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Hydroprene Prolongs Developmental Time and Increases Mortality of Indianmeal Moth (Lepidoptera: Pyralidae) Eggs
Abstract
Eggs of the Indianmeal moth, Plodia interpunctella (Hübner), were exposed to the labeled rate of hydroprene (1.9 x 10(-3) mg [AI]/cm2) sprayed on concreted petri dishes. These eggs were exposed for 1, 3, 6, 12, and 18 h and until hatching (continuous exposure) at temperatures of 16, 20, 24, 28, and 32 degrees C and 57% RH until the emergence of first instars. The developmental time and egg mortality were significantly influenced by temperature and exposure periods. At 16 degrees C, hydroprene did not cause differences in developmental time when eggs were exposed for different periods. At temperatures >16 degrees C, both exposure period and temperature influenced developmental time. The maximum developmental time (15.0 +/- 0.2 d) occurred at 16 degrees C, and the minimum developmental time (3.2 +/- 0.3 d) occurred at 32 degrees C. Mortality increased when eggs were exposed to hydroprene for longer periods at all of the five tested temperatures. The greatest mortality (81.6 +/- 2.1%) occurred when eggs were continuously exposed on treated surfaces at 32 degrees C. We used developmental time instead of rate (1/ developmental time) to fit simple linear or polynomial regression models to the development data. Appropriate models for developmental time and mortality were chosen based upon lack-of-fit tests. The regression models can be used in predictive simulation models for the population dynamics of Indianmeal moth to aid in optimizing use of hydroprene for insect management.
... Infestation begins in the field and moves with the date fruits to the storeroom, where it can reproduces for many generations with a great loss (Howard et al., 2001;El-Shafei, 2018;El-Shafei, et al. 2020). Plodia interpunctella is one of the most dangerous insects that infests a wide range of dried fruits, vegetables and stored materials such as stored date fruits (Perez-Mendoza and Aguilera-Pena, 2004;Mohandass, et al., 2006). Larvae of this pest decreases both quality and quantity of stored products through feeding, webbing, and fecal matter (Johnson et al., 1997;Hansen and Jensen, 2002;Johnson, et al., 1997). ...
The date palm is one of most important fruits in Middle East. Date fruits are exposed to infestation by many insect pests like Ephestia cautella (Walker) and Plodia interpunctella (Hübner) which decrease their quantity and quality. This study aimed to evaluate efficiency of two viruses (NPV and GV) on mentioned these insects. Seven concentrations of each virus were tested (1x10 1 to 1x10 7) against these two insects at various durations: 5, 7, and 10 days. Results showed that corrected larval mortality% of E. cautella and P. interpunctella increased by increasing viruses concentrations and exposed durations with highest percentages were 54.44 and 73.33% for E. cautella and P. interpunctella larvae respectively compared with control after treating with NPV virus 1x10 7 for 10 days. While these were 74.33 and 100% for E. cautella and P. interpunctella respectively in case of GV virus compared with control. Data obtained revealed that P. interpunctella larvae were more susceptible to tested viruses than E. cautella larvae. Further, the two insects were more susceptible to GV concentration than NPV concentrations. The corrected mortality percentages of E. cautella and P. interpunctella larvae were increased to 95.56 and 98.89% respectively after using mixture of LC50s of two viruses compared to LC50 of each virus separately. In addition, both viruses exhibited no-effect on tested chemical contents of date's fruits. As a conclusion, combination of both viruses increased their efficacy against E. cautella and P. interpunctella and this has to be considered in biocontrol programs of both insect pests.
... It is a cosmopolitan pest attacking a wide range of stored products including dried vegetable and fruits commodities. It can infest a variety of products and is perhaps the most economically important insect pest of processed food (Perez-Mendoza and Aguilera-Pena, 2004;Mohandass et al., 2006). ...
This study aimed to evaluate ozone (O3) technology as management tools to control all life stages of Indian meal moth, Plodia interpunctella (Hübner) (eggs, larvae, and pupae) infesting stored date and its effect on some larval enzymes activity and the quality of date fruits. Three concentration of ozone gas 100, 300 and 500 (ppm) has been tested against P, interpunctella life stages (eggs, larvae, and pupae) at various exposure times, which were ranged from 15 to 150 minutes. Results revealed that the mortality of tested life stages increased by increasing the exposure time in each ozone concentration. The required exposure time to reach 100 % mortality of the insect stages decreased by increasing the ozone con. from 100 to 500 (ppm). Corrected egg mortality reached 100% after 150 min. from exposure to 500 ppm ozone. The corrected second instar larval mortality recorded 100 % after 150 and 90 min. from exposure to 300 and 500-ppm ozone con. respectively. While the corrected mortality of 4th instar larvae reached 100 % after 150 and 120 min. of exposure to 300 and 500-ppm ozone con. respectively. On the other hand, pupal corrected mortality was 100 % just when its exposure to 500 ppm for 150 min. Results showed that the egg was the most tolerant stage to the ozone gas while the 2nd larval instar was the most susceptible one. On the other hands, 4th larval instar was more susceptible than the pupa. Also, data showed that ozone seemed to have no effect on tested chemical contents of dates fruits. In addition, results revealed that the larval rate of respiration was affected by ozone gas
... Also, developmental dynamics of P. intepunctella depends on nutritive quality and mechanical state of food (Locatelli and Limonta, 1998;Vukajlović and Pešić, 2012;Kočović, 2014). Many researchers reported that life-cycle of P. interpunctella ranges from 27 to 52 days depending on factors such as temperature, food odor, presence of oil in diet, type of food, size and physiological state of females, availability of drinking water, food source and temperature (Allotey and Goswami 1990;Johnson et al., 1992;Nansen and Phillips, 2003;Mohandass, 2006). However, diet is the most important factor for determining the developmental period of the insects (Mbata 1985; Johnson et al., 1992;Nansen and Phillips, 2003;Silhacek, et al., 2003;Silhacek and Murphy, 2005) and according to Vukajlović et al. (2017), when reared on whole wheat and rye kernels, this moth successfully completes life-cycle. ...
