Major Crop Pests Research Articles

Sugar Diet Affects Odor Reception but Variation in Sugar Concentration Plays Minimal Role in the Response of the Parasitoid, Microplitis croceipes (Hymenoptera: Braconidae), to Host-Related Plant Volatiles.

Parasitoids utilize various sugar resources in nature, and rely on odor cues from plants to locate their food and hosts. However, lack of sugar in the diet may negatively impact odor reception in parasitoids, thus affecting foraging efficiency. We used Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), a larval endoparasitoid of Heliothis virescens (F.) (Lepidoptera: Noctuidae), as a model species to test the hypothesis that variation in sugar diet of parasitoids affects their olfactory response to host-related odors. Heliothis virescens is a major pest of cotton and other important crops. Response of female M. croceipes fed different diet treatments (i.e., 40%, 20%, 10%, or 0% sucrose/water solution [w/v]) to select cotton volatiles were tested in electroantennogram (EAG) and Y-tube olfactometer bioassays. The following cotton plant odors were tested: cis-3-hexenol, α-pinene, 50/50 v/v binary mixture of cis-3-hexenol and α-pinene, and H. virescens-infested cotton. Sucrose-fed parasitoids showed higher EAG response to the binary mixture and host-infested plant volatile extract, compared with sucrose-starved (0% sucrose) parasitoids. However, there was no significant difference in EAG response of parasitoids to odor treatments among individuals fed 40%, 20%, or 10% sucrose. In a Y-tube olfactometer, female M. croceipes fed 40% sucrose were significantly more attracted to host-infested cotton than to a control (no plant). However, parasitoids were not significantly attracted to other odor stimuli. These results suggest that the availability of sugar diet affects odor reception in M. croceipes but variation in sugar concentration probably plays a minimal role in olfactory response of M. croceipes to host-related odors.

Evolution of imidacloprid resistance in Myzus persicae in Greece and susceptibility data for spirotetramat.

Myzus persicae s.l. is a major crop pest globally and has evolved resistance to a range of insecticide classes making it increasingly difficult to control in some areas. Here we compare bioassay monitoring data for two important compounds, imidacloprid and spirotetramat, on field samples/clones collected in Greece. A total of 122 aphid samples/clones from central and northern Greece were examined in dose-response bioassays with imidacloprid. There was an overall increase in the level of resistance (resistance factor = 15-40) within tobacco-collected samples from 78.7% in 2007 to 86.7% in 2015. The corresponding frequencies for peach samples were 13.3% and 6.7%. These results were confounded however by the first identification of the R81T target mutation in Greece during 2015 (4.3% as heterozygotes in peach) and 2016 (21.3% as heterozygotes in peach). No resistance to spirotetramat was found at the 60 clones collected in 2015. Resistance to imidacloprid is continuing to increase within Greek M. persicae s.l. populations and the situation is likely to deteriorate further with the recent identification of the R81T resistance mutation. Resistance to spirotetramat has not been found and is therefore a good alternative to neonicotinoids for resistance management. © 2017 Society of Chemical Industry.

Morphological and molecular characterizations of cereal cyst nematode Heterodera avenae Wollenweber, 1924 from the Czech Republic

The cereal cyst nematode, Heterodera avenae Wollenweber, 1924, is a major pest of cereal crops throughout the world and causes serious yield losses, especially of wheat. Previous studies have shown that this species is widely distributed in the Czech Republic. In this study, seven populations of H. avenae were molecularly studied, and one population was morphologically described. Three regions (18S, 28S, and internal transcribed spacer 1) of ribosomal DNA were sequenced and the analysis of the 18S gene of six populations did not reveal any variation, whereas the internal transcribed spacer 1 and 28S sequences of six populations differed by only two nucleotides from a population in Žilina. Precise and quick identification of cereal cyst nematodes is important for effective control measures and ribosomal sequence analyses of seven populations in this study will be useful in future phylogenetic studies of Heterodera spp. occurring in the Czech Republic.

