Fenvalerate Resistance Research Articles

Seasonal Dynamics of Metabolic Mechanisms Mediating Pyrethroid Resistance inHelicoverpa armigerain Central India

Very high cypermethrin and fenvalerate resistance frequencies were recorded in Helicoverpa armigera (Hiibner) populations in central India during the 1993-94, 1994-95 and 1995-96 cropping seasons. Synergism assays and biochemical analyses of detoxification enzyme levels indicated that mono-oxygenases and esterases were important metabolic mechanisms mediating pyrethroid resistance. Piperonyl butoxide- (PBO) and profenofos-suppressible pyrethroid resistance were correlated with enhanced levels of cytochrome P450 and general esterases respectively. Enzyme assay data indicated that high cytochrome P450 levels generally coincided with low esterase activity and vice versa. Similarly, synergist bioassays showed that PBO-insensitive resistance was frequently associated with profenofos-sensitive resistance and vice versa. Oxidase- and esterase-mediated mechanisms evidently alternated in a reciprocal manner, with perceptible shifts in relative importance occurring during mid-October in all three seasons and in late January in 1995. Apart from metabolic mechanisms, a synergist-insensitive resistance mechanism (believed to be nerve insensitivity), accounted for an average of 51, 30 and 28% of cypermethrin resistance during the 1993-94, 1994-95 and 1995-96 seasons respectively.

Multiple Allelic Variation in a Sodium Channel Gene from Populations of Australian Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) Detected via Temperature Gradient Gel Electrophoresis

Helicoverpa armigera, the cotton bollworm; is a significant pest of Australian field and vegetable crops and has a widespread incidence of resistance to pyrethroid insecticides. Naturally occurring variation in the para sodium channel gene was assayed in H. armigera. the polymerase chain reaction (PCR) was used to amplify part of the gene and temperature gradient gel electrophoresis (TGGE) used to detect differences in the melting properties of the amplified DNA fragments. A gene fragment of approximately 890 bp was characterised in a total of 66 individuals, comprising four sample groups: untreated controls and fenvalerate‐treated individuals from both the Namoi valley, NSW and the St. George irrigation area, Qld. At least sixteen alleles were detected for the 3′‐end, 250 bp, Hpall digest fragment of the amplified part of the gene. the Namoi and St. George allele distributions were significantly heterogeneous, making this locus a suitable marker for use, with others, in migratory studies among H. armigera populations. Since this gene is a candidate for pyrethroid resistance in the related American pest Heliothis virescens (F.) we looked for a difference in allele distributions between insecticide treated and untreated groups. No association between molecular variation in this gene and fenvalerate resistance was detected.

A survey of insecticide resistance in Helicoverpa armigera in the Indian subcontinent

AbstractHelicoverpa armigera (Hübner) larvae were collected from field crops and wild hosts in India, Nepal and Pakistan from 1991 to 1995, and ninety eight laboratory cultures established. Cypermethrin, fenvalerate, endosulfan, quinalphos, monocrotophos and methomyl insecticides were topically applied to 30–40 mg, first laboratory generation larvae and resistance determined from log dose probit bioassays. Significant levels of cypermethrin and fenvalerate resistance were found in all field strains, demonstrating that resistance to at least some pyrethroids is now ubiquitous in H. armigera populations in the Indian subcontinent; cypermethrin and fenvalerate resistance levels ranged from 5– to 6500–fold and 16– to 3200–fold respectively. Pyrethroid resistance levels were highest in the intensive cotton and pulse growing regions of central and southern India where excessive application of insecticide is common. In all field strains assayed, pre-treatment with the metabolic synergist piperonyl butoxide (pbo), resulted in significant suppression of pyrethroid resistance. However, in nearly all cases, full suppression of resistance was not achieved. This residual non-pbo-suppressible resistance was most likely due to a nerve-insensitivity resistance mechanism. Pbo-insensitive resistance was highest in regions of India where insecticides were frequently applied to cotton and legume crops. In some regions where insecticides were heavily overused, a second high order nerve-insensitivity mechanism (possibly a Super -Kdr type mechanism), may have been present. Incipient endosulfan resistance (1–28-fold), was present throughout India, Nepal and Pakistan. Low to moderate levels of resistance (2–59–fold), were reported to the phosphorothionate group organophosphate, quinalphos, in India and Pakistan, but there was no evidence of significant resistance (0.4–3–fold), to the phosphate group organophosphate, monocrotophos, under our bioassay conditions between 1993 and 1994. H. armigera strains collected in Nepal in 1993 and 1994 were susceptible to quinalphos, but by 1995, 4–5–fold resistance was detected. It is probable that much of the resistance to pyrethroid, organophosphate and carbamate insecticides in the Indian subcontinent can be attributed to an inherited or inducible mixed function oxidase complex. Non-pbo-suppressible resistance becomes significant in regions and periods in the season when insecticide selection pressure on resistant H. armigera larvae on cotton and legume crops is very high.

