Lethal and sublethal effects of a novel cis-nitromethylene neonicotinoid insecticide,cycloxaprid, on Bemisia tabaci

The tobacco whitefly, Bemisia tabaci (Gennadius), is an important pest because of its potential to threaten agricultural crops worldwide. Currently, this pest is controlled by the application of chemical insecticides. In our pursuit to identify better insecticides for an effective control of this insect pest, we investigated the lethal effects of five neonicotinoid insecticides including four commercial neonicotinoids and a novel neonicotinoid (cycloxaprid) on B. tabaci MED and MEAM1 cryptic species. In addition, we assessed the sublethal effects of cycloxaprid on B. tabaci MED. Lethal effects of the insecticides were determined using the leaf-dip bioassay, and the results showed that among the tested insecticides cycloxaprid was more toxic to B. tabaci MED and MEAM1 than others, with LC₅₀ values of 0.70 mg/L and 0.59 mg/L, respectively. Cycloxaprid at LC₂₅ (0.16 mg/L) induced sublethal effects in adult MED by prolonging the developmental periods and decreasing the survival rates of all larval instars, pseudopupal and adult stages. Moreover, it significantly shortened the oviposition period of females and decreased their fecundity. Hatching rate of eggs laid by females exposed to LC₂₅ was also markedly reduced. These results indicate that cycloxaprid is a novel alternate insecticide that may effectively control B. tabaci populations.     

Impacts of Cucurbit Chlorotic Yellows Virus (CCYV) on Biological Characteristics of Its Vector Bemisia tabaci (Hemiptera: Aleyrodidae) MED Species

Plant viruses can change the phenotypes and defense pathways of the host plants and the performance of their vectors to facilitate their transmission. Cucurbit chlorotic yellows virus (CCYV) (Crinivirus), a newly reported virus occurring on cucurbit plants and many other plant species, is transmitted specifically by Bemisia tabaci MEAM1 (B biotype) and MED (Q biotype) cryptic species in a semipersistent manner. This study evaluated the impacts of CCYV on B. tabaci to better understand the plant-virus-vector interactions. By using CCYV-B. tabaci MED-cucumber as the model, we investigated whether or how a semipersistent plant virus impacts the biology of its whitefly vector. CCYV mRNAs were detectable in nymphs from first to fourth instars and adults of B. tabaci with different titers. Nymph instar durations and adult longevity of female whiteflies greatly extended on CCYV-infected plants, but nymph instar durations and adult longevity of male whiteflies were not significantly influenced. In addition, the body length and oviposition increased in adults feeding on CCYV-infected plants, but the hatching rates of eggs and survival rates of different stages were not affected. Most interestingly, the sex ratio (male:female) significantly reduced to 0.5:1 in whitefly populations on CCYV-infected plants, while the ratio remained about 1:1 on healthy plants. These results indicated that CCYV can significantly impact the biological characteristics of its vector B. tabaci. It is speculated that CCYV and B. tabaci have established a typical mutualist relationship mediated by host plants.     

Genetic Variation and Geographic Differentiation Among Populations of the Nonmigratory Agricultural Pest Oedaleus infernalis (Orthoptera: Acridoidea) in China

The nonmigratory grasshopper Oedaleus infernalis Saussure (Orthoptera : Acridoidea) is an agricultural pest to crops and forage grasses over a wide natural geographical distribution in China. The genetic diversity and genetic variation among 10 geographically separated populations of O. infernalis was assessed using polymerase chain reaction-based molecular markers, including the intersimple sequence repeat and mitochondrial cytochrome oxidase sequences. A high level of genetic diversity was detected among these populations from the intersimple sequence repeat (H: 0.2628, I: 0.4129, H_s: 0.2130) and cytochrome oxidase analyses (H_d: 0.653). There was no obvious geographical structure based on an unweighted pair group method analysis and median-joining network. The values of F_ST, θ^II, and Gst estimated in this study are low, and the gene flow is high (N_m> 4). Analysis of the molecular variance suggested that most of the genetic variation occurs within populations, whereas only a small variation takes place between populations. No significant correlation was found between the genetic distance and geographical distance. Overall, our results suggest that the geographical distance plays an unimpeded role in the gene flow among O. infernalis populations.     