UPDATED CHECKLIST OF HOST PLANTS OF CALAPHIDINAE (APHIDIDAE : HEMIPTERA) IN INDIA

Background: The aphids (Aphididae: Hemiptera) are plant sap sucking insects and are major pests of crops, vegetables and fruit trees. Earlier food plant catalogue of Indian aphids dates back almost four decades. The researches on aphid taxonomy as well as their host plants is continued with the description of new taxa, the modified status of others, and the publication of other nomenclatural decisions. The family Aphididae consists of 24 subfamilies and their (subfamilywise) food plant catalogue is being initiated by us. It is the 6th in series of cataloguing the aphids belonging to subfamily Calaphidinae. The work will help to solve some needs pertaining to studies on Indian aphids, such as synonymic handling and their food plant checklist, as well as the lack of a complete and up-todate listing of the species.Materials & Methods: In preparing of this checklist, recent world literatures (published up to January, 2017) were scrutinized for synonymy of the species of aphids as well as their host plants along with the information available at websites: http://Aphid.SpeciesFile.org (version 5.0/5.0) for aphids, and http://www.ars-grin.gov and http://www.theplantlist.org (version 1.1) for plants accessed on January, 2017.   Results: The aphids are a group of over 5000 species of plant sap sucking insects distributed throughout the world, from the rainforest to the desert ground. Currently, the family Aphididae comprises 24 subfamilies, out of which the food plant catalogue of Indian  aphids belonging to subfamily Calaphidinae is provided in this compilation.Calaphidinae consists of 2 tribes: Calaphini and Panaphidini and each tribe consists of 2 subtribes: Calaphidina and Monophidina (Calaphidini), and Myzocallidina and Panaphidina (Panaphidini). In India, Calaphidina is represented by 5 genera and 14 species, while no species of Monaphidina was reported so far. Myzocallidina is represented by only 4 genera and 9 species, while Panaphidina is more diversed containing 16 genera and 25 species. All these 48 species feed on 62 plant species belonging mainly to Betulaceae, Fagaceae, Rosaceae, Juglandaceae, Fabaceae, Poaceae, and Ulmaceae.Conclusion: All members of Calaphidinae are monoecious, oligophagous and mostly associated with trees of Betulaceae (17 aphid species), Fagaceae (13 aphid species), Ulmaceae (2 aphid species), Anacardiaceae (4 aphid species), and Juglandaceae (6 aphid species) and herbaceous plants like Fabaceae (6 aphid species), Poaceae (8 aphid species) and Rosaceae (11 aphid species). Monoecious habit is considered a primitive character in this group and host plant alternation has apparently never or less evolved. The group is distributed mostly from east to west Himalayas. Keywords: Aphids, Callaphidinae, Panaphidini, Myzocallidina, food plant catalogue, checklist.Â

Effect of the Insecticide Dinotefuran on the Ultrastructure of the Flight Muscle of Female Sogatella furcifera (Hemiptera: Delphacidae).

Sogatella furcifera Horváth (Hemiptera: Delphacidae), is a major migratory pest of rice crops in Asia. The ultrastructure of the flight muscle directly affects the flight ability of insects. The ultrastructure of the flight muscle of some insects can be affected by insecticides. However, the ultrastructure of the flight muscle of S. furcifera and the effect of insecticides on the flight muscle of S. furcifera are not well understood. The present study was conducted to determine the effect of the insecticide dinotefuran on the ultrastructure of the flight muscle of S. furcifera females. In this study, the cross-sectional area and the diameter of the myofibril cross-sections of dinotefuran-treated S. furcifera females increased with the number of days after emergence (DAE), and they were higher than in untreated females. The sarcomere length of myofibrils increased with the number of DAE, and it differed from that of the untreated females. On the first day after emergence, the higher the concentration of dinotefuran, the smaller was the extent of decrease. On the third day after emergence, the higher the concentration of dinotefuran, the larger was the extent of enhancement. For the percentage of mitochondria, those of LC10 and LC20 dinotefuran-treated S. furcifera females increased with the number of DAE and were higher than in untreated females. LC10 dinotefuran-treated S. furcifera females exhibited the largest increase. Thus, our results suggest that the flight ability of S. furcifera increased with time. Some concentrations of dinotefuran can enhance the flight capacity of S. furcifera.

