Compatibility of the entomopathogenic fungus Lecanicillium muscarium and insecticides for eradication of sweetpotato whitefly, Bemisia tabaci

The compatibility of the entomopathogenic fungus Lecanicillium muscarium and chemical insecticides used to control the second instar stages of the sweetpotato whitefly, Bemisia tabaci, was investigated. The effect on spore germination of direct exposure for 24 h to the insecticides imidacloprid, buprofezin, teflubenzuron and nicotine was determined. Only exposure to buprofezin was followed by acceptable spore germination. However, all chemicals significantly reduced spore germination when compared to a water control. Infectivity of L. muscarium in the presence of dry residues of buprofezin, teflubenzuron and nicotine (imidacloprid is a systemic pesticide) on foliage were also investigated. No significant detrimental effects on the level of control of B. tabaci was recorded when compared with fungi applied to residue free foliage on either tomato or verbena plants. Fungi in combination with imidacloprid gave higher B. tabaci mortality on verbena foliage compared to either teflubenzuron or nicotine and fungi combinations. Use of these chemical insecticides with L. muscarium in integrated control programmes for B. tabaci is discussed.     

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

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

Evaluating the potential of the extract of Perilla sp. as a natural insecticide for Bemisia tabaci (Hemiptera: Aleyrodidae) on sweet peppers

The sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is a major pest on greenhouse crops including sweet pepper (Capsicum annuum L.), which is one of the leading greenhouse crops in South Korea. Synthetic insecticides, especially the neonicotinoids, have been used to conventionally control this pest. There have been continuous efforts to develop plant‐derived compounds as insecticides, deterrents, and repellents to reduce spraying synthetic insecticides. To develop new plant‐extract insecticides, we investigated the insecticidal effects of Perilla sp. (Perilla frutescens var. crispa) extract on B. tabaci in laboratory conditions. The Perilla sp. extract induced 90 % mortality within one hour, but phytotoxicity symptoms on sweet pepper leaves were also observed. We monitored the population change and spatial distribution of adult B. tabaci in an experimental sweet pepper greenhouse using yellow sticky traps, and analyzed distribution patterns by spatial analysis with distance indices (SADIE). Based on monitoring data and SADIE analysis, we concluded that B. tabaci aggregated near the greenhouse entrances, and it showed aggregation and association pattern as time passed. Therefore, we recommend spraying Perilla sp. extract near the entrances or wild host before the pest population penetrates. It will be one of the alternative pest management strategies to reduce B. tabaci population with fewer negative effects from chemical insecticide. Further study is required to reduce the phytotoxicity symptoms from Perilla sp. extract spray and insecticidal effect should be evaluated under field conditions.     

Field tests with insecticides and insect growth regulators to control insect pests of cowpea and its effects on certain beneficial insects

A small‐plot tests were conducted on cowpea, Vigna ungiculata (L.) Walp, to determine the effectiveness of 14 selected insecticides representing four insecticide classes (organophosphates, carbamates, pyrethroids, and insect growth regulators, IGRs), and four insecticide/IGR mixtures on cowpea insect pests and its effects on certain beneficial insects. By day 3 after treatement, the insecticides phenthoate, isoxathion, cyanophos, carbaryl, and cypermethrin used at sub‐recommended rates reduced the leafhopper, Empoasca spp., populations by >83% than those in the control. On that day, all insecticide treatments significantly reduced the cowpea aphid, Aphis craccivora, numbers below that of the control. The prothiofos, isoxathion, pirimicarb, and fenpropathrin treatments provided continuing control to both leafhoppers and aphids through day 21 after spraying. It seems that most insecticide treatments were not effective in whitefly, Bemisia tabaci, control. The best control of the whitefly immatures was obtained by day 3 after spraying in plots received thiodicarb (76%) and fenpropathrin (60%). All selected insecticides and rates used had very low residual effect against B. tabaci immatures. By day 3 posttreatment, the carbaryl (2.02 kg/ha) caused completely protection for cowpea pods frMw blue pea butterfly, Lampides boeticus, larvae. The IGRs, flufenoxuron and Dowco‐439, applied alone and those applied in mixtures with insecticides, carbaryl/teflubenzuron, chlorpyrifos/XRD‐473, and methomyl/ flufenoxuron, exhibited satisfactory control (>81%) to butterfly larvae on day 7 posttreatment. All treatments did not exhibit a considerable residual activity against L. boeticus larvae through 2–3 weeks followed spray. Most insecticides applied at the higher rates used significantly reduced the numbers of limabean pod borer, Etiella zinckenella, larvae found in cowpea pods collected on day 7 after application. The IGRs, flufenoxuron and Dowco‐439, applied alone, at 0.119 kg/ha, or in mixtures, methomyl/flufenoxuron (0.167 kg/ha) and chlorpyrifos/Dowco‐439 (0.911 kg/ha) caused >73% control of E. zinckenella larvae through day 21 posttreatment. The best control of cowpea weevil, Callosobru‐chus spp., adults (>83%), on day 3 after spraying, was obtained in treatments of cyanophos (1.19 kg/ha), prothiofos (1.43 kg/ha), flufenoxuron (0.119 kg/ha), and chlorpyrifos/Dowco‐439 (0.911 kg/ha). The IGR flufenoxuron applied alone or in mixture, methomyl/flufenoxuron (0.164 kg/ ha) exhibited satisfactory residual activity against Callosobruchus adults through day 21 posttreatment. Percentage seed damage by the larvae of cowpea weevils was significantly lower in most treatments than that of control. Populations of insect predators found in all treated plots were extremely reduced than those found in untreated plots. By day 21 after spraying, the IGRs flufenoxuron, XRD‐473, and Dowco‐439, applied at the low rate of 0.071 kg/ha, seemed to be less effect against insect predators than other insecticides used.     