Fenvalerate Resistance Mechanisms in Western Flower Thrips (Thysanoptera: Thripidae)

Pharmacokinetics were studied in two strains of western flower thrips, Frankliniella occidentalis (Pergande), that differed in their susceptibility to fenvalerate by 7-fold. Analyses at 1, 12, 24, and 48 h after continuous exposure revealed that fenvalerate- 14 C penetrated more slowly into thrips of the resistant KCM strain than into those of the more susceptible UMC strain. When expressed as percentage of total recovered radiocarbon, radioactivity in the internal extract of KCM thrips increased from 0.4% at 1 h to 2.5% at 48 h, whereas that in UMC thrips increased from 1.5 to 9.5% during the same time interval. However, fenvalerate- 14 C metabolism was faster in KCM thrips than in UMC thrips. Of the total radiocarbon in the internal extracts at the four sampling times, fenvalerate composed 43 2% in KCM thrips and 80 ± 2% in UMC thrips. Thus, decreased penetration and enhanced metabolism contributed to fenvalerate resistance in western flower thrips.

Development of Insecticide–Resistant and –Susceptible Spodoptera exigua (Lepidoptera: Noctuidae) Exposed to Furanocoumarins Found in Celery

When fed linear furanocoumarins throughout larval development, Spodoptera exigua (HÜbner) life history was affected as exposure to psoralen, xanthotoxin, and bergapten increased from control levels to those found in commercial 52–70HK celery and insect–resistant 87A 147–2 celery (0 to 0.0022 to 0.029% fresh weight of diet, respectively). As measured by life–history traits, the furanocoumarins were more biologically active in mixture than in isolation. Insecticide resistance status mediated the effect of furanocoumarins on some but not all life–history traits measured, and the type of resistance (methomyl and fenvalerate resistance) did not result in the same response in all measures. As compared with the methomyl and fenvalerahen larvae were exposed to the highest furanocoumarin concentration. As measured by survival, the insecticide–susceptible and fenvalerate–resistant colonies were more sensitive to furanocoumarin exposure than the methomyl–resistant colony. Pupal weight and egg production of those individuals surviving exposure did not indicate a furanocoumarin and insecticide resistance status interaction. Differences in monooxygnase activity, as measured by O–demethylation, were not detected in methomyl–resistant or insecticide–susceptible S.exigua larvae exposed or not exposed to furanocoumarins. These results suggest that differential selection for furanocoumarin tolerance among these populations may occur because of the diversity of S. exigua exposure to insecticides and host plants varying in linear furamocoumarin content.