Effect of Cardinium Infection on the Probing Behavior of Bemisia tabaci (Hemiptera: Aleyrodidae) MED

Facultative endosymbionts can affect the growth, physiology, and behavior of their arthropod hosts. There are several endosymbionts in the invasive whitefly Bemisia tabaci Mediterranean (MED, Q biotype) that influence host fitness by altering stylet probing behavior. We investigated the probing behavior of B. tabaci MED infected with the facultative endosymbiont Candidatus Cardinium hertigii (Cardinium (Sphingobacteriales: Flexibacteraceae)). We generated genetically similar Cardinium-infected (C^*+) and uninfected (C^-) clonal sublines and analyzed the probing behavior of newly emerged adult on cotton (Malvales: Malvaceae), Gossypium hirsutum L., using electropenetrography (EPG). The C^- subline demonstrated a longer duration of E2 (2.81-fold) and more events of E2 (2.22-fold) than the C^*+ subline, indicating a greater level of sustained ingestion of plant phloem. These findings provide insight into the fitness costs (fitness of a particular genotype is lower than the average fitness of the population) of the Cardinium-infected B. tabaci.     

Identification of the Population Structure of Myzus persicae (Hemiptera: Aphididae) on Peach Trees in China Using Microsatellites

In this study, we characterized the genetic structure of Myzus persicae (Sulzer) (Hemiptera: Aphididae) populations in China using microsatellites. We expected that these data will reveal the genetic relationships among various populations of M. persicae and will be of value in the development of better methods for pest control. Four hundred sixty individuals from 23 areas over 13 provinces were collected in the early spring of 2010, all from their primary host, Prunus persicae. The markers analyzed were highly polymorphic, as demonstrated by the expected heterozygosity value (H_e = 0.861) and the Polymorphism Information Content (PIC = 0.847), which indicated that M. persicae maintains a high level of genetic diversity. Analysis of molecular variance revealed an intermediate level of population differentiation among M. persicae populations (F_ST = 0.1215). Geographic isolation existed among these populations, and, consequently, the genetic structure of the populations was split into a southern group and a northern group divided by the Yangtse River.     

安徽省小麦赤霉病菌群体遗传多样性AFLP分析

为了解安徽省小麦赤霉病菌的群体分化和遗传变异规律,利用AFLP技术对安徽省4个地理群体的68个供试菌株进行了群体遗传多样性分析。结果表明,8对引物共扩增出245条带,供试菌株间的遗传距离为0.014~0.021。4个小麦赤霉病菌群体之间的遗传距离与地理分布没有明显的相关性。4个赤霉病菌群体的Shannon信息指数I为0.321,基因多样性指数H为0.193,表明具有一定的遗传多样性。方差分析表明,被测小麦赤霉病菌群体的遗传变异主要存在于群体内(99.80%),群体间的遗传变异仅占0.20%。4个赤霉病菌群体间存在较低的遗传分化(Gst=0.049)和频繁的基因交流(Nm=9.648)。相比较而言,北部群体和中部群体亲缘关系较近,而南部群体和中、北部群体亲缘关系较远。     

Cross-resistance, inheritance and stability of resistance to acetamiprid in cotton whitefly, Bemisia tabaci Genn (Hemiptera: Aleyrodidae)

