Major Pest (major + pest)

Distribution by Scientific Domains

Selected Abstracts

Oviposition preference and larval performance of the sweet potato butterfly Acraea acerata on Ipomoea species in Ethiopia

Ferdu Azerefegne
1The sweet potato butterfly Acraea acerata is an indigenous species in Ethiopia that has become a major pest on the introduced sweet potato Ipomoea batatas. To assess the role of wild Ethiopian Ipomoea species as host plants, the presence of larvae on wild ipomoeas was studied, and female oviposition choice and larval performance were tested on five wild ipomoeas, as well as on sweet potato. 2In laboratory tests, oviposition and larval development were successful on two wild ipomoeas (Ipomoea tenuirostris and Ipomoea cairica) but no oviposition occurred on the remaining three species. Of the latter, larvae did not feed on Ipomoea hochstetteri and Ipomoea indica, and survival rates were extremely low on Ipomoea purpurea. 3Sweet potato was a better host plant than I. tenuirostris and I. cairica in terms of oviposition preference, larval survival and pupal size; pupae were larger, resulting in more fecund female butterflies. 4In the wild butterfly populations were abundant on I. tenuirostris but absent on I. cairica. Females also tended to prefer I. tenuirostris to I. cairica in oviposition choice experiments. However, no significant differences in performance were found between larvae raised on I. tenuirostris and I. cairica in the laboratory. 5Wild populations of A. acerata also existed on Ipomoea obscura, a plant not investigated in the present study. 6The abundance of A. acerata on wild ipomoeas is too low to likely affect butterfly population densities on sweet potato. However, wild populations may act as reservoirs subsequent to butterfly population bottlenecks on sweet potato. [source]

Genes, gene flow and adaptation of Diabrotica virgifera virgifera

Nicholas J. Miller
Abstract 1,Diabrotica virgifera virgifera has emerged as a major pest of cultivated maize, due to a combination of its high capacity to inflict economic damage, adaptability to pest management techniques and invasiveness. 2,This review presents a survey of the current state of knowledge about the genetics of D. v. virgifera. In addition, the tools and resources currently available to Diabrotica geneticists are identified, as are areas where knowledge is lacking and research should be prioritized. 3,A substantial amount of information has been published concerning the molecular phylogenetic relationships of D. v. virgifera to other chrysomelids. 4,There is a growing literature focused on the population genetics and evolution of the species. Several adaptations to anthropogenic selection pressure have been studied, with resistance to synthetic insecticides providing some particularly well-characterized examples. 5,A notable deficiency is a lack of studies directed toward the formal genetics of D. v. virgifera. [source]

Characterization of Wheat Random Amplified Polymorphic DNA Markers Associated with the H11 Hessian Fly Resistance Gene

Dhia Bouktila
Abstract In Tunisia, the Hessian fly Mayetiola destructor Say is a major pest of durum wheat (Triticum durum Desf.) and bread wheat (T. aestivum L.). Genetic resistance is the most efficient and economical method of control of this pest. To date, 31 resistance genes, designated H1,H31, have been identified in wheat. These genes condition resistance to the insect genes responsible for virulence. Using wheat cultivars differing for the presence of an individual Hessian fly resistance gene and random amplified polymorphic DNA (RAPD) analysis, we have identified a polymorphic 386-bp DNA marker (Xgmib1-1A.1) associated with the H11 Hessian fly resistance gene. Blast analysis showed a high identity with a short region in the wild wheat (T. monococcum) genome, adjacent to the leaf rust resistance Lr10 gene. A genetic linkage was reported between this gene (Lr10) and Hessian fly response in wheat. These data were used for screening Hessian fly resistance in Tunisian wheat germplasm. Xgmib1-1A.1-like fragments were detected in four Tunisian durum and bread wheat varieties. Using these varieties in Hessian fly breeding programs in Tunisia would be of benefit in reducing the damage caused by this fly. (Managing editor: Li-Hui Zhao) [source]

Enabling technologies to improve area-wide integrated pest management programmes for the control of screwworms