Characterization and expression profiling of serine protease inhibitors in the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

BackgroundSerine protease inhibitors (SPIs) have been found in all living organisms and play significant roles in digestion, development and innate immunity. In this study, we present a genome-wide identification and expression profiling of SPI genes in the diamondback moth, Plutella xylostella (L.), a major pest of cruciferous crops with global distribution and broad resistance to different types of insecticides.ResultsA total of 61 potential SPI genes were identified in the P. xylostella genome, and these SPIs were classified into serpins, canonical inhibitors, and alpha-2-macroglobulins based on their modes of action. Sequence alignments showed that amino acid residues in the hinge region of known inhibitory serpins from other insect species were conserved in most P. xylostella serpins, suggesting that these P. xylostella serpins may be functionally active. Phylogenetic analysis confirmed that P. xylostella inhibitory serpins were clustered with known inhibitory serpins from six other insect species. More interestingly, nine serpins were highly similar to the orthologues in Manduca sexta which have been demonstrated to participate in regulating the prophenoloxidase activation cascade, an important innate immune response in insects. Of the 61 P.xylostella SPI genes, 33 were canonical SPIs containing seven types of inhibitor domains, including Kunitz, Kazal, TIL, amfpi, Antistasin, WAP and Pacifastin. Moreover, some SPIs contained additional non-inhibitor domains, including spondin_N, reeler, and other modules, which may be involved in protein-protein interactions. Gene expression profiling showed gene-differential, stage- and sex-specific expression patterns of SPIs, suggesting that SPIs may be involved in multiple physiological processes in P. xylostella.ConclusionsThis is the most comprehensive investigation so far on SPI genes in P. xylostella. The characterized features and expression patterns of P. xylostella SPIs indicate that the SPI family genes may be involved in innate immunity of this species. Our findings provide valuable information for uncovering further biological roles of SPI genes in P. xylostella.

How anthropogenic changes may affect soil-borne parasite diversity? Plant-parasitic nematode communities associated with olive trees in Morocco as a case study

BackgroundPlant-parasitic nematodes (PPN) are major crop pests. On olive (Olea europaea), they significantly contribute to economic losses in the top-ten olive producing countries in the world especially in nurseries and under cropping intensification. The diversity and the structure of PPN communities respond to environmental and anthropogenic forces. The olive tree is a good host plant model to understand the impact of such forces on PPN diversity since it grows according to different modalities (wild, feral and cultivated olives). A wide soil survey was conducted in several olive-growing regions in Morocco. The taxonomical and the functional diversity as well as the structures of PPN communities were described and then compared between non-cultivated (wild and feral forms) and cultivated (traditional and high-density olive cultivation) olives.ResultsA high diversity of PPN with the detection of 117 species and 47 genera was revealed. Some taxa were recorded for the first time on olive trees worldwide and new species were also identified. Anthropogenic factors (wild vs cultivated conditions) strongly impacted the PPN diversity and the functional composition of communities because the species richness, the local diversity and the evenness of communities significantly decreased and the abundance of nematodes significantly increased in high-density conditions. Furthermore, these conditions exhibited many more obligate and colonizer PPN and less persister PPN compared to non-cultivated conditions. Taxonomical structures of communities were also impacted: genera such as Xiphinema spp. and Heterodera spp. were dominant in wild olive, whereas harmful taxa such as Meloidogyne spp. were especially enhanced in high-density orchards.ConclusionsOlive anthropogenic practices reduce the PPN diversity in communities and lead to changes of the community structures with the development of some damaging nematodes. The study underlined the PPN diversity as a relevant indicator to assess community pathogenicity. That could be taken into account in order to design control strategies based on community rearrangements and interactions between species instead of reducing the most pathogenic species.