The cotton whitefly Bemisia tabaci, (Genn.) is an important pest of field crops, vegetables and ornamentals worldwide. Neonicotinoids are considered an important group of insecticides being used against B. tabaci for several years. B. tabaci has developed resistance to some of the compounds of the group. This study was designed to investigate if the selection of B. tabaci with acetamiprid would give a broad-spectrum of cross-resistance and to genetically classify the resistance. At G₁ a low level of resistance to acetamiprid, imidacloprid, thiamethoxam, thiacloprid and nitenpyram was observed with resistance ratios of 3-fold, 8-, 9-, 6- and 5-fold, respectively, compared with a laboratory susceptible population. After selection for eight generations with acetamiprid, resistance to acetamiprid increased to 118-fold compared with the laboratory susceptible population. Selection also increased resistance to imidacloprid, thiamethoxam, thiacloprid, nitenpyram, endosulfan and bifenthrin but no change in susceptibility to fipronil was observed. Furthermore resistance in a field population was stable in the absence of acetamiprid selection pressure. Genetic crosses between resistant and susceptible populations indicated autosomal and incompletely recessive resistance. Further genetic analysis suggested that resistance could be controlled by a single factor. The high level of cross-resistance and stability of incomplete resistance in the field population is of some concern. However, lack of cross-resistance between acetamiprid and fipronil or unstable resistance in the resistant population could provide options to use alternative products which could reduce acetamiprid selection pressure.     

新疆伊犁地区小麦条锈菌群体遗传结构分析

新疆伊犁地区是小麦条锈病的常发区和重发区，其年平均发生面积超过100×10⁴ hm²以上。为明确新疆伊犁地区小麦条锈菌群体的遗传结构，2021年，从新疆伊犁地区的新源县、巩留县、察布查尔县和伊宁县共采集到320份小麦条锈菌标样，利用16对小麦条锈菌SSR引物进行了群体遗传研究。结果表明，新疆伊犁地区条锈菌群体遗传多样性水平较高，群体间存在一定的遗传分化。群体间遗传变异仅占总变异的12%，群体内遗传变异占88%，不同群体间存在频繁的菌源交流，其中察布查尔县与新源县群体菌源交流最为频繁（N_m=4.717）。     

Managing Meloidogyne incognita and Bemisia tabaci with thiacloprid in cucumber crops in China

Field trials were conducted to determine the potential use of thiacloprid for integrated Meloidogyne incognita and Bemisia tabaci B biotype control in cucumber (Cucumis sativus Linn.) in China. The following five treatments were evaluated: three thiacloprid doses (7.5, 15, and 30 kg ha⁻¹), an avermectin treatment (7.5 L ha⁻¹) and an untreated control. All thiacloprid application rates were effective for reducing the M. incognita and B. tabaci B biotype populations. M. incognita was reduced by 51.0%∼86.7% on 60th day and B. tabaci B biotype was reduced by about 37.2%∼95.3% within 21 days, respectively. In addition, greater thiacloprid doses resulted in fewer nematodes and whiteflies. Over two successive years, the cucumber plants that were treated with thiacloprid at a dose of 15 kg ha⁻¹ had the greatest plant height, plant vigor and marketable yield, which were 134.1 cm, 91, 1514.3 g plant⁻¹, respectively in 2010–2011 and 151.9 cm, 93, 1651.4 g plant⁻¹, respectively in 2011–2012. In addition, thiacloprid was superior to avermectin. The results of this study demonstrated that thiacloprid could be used in cucumber production for the integrated control of M. incognita and B. tabaci B biotype. Furthermore, a dose of 15 kg ha⁻¹ of thiacloprid was recommended for controlling nematode and whitefly populations according to the control effect and marketable cucumber yield.     

Baseline susceptibility of Bemisia tabaci (Genn.) biotype B in southern Florida to cyantraniliprole