Abstract The economic devastation caused in the past by the New World screwworm fly Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) to the livestock industry in the U.S.A., Mexico and the rest of Central America was staggering. The eradication of this major livestock pest from North and Central America using the sterile insect technique (SIT) as part of an area-wide integrated pest management (AW-IPM) programme was a phenomenal technical and managerial accomplishment with enormous economic implications. The area is maintained screwworm-free by the weekly release of 40 million sterile flies in the Darien Gap in Panama, which prevents migration from screwworm-infested areas in Columbia. However, the species is still a major pest in many areas of the Caribbean and South America and there is considerable interest in extending the eradication programme to these countries. Understanding New World screwworm fly populations in the Caribbean and South America, which represent a continuous threat to the screwworm-free areas of Central America and the U.S.A., is a prerequisite to any future eradication campaigns. The Old World screwworm fly Chrysomya bezziana Villeneuve (Diptera: Calliphoridae) has a very wide distribution ranging from Southern Africa to Papua New Guinea and, although its economic importance is assumed to be less than that of its New World counterpart, it is a serious pest in extensive livestock production and a constant threat to pest-free areas such as Australia. In the 1980s repeated introductions and an expansion of Old World screwworm populations were reported in the Middle East; in the 1990s it invaded Iraq and since late 2007 it has been reported in Yemen, where a severe outbreak of myiasis occurred in 2008. Small-scale field trials have shown the potential of integrating the SIT in the control of this pest and various international organizations are considering using the release of sterile insects as part of an AW-IPM approach on a much wider scale. Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae) is a screwworm of temperate regions, which, although of limited agricultural importance, has invaded several new locations in the past few years. This special issue reports on the results of a 6-year project funded by the Joint Food and Agriculture Organization of the United Nations/International Atomic Energy Agency (FAO/IAEA) Programme of Nuclear Techniques in Food and Agriculture entitled ,Enabling Technologies for the Expansion of the SIT for Old and New World Screwworm'. A major goal of the project was to better understand population genetic variation in screwworms as an aid to the identification of isolated populations. The project also addressed issues related to genetic sexing, cuticular hydrocarbons, population dynamics, genetic transformation and chromosome analysis. [source]

Monitoring for imidacloprid resistance in the tobacco-adapted form of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), in the eastern United States

Lakshmipathi Srigiriraju
Abstract BACKGROUND: Imidacloprid is the primary insecticide for controlling the tobacco-adapted form of the green peach aphid (TGPA), Myzus persicae (Sulzer), a major pest of tobacco worldwide. This study used leaf-dip bioassays to assess TGPA resistance to imidacloprid in the eastern United States from 2004 through 2007. RESULTS: When combined over the 4 year study, 18, 14 and 3% of the TGPA had imidacloprid resistance ratios (RRs) of 10,20-fold, 20,30-fold and 30,90-fold, respectively, compared with the most susceptible colony tested. This indicates that some colonies have developed moderate levels of resistance to imidacloprid. A colony collected near Clayton, North Carolina, had the highest RR of 91 (LC50 value = 31 mg L,1). This resistance declined for six tests over a 3 year period in the laboratory culture from >130-fold RR (LC50 = 48 mg L,1) to 40-fold RR (LC50 = 15 mg L,1). Over the same period, the most susceptible colony and a standard colony not exposed to imidacloprid for over 7 years had consistently low LC50 values. CONCLUSION: Moderate levels of resistance to imidacloprid are noticed among TGPA colonies from the eastern United States. The variation in resistance indicates that the factors responsible are present in the populations at low frequencies and are just not enough to cause field failures yet. Copyright © 2010 Society of Chemical Industry [source]

Responses of the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), to seed treatments of canola (Brassica napus L.) with the neonicotinoid compounds clothianidin and imidacloprid