Evaluating potential trap crops for managing leaffooted (Hemiptera: Coreidae) and phytophagous stink bug (Hemiptera: Pentatomidae) species in peaches

The leaffooted bug (Leptoglossus spp.) and phytophagous stink bug species (Euschistus spp., Nezara viridula, Chinavia hilare) are the major hemipteran pests of fruit, vegetable, and grain crops in Alabama and other parts of the southeastern U.S.A. The present study evaluated six winter host crops (hairy vetch, oats, rye, triticale, wheat and winter peas) and six summer host crops (buckwheat, brown top millet, grain sorghum, southern pea, pearl millet and sunflower) as potential trap crops for leaffooted and stink bugs in peaches from 2011 to 2013 in Alabama. Experimental plots were arranged around a mature peach orchard in a randomized complete block design, and insect densities, as well as host plant phenology, were recorded at weekly intervals from March to May and July to August each year. Wheat and oats attracted a significantly higher number of target insects than any other treatments evaluated in the winter trials. Sunflower, pearl millet and sorghum recorded a significantly higher number of insects than any other host crops evaluated in the summer. When the insects sampled were totalled across the season, leaffooted bugs (Leptoglossus phyllopus) dominated the pest complex (>70%), followed by brown stink bugs (mainly Euchistus servus Dallas). Target insects colonized the hosts mainly during the reproductive phase (including flowering and seed development) until plant senescence. The results obtained in the present study suggests that a combination of wheat and oats may be used to detect the early presence of leaffooted and stink bugs in the spring, whereas sunflower, pearl millet and sorghum could be utilized during summer to detect and attract colonizing populations away from peach orchards.

Variability of Minisatellite Loci and mtDNA in Individuals with and without B Chromosomes from Populations of the Grasshopper Dichroplus elongatus

Dichroplus elongatus is an extensively distributed South American grasshopper considered a pest of major crops. Argentinean populations show a widespread B-chromosome polymorphism which could be maintained as the result trade-offs among opposite selective effects and interactions with their mitotic instability. The main objective of this study was to evaluate the relationships between B chromosomes and mtDNA sequences coupled with minisatellites loci, and verify the genotype/karyotype covariation in 12 populations located at both sides of Parana River (Eastern and Western Regions). B carrier individuals showed significantly higher genetic diversity (HE and X) respect to standard individuals. AMOVAs based on nuclear loci and mtDNA sequence datasets showed statistically significant levels of differentiation among karyotypes in the Eastern Region. Cluster analysis through Bayesian procedure considering nuclear loci splits B carriers and standard individuals into different genetic clusters in some Eastern populations. The Bayesian phylogenetic analysis showed two divergent mtDNA clades. Haplogroup 1 is composed exclusively of standard individuals, however all B chromosome carriers are included in haplogroup 2. There is an association between some haplotypes and B chromosomes and a strong effect of phylogenetic signal on B chromosome population structure. Genetic differentiation between karyotypes at Eastern Region revealed by AMOVA, Bayesian approaches and clustering analysis based on uniparental and biparental inherited markers may be due to the inherent nature of the B chromosome, to karyotype biased dispersal or to difference tolerance of B chromosomes on different genetic background. The combination of molecular and chromosome analysis performed in this study indicated that B chromosomes in D. elongatus is an important factor in explaining the genetic population structure at minisatellite and mitochondrial DNA levels.

Insecticide resistance in diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Punjab

The diamond back moth (DBM) Plutella xylostella (Linnaeus), a major destructive pests of brassica crops, is recurrently infesting vegetables in Punjab. It has led the farmers to frequently spray their crops with insecticides, but control failures occur with many insecticides. Hence this study with the objective to check whether resistance to insecticides could explain these failures. Populations of DBM from different locations viz., Amritsar, Ludhiana and Kapurthala were collected and toxicity of five insecticides viz., emamectin benzoate, spinosad, indoxacarb, chlorantraniliprole and cartap hydrochloride and a Bt formulation was evaluated. It was compared with its susceptible population, maintained for over 30 generations under laboratory conditions, using the standard leaf-disc dip technique. The susceptible population showed the maximum sensitivity to emamectin benzoate with lowest LC50 of 0.00003%, while it was minimum with cartap hydrochloride (0.00145%). Chlorantraniliprole was the most toxic against the field populations (LC50 was 0.00012- 0.00027%) followed by emamectin benzoate (0.00154–0.00336%), while cartap hydrochloride was the least effective. DBM population from Amritsar showed maximum resistance to all insecticides except indoxacarb, while the Ludhiana one was showing maximum resistance to all. Field populations exhibited maximum resistance to emamectin benzoate (51.3–112x) followed by cartap hydrochloride (26.33–52.84x), and minimum against chlorantraniliprole (2.4 to 5.4x). The results indicate that control failures were associated with resistance to some of the evaluated insecticides, reinforcing the need for resistance management strategies in vegetable growing areas of Punjab

Effect of 200 Gy as Gamma Sterilising Radiation on Reproductive Performance and Life Span of Male Moths, Spodoptera litura (Fabr.)