Cyantraniliprole 200 mg ai l⁻¹ (Cyazypyr™ 200 SC) is a new xylem systemic insecticide in the anthranilic diamide chemistry class. A systemic laboratory bioassay using cut stems of cotton seedlings was developed to quantify the baseline susceptibility of nymphs and adults of the sweet potato whitefly, Bemisia tabaci (Genn.) biotype B, to cyantraniliprole. Bioassays were conducted on a susceptible laboratory colony and nine field populations collected in 2008, 2009 and 2010 in southern Florida. Bioassays with cyantraniliprole on the susceptible colony (targeting nymphs with exposure initiated at the egg stage) revealed pooled LC₅₀ and slope values of 0.017 mg ai l⁻¹ and 1.766 (SE = 0.125) in 2008, respectively, and 0.013 mg ai l⁻¹ and 1.355 (SE = 0.156) in 2009, correspondingly. Adult bioassays generated pooled LC₅₀ and slope values of 0.049 mg ai l⁻¹ and 3.201 (SE = 0.367) in 2010, respectively. LC₅₀ and slope values targeting nymphs (as above) of field populations ranged from 0.013 to 0.023 mg ai l⁻¹ and 1.425 (SE = 0.167) to 1.923 (SE = 0.187), respectively, in 2008, and 0.023 to 0.034 mg ai l⁻¹ and 1.682 (SE = 0.140) to 2.318 (SE = 0.226), respectively, in 2009. Resistance ratio values at 50% mortality (RR₅₀) on nymphs of field colonies ranged from 0.784 to 1.346 in 2008 and from 1.760 to 2.589 in 2009. Bioassays with adult field populations yielded LC₅₀ and slope values ranging from 0.037 to 0.059 mg ai l⁻¹ and 2.639 (SE = 0.561) to 6.948 (SE = 1.294), respectively, in 2010. The RR₅₀ values for adults from field colonies ranged from 0.752 to 1.207. The overlapping fiducial limits of the LC₅₀ values, the low RR₅₀ values, and the lack of significant differences in the slopes of probit lines between laboratory and field colonies, indicate that the B. tabaci populations present in southern Florida fields were highly sensitive to cyantraniliprole. These data will be helpful in monitoring for any changes in susceptibility as a result of use of the insecticide. The baseline information developed in the present study confirmed the susceptibility of field populations in Florida to cyantraniliprole and will be an essential component of a resistance management program to help ensure the continued viability of cyantraniliprole for B. tabaci management.     

Effects of chlorfenvinphos on Bemisia tabaci Genn. and its parasites on cotton in the Sudan Gezira

Two large-scale field trials were carried out in consecutive cotton seasons to evaluate the effects of a chlorfenvinphos-based spray regime and a standard commercial spray regime on whiteflies (B. tabaci) and their parasites. During both trials B. tabaci was the dominant pest species and occurred in generally increasing numbers throughout October to January. The only abundant natural enemy of B. tabaci was an aphelinid parasite, Eretmocerus sp. This parasite occurred in very large numbers towards the end of the first cotton season but was less abundant in the following year. In both seasons, cotton fields treated with chlorfenvinphos had significantly lower populations of whiteflies than those treated with the standard commercial spray regime. In contrast, the percentage of parasitized whitefly scales and numbers of parasite adults was significantly higher in the chlorfenvinphos-treated fields. It is suggested that the better control of whiteflies achieved in fields sprayed with chlorfenvinphos is at least in part due to this greater conservation of natural enemies.     

中国节节麦基于ISSR标记的遗传多样性分析

为揭示中国节节麦的遗传多样性并发掘可能具有独特变异的节节麦种质资源,采用ISSR标记对75份中国节节麦的遗传多样性进行分析。结果表明,筛选出的9条ISSR引物共检测得到155个位点,多态性位点(138个)百分率为89.31%。Nei’s多样性指数(He)、Shannon’s信息指数(I)、基因分化系数(Gst)和基因流(Nm)分别为0.273 4、0.415 2、0.138 5和3.11,表明中国节节麦有较高的遗传多样性,群体间有中等程度的遗传分化。基于简单相似系数的UPGMA聚类分析表明,除5份河南和陕西节节麦聚类形成独立的分支Group 2(T078、T102和SC1)和Group 3(SX38和T006)外,绝大多数节节麦均聚类形成较大的分支Group 1,且在Group 1中,除4份节节麦(T002、T023、XJ6和XJ49)外,绝大多数节节麦均依据地理分布分别形成了黄河流域节节麦亚组和新疆节节麦亚组,在遗传距离约0.77处,又可依次分为河南、陕西和新疆节节麦小分支。二维主成分分析、群体的遗传一致度和分子变异分析也表明了类似的结果,同属于黄河流域节节麦亚组的河南、陕西节节麦遗传一致度(S=0.971 8)较高,群体内个体差异是中国节节麦变异的主要原因,但两大亚组和三居群的遗传差异分别占总变异的18.57%和10.38%。可见,不同节节麦的地理分布和生境差异,是导致中国节节麦居群遗传分化的主要原因,而聚类分析中单独形成独立分支Group 2和Group 3的5份黄河流域节节麦,可能是具有独特遗传变异的种质资源。     