Lloyd M Dosdall
Abstract BACKGROUND: The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), is a major pest in the production of canola (Brassica napus L.) in North America and Europe, and effective population control is often essential for economical crop production. In North America, neonicotinoid insecticides have been used for several years in canola as seed treatments for reducing herbivory by flea beetles. The neonicotinoids clothianidin and imidacloprid were investigated to determine their effects on preimaginal development and on emergence of new-generation adults of C. obstrictus in comparison with effects of lindane, a chlorinated hydrocarbon seed treatment. RESULTS: Mean numbers of second- and third-instar larvae were significantly higher in plants seed-treated with lindane than in plants treated with the neonicotinoid compounds, even though weevil oviposition was similar for all treatments. Emergence of new-generation adults was reduced by 52 and 39% for plants seed-treated with clothianidin and imidacloprid, respectively, compared with emergence from plants treated with lindane. CONCLUSION: Seed treatment with both clothianidin and imidacloprid produced systemic insecticidal effects on larvae of C. obstrictus, with clothianidin slightly more effective than imidacloprid. Use of clothianidin or imidacloprid as seed treatments can comprise an important component in the integrated management of cabbage seedpod weevil in canola. Copyright © 2009 Society of Chemical Industry [source]

Potential mechanism for detection by Apis mellifera of the parasitic mite Varroa destructor inside sealed brood cells

Caroline Martin
Abstract The parasitic mite Varroa destructor Anderson & Trueman is a major pest of the honeybee Apis mellifera L. throughout the world. Chemical agents currently used for mite control leave contaminating residues and promote pesticide resistance. As an alternative means of control, it would be useful to identify natural substances enabling bees to detect Varroa inside brood cells. These substances could then be used to trigger mite hygienic behaviour by bees. In this study several techniques were used to screen substances that might allow detection of infested brood cells by bees. Gas chromatography-mass spectrometry analysis was performed on substances extracted in dichloromethane from the contents of brood cells. Solid phase microextraction and solid injection were performed on substances obtained from living and dead Varroa, respectively. Electroantennography was performed to assess the sensitivity of olfactory receptors in bee antennae to some of these substances. Principal component analysis based on proportions of cuticular substances allowed discrimination between bees and other cell contents. Foundress Varroa exhibited the greatest dissimilarity to healthy pupae that were used as controls. Immature Varroa and faecal material were intermediate. High molecular weight compounds, mainly dimethylalkanes, were proportionally the most characteristic components of foundress Varroa. This finding suggests that these compounds would be the most apt to induce uncapping of cells infested by Varroa. Solid-phase microextraction and solid injection demonstrated the presence of aliphatic acids, esters, and one alcohol, eicosenol, in Varroa. Electroantennographic recordings showed that mite-resistant bees were more responsive to some acids and one ester. We speculate that these compounds may be involved in recognition of living Varroa by honeybees. [source]

Deleterious effects of plant cystatins against the banana weevil Cosmopolites sordidus

Andrew Kiggundu
Abstract The general potential of plant cystatins for the development of insect-resistant transgenic plants still remains to be established given the natural ability of several insects to compensate for the loss of digestive cysteine protease activities. Here we assessed the potential of cystatins for the development of banana lines resistant to the banana weevil Cosmopolites sordidus, a major pest of banana and plantain in Africa. Protease inhibitory assays were conducted with protein and methylcoumarin (MCA) peptide substrates to measure the inhibitory efficiency of different cystatins in vitro, followed by a diet assay with cystatin-infiltrated banana stem disks to monitor the impact of two plant cystatins, oryzacystatin I (OC-I, or OsCYS1) and papaya cystatin (CpCYS1), on the overall growth rate of weevil larvae. As observed earlier for other Coleoptera, banana weevils produce a variety of proteases for dietary protein digestion, including in particular Z-Phe-Arg-MCA-hydrolyzing (cathepsin L,like) and Z-Arg-Arg-MCA-hydrolyzing (cathepsin B,like) proteases active in mildly acidic conditions. Both enzyme populations were sensitive to the cysteine protease inhibitor E-64 and to different plant cystatins including OsCYS1. In line with the broad inhibitory effects of cystatins, OsCYS1 and CpCYS1 caused an important growth delay in young larvae developing for 10 days in cystatin-infiltrated banana stem disks. These promising results, which illustrate the susceptibility of C. sordidus to plant cystatins, are discussed in the light of recent hypotheses suggesting a key role for cathepsin B,like enzymes as a determinant for resistance or susceptibility to plant cystatins in Coleoptera. © 2009 Wiley Periodicals, Inc. [source]