Inheritance and Fitness Consequences of Resistance to Fenvalerate in Spodoptera exigua (Lepidoptera: Noctuidae)

Inheritance and fitness consequences of resistance to fen valerate in Spodoptera exigua (Hubner), the beet army worm, were evaluated with inbred lines of fenvalerate resistant and susceptible populations. Ancestors of the fen valerate-resistant population were exposed to a selection regime of multiple insecticides in the wild and were subsequently selected intensely with fenvalerate in the laboratory. Tolerance distributions of six generations of known relationship, derived from crosses of the inbred lines and their offspring, were estimated using susceptibility data. Because the tolerance distributions of the parental and F, generations overlapped, discrimination between a polygenic and monogenic model of fen valerate resistance inheritance was difficult. By fitting mean tolerance of these and the F. and two back cross generations to additive-dominance models, variation of mean tolerance among generations was adequately explained by a reduced polygenic model of five parameters that included epistatic effects of additive-by-additive and additive-by-dominance digenic interactions. Therefore, a polygenic model of inheritance seemed most plausible to explain fenvalerate resistance expression. Measurements of fecundity and development time differed among generations. Although an additive fitness cost explained a significant amount of the observed variation, resistance may be acting on these traits in a complex manner. Polygenic inheritance of resistance and fluctuating fitness effects because of changing patterns of fenvalerate use may contribute to the spatial and temporal variation in resistance seen in wild populations.

Classifying Resistance Severity in Field Populations: Sampling Inspection Plans for an Insecticide Resistance Monitoring Program

Detecting insecticide resistance before it increases above a critical level has been a driving force in developing tests to estimate resistance severity in field populations. Here, estimates of resistance severity ( r ) are classified into one of three categories. The classificationis based on comparing r with two preselected levels of resistance severity (θ) to obtain a three decision sampling plan. Using the example of fen valerate resistance in beet armyworm, Spodoptera exigua (Hubner), each θ was selected by comparing resistance test responses of populations that differed in resistance and exposure to insecticides. Test response wascorrected for survival of moths after exposure to a 1,000 μg/g concentration of fen valerate. This concentration was selected by comparing probit lines of susceptible and fen valerate-selected strains. The determination that r was greater or less than each θ was made using sampling inspection plans based on the binomial distribution. A sequential sampling plan using the sequential probability ratio test (SPRT) required less sampling effort than single sampling plans of equal strength and was suited to our operational needs. Using the same susceptibility test, sequential analysis of survival proportions from the 1,000 μg/gconcentration was also compared with probit analysis of survival proportions from multiple concentrations. Sampling effort required for the SPRT was substantially lower than that required for probit analysis. Despite differences in probit analysis and SPRT assumptions, probit estimates of resistance severity at 1,000 μg/gagreed with sequential classificationof r using a 1,000 μg/gconcentration.

Spatial Scale of Fenvalerate Resistance in Pear Psylla (Homoptera: Psyllidae) and Its Relationship to Treatment History

Data on fenvalerate susceptibility, pyre throed use, and related information for 48 sites in British Columbia, Washington, Oregon, and California were analyzed to clarify the spatial scale and causes of fenvalerate resistance in pear psylla, Psylla Agricola Foerster. LC50’s for fenvalerate varied significantly among regions and subregions. The number of pyrethroid treatments per site explained a significant portion of the variation in fenvalerate LC50 over all sites, within regions, and within subregions. For a given number of pyrethroid treatments, the expected LC50 for fenvalerate varied significantly among regions and subregions. Within-season timing of pyrethroid treatments, continuity of pyrethroid use, intensity of pear production in the surrounding area, and number of pyrethroid treatments at neighboring sites were not significantly associated with LC50’s for fenvalerate. Prospects for managing resistance to fenvalerate are best in Oregon and California (where levels of resistance were generally lower) compared with Washington and British Columbia. Results showing that local variation in LC50 for fenvalerate was significantly associated with local variation in pyrethroid use suggest that growers can reduce local increases in resistance by limiting pyrethroid treatments.