One of the most important pests of stored grains is Plodia interpunctella (Hübner), whose larvae feed primarily on germinal part of the kernels, causing a reduction of seed germination and seed viability. This is detrimental for seeds of high category. However, seeds of different species within the same taxonomic family have different morphology (thickness of seed-coat, presence or absence of palea, palea loose or firmly attached to the seed etc.), which affects the susceptibility of seeds to P. interpunctella attack. The hypothesis was that seed hardness and the absence of palea could also significantly influence the life history of this pest. We assessed the suitability of different seeds from family Poacae (maize, wheat, barley, oats, ray, forage sorghum (variety), forage sorghum (hybrid), Sudan grass and millet) for P. interpunctella development and seeds susceptibility to pest attack (expressed in Susceptibility index –SI). The following parameters were monitored: larval mortality, adult emergence, mean developmental duration (from egg to adult) and female fecundity. Observations were carried out weekly, for 49 days. Data were statistically analyzed using Duncan’s multiple range Test. The highest larval mortality, the lowest number of emerged moths and the lowest fecundity were recorded on millet, Sudan grass and forage sorghum (variety and hybrid). However, the shortest larval development (27.8 days) and the highest fecundity (109.5-115.6 eggs) were on standard laboratory diet, maize and wheat. Morphometric measures of moths indicate that on unsuitable mediums like millet, Sudan grass, and different sorghum varieties the body lengths were statistically significantly shorter (0.5-0.6 cm) compared to other treatments (0.8-0.9 cm). According to the SI, the most susceptible were maize, wheat, barley, oats and ray, while moderately resistant were Sudan grass and millet. Testing kernel hardness and continuous improving of kernel resistance to storage insect pests could provide lower losses in stored grain quality and quantity.
... Indian meal moth has been found to be distributed across the continent of the world and ranked as one of the most important storage pest in warm-temperate and sub-tropical climate (Rees, 2004). The life cycle of P. interpunctella has been reported by many researchers to ranges from 27 -52 days depending on factors such as temperature, food odour, presence of oil, type of food, size of female, availability of drinking water, physiological state of female, food source, depth of food, temperature among others (Bell 1981; Allotey and Goswami 1990;Johnson et al., 1992;Nansen and Phillips 2003;Mohandass 2006). Diet (food) is the most important factor for determining the developmental period of the insect and can feed on wide range of food (Mbata 1985; Johnson et al., 1992;Nansen and Phillips 2003;Silhacek, et al., 2003;Silhacek, and Murphy, 2005). ...
The life cycle stages of Indian meal moth, Plodia interpunctella (H) was studied on four different diets:whole maize flour, whole wheat flour, breadfruit flour and a formulated diet, under ambient laboratoryconditions of 28±2oC and 75±5% R.H. The proximate composition of the diets, oviposition, larva instarstages, and the complete developmental duration from egg to adult of the moth were examined on the fourdifferent diets. The result showed that the percentage protein value of the formulated diet was significantlyhigher (14.58) than other diets. The oviposition of the moth on the diets ranges between 1-3 days andabout 70% of the eggs laid were on the first day of oviposition in all the diets. The highest number of eggslaid was observed on moths reared on maize flour. Incubation of eggs examined on the diets ranges from3-4 days. Also, there were variations in the number of larva instar stages in the four diets. The formulateddiet recorded the lowest period of pupation (6.33 days) and the total developmental average period(23.50days). The study clearly showed that the formulated diet is suitable for rearing P. interpunctellaunder laboratory conditions.
... This insect is a worldwide pest of stored products and processed food commodities. It can infest a variety of products and is perhaps the most economically important insect pest of processed food (Perez-Mendoza and Aguilera-Pena, 2004;Mohandass et al., 2006). ...
Life table parameters of Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), on four pistachio cultivars (Akbari, Ahmad-Aghaii, Fandoghi and Kalehghouchi) were studied in laboratory at 28 ± 0.5 °C, 50 ± 5% RH and a photoperiod of 16:8 h (L:D). The larvae successfully developed on all cultivars. The shortest and longest larval periods were recorded on Akbari and Kalehghouchi, respectively. The fecundity of females varied from 109.19 to 157.81 eggs on Kalehghouchi and Akbari, respectively. The adult longevity varied from 6.19 to 6.75 days on Fandoghi and Akbari, respectively. The intrinsic rate of increase (rm) ranged from 0.0961 to 0.1382 (female/female/day) on Kalehghouchi and Akbari, respectively. The mean generation time (T) was found 35.67 to 31.83 days on Kalehghouchi and Akbari, respectively. The Kalehghouchi cultivar was less suitable, and the Akbari cultivar was the most suitable host for P. interpunctella in comparison with other cultivars. These results provide important information on population growth potential of P. interpunctella on four commercial pistachio cultivars.
... Arbogast et al. (2002) showed reduction in population of several stored-product pests, including P. interpunctella, when hydroprene was applied as a spot-treatment in a botanical warehouse. In laboratory tests, exposure of P. interpunctella eggs prolonged the development time of the eggs and caused mortality in a dose-dependent manner similar to the results described for larval exposure (Mohandass et al., 2006). ...
Insect growth regulators (IGRs) are insecticides that mimic insect-produced hormones that regulate the developmental process. They generally have little or no mammalian toxicity, and are considered reduced-risk insecticides that are often exempt from tolerance requirements of regulatory agencies. Although IGRs have been available for more than 30 years, there is increased interest and application for stored-product pest control. Insect growth regulators can be used for direct application to stored grains, and worldwide perhaps the most common IGR used for this purpose is methoprene. Within the last few years, there has been new research showing that this IGR is very effective against Rhyzopertha dominica (Coleoptera: Bostrichidae), one of the most destructive pests of stored grain worldwide. However, one of the limitations of IGRs is that they generally do not kill adult insects. Recent studies show that the addition of methoprene to diatomaceous earth (DE), a natural product, or a contact insecticide will give complete control of this species on stored grains. Another application of IGRs is as surface treatments to flooring structures of mills, warehouses, and processing plants. Hydroprene (Gentrol) is particularly effective against late-instars of Plodia interpunctella (Lepidoptera: Pyralidae), Tribolium castaneum and T. confusum (Coleoptera: Tenebrionidae). Other IGRs that are effective against these insects when used as surface treatments are methoprene and pyriproxyfen. The final category where IGRs can be used in pest management programs is as aerosol spray treatments. In the United States, there are a number of facilities that have integrated methoprene aerosols into their control programs. The use of IGRs can easily be integrated into pest management strategies to control stored-product insects in bulk grain and in milling, processing, and storage facilities.
... Insect growth regulators (IGRs) are receiving increased attention in many agricultural systems, including stored products. The IGR hydroprene limits egg hatching and larval development of P. interpunctella (Arbogast et al., 2002; Mohandass et al., 2006a, b). Methoprene and pyriproxifen have recently been labeled as aerosol treatments and for some surface applications, and they may also affect P. interpunctella in a manner similar to hydroprene. ...