The lepidopteran Spodoptera litura is an insect pest of scientific and economic importance. This insect pest is polyphagous pest of major crops like tobacco, cotton, rice and tomato. The characteristics like high reproductive capacity and ability to migrate over large distance in adult stage have resulted in it becoming a pest of many agricultural crops throughout its geographical range. In order to control this pest we need to suppress its reproductive potential. The present study reports the results from a laboratory experiment in which behavioural components of reproductive performance and life span of male moths (treated with 200 Gy of gamma radiation) were observed. When treated with 200 Gy of gamma radiation the mating percentage and copulation period observed were significantly different among treated and control group with p? 0.05. Survival period analysis also showed a statistically significant difference among treated and control group with p? 0.0001. Present results showed a significant variation in reproductive performance among radiation treated and control group suggesting the effect of 200 Gy as sterilising dose of gamma radiation on mating behaviour in male moths. Survival period analysis further supports significant effects of sterilising dose of gamma radiation on longevity of male moths.

Molecular Cloning, Characterization, and Functional Analysis of Catalase inFrankliniella occidentalis(Thysanoptera: Thripidae)

Catalase is an important antioxidant enzyme that protects aerobic organisms from oxidative damage by degrading hydrogen peroxide to oxygen and water. In order to indicate the role of catalase in the thermotolerance of the western flower thrips, Frankliniella occidentalis (Pergande), a major pest of agricultural and horticultural crops, we cloned the cDNA encoding catalase from F. occidentalis in this study. Sequence analyses indicated that the catalase gene from F. occidentalis (FoCAT) encoded a protein containing 506 amino acids, including three catalytic amino acid residues (His-73, Asn-146, and Tyr-356), the proximal heme-ligand signature sequence, 62FDRERIQERVVHAKGAG78, and the proximal active site, 352RIFSYADTH360. Phylogenetic analysis indicated that CAT from different insect species could be grouped into a well-supported cluster that included Diptera, Lepidoptera, and Hemiptera. qRT-PCR analyses initially indicated that FoCAT expression was significantly up-regulated under heat and cold stress. When F. occidentalis nymphs were incubated at 37 or − 6 °C, FoCAT expression showed a significant increase at 2 h for both temperatures and then declined when the temperature duration was 4 or 8 h. The enzymatic activity of FoCAT was significantly elevated at moderate heat stress (33 °C), but showed a significant decrease at − 6 °C. When F. occidentalis nymphs were incubated at 37 or − 6 °C, FoCAT activity showed a gradual decline for both temperatures and was lowest at the 8-h exposure time. In conclusion, FoCAT plays an important role in the thermotolerance of F. occidentalis, which may partially explain the widespread distribution of this important pest.

Eco-biology and conservation of potential insectivorous birds in the arable biomes of central Punjab

The present study was conducted to investigate the eco-biology of insect predator avian species and the effects of environmental factors on the eco-biology and bird populations in Punjab, Pakistan. Data on ecology and other aspects of bank myna was collected from three districts of Central Punjab including Faisalabad (an industrial area with large effects of heavy metals by usage of sewage water of industries in irrigation & pesticides), Sargodha (with medium level of industries & pesticides use) and Mandi Bahauddin (no industry and low use of pesticide). Specimens were collected to observe gut contents. Gut contents were analyzed to account for the prey and feeding niche. Major insect pests of crops were identified and listed from gut contents. Relative population density of useful birds was assessed and continuously monitored for population trends around the year. Breeding ecology of both predacious birds was studied to evaluate breeding success, mortality rate and to weigh up the effects of pesticides used and pollution. Breeding ecology, population dynamics and gut contents analysis were significantly (P ≤ 0.001; R2 ≥ 0.75) influenced by the use of pesticides. It was concluded that use of pesticides without studying their toxic effects is detrimental to these predacious birds. Blind sprays should be prohibited and alternatives should be adopted to conserve the predacious birds in order to achieve effective biological control. Keywords: Predacious birds; Eco-biology; Population dynamics http://dx.doi.org/10.19045/bspab.2016.50150

