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The cabbage aphid, Brevicoryne brassicae (L.), is one of the major insect pests of cole crops in Iran. In most instances outbreaks are normally kept under control by application of insecticides. In this study, the sublethal effects (LC30) of three insecticides, acetamiprid, buprofezin, and thiamethoxam-lambda cyhalothrin, (TLC) were evaluated on the population growth rate of the progeny of insecticide-treated cabbage aphid adults. The age-stage, two-sex life table method was used to analyze the collected data. The results indicated that the insecticide applications affected the duration of the preadult period, their survival, reproduction, life span/longevity, and consequently, the population growth rate of the F1 generation. The indicators of the greatest sublethal effects were noted in the progeny of the TLC-treated adults. These included the lowest net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and the longest mean generation time (T). The highest values of r, λ, R, and the lowest value of T occurred in the control group followed by, in order, the acetamiprid and buprofezin groups. These research findings will be useful in the development and implementation of future aphid management programs.

Forage alfalfa (Medicago sativa L. [Fabales: Fabacae]) is a major agronomic crop grown nationally and Montana ranks highly in acres harvested. The alfalfa weevil (Hypera postica Gyllenhal [Coleoptera: Curculionidae]) is the primary defoliating pest that requires insecticide applications to prevent yield loss, particularly pyrethroid active ingredients (a.i.) that are both efficacious and cost-effective. Reports from commercial alfalfa producers in Big Horn County, MT, suggested local populations of alfalfa weevil had developed resistance to the pyrethroid a.i. lambda-cyhalothrin (type II pyrethroid). Chemical control is an important component of integrated pest management (IPM) of alfalfa weevil and the loss of pyrethroid a.i. as an effective tool would result in additional production costs. Two locations in southern Big Horn County and nine locations in four other Montana counties where resistance has not been reported were sampled and assayed for resistance to lambda-cyhalothrin. Populations from three counties were susceptible, the concentration causing 50% mortality (LC50) ranged from 0.02 to 0.10 µg/cm2. In contrast, populations from Big Horn County did not reach 50% mortality at the highest concentration of lambda-cyhalothrin tested (3.30 µg/cm2), indicating high levels of resistance have developed in these populations. A field trial in Big Horn County supported laboratory results of resistance; lambda-cyhalothrin at the highest label rate did not reduce alfalfa weevil populations. Additional bioassays suggest cross-resistance to zeta-cypermethrin (type II pyrethroid), but only partial cross-resistance to permethrin (type I pyrethroid).

The green peach aphid, Myzus persicae (Sulzer), is a pest mainly controlled with insecticides, and it can acquire resistance through different mechanisms. Pyrethroids can select the knock down resistance (kdr) mutation in M. persicae and can also produce lethal and sub-lethal effects on its main parasitoid, Aphidius colemani Viereck. However, kdr-resistant M. persicae exhibits a reduced response to alarm pheromone and increased vulnerability to natural enemies. To study the effects of sub-lethal concentrations of a pyrethroid on the aphid-parasitoid interaction, kdr-resistant and susceptible M. persicae were confronted with A. colemani with residual sub-lethal concentrations of λ-cyhalothrin. The behavior, survival, and development of parasitoids were evaluated after exposure to λ-cyhalothrin LC20 for adult parasitoids (0.52 mg/liter) for susceptible (Mp-SS, 0.56 mg/liter) and kdr-resistant M. persicae (Mp-RR, 12.15 mg/liter). The foraging and oviposition behaviors of the parasitoids were not affected by the lower parasitoid or Mp-SS LC20. Conversely, the higher Mp-RR LC20 significantly reduced parasitoid walking, the frequency of sting attempts, and successful stings, as well as aphid defensive behaviors, such as walking, kicking, and jerking. Therefore, the higher vulnerability of kdr-resistant M. persicae could not be capitalized by A. colemani parasitoids under a high concentration of λ-cyhalothrin. Similarly, the parasitism rate, survival of progeny, productivity, sex ratio (proportion of females), longevity, and adult body mass were reduced, and the development time increased with a higher Mp-RR LC20. Our results suggest that A. colemani could efficiently control kdr-resistant and susceptible M. persicae only at lower λ-cyhalothrin concentrations.