Plodia interpunctella (Hübner), the Indian meal moth, is a world-wide insect pest of stored-products and processed food commodities. It can infest a variety of products and is perhaps the most economically important insect pest of processed food. In this review, we summarize the biology of P. interpunctella, discuss oviposition and development in relation to temperature, environment and food source, examine studies involving sampling and detection, describe various aspects of integrated control, summarize the current knowledge regarding management of P. interpunctella, and address potential areas for new research. The use of reduced-risk insecticides, non-chemical control, targeted pest management through spatial analysis and other means of identifying specific locations of infestations, and computer models that simulate population growth, are examples of some of those new areas of research.
... These results are similar to those for the IGR hydroprene (Mohandass et al. 2006b). However, the relatively low control of eggs and wanderingphase larvae exposed to surface applications of methoprene contrasts with results reported by Arthur (2004) and Chanbang et al. (2007) with eggs and early instars of the lesser grain borer, Rhyzopertha dominica (F.), exposed on wheat, Triticum aestivum L., and rice, Oryza sativa L., treated with methoprene. ...
A series of studies was conducted to determine the effects of temperature on toxicity of the insect growth regulator methoprene to eggs and larvae of Plodia interpunctella (Hübner), the Indianmeal moth. When methoprene was applied to Kraft paper at the rate of 0.0003 mg of active ingredient [(AI)]/cm2, there was little direct toxicity against eggs of P. interpunctella, and temperature did not affect insecticide efficacy. Similarly, exposure of eggs on a paperboard surface treated with different rates of methoprene resulted in delayed adult emergence but not a reduction in adult emergence. However, wandering-phase larvae ofP. interpuctella were susceptible to methoprene, and exposure of larvae for 0.5, 1, and 2 h on different packaging materials resulted in reduced adult emergence. There was variation in emergence depending on the specific surface, but temperature had no effect on resulting adult emergence from exposed larvae. A partial budget analysis described treatment costs and reduction of risks associated with control of eggs and larvae of P. interpunctella. Results indicate methoprene could be used in management programs to control larvae of P. interpunctella, but eggs may be able to compensate for exposure to methoprene residues on treated surfaces.
The present study was established to evaluate the potential of insect growth regulator on the growth and development of Tribolium confusum Azadirachtin, a neem derivative which considered as insect growth regulator due to its chitin inhibitor activity was tested topically at four doses (0.5, 1, 1.5 and 2 μg insect-1) on adults of Tribolium confusum (Coleoptera: Tenebrionidae) and first evaluated on fecundity, hatchability and viability of eggs, longevity and morphometric of oocytes. Results show that the compound reduces the longevity and the fecundity. Generally, treatment with azadidrachtin affected growth and development of oocytes and egg-viability as shown by calculating the number of oocytes per ovaries and the size of basal follicle. The width of the follicle has not been affected significantly by these treatments. In the second group of experiments, this IGRs don't induce significant reduction in percentage of hatchability, the hatching rate of eggs laid by Fl females was not affected by the treatment (F = 2.86, DF = 99, p = 0.5) but it affect very significantly the viability rate of eggs laid by first female generation Fl (F = 7.5, DF = 99, p>0.0001). However, the azadirachtin lengthened very significantly the total duration of life cycle. Duration of the embryonic and post embryonic development of eggs laid by treated female increase when the concentration varied from 0 to 2 μLl. This data confirm the efficiency of growth regulators derived from neem plant, on the development of stored product insect pests.
Since the initial suggestion of using insect hormones or their mimics as the third-generation insecticides, great strides have been made in the discovery of three classes of such insect growth-disrupting insecticides. We propose the use of the term " insect growth disruptors" instead of the mis-named term " insect growth regulators" We review the commercial insecticides that mimic the mode of action of the insect growth and development hormones, the sesquiterpenoid juvenile hormones and the steroidal 20-hydroxyecdysone and the third class of insecticides that disrupt growth and development by interfering with chitin synthesis in target insect pests. In this chapter, the emphasis is on the application of these insecticides to control insect pests and development of resistance. Since the non-steroidal ecdysone agonist insecticides have been extensively reviewed in other chapters of this volume and elsewhere, only salient features of these novel insecticides are discussed.
Insect juvenile hormones (JHs) are important regulators of development and reproduction. Perturbation in the homeostasis at inappropriate times in the various developmental and reproductive stages of an insect, which normally requires controlled release and metabolism of this and other hormones, results in abnormal development or lethal consequences. Such deliberate consequences have been possible by the discovery and use of Juvenile Hormone Analogs (JHAs), the synthetic chemicals that mimic JH action, which have also been utilised as insecticides for several decades. With the availability of molecular tools and improvement in pharmacophore analyses in the recent years, there has been considerable advancement in the understanding of the mode of action of JHAs and development of methods for discovery of novel JHAs. Although there is limited use of JHAs for insect pest control, the list of new insect species susceptible to these compounds has been expanding revealing the potential for future use of this class of insecticides. The relatively fewer effects of JHAs on non-target insects and animals and favourable environmental fate of these compounds make them attractive insecticides for inclusion in integrated pest management programmes. In this review, we provide a comprehensive overview of JHAs, as endocrinological and insecticidal tools covering all the relevant research topics on JHAs research during the past three decades.
Objectives
Despite multiple attempts at eradication, many ectoparasites of humans and domestic livestock remain a persistent problem in the modern world. For many years, a range of pesticide drugs including organophosphates, organochlorides and synthetic pyrethroids provided effective control of these parasites; but intensive use of these drugs has led to the evolution of resistance in many target species. This paper aims to review the effectiveness of current control methods and discuss potential alternatives for the long term sustainable control of ectoparasites.Key FindingsImportant medical ectoparasites such as scabies mites, head lice and bed bugs present a significant public health problem, and so adequate control methods are essential. Ectoparasites of domestic livestock and farmed fish (for example sheep scab mites, poultry mites and sea lice) are also of concern given the increasing strain on the world's food supply. These parasites have become resistant to several classes of pesticide, making control very difficult. Recently, an increasing amount of research has focussed on alternative control methods such as insect growth regulators, biological control using essential oils or fungi, as well as vaccine development against some ectoparasites of medical and veterinary importance.SummaryDrug resistance is prevalent in all of the ectoparasites discussed in this review. A wide variety of alternative control methods have been identified, however further research is necessary in order for these to be used to successfully control ectoparasitic diseases in the future.