Resistance to the pyrethroid fenvalerate in pear psylla, Psylla pyricola Foerster (Homoptera: Psyllidae), in the Northwestern USA

Resistance to the pyrethroid, fenvalerate, was studied in pear psylla, Psylla pyricola Foerster, from several pear-production areas of the northwestern USA. Bioassays showed that a psylla population from Wenatchee, Washington, was highly resistant (242-fold) compared with a susceptible strain. Populations from Yakima, Washington, and Hood River and Medford, Oregon, were moderately resistant (26-fold), and a population from Corvallis, Oregon, showed only low levels of resistance (tenfold). Fenvalerate resistance appears to be polygenic and semi-recessive or intermediate in nature. Low levels of resistance are maintained in F 1 and backcross progency. Piperonyl butoxide synergized fenvalerate in all resistant strains, but caused its greatest effect on highly resistant psylla. Use of piperonyl butoxide in overcoming fenvalerate resistance in the field is discussed. Because pear psylla can rapidly develop pyrethroid resistance, careful monitoring is recommended.

LOCAL AND REGIONAL RESISTANCE TO FENVALERATE IN PSYLLA PYRICOLA FOERSTER (HOMOPTERA: PSYLLIDAE) IN WESTERN NORTH AMERICA

AbstractFenvalerate resistance was monitored in Psylla pyricola Foerster populations at 51 sites in Washington, Oregon, California, and British Columbia during early 1988. Resistance levels ranged from susceptible in an organic orchard in the Willamette Valley, OR, and at several other sites in Oregon and California, to highly resistant (> 100-fold compared with a susceptible strain) at several sites in central Washington. Generally, resistance levels were greater in the north than the south. In the Wenatchee and Yakima/Ellensburg, WA, areas, pyrethroid resistance was areawide, showing similar levels in both heavily treated and untreated orchards. In the Willamette Valley, OR, pyrethroid resistance was local and more consistent with the treatment histories of individual orchards. Factors influencing regional resistance appeared to be the species pool size of resistant and susceptible pear psylla, the intensity of spraying, and the unique host plant, life cycle, and dispersal attributes of this pest. Reasons for high regional resistance in central Washington and not in southerly areas are unknown, but this pattern is consistent with earlier patterns of insecticide resistance in pear psylla. The observed trends in fenvalerate resistance are discussed in relation to limiting resistance in pear psylla.

Microsomal monooxygenases in diamondback moth larvae resistant to fenvalerate and piperonyl butoxide

The microsomal monooxygenase activities toward several model substrates were measured in larval homogenates of strains of diamondback moth exhibiting different levels of fenvalerate resistance, ranging from ca. 300- to > 11,000-fold. Aldrin epoxidase activities varied only <2-fold. Activities of 7-methoxyresorufin O-demethylase, 7-ethoxyresorufin O-deethylase, and 7-ethoxycoumarin O-deethylase were significantly increased in the resistant strains, up to 16-, 5-, and 18-fold, respectively, over those in the susceptible FS strain. 7-Pentoxyresorufin O-depentylase was not detected in any strains. No changes in the sensitivity of these microsomal monooxygenases to in vivo and in vitro inhibition by piperonyl butoxide (PBO) were observed in the strains resistant to PBO, as compared with the FS strain. PBO resistance in diamondback moth was probably also caused by an enhanced microsomal degradation of this synergist.

Cuticular penetration of S-fenvalerate in fenvalerate-resistant and susceptible strains of the diamondback moth, Plutella xylostella (L.)

The cuticular penetration of fenvalerate was investigated in two fenvalerate-resistant (OKR 84-FR and KAR 84-FR) and two susceptible (OKR 84 and KAR 84) strains of the diamondback moth, Plutella xylostella (L.). Cuticular penetration of S-[ 14C]fenvalerate into larvae of the resistant stains was slower than that of the susceptible strains. The resistant strains showed lower amounts of internal accumulation of S-[ 14C]fenvalerate. However, the susceptible strains seemed to show higher rates of S-[ 14C]fenvalerate excretion than the resistant strains. Reduced cuticular penetration of S-[ 14C]fenvalerate was considered to be an important mechanism of fenvalerate resistance in the diamondback moth.