Insecticides can affect biological control by parasitoids. Here, we examined the lethal and sublethal effects of two conventional insecticides, imidacloprid and lambda-cyhalothrin, and a reduced-risk bioinsecticide, spinosad, on the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae). Concentration-mortality curves generated from insecticide residue bioassays found that wasps were nearly 20-fold more susceptible to spinosad than imidacloprid and lambda-cyhalothrin. Imidacloprid and lambda-cyhalothrin compromised adult parasitoid longevity, but not as dramatically as spinosad: concentrations >200 ng spinosad/cm2 reduced wasp longevity by half. Imidacloprid and lambda-cyhalothrin also compromised aphid parasitism by wasps. Although increasing imidacloprid concentrations led to increased host viability and reduced progeny production, lambda-cyhalothrin did not affect viability of parasitized hosts or parasitoid progeny production in a dose-dependent manner. Our results demonstrate that reduced risk bioinsecticide products like spinosad can be more toxic to biological control agents than certain conventional insecticides.

Sublethal insecticide exposure may affect foraging of insects, including natural enemies, although the subject is usually neglected. The lady beetle Eriopis connexa (Germar, 1824) (Coleoptera: Coccinelidae) is an important predator of aphids with existing pyrethroid-resistant populations that are undergoing scrutiny for potential use in pest management systems characterized by frequent insecticide use. However, the potential effect of sublethal pyrethroid exposure on this predator’s foraging activity has not yet been assessed and may compromise its use in biological control. Therefore, our objective was to assess the effect of sublethal lambda-cyhalothrin exposure on three components of the prey foraging activity (i.e., walking, and prey searching and handling), in both pyrethroid-susceptible and -resistant adults of E. connexa. Both lady beetle populations exhibited similar walking patterns without insecticide exposure in noncontaminated arenas, but in partially contaminated arenas walking differed between strains, such that the resistant insects exhibited greater walking activity. Behavioral avoidance expressed as repellence to lambda-cyhalothrin was not observed for either the susceptible or resistant populations of E. connexa, but the insecticide caused avoidance by means of inducing irritability in 40% of the individuals, irrespective of the strain. Insects remained in the insecticide-contaminated portion of the arena for extended periods resulting in greater exposure. Although lambda-cyhalothrin exposure did not affect prey searching by susceptible lady beetles, prey searching was extended for exposed resistant predators. In contrast, prey handling was not affected by population or by lambda-cyhalothrin exposure. Thus, sublethal exposure to the insecticide in conjunction with the insect resistance profile can affect prey foraging with pyrethroid-exposed resistant predators exhibiting longer prey searching time associated with higher walking activity reducing its predatory performance.

Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is an important pest of several crops in the western hemisphere. This insect has genetically differentiated into two host-associated populations: the corn (Zea mays L.) and the rice (Oryza sativa L.) strains. The corn strain also is found in cotton (Gossypium hirsutum L.) and sorghum and the rice strain in Bermuda grass [Cynodon dactylon (L.) Pers.] and millet. In the United States and Brazil, lines from corn, rice, Bermuda grass, and millet were used to evaluate the resistance of both strains to various insecticides, and found that the corn strain is more resistant than the rice strain. However, in these studies the larvae were not genotyped. In Colombia, genotyping of fall armyworm is necessary because the rice strain also can be found in corn fields. In this work, collected larvae from corn and rice fields from Tolima (central Colombia) were genotyped and evaluated for the resistance to methomyl and lambda-cyhalothrin. We found that the rice strain does not significantly differ in resistance to methomyl compared with the corn strain but it develops tolerance more rapidly to lambda-cyhalothrin. The eggs viability of treated females also was significantly affected by methomyl on each generation. The realized heritability of resistance was higher for lambda-cyhalothrin (0.23-0.42) than for methomyl (0.04-0.14). The number of generations needed for 10-fold increase in resistance is approximately 11.5 generations for methomyl and 6.5 for lambda-cyhalothrin. Finally, the genetic basis of resistance to both insecticides involves few recessive autosomal genes. The results obtained here suggest that methomyl is a better option than lambda-cyalothin to control fall armyworm.

Polyethylene film impregnated with lambda-cyhalothrin was placed over a sand plot and covered with a concrete slab to allow insecticide movement into the sand for a period of 5.5 yr. Discs of polyethylene film and sand beneath them were sampled annually for 5 yr and at 5.5 yr for bioassay with the Formosan and eastern subterranean termite. Results demonstrated that sufficient quantities of lambda-cyhalothrin were released from the impregnated polyethylene film into adjacent sand to prevent termite penetration. The impregnated film has less environmental impact than conventional liquid termiticides because the insecticide is held in the polymer. Other advantages include its dual function as a construction moisture barrier and ease in verifying its proper installation.