Can insecticide mixtures be considered to surmount neonicotinoid resistance in Bemisia tabaci?

Cotton whitefly, Bemisia tabaci is an important polyphagous pest worldwide. It is exposed to various chemical insecticides throughout the year, resulting in the rapid development of insecticide resistance. Mixtures of insecticides with distinct modes of action could enhance the toxicity of chemicals more effectively than sequences or rotations in resistant pest populations. Bioassays were conducted to study the efficacy of mixtures of neonicotinoid and ketoenol insecticides at different ratios against a laboratory susceptible (Lab-WB) and a neonicotinoid resistant (TMX-SEL) strain of B. tabaci Asia I. The results showed that mixtures of imidacloprid, acetamiprid, thiamethoxam or dinotefuran with spiromesifen at 1:1, 1:10 and 1:20 ratios and of imidacloprid, thiamethoxam or dinotefuran with spirotetramat at 1:1 ratio significantly increased (p < 0.05) toxicity to neonicotinoids in TMX-SEL strain. The combination indices of each tested neonicotinoids + ketoenols at 1:1 ratio and of acetamiprid + spiromesifen, and imidacloprid or dinotefuran + spirotetramat at 1:10 ratio for TMX-SEL strain were significantly below 1, suggesting synergistic interactions. The inhibitors PBO and DEF largely overcame resistance to the tested neonicotinoids, while none of the synergists significantly restored the susceptibility of B. tabaci to ketoenols. Increased activities of P450 monooxygenase and esterase were observed in TMX-SEL strain with an elevated 2.76 and 1.32-fold, respectively. Mixtures of neonicotinoids with spiromesifen or spirotetramat at a 1:1 ratio could be used to restore the neonicotinoid susceptibility in B. tabaci.     

The insecticidal activity and action mode of an imidacloprid analogue, 1‐(3‐pyridylmethyl)‐2‐nitroimino‐imidazolidine

Neonicotinoids, such as imidacloprid, are key insecticides extensively used for control of Nilaparvata lugens. However, imidacloprid resistance has been reported in many Asian countries in recent years. To understand the roles of the chlorine atom of pyridyl group on insecticidal activity and resistance, the atom was removed to generate an imidacloprid analogue DC‐Imi (DesChlorine Imidacloprid). DC‐Imi showed significantly higher toxicity than imidacloprid in the susceptible strain of N. lugens, but had medium level cross‐resistance in an imidacloprid‐resistant strain. In Xenopus oocyte expressed nicotinic acetylcholine receptors (nAChRs) Nlα1/rβ2, the inward currents evoked by DC‐Imi were detected and could be blocked by typical nAChRs antagonist dihydro‐β‐erythroidine (DHβE), which demonstrated that DC‐Imi acted as an agonist on insect nAChRs. The efficacy of DC‐Imi on Nlα1/rβ2 was 1.8‐fold higher than that of imidacloprid. In addition, the influence of an imidacloprid resistance associated mutation (Y151S) on agonist potencies was evaluated. Compared with the wild‐type receptor, the mutation reduced maximal inward current of DC‐Imi to 55.6% and increased half maximal effective concentration (EC₅₀) to 3.53‐fold. Compared with imidacloprid (increasing EC₅₀ to 2.38‐fold of wild‐type receptor), Y151S mutation decreased DC‐Imi potency more significantly. The results indicated that the selective and possibly high toxicities could be achieved through the modification of 6‐chloro‐3‐pyridyl group in imidacloprid and other neonicotinoids.     