Experiments were performed to determine the relative impact of different mechanisms of methoprene horizontal transfer between Tribolium castaneum (Herbst) individuals. Larvae provided during later development with only dead methoprene-treated developmental stages (late-stage larvae, pupae, or adults) resulted in no survival to adulthood. This suggests that transfer through cuticle contact could be involved, but some cannibalization also occurred. The average level of cannibalization was not different between methoprene and control treatments, but the distribution of the amount of feeding did appear to be shifted to greater consumption by larvae exposed to methoprene-treated individuals compared to water-treated. The potential impact of cannibalism on horizontal transfer was further evaluated by scoring the level of feeding by untreated larvae on either water or methoprene-treated pupa and then comparing larval development and survival after different levels of cannibalization. In this experiment, the level of feeding on methoprene-treated individuals did not affect the percentage of normal surviving adults (insects which emerged as adults, exhibited no external morphological malformations, and were alive at the end of the observational period), suggesting that consumption of treated individuals was not contributing significantly to horizontal transfer. Short-term confinement of a methoprene or water treated adult with an untreated late-stage larva did not effect larval development and survival compared to the controls, indicating that brief contact between individuals was not sufficient for detectable negative effects. Transfer of methoprene from treated individuals to a flour substrate and then to an untreated individual through contact with and/or feeding on the flour was evaluated. Exposure of larvae to methoprene-contaminated flour during development resulted in a significantly lower number of normal surviving adults compared to controls. These results suggest that horizontal transfer of methoprene is probably due to prolonged contact with methoprene-treated individuals or methoprene-contaminated flour.
The insect growth regulator (IGR) hydroprene is a juvenile hormone analogue used in urban and stored-product insect control programs in the United States and in other developed countries. Hydroprene can be considered as an alternative to conventional insecticides because of its specific activity against immature insect stages, low persistence in the environment, and virtually non-toxic effects on mammals. Several published records demonstrate the excellent potential of hydroprene to control many stored-product insects. However, there are concerns of insect resistance to all insecticides, including IGRs. We review the mode of action of hydroprene in insects, examine how hydroprene is used in agricultural and urban pest management systems, describe research with hydroprene in stored-product pest management, and discuss potential mechanisms by which insects could develop resistance to this chemical. We also identify potential areas of further research with hydroprene that include, but are not limited to, the estimation of effects of hydroprene on different flooring surfaces, evaluation of multiple methods of hydroprene application in a facility, identification of other control methods to be used in combination with hydroprene, identification of specific life stages of stored-product insects that are especially vulnerable to hydroprene, and inclusion of the effects of hydroprene in stored-product insect population models.
Wandering phase Indianmeal moth, Plodia interpunctella (Hübner), larvae were exposed to the label rate of hydroprene (1.9 x 10(-3) mg [AI] /cm2) sprayed on concreted petri dishes. Larvae were exposed for 1, 3, 6, 12, 18, 24, and 30 h and maintained at 16, 20, 24, 28, and 32 degrees C and 57% RH until adult emergence. Larval developmental time and mortality were significantly influenced by temperature and exposure intervals. Maximum developmental time (47.2 +/- 1.3 d) occurred at 16 degrees C, and the minimum developmental time (7.0 +/- 0.5 d) occurred at 32 degrees C. Larval mortality generally increased at all of the five tested temperatures as exposure period increased. The greatest mortality (82.0 +/- 0.1%) occurred when larvae were exposed for 30 h at 28 degrees C, and minimum mortality (0.0 +/- 0.5%) occurred at 16 degrees C when larvae were exposed for 1 h. The relationships between temperature, exposure period, and developmental time were described by polynomial models, based on lack-of-fit tests. Hydroprene has potential to be an effective alternative to conventional insecticides in surface treatments for Indianmeal moth management. Response-surface models derived from this study can be used in simulation models to estimate the potential consequences of hydroprene on Indianmeal moth population dynamics.
Inhibitory Effect of S-Hydroprene on Egg Maturation in Cator semilooper, Achoea janata Linn (Lepidoptera: Noctuidae)
Thirteen maize varieties were investigated for suitability for oviposition and development of Plodia interpunctella (Hubner). The hybrid varieties (8329–15, 8321–18, 8425–8 and 8326–18W) were highly preferred for oviposition and had between 108.4 and 140.3 eggs deposited on them while the local variety and TZPBSR had very few eggs (41.3–46.9) deposited on them. The local variety was a more acceptable substrate than glass for egg deposition. Development from egg hatch to adult on the whole kernels of the varieties was fastest (31.2 days) on TZSR‐W‐1 and slowest (37.0 days) on 8321–18. Rearing the moths on broken kernels of the maize varieties generally shortened their developmental period. The maize varieties 8329–15 and 8326–18W were poor diets for the development of the moths as the moths did not develop on whole kernels of these varieties, and had prolonged developmental period on broken kernels of these varieties. These varieties and the local variety were therefore considered not suitable for the development of the moth. The maize varieties MSC Opaque, Farz 23, DMR‐YE, TZSR‐W‐1 and TZPB‐SR were very suitable for the development of the moth and they suffered more damage to the infestation by the moth.
Insecticide resistance in the sweetpotato whitefly, Bemisia tabaci (Gennadius), was monitored during 1991 and 1992 in a rose greenhouse and in adjacent cotton fields located in the western Negev of Israel. The whiteflies were collected and exposed to a series of concentrations of the insect growth regulators (IGRs) buprofezin and pyriproxyfen. Assays done on whiteflies obtained from the greenhouse indicated an ≍4-fold increase in tolerance to buprofezin after two successive applications of this compound. A relatively high level of resistance to pyriproxyfen was recorded after three successive applications of this compound. At LC50, the resistance ratio value for suppression of egg-hatch was 554-fold; for adult emergence failure, the resistance ratio was 10-fold. In contrast, one treatment of pyriproxyfen in cotton fields during the summer seasons (in accordance with the cotton insecticide resistance management [IRM] strategy) did not alter the susceptibility of B. tabaci appreciably to this compound. The rapid development of resistance to the novel IGRs demonstrates the need for IRM strategy, in both field and greenhouse crops. To prevent development of resistance to these compounds, use of both pyriproxyfen and buprofezin should be restricted to one treatment per crop season during the period of peak activity of the pest.
The Indianmeal moth, Plodia interpunctella, is a serious pest on dried fruit and oil-rich food products, such as pet food, cereals, flour products, and candy bars. We examined the P. interpunctella oviposition on unscreened food dishes with whole-wheat kernels treated with one of 18 different oils diluted in hexane (oil-treated) compared with a second unscreened food dish with whole-wheat kernels treated with hexane only (control). For eight of the 18 oils, the same two-choice experiment was conducted with screened food dishes. We concluded that (1) total oviposition was significantly lower when food dishes were screened compared with experiments with unscreened dishes; (2) using unscreened food dishes, P. interpunctella females laid significantly more eggs in 17 types of oil-treated wheat compared with dishes with control wheat kernels; and (3) using screened food dishes, P. interpunctella females only laid significantly more eggs in walnut oil-treated wheat compared with dishes with control wheat kernels. A nine-choice experiment was conducted in a large arena with unscreened food dishes, in which one dish contained control wheat kernels and eight other food dishes contained wheat treated with different oils. In the nine-choice experiment, P. interpunctella females showed the strongest response to wheat kernels treated with oil from walnut. This study provides the basis for chemical identification of oviposition stimulants for P. interpunctella from food oils.