Effects of droplet size and volumetric application rate of tractor-applied lambda cyhalothrin (Karate Z 2.08 SC) on larval tobacco budworm, Heliothis virescens (F.), mortality and insecticide deposition on and within the canopy of mature cotton were explored by use of a laboratory bioassay incorporating field-sprayed cotton and a field trial incorporating natural insect infestations. Insecticide was applied in all combinations of three distinct droplet sizes and three volumetric application rates. Mortality of third-instar tobacco budworm occurring in leaf-disk bioassays was highly correlated with insecticide deposits (microg/leaf disk) at upper- and midcanopy levels. At the upper canopy level, mortality was negatively correlated with volumetric application rate and was not significantly correlated with droplet size. Deposit was negatively correlated with volumetric application rate at the lower plant level and larval mortality decreased with increasing droplet size. Results from this study do not support the recommendations of high volumetric application rates; and although droplet size was less influential than volumetric application rate in deposit and insect mortality, the data indicate a significant trend toward increased midcanopy larval mortality with smaller droplets.

Pyrethroid resistance was found in 54 field strains of Helicoverpa armigera collected between 1995 and 1999 from 23 districts in seven states of India. LD50 values of the field strains ranged from 0.06 to 72.2 μg/larva with slopes of 0.5–3.1. Resistance was highest in regions where pyrethroid use was frequent (four to eight applications per season). Resistance to deltamethrin was exceptionally high with resistance ratios of 13,570 and 27,160 in two strains collected during February 1998 in central India. Resistance to cypermethrin, fenvalerate and cyhalothrin also was high with resistance ratios of >1,000 in four strains collected from central and southern India. Resistance ratios were below 100 in >50% of the strains tested. Pyrethroid resistance was high in strains collected from the districts in Andhra Pradesh where a majority of the cotton farmer suicide cases in India were reported. Resistance to pyrethroids appeared to have increased over 1995–1998 in most of the areas surveyed. Studies carried out through estimation of detoxification enzyme activity and synergists indicated that enhanced cytochrome p450 and esterase activities were probably important mechanisms for pyrethroid resistance in field strains. Pyrethroid nerve insensitivity also was found to be a major mechanism in some parts of the country where the use of pyrethroids was high. The information presented illustrates the importance of proper insect management programs to avoid the consequences associated with improper insecticide use.

We evaluated the toxicity of three insecticides (lambda cyhalothrin, spinosad, and S-1812) to the natural enemies Bracon mellitor Say, Cardiochiles nigriceps Viereck, Coleomegilla maculata De Geer, Cotesia marginiventris (Cresson), Geocoris punctipes (Say), and Hippodamia convergens Guerin-Meneville, in topical, residual, and field assays. Lambda cyhalothrin exhibited the greatest toxicity to the natural enemies. In topical toxicity tests, lambda cyhalothrin adversely affected each natural enemy species studied. Residues of lambda cyhalothrin on cotton leaves were toxic to B. mellitor, C. nigriceps, C. maculata, and G. punctipes. Interestingly, residues of this insecticide were not very toxic to C. marginiventris and H. convergens. Geocoris punctipes and C. maculata numbers in the field generally were significantly lower for lambda cyhalothrin treatments than for the other four treatments, substantiating the previous tests. Although cotton aphids began to increase over all treatments around the middle of the test period, the number of cotton aphids in the lambda cyhalothrin plots was significantly higher than the number in any of the other treatments. As cotton aphids increased in lambda cyhalothrin field plots, the predator H. convergens also increased in number, indicating that lambda cyhalothrin did not adversely affect it in accordance with the residual tests. Spinosad exhibited marginal to excellent selectivity, but was highly toxic to each parasitoid species and G. punctipes in topical toxicity tests and to B. mellitor in residual tests. Spinosad generally did not affect the number of G. punctipes, H. convergens, and C. maculata in the field except for one day after the second application for G. punctipes. S-1812 exhibited good to excellent selectivity to the natural enemies. Some reduction of G. punctipes occurred for only a short period after the first and second application of this insecticide in the field. H. convergens and C. maculata were affected very little by S-1812.