Efficacy of ketoenols on insecticide resistant field populations of two-spotted spider mite Tetranychus urticae and sweet potato whitefly Bemisia tabaci from Greece

Tetranychus urticae (two-spotted spider mite) and Bemisia tabaci (sweet potato whitefly), two of the most important agricultural pests worldwide, have developed resistance to almost all chemical classes of insecticides. Here we investigated the efficacy of the ketoenols spirodiclofen and spiromesifen against, respectively, T. urticae and B. tabaci populations from Greece with variable levels of resistance to other pesticides in order to evaluate their potential role in insecticide resistance management strategies for sustainable control of both pests. No resistance of T. urticae populations against spirodiclofen was observed. Nine out of ten T. urticae populations exhibited moderate levels of resistance to pirimiphos-methyl (up to 23-fold), pyridaben (up to 39-fold) and fenazaquin (up to 42-fold). Two of them exhibited high resistance ratios (RR) to bifenthrin (RR = 81, 351) and one to fenbutatin oxide (RR = 146). Moreover these nine populations were not cross resistant to spirodiclofen (RR < 5). A single population from greenhouse roses exhibited high resistance levels to most of the pesticides tested (RR = 8413, 1494, 434, and 74 to bifenthrin, fenbutatin oxide, abamectin and pirimiphos-methyl, respectively) showed decreased susceptibility to spirodiclofen (RR = 12). In B. tabaci the variation in response to spiromesifen treatments was very low among the eleven field populations. Most of them exhibited high levels of resistance to imidacloprid, and alpha-cypermethrin. The LC₅₀ of spiromesifen ranged from 4.5 to 14 mg/l and the corresponding LC₉₅ values were in general well below the recommended field doses. Ketoenol resistance risk potential was also investigated by applying constant selection pressure under laboratory conditions against populations from both species, but no increase in LC₅₀s was detected. Ketoenols can be used for resistance management purposes for both pests in Greece as an effective chemical tool in rotation with other pesticides.     

Evaluation of a modified sticky card to attract Bemisia tabaci (Hemiptera: Aleyrodidae) and a behavioural study on their visual response

Sticky cards with a yellow circle in black background originally developed to attract anthophilous thrips were also found to attract whiteflies. The potential of the new sticky cards for capture of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) was evaluated in oriental melon greenhouses in comparison with ordinary rectangular yellow sticky cards. Two types of the new sticky card (24W × 39L cm) were designed to contain either two large yellow circles (18D cm) or two small yellow circles (13D cm) in a black background on both sides. In each greenhouse, 18 sticky cards of each type were installed. The cards with small circles captured 1.8 times more B. tabaci per unit area than the rectangular yellow sticky cards. In the examination of on-site flight activity of B. tabaci, the cards with large circles attracted 70% of the B. tabaci that took off from the plant canopy. The card with small yellow circles captured 49% and the rectangular yellow sticky card captured 32%. In laboratory behavioural studies, sticky cards with different backgrounds and shapes were attached inside acrylic cages and B. tabaci on tomato leaves were released. Yellow sticky cards with a black background were 2.1 times more attractive than sticky cards with a green background, and triangular-shaped yellow sticky cards with a black background attracted 1.5 times more B. tabaci than those with squares. In conclusion, sticky cards with yellow circles in a black background attracted more B. tabaci per unit area than ordinary rectangular yellow sticky card, and thus could be an improvement for monitoring or managing B. tabaci.     