The integrated use of chemical insecticides and the entomopathogenic nematode,Steinernema carpocapsae (Nematoda: Steinernematidae), for the control of sweetpotato whitefly,Bemisia tabaci (Hemiptera: Aleyrodidae)

The integration of chemical insecticides and infective juveniles of the entomopathogenic nematode Steinernema carpocapsae (Wesier) (Nematoda: Steinernematidae), to control second instars of the sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) was investigated. Using a sand bioassay, the effects of direct exposure of S. carpocapsae for 24 h to field rate dilutions of four insecticides (spiromesifen, thiacloprid, imidacloprid and pymetrozine) on infectivity to Galleria mellonella larvae were tested. Although all chemicals tested, except spiromesifen, produced acceptable nematode infectivity rates, they were all significantly less than the water control. The effect of insecticide treatment (dry residues of spiromesifen, thiacloprid and pymetrozine and soil drench of imidacloprid) on the efficacy of the nematode against B. tabaci was also investigated. Nematodes in combination with thiacloprid and spiromesifen gave higher B. tabaci mortality (86.5% and 94.3% respectively) compared to using nematodes alone (75.2%) on tomato plants. There was no significant difference in B. tabaci mortality when using the chemicals imidacloprid, pymetrozine and spiromesifen in conjunction with nematodes compared to using the chemicals alone. However, using thiacloprid in combination with the nematodes produced significantly higher B. tabaci mortality than using the chemical alone. The integration of S. carpocapsae and these chemical agents into current integrated pest management programmes for the control of B. tabaci is discussed.     

Bemisia tabaci: The current situation in the UK and the prospect of developing strategies for eradication using entomopathogens

Abstract The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) remains a serious threat to crops worldwide. The damaging B‐biotype is of specific economic concern because it is an effective vector of over 111 viruses from several families, particularly geminiviruses. Bemisia tabaci is regularly intercepted on plants coming into the UK where it is subjected to a policy of eradication. The UK maintains Protective Zone status against this pest. A main pathway of entry of B. tabaci into the Protected Zone involves propagating material, especially Poinsettia (Euphorbia pulcherrima). With increased insecticide resistance continuously being recorded, B. tabaci is becoming more difficult to control/eradicate. Recent research involving both entomopathogenic nematodes and fungi is showing much potential for the development of control programs for this pest. Both the nematode Steinernema feltiae and the fungus Lecanicillium muscarium have been shown to be most effective against second instar B. tabaci. Fine‐tuning of the environmental conditions required has also increased their efficacy. The entomopathogens have also shown a high level of compatibility with chemical insecticides, all increasing their potential to be incorporated into control strategies against B. tabaci.     

Interactions of fungal entomopathogens with synthetic insecticides for the control of Kuschelorhynchus macadamiae (Coleoptera: Curculionidae)

This study investigated the interactions between insecticides (acephate and indoxacarb) and fungal entomopathogens (Beauveria bassiana [Bals.-Criv.] Vuill. strain B27, Metarhizium anisopliae [Metschn.] Sorokin strain ECS1, and a commercial B. bassiana product, Velifer^® Biological Insecticide) for controlling the macadamia seed weevil, Kuschelorhynchus macadamiae Jennings and Oberprieler, in the laboratory and glasshouse. In the laboratory, additive interactions between insecticides at their full field concentrations (776 mg AI/L of acephate and 75 mg AI/L of indoxacarb) and fungal entomopathogens at 10⁷ conidia/ml (ECS1 and B27) or at full field concentration (0.5 ml of Velifer^®/L) were seen at 6 days and 12 days post-application. Under the same experimental conditions, synergistic interactions against K. macadamiae were observed 6 days post-application when fungal entomopathogens at 2.5 × 10⁶ conidia/ml or at 25% of full field concentration (Velifer^®) were co-applied with insecticides at 25% of their full field concentrations, whilst additive interactions were again observed at 12 days post-application. In the glasshouse, additive interactions between insecticides (at full field concentrations) and fungal entomopathogens (at 10⁷ conidia/ml, or at full field concentration for Velifer^®) were obtained at 6 days and 12 days post-application. The results from this study suggest that acephate and indoxacarb have both synergistic and additive effects against K. macadamiae when deployed together with fungal entomopathogens, depending on the initial concentrations of mixture components. Combined application of entomopathogens with compatible insecticides promises to provide more effective management of K. macadamiae than individual chemical applications.     

