but 58.9‐fold in leaf residual bioassays for the population collected from greenhouses in the Topçular district. There were differences of resistance levels at LC₉₅, ranging between 2.6‐ and 23.9‐fold using topical bioassays and between 5.0‐ and 58.9‐fold in residual bioassays, in populations collected from greenhouses from various districts. Populations from cotton showed lower resistance levels against dicofol than populations from greenhouses. Resistance to dicofol at LC₅₀ as indicated by topical and residual bioassays increased 19.7‐ and 100.7‐fold, respectively, in a colony from the laboratory strain of T cinnabarinus selected with dicofol alone for 16 cycles. However, the dicofol resistance at LC₅₀ increased 19.4‐ and 52.0‐fold in another colony selected in rotation with dicofol and tetradifon for six and eight cycles, respectively. The changes in resistance to dicofol 5 months after the selection ceased were as follows: in the colony selected for dicofol alone, using topical and residual bioassays, the resistance levels at LC₅₀ decreased to 11.7‐ and 99.1‐fold, respectively, and in the colony selected in rotation with dicofol and tetradifon to 10.8‐ and 15.8‐fold, respectively. © 2001 Society of Chemical Industry     

Fumigant toxicity of volatile natural products from Korean spices and medicinal plants towards the rice weevil,Sitophilus oryzae (L)

The fumigant toxicity of various volatile constituents of essential oils extracted from sixteen Korean spices and medicinal plants towards the rice weevil, Sitophilus oryzae L (Coleoptera: Curculionidae), was determined. The most potent toxicity was found in the essential oil from Mentha arvensis L var piperascens (LC₅₀ = 45.5 µl litre^?1 air). GC–MS analysis of essential oil from M arvensis showed it to be rich in menthol (63.2%), menthone (13.1%) and limonene (1.5%), followed in abundance by β‐pinene (0.7%), α‐pinene (0.6%) and linalool (0.2%). Treatment of S oryzae with each of these terpenes showed menthone to be most active (LC₅₀ = 12.7 µl litre^?1 air) followed by linalool (LC₅₀ = 39.2 µl litre^?1 air) and α‐pinene (LC₅₀ = 54.9 µl litre^?1 air). Studies on inhibition of acetylcholinesterase activity of S oryzae showed menthone to have a nine‐fold lower inhibitory effect than menthol, despite menthone being 8.1‐fold more toxic than menthol to the rice weevil. Different modes of toxicity of these monoterpenes towards S oryzae are discussed. © 2001 Society of Chemical Industry     

Responses of striped stem borer,Chilo suppressalis (Lepidoptera: Pyralidae), from Taiwan to a range of insecticides

BACKGROUND: Information on the insecticide susceptibility of striped stem borer, Chilo suppressalis (Walker), is essential for an effective pest management programme. An early detection of resistance development can prompt the modification of current control methods and increase the lifespan of insecticides through the rotation of chemicals with different modes of action. In this study, the susceptibility of this pest in Taiwan to four classes of insecticides has been examined. RESULTS: Over 1000‐fold resistance to carbofuran was detected in C. suppressalis collected from Chiayi and Changhua prefectures, with estimated LC₅₀ values of > 3 mg cm^?2. In addition, 61‐fold resistance to cartap was found in the Chiayi population. On the other hand, all tested populations of rice stem borer were still relatively susceptible to chlorpyrifos, fipronil and permethrin, with LC₅₀ values ranging from 30 to 553 ng cm^?2. Chilo suppressalis populations collected from the central parts of Taiwan have a higher degree of resistance to the tested insecticides than those from northern areas. CONCLUSION: The occurrence of high resistance to carbofuran in the Chiayi and Changhua areas suggests that this compound should be replaced with chemicals having a different mode of action, such as chlorpyrifos, fipronil and permethrin, to which low cross‐resistance has been detected. Copyright © 2010 Society of Chemical Industry     

Acaricidal activities of Santolina africana and Hertia cheirifolia essential oils against the two-spotted spider mite (Tetranychus urticae)