Insecticide Cross-Resistance in Pyrethroid-Resistant Strains of Tobacco Budworn (Lepidoptera: Noctuidae)

Dose-mortality regressions were estimated for eight pyrethyroids applied to fenvalerate-resistant strain of tobacco bud worm, Helios this viruses (F.), collected during 1986. A broad spectrum of cross-resistance was detected to permethrin (16.0-fold), cypermethrin 9.4-fold), flu validate (15.5-fold), biphenthrin (11.9-fold), esfenvalerate (10.4-fold), and deltamethrin (6.7-fold), although only cypermethrin, fenvalerate, and permethrin have been used extensively in the field. Cross-resistance to lambda-cyhalothrin was consistently low (1-2-fold) on several strains of tobacco bud worm. Pyrethroid-resistant strains tested with methyl parathion and profenofos exhibited 2.0-15.8-fold and 4.1-5.1-fold levels of resistance, respectively. Methyl parathion resistance was correlated with increasing levels of fenvalerate resistance.

Fenvalerate resistance and aldrin epoxidation in larvae of the diamondback moth

Three types of fenvalerate resistance have been observed in larvae of field and laboratory-selected strains of diamondback moth, Plutella xylostella (L.): (1) stable and of intermediate level, suppressible by synergists piperonyl butoxide, MGK 264, and sulfoxide; (2) stable and of high level, suppressible by the three synergists; (3) unstable and of high level, insuppressible by the synergist used in the selection mixture, suppressible by the other two synergists. Thus, aldrin epoxidation was measured in larvae of this insect pest. Protein concentration of the crude enzyme solution had to be kept below 0.2 mg (ca. equivalent to 1 larva) per 2 ml incubation mixture in order to keep the endogenous materials released during homogenization of whole fourth instar larvae from inhibiting aldrin epoxidation. NADH was found to synergize NADPH in facilitating this oxidation in the larval homogenate. While larvae of all resistant strains (with resistance ratios ranging from 300- to 7600-fold) exhibited higher rates of aldrin epoxidation than susceptible ones, the largest difference did not exceed 4-fold.

A simple bioassay for detecting and characterising insecticide resistance

AbstractA simple and rapid paralysis assay was developed to detect and characterise knockdown resistance in larvae of the house fly and pink bollworm. Pyrethroidtreated larvae unable to perform a stereotypic curling movement when probed with a warm needle, 10 min (house fly) or 60 min (pink bollworm) after treatment, were considered to be paralysed. Responses in a susceptible strain of house fly were compared with those of the pyrethroid‐resistant strains kdr and super‐kdr. In this assay, the kdr strain displayed over 28 fold resistance to deltamethrin, and super‐kdr larvae were unaffected by doses up to 100μg. These results are in good qualitative agreement with previous studies. The assay detected no significant fenvalerate resistance in pink bollworm larvae collected from the field; this was consistent with mortality bioassays performed on wild adult males. The limitations and potential utility of the paralysis bioassay in resistance screening are discussed.

Diamondback Moth Resistance to Several Synthetic Pyrethroids12

Most field strains of Plutella xylostella (L.) in Taiwan developed resistance to the four major synthetic pyrethroids—permethrin, cypermethrin, decamethrin, and fenvalerate—and the resistance levels to the three α-cyano 3-phenoxybenzyl esters were generally higher than that to permethrin. A diazinon-resistant strain showed significant cross resistance to all four compounds, whereas a methomyl-resistant strain had slight, yet consistent negative cross resistance to these compounds, except fenvalerate. Synergism of pyrethroid toxicity by piperonyl butoxide, but not DEF, was observed against a highly resistant strain. Fenvalerate resistance in the diamondback moth lacked sex linkage and was partially recessive and due to more than one gene.