Use of a Fluorophore to Tag Arthropods for Mark-Release-Recapture Type Research

We examined the feasibility of externally marking insects with the liquid fluorescent forensic theft deterrent, SmartWater (SmartWater CSI, LLC.). We sprayed captive Lygus hesperus (Knight) (Hemiptera: Miridae), Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), and Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) with SmartWater fluorophore, and then qualitatively examined them for fluorescence by visual inspection under ultraviolet (UV) light and quantitatively measured them with a multiwavelength microplate fluorometer. The results indicate that this product has enormous potential as a taggant for L. hesperus and B. tabaci. However, the marking efficiency for H. convergens was only adequate. The advantages and limitations of using SmartWater as a biological marker for arthropod mark-release-recapture research are discussed.     

Effectiveness of imidacloprid in combination with a root nitrogen fertilizer applied to tomato seedlings against Bemisia tabaci (Hemiptera: Aleyrodidae)

The whitefly Bemisia tabaci (biotype B) is a worldwide pest of vegetables and field crops. We tested the efficacy of imidacloprid (IM) with a root fertilizer ‘Root Feed (RF)’ (9% N, 7% Ca, 1.5% Mg and 0.1% B) sub-irrigated in the growing medium against the whitefly on tomato. Tomato seedlings (3–4 true leaves) were treated with 0, 3, 6 or 12 mg active ingredient (a.i.) seedling⁻¹ of IM and with RF (0, 0.02, 0.04 or 0.08 ml seedling⁻¹). The efficacy of 12 mg IM seedling⁻¹ was further evaluated in the greenhouse for 60 days. The survival of B. tabaci adults, nymphs, and egg production were negatively affected by the treatments in a dosage-dependent manner. Treatment of 12 mg IM seedling⁻¹ caused >60% adult and nymph mortality 50 days after treatment (DAT). The active ingredient of IM in tomato leaves also increased with the increase of IM dosage. The RF exhibited a limited effect on B. tabaci. However, the mortality of whitefly adults and nymphs treated with RF (0.02 or 0.04 ml seedling⁻¹) positively interacted with IM, and was greater than IM alone. In the greenhouse, 12 mg IM seedling⁻¹ greatly reduced the number of whitefly adults and increased the dry weight of the tomato plants at 30 DAT. In conclusion, application of 12 mg IM seedling⁻¹ on tomato seedlings before transplanting effectively controled B. tabaci for up to 50 days, and the efficacy of IM combined with 0.02 ml RF seedling⁻¹ performed even better. This could be a cost-effective method for managing B. tabaci on tomato and other vegetables.     

Lethal and sublethal effects of buprofezin and imidacloprid on Bemisia tabaci (Hemiptera: Aleyrodidae)

The sweetpotato whitefly, Bemisia tabaci (Gennadius), has become a major threat to agriculture worldwide. The development of insecticide resistance in B. tabaci has necessitated the exploration of new management tactics. The toxicity of imidacloprid and buprofezin to various life stages of B. tabaci was determined in the laboratory. Also, the sublethal effects of both insecticides were studied on demographic and biological parameters of B. tabaci. Both insecticides were very toxic against first stage larvae of the pest with LC₅₀ values of 1.0 and 19.3 ppm for buprofezin and imidacloprid, respectively. Toxicities decreased between successive stages (LC₅₀ values ranging from 1.0 to 2854.0 ppm). The LC₅₀ values of imidacloprid for adult males, females and eggs were 11.8, 71.6 and 151.0 ppm, respectively. Buprofezin had no significant effect on adults and eggs. The sublethal concentration of imidacloprid had no significant effect on demographic and biological parameters of B. tabaci but the maximal value for the mean generation time (T) (18.8 day) was observed in imidacloprid treatment. Buprofezin significantly decreased stable population and biological parameters of B. tabaci except it did not decrease the rate of population increase or the sex ratio of offspring.     