The influence of sterilization by hydroprene on population dynamics in the German cockroach, Blattella germanica (L.), was studied in the laboratory where more detailed and accurate assessments could be achieved than would be possible under typical field situations. The gradual accumulation of sterile adultoids (i.e., adults with twisted wings, indicating exposure to hydroprene) during treatment, or their decreasing abundance after treatment, produced distinctive patterns in the dynamics of treated populations. The percentage of gravid females (a reproductive index) was first to respond to treatments, because increases (or decreases) in the percentage of gravid females preceded reductions (or recoveries) in sample density and nymph-to-adult ratios by 4-6 wk. Trends in the percentage of adultoids were negatively correlated with the percentage of gravid females and indirectly measure the activity of hydroprene. Initial reductions in the percentage of gravid females, sample density, and nymph-to-adult ratios began at or about the time when approximately 80% of adults had twisted wings (i.e., were adultoids). As the percentage of adultoids attained (or declined below) the 80% level, we can accurately predict the subsequent decline (or recovery) in nymph-to-adult ratios and, thus, sample density. These data support a proposal to adopt the 80% level of adultoids as an action threshold for regulating juvenoid treatments to maximize population suppression. The role of this action threshold in the long-term management of chronic B. germanica infestations or insecticide resistant populations is discussed.
Stored-product insects are a perennial problem in retail stores, where they damage and contaminate susceptible merchandise such as food products and animal feed. Historically, pest management in these stores has relied heavily on chemical insecticides, but environmental and health issues have dictated use of safer methods, and these require better monitoring. A monitoring procedure that employs an array of moth and beetle traps combined with spatial (contour) analysis of trap catch was tested in three department stores and two pet stores. The rate of capture increased with the level of infestation but was essentially constant over 4- to 5-d trapping periods. Contour analysis effectively located foci of infestation and reflected population changes produced by applications of the insect growth regulator (S)-hydroprene. The most abundant insects were Plodia interpunctella (Hiibner), Lasioderma serricorne (F.), Oryzaephilus mercator (Fauvel), Tribolium castaneum (Herbst), and Cryptolestes pusillus (Schönherr). The results indicate that contour analysis of trap counts provides a useful monitoring tool for management of storage pests in retail stores. It identifies trouble spots and permits selection, timing, and precision targeting of control measures to achieve maximum pest suppression with minimum pesticide risk. It permits managers and pest control operators to visualize pest problems over an entire store, to monitor changes over time, and to evaluate the effectiveness of control intervention. The contour maps themselves, along with records of control applications and stock rotation, provide permanent documentation of pest problems and the effectiveness of pest management procedures.
The dynamics of pyriproxyfen resistance in Bemisia tabaci (Gennadius) have been studied intensively in cotton fields and greenhouses in Israel. High resistance to pyriproxyfen evolved one year after its introduction for use on flowers in greenhouses, after three successive applications. After ten years of pyriproxyfen use in cotton fields, with only one application per season, a high level of resistance was observed, but its rate of development differed among localities. It is hypothesized that these differences reflect temporal and spatial variations in the availability of alternative host plants for B tabaci , and that pyriproxyfen resistance evolved most readily in geographically isolated areas. It is also likely that the occurrence and development of resistance is partially biotype‐related. Pyriproxyfen use has ceased in high‐resistance localities, but in areas with low frequencies of resistance, cotton growers have continued to achieve acceptable control of B tabaci with pyriproxyfen. Due to the absence of applications of pyriproxyfen in some cotton fields, resistance levels tended to decline between 1998 and 2001. Laboratory experiments support the hypothesis that this decline reflects, in part, fitness costs associated with pyriproxyfen resistance.
© 2002 Society of Chemical Industry
Several display techniques were compared for representing scientific data in the context of a feature detection task. The data sets were rendered on a Silicon Graphics workstation using four display formats: linearized gray scale; rainbow scale; reduced hue (blue-green-yellow-white) scale; and a 3D-topographic format viewed in stereo. The task involved searching for features that were embedded in scientific data sets consisting of two spatial and one scalar variable. Data sets were drawn from three scientific domains: Landsat, medical MRI, and global atmospheric data bases. Two types of features were embedded within the data sets: circular (blob-like) discontinuities, and linear (cliff-like) discontinuities. Results showed a general advantage for the gray scale, and a marked disadvantage for the 3D-topographic format in both accuracy and response latency. Performance in the two color scale formats was intermediate, with the reduced hue scale supporting faster, if not more accurate performance than the full rainbow scale. Performance differences were found across data base domains, as well. Directions for future research are discussed.
The Indianmeal moth, Plodia interpunctella, is a serious pest on dried fruit and oil-rich food products, such as pet food, cereals, flour products, and candy bars. We examined the P. interpunctella oviposition on unscreened food dishes with whole-wheat kernels treated with one of 18 different oils diluted in hexane (oil-treated) compared with a second unscreened food dish with whole-wheat kernels treated with hexane only (control). For eight of the 18 oils, the same two-choice experiment was conducted with screened food dishes. We concluded that (1) total oviposition was significantly lower when food dishes were screened compared with experiments with unscreened dishes; (2) using unscreened food dishes, P. interpunctella females laid significantly more eggs in 17 types of oil-treated wheat compared with dishes with control wheat kernels; and (3) using screened food dishes, P. interpunctella females only laid significantly more eggs in walnut oil-treated wheat compared with dishes with control wheat kernels. A nine-choice experiment was conducted in a large arena with unscreened food dishes, in which one dish contained control wheat kernels and eight other food dishes contained wheat treated with different oils. In the nine-choice experiment, P. interpunctella females showed the strongest response to wheat kernels treated with oil from walnut. This study provides the basis for chemical identification of oviposition stimulants for P. interpunctella from food oils.
Preface.Vectors of Random Variables.Multivariate Normal Distribution.Linear Regression: Estimation and Distribution Theory.Hypothesis Testing.Confidence Intervals and Regions.Straight-Line Regression.Polynomial Regression.Analysis of Variance.Departures from Underlying Assumptions.Departures from Assumptions: Diagnosis and Remedies.Computational Algorithms for Fitting a Regression.Prediction and Model Selection.Appendix A. Some Matrix Algebra.Appendix B. Orthogonal Projections.Appendix C. Tables.Outline Solutions to Selected Exercises.References.Index.