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

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

Resistance to neonicotinoid insecticides and expression changes of eighteen cytochrome P450 genes in field populations of Bemisia tabaci from Xinjiang,China

The occurrence of Bemisia tabaci poses an increasingly serious threat to cotton and vegetable crops in Xinjiang, China. Currently, neonicotinoid insecticides are commonly used to control the insect, to which resistance is inevitable due to intensive use. However, the resistance status and mechanism of B. tabaci to neonicotinoid insecticides in Xinjiang are poorly understood. Cytochrome P450 monooxygenases represent a key detoxification mechanism in the neonicotinoid resistance of B. tabaci. In this study, the resistance level to imidacloprid and thiamethoxam was investigated using the leaf dipping method in five field populations of B. tabaci from Turpan (TP, two sampling sites), Shache (SC), Hotan (HT) and Yining (YN) in northern and southern Xinjiang. The expression changes of eighteen cytochrome P450 genes from the select B. tabaci populations were determined by real‐time fluorescence quantitative PCR (qPCR). The bioassay revealed that the five populations tested had developed moderate to high levels of resistance to imidacloprid (12.26–46.07‐fold), while the populations remained sensitive to thiamethoxam except for HT, which had a low level of resistance. The qPCR results showed that the expression levels of five P450 genes, CYP4G68, CYP6CM1, CYP303A1‐like, CYP6DZ7 and CYP6DZ4, were significantly higher in some resistant field populations than in the susceptible strain. Resistance to imidacloprid in field populations of B. tabaci might be associated with the increased expression of these five cytochrome P450 genes. The results are useful for further understanding the mechanism of neonicotinoid resistance and will contribute to the management of insecticide‐resistant B. tabaci in Xinjiang.     

Compatibility of Lecanicillium longisporum with acetamipride and imidaclopride under laboratory conditions

Lecanicillium longisporum is one of the facultative insect pathogens with significant host range and host specificity. The conidia survival may be affected by environmental factors or by bio-pesticides and chemical products used to protect crop plants. In this research, the compatibility of the mentioned fungi with acetamipride and imidaclopride and the effect of these insecticides on conidial germination and vegetative growth were studied. The formulations of insecticides were tested in three concentrations (mean concentration (MC), half MC and twice the MC). The study was conducted in completely randomised design (CRD) with four replications. The results indicated that acetamipride and imidaclopride in half MC were compatible with L. longisporum (isolate LRC195). However, based on the results, imidacloprid compared to acetamipride is adaptable with L. longisporum. These insecticides could be used simultaneously in low concentration with this entomopathogenic fungus in integrated pest management.     

Enhanced virulence of Beauveria bassiana against Thrips tabaci by the addition of bacterial metabolites derived from Xenorhabdus hominickii

Xenorhabdus and Photorhabdus are two bacterial genera specifically symbiotic to Steinernema and Heterorhabditis, which are the entomopathogenic nematode genera, respectively. These bacteria are well known to produce potent secondary metabolites suppressing insect immune responses. This study aimed to develop a potent microbial insecticide against the onion thrips, Thrips tabaci, using the bacterial metabolites. Among the chemical insecticides that have been used to control the thrips, spinosad was highly effective against both larvae and adults of T. tabaci. Three different entomopathogenic fungi were also effective to kill the thrips. However, the fungal virulence was much less than the control efficacy of the chemical insecticide, spinosad. To enhance the fungal virulence of Beauveria bassiana (Bb), the bacterial culture broth of Xenorhabdus/Photorhabdus was added to suppress the thrips immune defense. Among six different bacterial species, X. hominickii (Xh) produced highly potent metabolites to enhance the fungal virulence. Indeed, four different bacterial metabolites (GameXPeptide, benzylideneacetone, oxindole, and 3-ethoxy-4-methoxyphenol) of the bacteria suppressed the gene expressions of an antimicrobial peptide, lysozyme, which was highly inducible to the fungal infection. To optimize the mixture ratio of fungal and bacterial pathogens, the fungal conidia and bacterial culture broth were freeze-dried and mixed in different ratios. Laboratory and field assays showed that a mixture spray of freeze-dried Xh culture broth (3 g) and Bb conidia (1.17 × 10⁹ conidia) in a liter was effective to control T. tabaci infesting welsh onion.     