Esterase-based resistance in the tobacco-adapted form of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) in the eastern United States

Lakshmipathi Srigiriraju
Abstract Organophosphates and carbamates represent alternative insecticides in managing the tobacco-adapted form of the green peach aphid (TGPA), Myzus persicae (Sulzer), a major pest of tobacco in the United States and around the world. General esterases that detoxify these insecticides were assessed in green, red, and orange morphs of field-collected M. persicae. A total of 136 aphid colonies were collected from 2004 though 2007 and screened for total esterase activity. The green morphs had lower esterase levels, with a mean of 77±6.6,nmol/min/mg protein, as compared to red (84±2.9,nmol/min/mg protein) and orange morphs (172±16.5,nmol/min/mg protein). Overall esterase activities, and those for the red and green morphs, were positively correlated with LC50 values for acephate (organophosphate) and methomyl (carbamate) assessed in leaf-dip bioassays. Esterase genes responsible for higher esterase activities were diagnosed by gene amplification studies. Twenty-three of 24 colonies tested had either the E4 or FE4 gene amplified, both known to confer esterase-based resistance. Fifteen out of the 24 colonies tested had amplified E4 gene and four colonies had FE4 gene amplification. All orange morphs and one green morph had both E4 and FE4 genes amplified. This unique phenotype, where two esterase genes were amplified had an 865-bp band characteristic of the FE4 gene and an additional 381-bp band characteristic of a deleted upstream region of the E4 gene. Changes that occurred in esterase-based resistance in the TGPA over the past two decades and their implications on insecticide resistance management are discussed. © 2009 Wiley Periodicals, Inc. [source]

Australian populations of onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), are resistant to some insecticides used for their control

Grant A Herron
Abstract Onion thrips, Thrips tabaci Lindeman, is a major pest of Australian field onion Allium cepa Linnaeus with their control heavily reliant on a few insecticides. An earlier study after grower complaints of control failures did not detect resistance in three populations. After testing an additional nine populations via a Potter spray tower laboratory bioassay unequally against ,-cypermethrin, diazinon, dimethoate, ,-cyhalothrin, malathion and methidathion, we document resistance in T. tabaci for the first time in Australia. The maximum difference in response (resistance) for each insecticide was detected by dividing the most resistant LC50 response by the least resistant LC50 response. Comparison of the most susceptible to the least susceptible population tested produced ,-cypermethrin and ,-cyhalothrin resistance at 164- and 606-fold, respectively. Diazinon and dimethoate resistance was also detected at 27-fold and 5.2-fold respectively although omethoate, malathion and methidathion resistance were not detected. [source]

Temperature-dependent development and distribution in the soil profile of pupae of greyback canegrub Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae) in Queensland sugarcane

David P Logan
Abstract, The temperature-dependent development rate of pupae of greyback canegrub, Dermolepida albohirtum (Waterhouse) (Coleoptera: Scarabaeidae), a major pest of sugarcane in central and northern Queensland, was determined under six constant temperature regimes: 18, 20, 23, 25, 27 and 30°C, and for four geographically separated populations. Development rate increased significantly with increasing temperature. Parameters of the linear regression equation did not differ among populations and common coefficients were calculated. Developmental zero, at and below which no development occurs, for pupae was 12.0°C and the thermal constant was 476 day-degrees (D°). Minimum and maximum periods for pupal development were 26 days at 30°C and 75 days at 18°C, respectively. The phenology of pupae was determined in soil-filled cubicles in a shade house and in the field at Ayr (19°35,S, 147°25,E), north Queensland, using D. albohirtum field-collected as late-stage third-instar larvae and kept in containers. Pupation of D. albohirtum began in late August or early September and eclosion was complete by mid- to late October. The phenology data were used to validate the development model. Eclosion was predicted by summing hourly fractions of day-degrees until 476 D° was reached and was close to actual eclosion. As temperature, and hence pupal development rate, varies with soil depth, the distribution of the third instars in pupal cells in the soil profile was determined in recently harvested fields of sugarcane in the Burdekin sugarcane district centred on Ayr. Numbers of late third instars in pupal cells peaked at 300,400 mm, with pupae found from 30 to 700 mm. Pupal development was simulated using hourly soil temperatures measured at depths of 200 and 400 mm at Ayr and at Sarina (21°22,S, 149°13,E). The pupal stage was predicted to take up to 2,10 days longer at 200 mm deep than at 400 mm depending on pupation site and date. When pupation was simulated in late August, as is likely in the field, pupal development at 400 mm deep took 48,56 days at Ayr and 58,62 days at Sarina. [source]