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

We compared laboratory and field efficacies of pyrethroid insecticides (Baythroid, ‘FCR 4545’ [both cyfluthrin], Karate [lambda cyhalothrin]) and insect growth regulators (Confirm [tebufenozide], ‘RH-2485’ [methoxyfenozide]) against the Mexican rice borer, Eoreuma loftini (Dyar), a key pest of sugarcane in south Texas. We also studied treatment effects on longevity and survivorship of its braconid parasitoid, Allorhogas pyralophagus Marsh. In the 1996 field season, Baythroid resulted in lower percentages of bored internodes compared with the other treatments. In the 1997 season, less borer damage was found in ‘FCR 4545’ (an isomer of Baythroid), relative to the other treatments. The differences may be partially attributed to the different application methods (tractor sprayer versus aerial). In both field seasons, no significant treatment effects could be found in any of the yield or juice quality measurements, suggesting that improvements must be made in application technology, or the biorational insecticides must be used in conjunction with other control agents, such as biological controls. Efficacy may be improved if applications can be timed to windows of susceptibility based on either plant phenology or pest lifecycle. Baythroid and FCR 4545 were generally most effective in reducing damage caused by E. loftini, although residual toxicity of Baythroid was higher than FCR 4545 against both E. loftini and A. pyralophagus. Comparisons between similar bioassays showed that Baythroid and tebufenozide were more toxic to E. loftini than to A. pyralophagus. Therefore, if A. pyralophagus or a similar parasitoid were to be used in conjunction with an insecticide, an effective approach may be to use a less toxic biorational, such as the insect growth regulator tebufenozide, or to time the release of the parasitoids after residual toxicity has declined in a biorational such as FCR 4545.

I propose that the high level of resistance to cyanopyrethroids found in cyhalothrin- selected horn flies is caused by an enzyme system that oxidatively inactivates the cyano group. This theory is supported by lower resistance to noncyano pyrethroids, lower response to the synergist piperonyl butoxide with noncyano pyrethroids, resistance ratios and synergism coefficients among the cyanopyrethroids that follow a pattern predicted by chemical stability of the molecule, and reported literature of distinctly different responses to cyano and noncyano pryrethroids in other animal systems.

We evaluated the 24-h contact toxicity of lambda-cyhalothrin for adult Asian longhorned beetle, Anoplophora glabripennis Motschulsky, by using topical application. Results showed that beetles are sensitive to lambda-cyhalothrin: the LD50 and LD90 were 0.13639 and 0.78461 µg/beetle, respectively. Residual activity of a commercial formulation of lambda-cyhalothrin was evaluated in a walking bioassay: Adult beetles walked across the surface of Denier bands treated with a series of concentrations of the formulation and exposed to the natural environment for 10, 20, 45, 69, and 90 d. Beetle mortality was recorded after 24 h. At the dosages of 150, 300, 450, and 600 mg/liter, residual activity declined slowly over the 90-d test period. All dosages provided 100% mortality up to 20 d posttreatment. No significant differences were detected in mortality among the dosages at each test interval until day 90 posttreatment, when the 450 and 600 mg/liter doses provided 100% mortality, which was significantly greater than percentage mortality provided by the 150 (20%) and 300 mg/liter (50%) doses. The 1200, 1500, and 1800 mg/liter doses provided 100% mortality for 158 d. The formulation may represent a new, alternative and complementary control strategy against A. glabripennis due to its high toxicity to adult A. glabripennis, its long residual activity, its rapid knock-down ability, and its potential use in specialized areas where current control strategies are not desirable or feasible.

Distribution and importance of woolly whitefly (Aleurothrixus floccosus) (Maskell) (Hemiptera: Aleyrodidae), was studied in Ethiopia with an evaluation of treatments against it. Results showed that the pest is distributed in most citrus-growing parts of the country equally infesting all types of citrus crops. Only one pupal parasitoid, Amitus sp., was recorded at Melkaoba. During 2006-2007, eight treatments gave better control of woolly whitefly compared with the control: endod (Phytolacca dodecandra L'Herit) berry extract, white oil 80%, neem oil, omo detergent soap, band application of gasoline, cyhalothrin (karate) 5% EC, selecron (profenofos) 500 EC, and rimon (novaluron) 10 EC. Treatments were applied on 6-8 yr-old orange trees at Melkaoba and Nazareth. At Melkaoba, application of cyhalothrin, selecron, white oil, and Neem gave better control of woolly whitefly compared with the control. All the treatments resulted in a lower number of ants than the control. Ants disrupt biocontrol agents of honeydew-secreting pests, including woolly whiteflies. Mean infestation score was higher in the control than the rest of the treatments. Similarly, at Nazareth, woolly whitefly numbers were lower recorded on cyhalothrin-treated plants. However, the numbers of eggs were significantly higher in endod extract-sprayed plants than the control. All treatments controlled ants better than the control except endod. Infestation scores were lower on endod- and cyhalothrin-treated plants than the control. Mean number of adult woolly whiteflies and eggs were significantly higher on newly grown leaves than older leaves. In general, the number of live adult woolly whiteflies showed a decreasing trend at both sites after treatment applications compared with the control.