Application of juvenile hormone analogues, s-methoprene and s-hydroprene, at 1.0, 10.0 and 50.0 μg/pupa of Achaea janata, resulted in formation of compound egg chambers at the basal region of ovarioles. s-Methoprene (1.0 μg/pupa) was, however, not effective. Number of oocytes/chamber varied from 5 to 19 depending upon age of the pupa. Such derangements caused sterility in this moth.
An arbitrary arrangement of plots on a page can be achieved by specifying the location (left, bottom) and dimensions (width, height) of each individual plot. However, this sort of specification is unintuitive and, especially for simple arrangements, inconvenient and inefficient. This article describes a mechanism for specifying an arrangement of plots by constructing a matrix of plot names. The mechanism is intuitive, simple and, with the help of a few additional parameters, can produce quite sophisticated arrangements. The mechanism was developed as part of a prototype software package, but it does not rely heavily on any of the features of that package and it could be implemented in any statistical system.
The effect of the insect growth regulator, hydroprene, was observed on Callosobruchus maculatus (F.). Hydroprene was applied topically to the last 2–3 sternites of unmated males and females with a micropipette. No significant decrease in fecundity was observed even with the highest dose of 0.75 μg of hydroprene, whereas the fertility of the eggs laid by treated females was affected on the first day of the oviposition period even with the lowest dose of 0.1 μg, and the effect was diluted with time. Male fertility was also affected. The emerged F1 adults showed morphological abnormalities and the developmental period was prolonged.
Substrates contaminated by wandering fifth instar larvae of Plodia interpunctella (Hübner)(Lepidoptera: Pyralidae) elicit oviposition by conspecific female moths, and larval rearing diet enhances oviposition and also induces upwind flight. Two-choice oviposition assays determined that four-day-old gravid female P. interpunctella preferred to lay eggs on dishes containing cornmeal-based rearing diet compared to empty dishes. Pieces of cheesecloth contaminated by fifth instar larvae elicited more oviposition than untreated cheesecloth or dishes with food. The combination of larval contamination and food was preferred over food only or larval contamination only in both two- and four-choice experiments. The factor(s) in larval contamination responsible for eliciting oviposition in female moths was extracted in hexane, confirming that organic semiochemicals are responsible for the effect. The oviposition-eliciting activity of larval contamination was retained on cheesecloth for up to 30 days following treatment with larvae, suggesting the active component(s) is stable and of low relative volatility. In two-choice windtunnel bioassays female moths initiated flight only when rearing food was present in one of the treatments, and they displayed the highest landing responses to a combination of larval contamination and food. Earlier work on P. interpunctella and related pyralid species found that larval contamination due to secretions from the mandibular glands acted as both a spacing pheromone for wandering larvae and as a kairomone for host-seeking parasitoid wasps. The present study suggests that the same or a similar secretion acts as an oviposition-eliciting pheromone for conspecific females.
Three- and 4-week-old Tribolium castaneum (Herbst), the red flour beetle, and Tribolium confusum (du Val), the confused flour beetle, were exposed at five different temperature–relative humidity (r.h.) combinations to a volatile formulation of the insect growth regulator (IGR) hydroprene (called Pointsource™). Typical effects associated with IGR exposure, such as arrested larval growth, morphological deformities in adults, twisted and deformed wings, and incomplete adult emergence were produced in both species. Tribolium castaneum and T. confusum were susceptible to Pointsource™, but T. castaneum appeared to be the more susceptible species. More 3-week-old larvae of both species were arrested in that stage compared to the 4-week-old larvae. Nearly all of the 3- and 4-week-old T. castaneum larvae that were able to complete development to the adult stage quickly died after they emerged and were grossly morphologically deformed. In contrast, some emerged adult T. confusum remained alive after they emerged and were not deformed in any manner or had only twisted and incomplete wings. A greater percentage of larvae of both species were arrested in the larval stage and more adults died after they emerged in exposure studies conducted at 32°C, 75% r.h. as compared with 32°C, 30% r.h., but the reverse was true for exposures conducted at 27°C. Pointsource™ appears to have excellent potential for use in controlling Tribolium species within indoor facilities.
An evaluated compilation of equilibrium relative humidities in air vs. temperature from pure phase to approximately 10**5 pascal (1 atm) in pressure is presented for 28 binary saturated aqueous solutions. The relative humidities of the solutions range from about 3 to 98%. Using a data base from 21 separate investigations comprising 1106 individual measurements, fits were made by the method of least squares to regular polynomial equations with two through four coefficients. Equations and tables are presented along with the estimated uncertainties in the correlated results.
Oviposition by a strain of the Indian meal moth, Plodia interpunctella (Hübner), and by 2 strains of the almond moth, Ephestia cautella (Walker) was usually stimulated by the presence of moth rearing medium, peanuts, or dates and was influenced by the type of food. Moths taken from a specific food source laid most eggs. The P. interpunctella originated from peanuts, one strain of the E. cautella originated from peanuts, and the other from dates. The possibility that the 2 strains of E. cautella are sibling species is discussed.
Two insect growth regulators (IGR), hydroprene and methoprene. when applied to wheat and corn kernels at concentrations ranging from 2 to 10 ppm, prevented the metamorphosis of the Indian meal moth, Plodia interpunctella (Hübner), and effectively reduced the F1 populations of the lesser grain borer, Rhyzopertha dominica (F.), the confused flour beetle, Tribolium confusum Jacquelin duVal, and the sawtoothed grain beetle, Oryzaephilus surinamensis (L.). However, they were not as effective against the rice weevil, Sitophilus oryzae (L.), since substantial numbers of progeny developed in wheat kernels treated at a rate of 10 ppm with either of the compounds.
Degree-days for egg to adult development were determined for a laboratory and a wild-type isolate of the Indianmeal moth, Plodia intcrpunctella (Hübner), reared on wheat bran diet, almonds, pistachios, walnuts, raisins, and prunes. To avoid problems with temperature-induced diapause and effects of diet, eggs and pupae were used to estimate developmental thresholds used in degree-day determinations. Lower developmental thresholds for eggs (14.8) and pupae (13.8) of both isolates were identical. A threshold of 14 was used for degree-day determinations for both isolates. Egg hatch on all diets was lower for the wild-type isolate, but postembryonic survival of the wild-type isolate was similar to the laboratory isolate. Survival was <12% on dried fruits, 76.5-91.7% on nuts, and 9.5.3-97.3% on wheat bran. Degree-days for the laboratory isolate for each diet was lower than those for the wild-type isolate. Degree-days for each isolate' was lowest when reared on wheat bran and highest when reared on dried fruits. The determination of developmental thresholds for eggs and pupae allows the use of a single lower threshold for all models, although different degree-days will be necessary for each commodity.