Population dynamics and integrated pest management of Thrips tabaci on leek under field conditions in northwest Italy

Thrips tabaci Lindeman (Thysanoptera: Thripidae) is a major pest of leek, Allium porrum L. (Alliaceae), in Piedmont, northwest Italy, and to control its infestation the leek crop is sprayed intensively with insecticides during the summer period. In order to find the most efficient and environment‐friendly method of thrips control, research was conducted on six commercial farms during 2005–2006 to assess thrips population composition and infestation levels, and in an experimental field during 2005–2007. Biological and chemical control were compared during 2005–2006, whereas integrated pest management was adopted during 2007. During the growing season, thrips and natural enemy populations were monitored at 14‐day intervals by beating plants; new leaves of plants were also visually inspected for thrips‐feeding symptoms. Furthermore, in the experimental field at harvest‐time, the level of thrips injury to plants was assigned to one of five classes, depending on the percentage of leaf area damaged. Over 99% of phytophagous adult thrips found were male and female T. tabaci. Infestations were very variable in the crops surveyed, partly due to broad‐spectrum chemical treatments against the leek pests, which often failed to control thrips. In general, populations peaked in September, when they reached the maximum mean values ranging between 1.7 and 33.1 thrips per plant. At harvest, none of the surveyed farms experienced quality losses due to thrips injuries. In the experimental field during 2005–2006, the mean number of thrips per plant was greater in the chemical than in the biological control treatment, even though damage indices showed no significant differences between the two treatments. Predatory thrips of the genus Aeolothrips (Thysanoptera: Thripidae) and predatory bugs of the genus Orius (Heteroptera: Anthocoridae), mostly Orius majusculus Reuter, were particularly abundant during 2007, supporting the importance of management with selective insecticides to encourage natural colonization by predators.     

Effect of Isaria fumosoroseus on mortality and fecundity of Bemisia tabaci and Plutella xylostella

Abstract Entomopathogenic fungi have been used recently for the management of whitefly (Bemisia tabaci) and diamondback moth (Plutella xylostella). In previous studies, Isaria fumosoroseus has shown some potential to control these insect pests. In this paper, the effects of I. fumosoroseus (strain PF01-N4) on the mortality, fecundity and other life table parameters were observed under laboratory conditions. As a first step, the susceptibility of second instars of B. tabaci and P. xylostella was examined in dose-response experiments, which was followed by the studies on the effect of I. fumosoroseus on reproduction. Both B. tabaci and P. xylostella, were susceptible to I. fumosoroseus having median lethal concentration values of 1.10 × 10⁴ and 0.48 × 10⁴ conidia/mL after 12 and 11 days treatment, respectively. The fungal infection significantly reduced the longevity and fecundity of B. tabaci. At 1 × 10⁷ conidia/mL, a minimum average longevity of 9 days was observed as compared to 16.3 days for the control. Similar results were also observed in P. xylostella with an average longevity of 5.6 days as compared to 17.68 days in the control. In case of reproduction, the number of progeny produced by B. tabaci and P. xylostella decreased with an increase in conidial concentration, with the average values of 83.67 and 26.85, 10.92 and 225.51, 112.08 and 31.02 eggs/female for control, 1 × 10⁴ and 1 × 10⁷ conidial/mL, respectively. There was a significant effect of I. fumosoroseus on intrinsic rate of natural increase.     

In Vitro and <Emphasis Type="Italic">In Planta</Emphasis> Compatibility of Insecticides and the Endophytic Entomopathogen, <Emphasis Type="Italic">Lecanicillium lecanii</Emphasis>

In an attempt to clarify the potential role of endophytic fungi in integrated pest management, the compatibility of an endophytic isolate of Lecanicillium lecanii (Zimmermann) Gams & Zare (Hyphomycetes) with nine insecticides used against Aphis gossypii Glover (Homoptera : Aphididae) was examined both in vitro over 14 days and in planta. In the laboratory, most insecticides partially or completely inhibited the germination of conidia and growth of hyphae in nutrient-rich conditions. Endosulfan completely inhibited the germination of conidia and hyphal growth. In contrast, all insecticides were compatible with L. lecanii in planta, and the fungus was readily recovered from inoculated, colonized leaves. These data support the hypothesis that endophytic L. lecanii will be unaffected by insecticides and could be integrated in the management of pests in cotton.     

Biotype and status of insecticide resistance of whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) in Alhassa oasis,Eastern Province of Saudi Arabia.