Gamma-Cyhalothrin was proposed as an agent for management of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), in Australian broiler houses. From 2007 to 2009, baseline susceptibility of 20 Australian broiler farm beetle populations plus an insecticide-susceptible laboratory population was determined for gamma-cyhalothrin by using topical application. In addition, repeat testing and regression analyses of specific beetle populations to gamma-cyhalothrin showed that topical application was a very reliable and repeatable testing method. The 21 populations were tested with a cyfluthrin discriminating concentration (based on LC(99.9), 0.0007% [AI]) to identify possible cross-resistance. Across all populations, there was a significant linear relationship between the gamma-cyhalothrin LC50 value and mortality induced by the cyfluthrin LC(99.9). Full cyfluthrin baseline studies of seven populations indicated that gamma-cyhalothrin was twice as toxic as cyfluthrin, even against susceptible beetles and resistance ratios at the cyfluthrin LC50 and LC(99.9), varied considerably, with maxima of 56.6 and 83.6 respectively. Corresponding ratios for gamma-cyhalothrin for the same populations were 8.6 (LC50) and 7.9 (LC(99.9)). There were no significant correlations between beetle weights and gamma-cyhalothrin LC50 or LC(99.9), values. A discriminating concentration of 0.005% (AI) gamma-cyhalothrin was chosen to detect any future changes in susceptibility. Results of this study suggest that cyfluthrin can confer cross-resistance to gamma-cyhalothrin in A. diaperinus, but the magnitude of this resistance is unpredictable. Thus, widespread and frequent cyfluthrin use in broiler houses in eastern Australia, which has selected for cyfluthrin resistance, also has resulted in reduced susceptibility to gamma-cyhalothrin. Due to its higher relative toxicity, gamma-cyhalothrin is still potentially useful for management of lesser mealworm, but due to cross-resistance issues, adoption of gamma-cyhalothrin for broiler house use will require a cautious and judicious approach.

Thirty strains of Blattella germanica (L.) reported to be pyrethroid resistant were collected from three continents. Greater than 2-fold resistance to the pyrethroids cyfluthrin, fenvalerate, cypermethrin, and lambda cyhalothrin appeared in 15 of these strains. Twelve of these strains were also resistant to chlorpyrifos and propoxur. All the field strains tested were heterogeneous with regard to resistance. Possible resistance mechanisms detected in these populations included elevated levels of cytochrome P450, general esterase and glutathione S-transferase, and nerve insensitivity (kdr-type resistance). The elevated esterases and oxidase-based resistance were the most prevalent; 11 and 10 strains, respectively, had evidence of these mechanisms. Resistance was synergized by piperonyl butoxide in some strains. In some strains, elevated esterases, although present, were primarily correlated with organophosphate resistance. Pyrethroid insecticides may still be effective against many of these populations because of the low levels of resistance detected. However, potential exists for more serious resistance problems to develop if only pyrethroids are used. Because many of these strains are already resistant to organophosphorus and carbamate insecticides, prospects for the future chemical control of these populations must be carefully considered.

Ear tags impregnated with a mixture of cyhalothrin-piperonyl but oxide-DEF (S,S,S,-tributyl phosphorotrithiolate) or cypermethrin-piperonyl butoxide-chlorpyrifos were evaluated for the management of pyrethroid-resistant horn flies, Haematobia irritans (L.), on cattle in Kentucky. At the time of treatment, all horn fly populations were resistant to the pyrethroids in these mixtures. Although acceptable control of horn flies (average > 92%) was generally achieved on treated animals, LC50s for the pyrethroid mixture tested on each population were 2-33 times greater after 14 wk exposure compared with values before treatment. At the end of this exposure period, the frequency of pyrethroid-resistant individuals remaining in each of the treated horn fly populations was 100%.

The formamidines chlordimeform (CDF), desmethyl-CDF, BTS-27271 (NOR-AM 49844) and amitraz; the pyrethroid lambda-cyhalothrin ; and the carbamate thiodicarb were evaluated for ovicidal activity and effects on octopamine titers in eggs of the tobacco budworm, Heliothis virescens (F.). CDF and lambda-cyhalothrin were the most toxic of the compounds examined, followed by desmethyl-CDF and BTS-27271. Although octopamine is not detectable in untreated eggs of H. virescens , three formamidines caused the appearance of octopamine in treated eggs. lambda-cyhalothrin , amitraz, and thiodicarb had no apparent effect on octopamine titers. In vivo metabolism studies of radiolabeled amitraz by eggs of H. virescens indicate that BTS-27271 is a likely metabolite. Because octopamine is involved in insect behavior and energy mobilization, the formamidine-induced alteration of octopamine titers might alter behavioral responses or energy availability during the critical hatching process leading to increased mortality.

Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), has become the economically most important insect defoliator of potatoes, Solanum tuberosum L., in northern Xinjiang Uygur autonomous region in China. Currently, control of Colorado potato beetle relies mainly on chemical insecticides. And this may result in insecticide resistance. In this study, LD50 values were measured by a topical bioassay for 14 conventional insecticides in seven local populations from Urumqi, Changji, Tacheng, Nilka, Gongliu, Qapqal, and Tekes counties (cities). The Tekes field population was the most susceptible population and was selected as a reference strain. Compared with the Tekes strain, the Changji, Qapqal, Nilka, Tacheng, and Gongliu populations exhibited moderate to very high levels of resistance to cyhalothrin. The Qapqal and Changji populations showed a moderate and a very high resistance to deltamethrin, respectively. And the Changji population developed a high resistance against alpha-cypermethrin. Moreover, the Qapqal population had a moderate resistance to carbofuran, and the Urumqi population reached high level of resistance to endosulfan. Possible resistance mechanisms of the Changji and Qapqal populations were determined using three enzyme inhibitors. Triphenyl phosphate (TPP), diethylmeleate, and piperonyl butoxide (PBO) had little synergism to cyhalothrin in the two populations. In contrast, PBO and TPP exhibited some synergistic effects to carbofuran in the Qapqal population, indicating the involvement of monooxygenases and esterases in conferring carbofuran resistance. It seems that additional mechanisms, such as target site insensitivity, should play an important role in Colorado potato beetle resistances to cyhalothrin and carbofuran in northern Xinjiang local populations.

A study was conducted to determine the efficacy of cyhalothrin and lambdacyhalothrin as a whole-body spray and lambdacyhalothrin as a pour-on application on cattle infested with Boophilus microplus (Canestrini). A laboratory bioassay was also done with both spray formulations. Cattle were infested with all parasitic life stages of B. microplus , then treated with 0.007 or 0.01% (AI) concentrations of cyhalothrin as a spray; 0.005, 0.007, or 0.01% (AI) concentrations of lambdacyhalothrin as a spray, or 1% (AI) lambdacyhalothrin as a pour-on. As determined by calculations of the index of reproduction (IR), the 0.007 and 0.01% (AI) cyhalothrin provided 92.4 and 97.3% control, respectively; the 0.005, 0.007, and 0.01 % (AI) lambdacyhalothrin provided 92.4, 98.2 (average of two treatments) and 99.3% control, respectively; and the lambdacyhalothrin pour-on treatment provided

The time required for two symptoms of poisoning, ataxia and prostration (i.e., knockdown), to occur in third-instar cabbage loopers, Trichoplusia ni (Hubner), treated topically with cis -permethrin, esfenvalerate, and λ-cyhalothrin was determined at 15.6, 26.7, and 37.8°C. The toxicity of the pyrethroids also was examined at the three temperatures. ci8-Permethrin and λ-cyhalothrin had negative temperature coefficients of toxicity between 15.6 and 37.8°C, whereas esfenvalerate was equally toxic at both temperatures. The onset of ataxia and prostration in larvae treated with these pyrethroids occurred more rapidly as the temperature increased, thus was positively correlated with temperature. λ-Cyhalothrin was the most toxic pyrethroid; however, cis -permethrin was generally the most effective in producing ataxia and prostration in treated larvae.

Populations of onion thrips, Thrips tabaci Lindeman, from commercial onion fields in New York were evaluated for their susceptibility to the commonly used pyrethroid, lambda-cyhalothrin (Warrior T), using a novel system called the Thrips Insecticide Bioassay System (TIBS). To use TIBS, thrips are collected directly from the plant into an insecticide-treated 0.5-ml microcentrifuge tube that has a flexible plastic cap with a small well into which 0.08 ml of a 10% sugar-water solution with food colorant is deposited. The solution is sealed into the well with a small piece of stretched parafilm through which the thrips can feed on the solution. Thrips mortality is assessed after 24 h with the help of a dissecting stereoscope. In 2001, onion thrips populations were collected from 16 different sites and resistance ratios were1,000 in five populations. Percent mortality at 100 ppm, a recommended field rate, varied from 9 to 100%, indicating high levels of variation in susceptibility. Particular instances of resistance appeared to be the result of practices within an individual field rather than a regional phenomenon. In 2002, we also observed large differences in onion thrips susceptibility, not only between individual fields but also between thrips collected in a single field at mid season and late season, again suggesting that insecticide-use practices within an individual field caused differences in susceptibility. Additional tests indicated no differences in susceptibility between adult and larval onion thrips populations and only relatively minor differences between populations collected from different parts of the same field. Using TIBS, several populations of onion thrips with different susceptibilities to lambda-cyhalothrin were identified and then subjected to lambda-cyhalothrin-treated onion plants. There was a highly significant positive relationship between percent mortality of thrips from TIBS and percent mortality from the treated onion plants, indicating that results from TIBS could be used to predict spray performance. These data suggest that use of TIBS for evaluating susceptibility to particular insecticides could be instrumental for developing a resistance management strategy for onion thrips.