Evaluation of Genetic Variation Among Wild Populations and Local Varieties of Rice

Cultivated rice (Oryza sativa L.) is derived from Asian wild rice (Oryza rufipogon Griff). Vietnamese local varieties and wild natural populations in Vietnam and Myanmar were examined to evaluate the levels of genetic variation in cultivated and wild rice. In total, 222 Vietnamese local varieties were analyzed with ten microsatellite markers. Using marker genotype and gene diversity data, the local varieties were differentiated based on geographical distribution, cropping season, and human preference. A total of 976 wild plants were collected at six natural sites of wild populations (three each in Myanmar and Vietnam), and the degrees of variation among populations were analyzed with five microsatellite markers. Phylogenetic analyses revealed wide genetic differentiation among wild populations. The diversity values detected in a single wild population in Vietnam were higher than those in whole Vietnamese local varieties. These results indicate that wild rice has much greater genetic variation than cultivated rice.     

Eradicating Bemisia tabaci Q biotype on poinsettia plants in the UK

The sweetpotato whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) continues to be a serious threat to crops worldwide. The UK holds Protected Zone status against this pest and, as a result, B. tabaci entering on plant material is subjected to a policy of eradication. Q biotype (Mediterranean species) is the predominant whitefly now being intercepted entering the UK. With increasing reports of neonicotinoid resistance in this biotype, it is becoming more problematic to control/eradicate. The current study evaluated sequential insecticide applications of a range of chemicals and two entomopathogenic fungi, Beauveria bassiana and Lecanicillium muscarium, applied within the first 21 days after potting poinsettia cuttings. All sequential treatment programmes tested eradicated Q biotype from poinsettia plants. The efficacy of chemicals and fungi against various Q biotype life-stages was also evaluated as individual treatments. Against the egg stage, abamectin (Dynamec), acetamiprid (Gazelle), refined petroleum spraying oil (Tri-Tek) and the physically acting product SB-Plant Invigorator all proved excellent. None of the products gave total control of second instar larvae. However, Agri-50E, B. bassiana, Tri-Tek and SB-Plant Invigorator all gave over 71% mortality. For adult control, B. bassiana and the oil based products (Addit, Tri-Tek and Spraying Oil) all produced 100% mortality. The work also demonstrated that B. bassiana offers better control of B. tabaci than L. muscarium. Investigating direct tank-mixing of the fungi with the chemical products proved that Majestic (physically acting product), spiromesifen (Oberon), Savona (physically acting product) and SB-Plant Invigorator significantly reduced germination of B. bassiana spores and so could not be recommended as mixes. Tri-Tek Oil, Spraying Oil, Addit, Dynamec and Gazelle showed best potential to be used as tank-mixes with over 90% B. bassiana spore germination following exposure to the test products for 24 h. A direct tank mix of L. muscarium with Tri-Tek allowed full fungal spore germination. The implications of the work in regards to continued protection of the UK horticultural industry from B. tabaci and overcoming insecticide resistance among biotypes are discussed.     

Understanding the dynamics of neonicotinoid activity in the management of Bemisia tabaci whiteflies on poinsettias

The relative efficacies of registered label rates for foliar and soil drench treatments of imidacloprid and dinotefuran at preventing the establishment of Bemisia tabaci B biotype whitefly populations on newly infested poinsettia plants were evaluated. Pesticide levels within and on plant leaves were monitored for 10 weeks by ELISA and LC/MS in an effort to better understand the dynamics of neonicotinoid activity against this insect and to estimate insecticide concentrations needed to kill the nymphal and adult stages. While all treatments proved equally effective as a remedial measure for the control of the resident adult populations, thereby accomplishing the objective of foliar contact treatments, the dinotefuran soil drench application was the only treatment that provided multi-generational control of Bemisia populations.