BACKGROUND: Many plant essential oils show a broad spectrum of activity against pests. This study investigated the effects of two essential oils on Tetranychus urticae, one of the most serious pests in the world. RESULTS: The chemical composition of the two oils was characterised by GC‐MS. The most abundant component in the Santolina africana (Jord. & Fourr) oil was terpinen‐4‐ol (54.96%), while thymol (61%) was prevalent in the Hertia cheirifolia (L.) oil. Mortality and fecundity were measured upon treatment with oil concentrations ranging from 0.07 to 6.75 mg L^?1 with a Potter spray tower. Mite mortality increased with oil concentration, with LC₅₀ values of 2.35 mg L^?1 for S. africana and 3.43 mg L^?1 for H. cheirifolia respectively. For both oils, a reduction in fecundity was observed at concentrations of 0.07, 0.09 and 0.29 mg L^?1. Artificial blends of constituents of oils were also prepared and tested with individual constituents missing from the mixture. The results showed that the presence of all constituents was necessary to equal the toxicity of the two natural oils. CONCLUSION: S. africana and H. cheirifolia oils can provide valuable acaricide activity with significantly lower LC₅₀ values. Thus, these oils cause important mortality and reduce the number of eggs laid by females. Copyright © 2012 Society of Chemical Industry     

Toxicity of spiromesifen to the developmental stages of Bemisia tabaci biotype B

BACKGROUND: Spiromesifen is a novel insecticidal/acaricidal compound derived from spirocyclic tetronic acids that acts effectively against whiteflies and mites via inhibition of acetyl‐CoA‐carboxylase, a lipid metabolism enzyme. The effects of spiromesifen on the developmental stages of the whitefly Bemisia tabaci (Gennadius) were studied under laboratory conditions to generate baseline action thresholds for field evaluations of the compound. RESULTS: Adult B. tabaci mortality rate after spiromesifen treatment (5 mg L^?1) was 40%. Treatment with 0.5 mg L^?1 reduced fecundity per female by more than 80%, and fertility was almost nil. LC₅₀ for eggs was 2.6 mg L^?1, and for first instar 0.5 mg L^?1. Scanning electron microscopy revealed that eggs laid by treated adult females had an abnormally perforated chorion, and females were unable to complete oviposition. Light and fluorescent microscopy showed significantly smaller eggs following treatment, and smaller, abnormally formed and improperly localized bacteriomes in eggs and nymphs. The number of ovarioles counted in females treated with 5 mg L^?1 was significantly reduced. Spiromesifen showed no cross‐resistance with other commonly used insecticides from different chemical groups, and resistance monitoring in Israel showed no development of field resistance to this insecticide after 1 year of use. CONCLUSION: The strong effect on juvenile stages of B. tabaci with a unique mode of action and the absence of cross‐resistance with major commonly used insecticides from different chemical groups suggest the use of spiromesifen in pest and resistance management programmes. Copyright © 2008 Society of Chemical Industry     

Common oils and insecticidal control and their resistance to Aleuroclava jasmini (Hem.: Aleyrodidae) on paper mulberry in Iran

Abstract

Aleuroclava jasmini (Hemiptera: Aleyrodidae) is a major insect pest of paper mulberry (Broussonetia papyrifera) in Iran, negatively affecting its production. Considering the importance of oils in the integrated management programs of such pests, the present study examined the possibility of whitefly control on paper mulberry plant to assess mortality rate (MR), synergistic rate (SR), resistance rate (RR), and lethal concentration for 50% of the population (LC₅₀) of oils and common insecticide in populations from four areas of Tehran, Iran (one susceptible and three non-susceptible). The best chemical treatments against A. jasmini adults and nymphs in paper mulberry plants were neem oil (1?ml L^?1) mixed with deltamethrin (0.5?ml L^?1) or with buprofezin (1?ml L^?1). The neem, akylarylpolyglyglycol ether and volk oils mixed with deltamethrin or buprofezin also had synergistic effects on adults and nymphs of A. jasmini, respectively, in Azadi, Shahrake Gharb, and Vanak areas (non-susceptible populations), but with higher concentrations (> LC₅₀) and lower SR than in Garm Dareh area (susceptible population). We observed that A. jasmini adults showed the greatest resistance to deltamethrin in Vanak area and nymphs of this pest to buprofezin in Shahrake Gharb area.     