Evolutionary ecology of insect adaptation to Bt crops

Yves Carrière
Abstract Transgenic crops producing Bacillus thuringiensis (Bt) toxins are used worldwide to control major pests of corn and cotton. Development of strategies to delay the evolution of pest resistance to Bt crops requires an understanding of factors affecting responses to natural selection, which include variation in survival on Bt crops, heritability of resistance, and fitness advantages associated with resistance mutations. The two main strategies adopted for delaying resistance are the refuge and pyramid strategies. Both can reduce heritability of resistance, but pyramids can also delay resistance by reducing genetic variation for resistance. Seasonal declines in the concentration of Bt toxins in transgenic cultivars, however, can increase the heritability of resistance. The fitness advantages associated with resistance mutations can be reduced by agronomic practices, including increasing refuge size, manipulating refuges to increase fitness costs, and manipulating Bt cultivars to reduce fitness of resistant individuals. Manipulating costs and fitness of resistant individuals on transgenic insecticidal crops may be especially important for thwarting evolution of resistance in haplodiploid and parthenogenetic pests. Field-evolved resistance to Bt crops in only five pests during the last 14 years suggests that the refuge strategy has successfully delayed resistance, but the accumulation of resistant pests could accelerate. [source]

Molecular identification and population dynamics of two species of Pemphigus (Homoptera: Pemphidae) on cabbage

INSECT SCIENCE, Issue 2 2009
Naiqi Chen
Abstract The poplar petiole gall aphid, Pemphigus populitransversus Riley, has been one of the major pests on cruciferous vegetable in the Rio Grande Valley (LRGV) of Texas since the late 1940s. It normally migrates from poplar trees to cruciferous vegetables in the fall, and migrates back to the trees in early spring of the coming year. Some root-feeding aphids were found on cruciferous vegetables in late spring and early summer in 1998 and the following years. Those aphids have been identified as Pemphigus obesinymphae Moran. This discovery completely changed the current knowledge about the root-feeding aphids on cruciferous vegetables in the LRGV. Due to their small size, morphological and feeding similarities between P. populitransversus and P. obesinymphae, their identification and distinction are difficult. In this study, random amplification of polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) were used to distinguish these two species over a period of time when the two species occurred together, or separately, in cabbage fields. The two species occurred on cabbage at different times of the year, and overlapped from October to June. From May to October, both species migrated to their primary hosts. The apterous aphids found on cabbage in winter contained mainly P. obesinymphae, whereas in early spring more apterous P. populitransversus were recovered. The root-feeding aphids would feed on cabbage plants as long as this host was available even during the hot, dry summer in the LRGV, although their populations were generally low. Both RAPD and AFLP techniques were efficient in discriminating the two species that showed obviously genetic variability. These molecular techniques confirmed the existence of the two aphid species in apterous samples collected from the soil in cabbage fields in the LRGV, and the results performed by RAPD were confirmed by AFLP. Furthermore, the results suggest that RAPD technique was a better choice despite its reproducibility problem, as it was less time-consuming and required less technology, labor and expense than AFLP. [source]

The nature and reality of the aphid clone: genetic variation, adaptation and evolution