Four insect growth regulators (IGRs) were tested for efficacy in suppressing populations of Ephestia cautella (Walker) in inshell peanuts. In laboratory tests, peanuts were sprayed with several concentrations of either hydroprene, methoprene, diflubenzuron, or Stauffer MV-678 (1-(8-methoxy-4,8-dimethylnonyl)-4-(I-methylethyl)benzene) and infested with 200 eggs of almond moths. Concentrations below 100 ppm of all IGRs except diflubenzuron (hydroprene, 5 ppm; methoprene, 25 ppm; MV-678, 90 ppm) completely suppressed adult emergence. These IGRs also reduced fecundity at lower concentrations. MV-678 at ca. 30 ppm completely inhibited oviposition. Residues of hydroprene, methoprene, and MV-678 were as effective as residues of malathion (35 ppm) against the almond moth after at least 8 months of storage.
Six species of stored-products insects were reared on diets treated with methoprene and hydroprene at 1, 5, 10, and 20 ppm. Both compounds at 20 ppm prevented emergence of pupae of Tribolium castaneum (Herbst) and substantially reduced it in T. confusum Jacquelin duVal. At 5 ppm or higher, they inhibited oviposition in both species. Larvae that failed to pupate in treated food continued to molt, and those that survived to 120 days or longer after emergence were larger than normal larvae.
Methoprene at one ppm or higher prevented emergence of adults of Oryzaephilus mercator (Fauvel), and O. surinamensis (L.) in treated rolled oats or cornmeal. Hydroprene produced a similar effect in cornmeal treated at 5 ppm or higher. Both compounds caused morphogenetic malformities in flour beetles and grain beetles. None of the pupal-adult intermediates or malformed adults survived.
Hydroprene at 10 and 20 ppm in wheat almost completely inhibited progeny production by Sitophilus granarius (L.). Both compounds caused decreasing productivity with increasing concentration in S. oryzae (L.) but not enough to provide useful control.
A potential problem exists when rate (1/time) is used for parameter estimation instead of time in least-squares estimation of nonlinear development models, because the squared error is the quantity that is minimized by this technique. Minimizing the squared error in the rates is not equivalent to minimizing the squared error in time. This is of particular significance in modeling insect development because, when development times are largest, rates are small and squared errors in the rates produce large errors in time predictions. The purpose of this study was to show that, in many cases, parameters should be evaluated in terms of the observed data. Using least-squares techniques on rates did not allow for the minimization of the absolute squared error in time at low temperatures. Least-squares techniques applied to development time produced good predicted values throughout the temperature range in particular cases. These results show that when parameters are not evaluated in terms of the observed data but rather in some modified form such as rate, erroneous predictions may result.
The synthetic juvenile hormone analogue (JHA) hydroprene was applied as a space spray against three species of stored products insect. Food media in glass crystallising dishes was placed in open and in enclosed situations under simulated food production conditions. The area was treated with hydroprene on three occasions: three months before the introduction of insect eggs into the food media, two days before infestation of the media, and three months after infestation. Space spray applications of the commercial formulation of hydroprene (Protrol®) were conducted using a cold fogger at a rate of 18 mg/m2 floor area. Hydroprene, which appeared to accumulate in the food media, disrupted the normal development of the three species tested leading to lengthened larval development time and increased sterility in adults. With food media in the open, non-deformed adult emergence was reduced by 100% for Tribolium castaneum and Ephestia cautella and by 94% for Tribolium confusum. With the food media enclosed, to simulate the situations found in food processing machinery, the effect of hydroprene was somewhat reduced but was still considered promising.
A comparison was made of the effects of methoprene (isopropyl 11-methoxy-3, 7, 11-trimethyl-2,4-dodecadienoate) and hydroprene (ethyl 3, 7, 11-trimethyl dodeca-2,4 dienoate) on the developmental survival of three malathion-resistant strains of Tribolium castaneum (Herbst) and one of T. confusum J. du Val, with a malathion-susceptible strain of each species. No cross-resistance to either IGR in any of the malathion-resistant strains was detected.
SUSCEPTIBILITÉ DE LIGNÉES DE TRIBOLIUM CASTANEUM ET DE T. CONFUSUM, RÉSISTANTES AU MALATHION, AUX RÉGULATIONS DE CROISSANCE METHOPRENE ET HYDROPRENE
On a fait une comparaison des effets de methoprene (isopropyl 11-methoxy-3, 7, 11-trimethyl-2, 4-dodecadienoate) et hydroprene (ethyl 3, 7, 11-trimethyldodeca-2, 4 dienoate) sur le développement de trois races de Tribolium castaneum reśistantes au malathion, et une race de T. confusum résistante au malathion, avec une race de chaque espèce prédisposée au malathion. Aucune résistance croisée a l'un ou l'autre IGR ne fut découverte dans les races résistantes au malathion.
In laboratory trials, concrete was treated with cyfluthrin wettable powder (WP) at 40 mg active ingredient [AI] cyfluthrin WP/m2, then heated for 4, 8, or 16 h at either 45°C or 55°C, or treated but not heated (seven treatment combinations). Bioassays were conducted by exposing adult Tribolium castaneum (Herbst) for 0.5, 1, and 2 h. Survival of T. castaneum was generally greater on unheated concrete compared with the heating treatments, and survival appeared to decrease as heating time increased at both 45°C and 55°C. In a second laboratory trial, concrete was treated with hydroprene (Gentrol) at the label rate of 1.9×10−3 mg [AI]/cm2, and bioassayed by exposing late-instar T. castaneum larvae on the treated surface. There were significant differences between untreated controls and the heat treatment regimes (P<0.05) with respect to the percentage of live emerged adults, the percentage of those adults with deformities, and the percentage of dead adults, but heating did not reduce efficacy of hydroprene. In a field trial, concrete was treated with cyfluthrin at 2 mg [AI] cyfluthrin WP/m2, and placed in a flour mill undergoing an experimental heat treatment and in an unheated office. Treated concrete was bioassayed by continually exposing adult T. castaneum for 0.5–120 h. The effect of heating time on insect mortality was not significant (P⩾0.05). Except for T. castaneum exposed for 0.5 h, the percentage of beetle survival on unheated concrete was greater (P<0.05) than survival on concrete that had been heated in the mill, indicating a possible beneficial effect on cyfluthrin toxicity due to heating. Results of these studies show that short-term exposures to high temperatures may have no appreciable effect on efficacy of either cyfluthrin WP or hydroprene, and combination treatments of heat plus either of these insecticides may be effective alternatives to methyl bromide for disinfesting milling facilities.