Use of natural pyrethrum to control the red swamp crayfish Procambarus clarkii in a rural district of Italy

BACKGROUND: The crayfish Procambarus clarkii inflicts severe ecological and economic damages in Europe. To develop an efficient method for its control, four experiments were carried out to assess the impact of natural pyrethrum (i.e. Pyblast) on crayfish: (1) the 24 h LC₁₀₀ and LC₅₀ were quantified on crayfish; (2) the breakdown time of the 24 h LC₁₀₀ was assessed using Daphnia magna as a bioindicator; the effects of 24 h LC₁₀₀ on crayfish were investigated by applying the biocide into burrows (3) and in a drainage channel (4). RESULTS: Pyblast concentrations of 0.05 and 0.02 mg L^?1 corresponded to 24 h LC₁₀₀ and LC₅₀ respectively. The concentration of 0.05 mg L^?1 broke down after 72 h, whereas 0.02 mg L^?1 did not cause any significant mortality in D. magna after 24 h. However, 0.05 mg L^?1 had no effect on crayfish when introduced into the burrows, but led to a mortality of 95% when applied in the water. CONCLUSION: Experimental evidence is provided for the efficacy of Pyblast to control invasive crayfish. Obviously, before its use on a large scale, further studies are needed to find a concentration that will achieve the target 100% mortality with the shortest recovery time of the environment. Copyright © 2012 Society of Chemical Industry     

Inheritance of resistance to fenoxaprop‐p‐ethyl in sprangletop (Leptochloa chinensis L. Nees)

Sprangletop (Leptochloa chinensis L. Nees) is a serious grass weed in direct‐seeded rice cropping systems in Thailand. One population of sprangletop, BLC1, was found to be resistant to fenoxaprop‐p‐ethyl at 62‐fold the concentration of a susceptible biotype, SLC1. This study elucidated the inheritance of resistance to fenoxaprop‐p‐ethyl in this sprangletop BLC1 genotype. The reaction to the herbicide at 0.12–2.4 mg ai L^?1 was determined in the seedlings of self‐pollinated resistant BLC1, susceptible SLC1 and SLC1 that had been allowed to cross‐pollinate with BLC1. At 0.24 mg ai L^?1, all the seedlings of SLC1 were killed, while 99% of BLC1 survived, along with 5% of the cross‐pollinated SLC1 seedlings, which were considered to be putative F₁ hybrids. The root and shoot lengths of the F₁ hybrids in 0.24 mg ai L^?1 of fenoxaprop‐p‐ethyl, relative to those in the absence of the herbicide, were close to or the same as the resistant parent, indicating that the resistance is a nearly complete to complete dominant trait. One‐hundred‐and‐forty‐one of the F₂‐derived F₃ families were classified by their response to the herbicide at 0.24 and 0.48 mg ai L^?1 into 39 homozygous susceptible : 72 segregating : 30 homozygous resistant, fitted with a 1:2:1 ratio at χ² = 1.21 and P = 0.56, indicating that the resistance to fenoxaprop‐p‐ethyl in the sprangletop BLC1 genotype is controlled by a single gene.     

Species-specific insecticide resistance to imidacloprid and fipronil in the rice planthoppers Nilaparvata lugens and Sogatella furcifera in East and South-east Asia

BACKGROUND: In 2003 the development of insecticide resistance against neonicotinoids in the brown planthopper (BPH), Nilaparvata lugens (Stål) (Homoptera: Delphacidae), was first observed in Thailand and has since been found in other Asian countries such as Vietnam, China and Japan. However, the LD₅₀ values of BPH and the whitebacked planthopper (WBPH), Sogatella furcifera (Horváth), against both neonicotinoid and phenylpyrazole insecticides have been poorly reported in many Asian countries. RESULTS: The topical LD₅₀ values for imidacloprid in the BPH populations collected from East Asia (Japan, China, Taiwan) and Vietnam in 2006 were 4.3–24.2 µg g^?1 and were significantly higher than those collected from the Philippines (0.18–0.35 µg g^?1). The BPH populations indicated a positive cross‐resistance between imidacloprid and thiamethoxam. Almost all the WBPH populations from Japan, Taiwan, China, Vietnam and the Philippines had extremely large LD₅₀ values (19.7–239 µg g^?1 or more) for fipronil, except for several populations from the Philippines and China. CONCLUSION: Species‐specific changes in insecticide susceptibility were found in Asian rice planthoppers (i.e. BPH for imidacloprid and WBPH for fipronil). Insecticide resistance in BPH against imidacloprid occurred in East Asia and Indochina, but not in the Philippines. In contrast, insecticide resistance in WBPH against fipronil occurred widely in East and South‐east Asia. Copyright © 2008 Society of Chemical Industry