The Nantucket pine tip moth, Rhyaciona frustrana (Comstock), a common regeneration pest of loblolly pine, Pinus taeda L., has been shown to reduce tree volume yields through larval feeding. Chemical applications can be effective in protecting trees from the growth losses associated with this feeding, and optimum spray timing values are commonly used to reduce the number of necessary applications and to increase insecticide efficacy. Optimal spray timing values for the Georgia Piedmont were obtained for the following four insecticides available for use in loblolly pine plantations: permethrin (Pounce), lambda-cyhalothrin (Warrior T), spinosad (SpinTor 2 SC), and Bacillus thuringiensis variety kurstaki Berliner (Foray 48B). Optimal timing values were similar between the first and second generations for each of these compounds. All of the insecticides used in this study significantly reduced tip moth damage below the control treatment levels. Lambda-cyhalothrin was the most efficacious and had the longest spray timing window. B. thuringiensis was the least effective and had the shortest timing window. Spinosad and permethrin were similar in efficacy and spray timing values. This information is applicable to regions where there are three tip moth generations per year, as found in the southern Piedmont region and the coastal plain of Virginia and most of North Carolina.

Lambdacyhalothrin cattle ear tags controlled horn fly, Haematobia irritans (L.), for 14 wks or longer during 1986-1988 in Georgia, USA. In 1989 and 1990, control of50 horn flies per side of cow was achieved foror = 4 wk because of high levels of pyrethroid resistance in horn flies selected with lambdacyhalothrin. The highest resistance ratios (RRs) were seen in 1989. These were 498 for lambdacyhalothrin; 92,000 for fenvalerate; and 54 for permethrin. RRs for cypermethrin as high as 8,800 were estimated in 1990 when the RR for fenvalerate was only 1,060. No cross-resistance to diazinon was detected. These high levels of pyrethroid resistance seem to have a large component of metabolic resistance. Synergistic coefficients as high as 3,600 were determined by addition of nonlethal amounts of piperonyl butoxide. Resistance development in a no-pyrethroid-use area indicates movements ofor = 3km by sufficient numbers of horn flies can significantly change the RR.

A field-collected strain of the German cockroach, Blattella germanica (L.), was highly resistant to 10 pyrethroid insecticides (cyfluthrin, cyhalothrin, cypermethrin, fenvalerate, esfenvalerate, fluvalinate, permethrin, resmethrin, sumithrin, tralomethrin) based on topical applications and comparison with a known susceptible strain. Resistance ratios ranged from 29 to 337. In general, pyrethroid compounds with an alpha-cyano functional group were more toxic than those lacking this moiety, but resistance ratios were similar for both classes of compound. The metabolic inhibitors DEF and PBO were tested for synergism in conjunction with cypermethrin (alpha-cyano) and permethrin (non alpha-cyano). Application of synergists resulted in partial elimination of resistance, suggesting that the basis of resistance involves enhanced metabolism as well as target site insensitivity. These results suggest that pyrethroid insecticides may have a very short functional life in German cockroach control unless they are used judiciously.

The effect of previous insecticide use patterns for horn fly control on the susceptibility spectrum of horn fly (Haematobia irritans [L.]) populations from Kentucky and Arkansas is described. Populations of horn flies from both states were tested with three pyrethroids (cyhalothrin, cypermethrin, and permethrin), three organophosphates (diazinon, pirimiphos methyl, and tetrachlorvinphos), and a chlorinated hydrocarbon (methoxychlor). Dose-mortality data indicated insecticide resistance in Arkansas and Kentucky. Two permethrin-resistant horn fly populations in Kentucky that did not have a history of exposure to methoxychlor were cross-resistant to this chlorinated hydrocarbon. Horn fly populations from both states with a history of at least three consecutive years of exposure to various pyrethroid ear tags were subsequently exposed to cattle tagged with cyhalothrin-impregnated ear tags for 15-16 wk. Such exposure resulted in a decrease in susceptibility to this pyrethroid (ranging from approximately 30 to greater than 100-fold) when compared with levels before treatment. Horn fly populations from Arkansas resistant to cyhalothrin (as a result of exposure to cyhalothrin ear tags) were cross-resistant to pirimiphos methyl. Seasonal exposure of an Arkansas and Kentucky horn fly population to cattle with ear tags impregnated with pirimiphos methyl resulted in a significant decrease in susceptibility to this organophosphate.