Hugh D. Loxdale
Abstract 1,When aphid clones and clonality are discussed, it is still often said that they are ,genetically identical', a statement for which there is no direct evidence, and certainly not for the entire genome. By contrast, there is a growing body of empirical data from the application of high resolution molecular (DNA) markers that aphid asexual lineages rapidly mutate and that, in some documented cases, this variation is selectable, either positively or negatively. 2,Although it is true that, in enclosed conditions (e.g. laboratory or field cage), a so-called clone as defined as the asexual progeny of a single foundress may be traceable, this is rarely if ever possible in the field without the use of genetic markers, and even then, usually only at a relatively few loci (multilocus genotypes, ,MLGs'). 3,The continued use of the term clone without qualification of its true nature and the reality of its interesting biology is likely to hamper a proper understanding of the ecology and evolution of these insects (which are interesting in their own right because of their complex life histories, but also because they are important as major pests globally, both by causing direct feeding damage and by transmitting pathogenic plant viruses and thereby leading to huge economic losses in the agricultural, horticultural and forestry industries). 4,In this short review, I provide evidence of what is now known about aphid clonality after the widespread use of molecular markers, comprising information mainly gained within the last 15 years or so. 5,The data demonstrate widespread adaptation and evolution, sometimes involving introgression and hybridization. Because of this new knowledge, our ideas of what constitutes a clone are in need of serious re-evaluation. [source]

A laboratory-based comparison of a molluscicide and an alternative food source (red clover) as means of reducing slug damage to winter wheat

Andrew S Brooks
Abstract Slugs are major pests of many crops in the UK, including winter wheat, yet current methods of control are often unreliable. This study investigates the potential use of red clover, as an alternative food source, to reduce the amount of damage caused to winter wheat by the field slug, Deroceras reticulatum (Müller). Two laboratory-based studies, each conducted over a 7-day period, investigated the effects of red clover seedlings and commercial metaldehyde pellets on damage to winter wheat seeds and seedlings. The results indicate that metaldehyde applications, in the form of commercially available pellets, resulted in significantly greater protection to wheat seeds compared with red clover, whereas metaldehyde and red clover were equally as effective in reducing damage to wheat seedlings. A further laboratory experiment investigated the effect of two slug population densities (48 and 16 adults m,2) and high and low red clover seed rates (125% and 75% of a standard rate) on damage to wheat seeds. Results showed that, at the highest slug population density, red clover sown at 125% of the standard rate gave 99% protection to wheat seeds, compared with the 75% seed rate which gave 55%. At the lower slug population density, both seed rates of red clover resulted in similar levels of protection. Implications for the potential use of red clover as an alternative food source for reducing damage to winter wheat in field conditions are discussed. Copyright © 2005 Society of Chemical Industry [source]

A laboratory evaluation of the palatability of legumes to the field slug, Deroceras reticulatum Müller

Andrew S Brooks
Abstract Slugs are major pests of many crops, including winter wheat, in temperate climates, yet current methods of control are often unreliable. The aim of this study is to investigate the potential for common legume species to act as an alternative source of food, or trap crop, for the most damaging agricultural pest species, the grey field slug, Deroceras reticulatum Müller, thereby reducing damage to the wheat crop. A series of three controlled-environment experiments were designed to assess this aim. Individual slugs were fed leaves of one of ten legume species together with winter wheat leaves for a 72-h period. A clear hierarchy of acceptability was shown, with red clover, lucerne, lupin and white clover showing significantly higher Acceptability Indices than the other six species tested. Red clover produced the greatest reduction in mean wheat consumption (78%) from day 1 to day 3. When species were fed individually, red clover was consumed in significantly greater quantities than any of the other treatments: 40% more than white clover and 56% more than wheat. Furthermore, when fed with red clover the amount of wheat consumed was some 50% less than when the latter was fed alone. The results indicate that legumes vary greatly in their acceptability to D reticulatum and it is essential that a legume with a high Acceptability Index is chosen, which results in the least amount of wheat consumed. © 2003 Society of Chemical Industry [source]