A model warehouse with carefully regulated environmental conditions was used to study the behavior of adult Indian meal moths during commodity infestation. Sequences of moth distributions in the warehouse, calculated by spatial analysis, clearly showed the coordinated movements of moth populations from eclosion to death. Many facets of adult behavior in a warehouse were coordinated with the photoperiod. Adult moths emerged at the end of a photophase and fairly rapidly moved to the walls and, to a lesser extent, to the undersides of the commodity pallets. Most females are mated in the first 24 h after emergence, largely during the scotophase. Air circulation within the warehouse probably compromised pheromone-directed guidance of males to females, although pheromones may still have a major role in regulating other aspects of male mating behavior. When mating subsided, many of the males flew upwind to the air circulating unit, but only during the photophases. The females moved to the return air side of the warehouse and then migrated towards the same end as the males, but only during the scotophases. They moved from pallet to pallet largely by walking on the warehouse floor and laid eggs in or on the cups of commodity. Direct oviposition on the commodity during the infestation period was lower than expected, probably because commodity odors were dissipated by air circulation and did not provide appropriate orientation. At 144 h after emergence, 90% of the moth population had died.
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Life history of immature maize weevils, Sitophilus zeamais Motschulsky. was studied at 10-40 degress C and 43-76% RH. The optimal quantity of corn for minimizing density effects and the optimal observation frequency for minimizing disturbance effects were determined at 30 degrees C and 75% RH. The quantity of corn (32-256 g) provided to five females ovipositing for 24 h did not affect duration of development, but the number of progeny produced increased asymptotically as the quantity of corn provided increased. Frequency of observation (from 1- to 14-d intervals) did not affect duration of development or number of progeny produced. Using moisture contents measured in the life history study, an equation was developed for predicting equilibrium moisture content of corn from temperature and relative humidity. Duration of immature development did not vary with sex, but did vary with test. This suggests that insect strain or chemical composition of the corn must be included as factors in a model predicting effects of environment on duration of immature development. Survival from egg to adult emergence was greatest at 95 degrees C. Sex ratio of emerging adults did not differ from 1:1. The number of multiply-infested kernels was low at all environmental conditions, and survival from egg to adult emergence in these kernels averaged 18%. Maximum daily rate of fecundity, duration of development, and number of progeny produced were optimal at 30 degrees C and 75% RH. An index of environmental suitability indicated that 30 degrees C and 75% RH was the optimal environment for growth of maize weevil populations on corn. Implications of the results for managing maize weevil populations are discussed.
Red flour beetles, Tribolium castaneum (Herbst), were exposed for 0.5, 1, and 2 h at 20, 25, 30, and 35 degrees C on concrete treated with 100 mg/m(2) 20% (AI) cyfluthrin wettable powder (WP) at biweekly intervals for 8 wk. Knockdown typically averaged 80-100% at all exposure intervals and temperatures until week 8, with no significant differences among temperatures. Although the overall F-test indicated a significant difference in survival among the 3 exposure intervals, the only significant difference detected was at week 4. After week 0, beetles exposed at 25, 30, and 35 degrees C began to recover from knockdown, and by week 6 survival was at least 90%, with 1 exception. Survival of beetles exposed at 20 degrees C was 0.0 and 7.5% for weeks 0 and 2, and <30% for weeks 4, 6, and 8. Beetles were able to tolerate exposure to cyfluthrin WP at successively lower temperatures as residues aged on the concrete.
Salt-marsh mosquitoes (Aedes taeniorhynchus), collected on 2 barrier islands in Lee County, Florida, that had been treated from 1989 to 1994 with 150-day methoprene briquets, were bioassayed with technical s-methoprene in the laboratory. Susceptibility of the indigenous Captiva strain (median lethal concentration [LC50] estimate, 6.71 ppb) collected from Captiva Island was 14.9-fold lower than the naive Flamingo strain (LC50 estimate, 0.45 ppb) from Everglades National Park. The Lover's Key strain (LC50 estimate, 6.66 ppb) was 14.8-fold less susceptible than the naive strain. Determinations of the susceptibility of nearby foci of the mainland mosquitoes exposed in the past several years to methoprene have not been completed, but probit analysis of laboratory exposures revealed that the only mainland strain tested (Burnt Store) was no less susceptible (1.06-fold) than the naive Flamingo strain. These findings support the theory that the observed resistance might be restricted to the barrier islands. The known resistance foci (generated with briquet formulations) are located west of the mainland where there is minimal likelihood of inflow of genome from the mainland. On the other hand, the mainland mosquitoes, which were exposed to liquid formulations of methoprene from 1987 to 1994, are believed to have substantial gene flow between exposed and nonexposed populations and thus a reduced likelihood of selection for resistance.
Methoprene, a juvenile hormone analogue, has been used for at least 20 years as the primary insecticide to control the pasture mosquito Aedes nigromaculis in Fresno County, California. First reports of apparent methoprene control failures were noted in a pasture west of Fresno in September 1998. Insufficient control was noted in 12 different pastures the following season from April to September 1999. In September of 1999, field trials were conducted to better ascertain the level of control. Results based on pupal counts from different methoprene formulations and rates of application indicated that in some pastures low levels of control were achieved with Altosid (Liquid Larvicide) and Altosid XR-G. Control with Altosid Pellets was reported at 52-99%.
In the summer of 1998, failures of methoprene field applications to control the mosquito Ochlerotatus nigromaculis (Ludlow) were noticed in several pastures in the outskirts of Fresno, California, USA. Effective control with methoprene had been achieved for over 20 years prior to this discovery. Susceptibility tests indicated that the Fresno Oc nigromaculis populations had developed several thousand‐fold higher LC 50 and LC 90 tolerance levels to methoprene compared with methoprene‐naïve populations. The synergists piperonyl butoxide (PBO), S,S,S ‐tributyl phosphorotrithioate and 3‐octylthio‐1,1,1‐trifluoro‐2‐propanone had little synergistic effect, suggesting that the mechanism of methoprene tolerance was not mediated by P450 monooxygenase or carboxylesterase enzyme degradation. As part of initiating a resistance management strategy, partial reversion back to methoprene susceptibility was achieved in a resistant population after six consecutive applications of Bacillus thuringiensis israelensis Goldberg & Marga coupled with two oil and two pyrethrum + PBO applications.
© 2002 Society of Chemical Industry
Ovicidal effect of three insect growth regulators on Corcyra cephalonica
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