During 1984-1987, variable seasonal weather patterns offered an opportunity to evaluate the influence of rainfall and sunlight on pyrethroid treatments applied on a 7-d schedule for control of boll weevil, Anthonomus grandis grandis (Boheman), and bollworm, Heliothts spp., damage. Conditions ranged from drought (with daily highs above 35°C) to frequent rain during the 4-yr period. All of the pyrethroids tested maintained high levels of bollworm control through all weather patterns with no significant differences. Highest overall efficacy for boll weevil occurred in 1984, which was intermediate among the four seasons in terms of rainfall and sunlight received. In 1985 and 1987, rain frequently fell within 2 d after insecticide applications; efficacy and consistency of all treatments for boll weevils were reduced compared with 1984 or 1986, but relative efficacy rankings did not change. Rain just after insecticide treatments in 1984 and 1986 also corresponded with reduced efficacy. Rain falling more than 2 d after spraying had no apparent effect on efficacy. In 1986, the efficacy of flucythrinate (0.028 kg [AI]/ha) and tralomethrin (0.0168 kg [AII/ha) for boll weevil declined rapidly during a 3-wk period with clear skies and a mean daily high temperature above 37°C and rebounded as daily high temperatures moderated. Control of boll weevil damage by cypermethrin (0.0672 kg [AI]/ha), esfenvalerate (0.0336 kg [AI]/ha to 0.040 kg [AIl/ha) and cyhalothrin (0.028 kg [AIl/ha to 0.0392 kg [AIl/ha) gradually decreased during this hot period and rose again as temperatures abated. Cyfluthrin (0.028 kg [AII/ha) maintained 85% control of boll weevil damage throughout the hot interval.

Field experiments with strains of Heliothis armigera (Hűbner), either resistant or susceptible to pyrethroids, were done to determine when selective mortality occurred. Eggs and larvae from neonates to 6 d old were placed on leaves collected from cotton fields 0-8 d after the crop had been sprayed with the pyrethroids cypermethrin, fenvalerate, deltamethrin, or cyhalothrin, by commercial application. In a second experiment, eggs of known phenotype were placed in fields just before a commercial application of a pyrethroid. After 48 h, high mortality rates were observed in 0-3-d-old larvae of both phenotypes when they were placed on leaves freshly sprayed with pyrethroids. Selective mortality occurred in older larvae when they were placed on freshly sprayed leaves and in all larvae tested when they were placed on leaves on which there had been dilution or decay of the insecticide. These experiments demonstrate that resistance alleles can be made recessive or neutral by spraying a sensitive life stage rather than by increasing the dose of insecticide.

Permethrin and cyhalothrin in combination with piperonyl butoxide (PB), DEF (S,S,S-tributyl phosphorotrithiolate), pirimiphos-ethyl and -methyl were evaluated in the laboratory and the field for activity against pyrethroid-resistant and susceptible horn flies, Haematobia irritants (L.). Horn fly adults from the pyrethroid-resistant population were resistant to permethrin (12.5-fold) but displayed a lower level of resistance to cyhalothrin and cyhalothrin-K (5.4- and 1.7-fold, respectively). Combinations of permethrin plus PB or DEF or both produced a low level of synergism (1.4 to 4.6-fold) but did not reduce the level of resistance present in the pyrethroid-resistant horn flies. The levels of synergism (2.0- to 6.6-fold) observed for combinations of PB, DEF, and PB + DEF with cyhalothrin were marginally higher than for permethrin. Unlike permethrin, the combination of cyhalothrin + PB + DEF resulted in a decreased level of resistance. Pirimiphos-ethyl and -methyl were highly toxic to the horn fly, with virtually no cross-resistance in the pyrethroid-resistant population. Mixtures of pirimiphos-ethyl plus either permethrin or cyhalothrin were highly effective against the resistant horn fly population, but no more so than pirimiphos-ethyl alone. Field studies in 1985 demonstrated that, although the combination of permethrin + PB + DEF was more effective than permethrin alone, control was still inadequate. In these same studies, cyhalothrin provided marginal control while cyhalothrin + PB + DEF produced good results. In 1986, the use of cyhalothrin-K and pirimiphos-methyl resulted in excellent control of the horn fly throughout the season, as did a higher concentration of cyhalothrin and cyhalothrin + pirimiphos-methyl.