The tobacco whitefly, Bemisia tabaci, is one of the major insects infesting vegetable plants. This pest is well known in Alhassa oasis, Saudi Arabia; which is historically agricultural land cultivated with date palm trees and different vegetables. A molecular key based on the sequence of the mitochondrial cytochrome oxidase gene CO1 was used for the identification of strains of the tobacco whitefly Bemisia tabaci collected from farms located in four areas of the Alhassa oasis; Northern, Southern, Eastern and Western. Only one biotype (B‐biotype) of B. tabaci was reported in the oasis. Resistance of B. tabaci was tested against eight insecticides, the results showed moderate to low levels of resistance to the tested insecticides. However, the resistance to neonicotinoid insecticides was low and established at 1.3 fold to both Imidacloprid and Acetamiprid. In addition, medium levels of resistance were detected to the insect growth regulator Pyriproxyfen (30 fold), and the pyrethroid Deltamethrin (30 fold), Bifenthrin (24 fold) and Cypermethrin (13 fold). A medium level of resistance was also detected to the carbamate insecticide Carbosulfan and was 40 fold of the laboratory strains. A low level of resistance to the organophosphorus insecticide was detected to Phenthoate (11 fold). However, these results reflect that the farmers were less dependent on the use of insecticides to control B. tabaci in the oasis and they may be implementing other environmentally sound techniques to keep the pest below the damage threshold.     

Laboratory and greenhouse evaluation of a new entomopathogenic strain of Beauveria bassiana for control of the onion thrips Thrips tabaci

Abstract

The onion thrips Thrips tabaci is one of the most important pests of greenhouse and open-field broccoli, onion and other crops. However, the current strategy of using synthetic pesticides for its control is inadequate and unsustainable, leading to a growing interest in novel and effective biological control alternatives such as entomopathogenic fungi. Among 20 isolates of Beauveria bassiana tested for virulence against T. tabaci in laboratory bioassays, we found strain SZ-26 as the most potent, causing 83–100% mortality in adults at 1×10⁷ mL^?1conidia after 4–7 days. Further experiments in greenhouses showed the strain SZ-26 significantly lowered the numbers of adult and larval stages.     

Chiral Ligand‐Exchange Resolution of Underivatized Amino Acids on a Dynamically Modified Stationary Phase for RP‐HPTLC

The synthesis of Spi(τ‐dec), derived from the selective alkylation of L‐spinacine (4,5,6,7‐tetrahydro‐1H‐imidazo[4,5‐c]pyridine‐6‐carboxylic acid) at the τ‐nitrogen of its heteroaromatic ring, with a linear hydrocarbon chain of 10 carbon atoms, is described here for the first time. Spi(τ‐dec) was successfully employed in the past to prepare home‐made chiral columns for chiral ligand‐exchange high‐performance liquid chromatography. In the present article a new method is described, using Spi(τ‐dec) as a chiral selector in high‐performance thin‐layer chromatography (HPTLC): commercial hydrophobic plates were first coated with Spi(τ‐dec) and then treated with copper sulfate. The performance of this new chiral stationary phase was tested against racemic mixtures of aromatic amino acids, after appropriate optimization of both the conditions of preparation of the plates and the mobile phase composition. The enantioselectivity values obtained for the studied compounds were higher than those reported in the literature for similar systems. The method employed here for the preparation of chiral HPTLC plates proved practical, efficient, and inexpensive. Chirality 26:313–318, 2014. © 2014 Wiley Periodicals, Inc.     

Effects of coadministration of chemical insecticides with nucleopolyhedrovirus SpltNPV on the dietary intake of the common cutworm <Emphasis Type="Italic">Spodoptera litura</Emphasis> (Lepidoptera: Noctuidae)

Chemical insecticides were administered to larvae of the common cutworm Spodoptera litura (Fabricius) concomitantly with a viral insecticide containing nucleopolyhedrovirus SpltNPV, in order to decrease the level of dietary intake of the virus-infected larvae. Aqueous solutions of imidacloprid (Admire), flubendiamide (Phenix), or cartap (Padan) at non-lethal doses, together with a lethal dose of SpltNPV occlusion bodies (Hasumon-Tenteki), were prepared. The surfaces of small blocks of food were treated with the mixtures and presented to S. litura larvae for 24 h. On the following day, a new diet block was provided which had been treated with one-third or one-fourth of the initial dose of the chemical insecticide. The larvae were reared for 5 days and the level of dietary intake was recorded. The administration of flubendiamide and cartap decreased the dietary intake more strongly in virus-infected larvae than in non-infected larvae.