In vitro interaction of Metarhizium anisopliae Ma9236 and Beauveria bassiana Bb9205 with Heterorhabditis bacteriophora HNI0100 for the control of Plutella xylostella.

The diamondback moth (Plutella xylostella) is a major pest of broccoli crops in Colombia. To control P. xylostella, we evaluated the interaction of Beauveria bassiana Bb9205 and Metarhizium anisopliae Ma9236 with Heterorhabditis bacteriophora HNI0100 and its bacterial symbiont Photorhabdus luminescens HNI0100. We used antagonism and disk diffusion assays with fungal extracts to test the interaction between symbiotic bacterium and fungi. P. luminescens inhibited the growth of B. bassiana and M. anisopliae up to 40% by the secretion of secondary metabolites, whereas fungal extracts did not inhibit P. luminescens; this explains the in vivo interactions of these biological control agents. To test the interaction between fungi and nematodes, we first inoculated the fungi followed by the nematodes on different days (0, 2, 4, and 6). We identified the type of interaction using the formula by Nishimatsu and Jackson (J Econ Entomol 91:410–418, 1998) and established that on days 0, 2 and 4 there was an antagonistic interaction, while a synergistic interaction occurred on day 6. Therefore, the use of the interaction between H. bacteriophora HNI0100 with M. anisopliae Ma9236 and B. bassiana Bb9205 is an innovative alternative for the control of P. xylostella.

Review of the genus Genaemirum Heinrich (Hymenoptera, Ichneumonidae, Ichneumoninae) with interactive identification keys to species.

We describe Genaemirum phagocossorum Rousse, Broad & van Noort, sp. n., a new ichneumonine parasitoid wasp reared from Eucalyptus nitens logs infested by the cossid moth Coryphodema tristis, which is considered a major pest of forestry and food crops in South Africa. This is the first plausible host association for the genus, and fits with the host association predictions of Heinrich. Two further undescribed species were found in the collections of the Natural History Museum in London and are described as Genaemirum phacochoerus Broad, Rousse & van Noort, sp. n. and Genaemirum fumosum Broad, Rousse & van Noort, sp. n. An identification key to the eight known species and a diagnosis for each species are provided, including photographs of all the primary type specimens. Online Lucid interactive identification keys are available at: http://www.waspweb.org.

Experimentally evolved populations of the potato cyst nematode Globodera pallida allow the targeting of genomic footprints of selection due to host adaptation

In the current agronomical context of pesticide use reduction, deciphering the genetic bases of pathogen adaptation to plant defences is of major importance to improve durability of resistance. Indeed, knowledge of virulence gene frequencies in pathogen populations could allow the prediction of resistance durability before deployment. Globodera pallida is a major pest of potato crops for which a promising resistance QTL, GpaVvrn, has been identified in Solanum vernei. An experimental evolution study, in which G. pallida lineages evolved on resistant or susceptible potato genotypes for up to eight generations, previously showed that G. pallida was able to rapidly overcome GpaVvrn resistance. However, it was not known if enough genetic mixing occurred in these lineages to be able to detect islands of differentiation in a genome scan approach. Here, this question was investigated using 53 polymorphic microsatellite markers distributed along the genome and three different tests based on genetic differentiation and heterozygosity. Eight outlier loci were identified, indicative of genomic regions putatively involved in host adaptation. Several loci were identified by multiple detection methods and/or in two independent adapted lineages. Some candidate genomic regions identified also seemed to be involved in overcoming resistance to nematodes in a plant genotype harbouring the same resistance QTL in a different genetic background. These results validate the feasibility of a genome scan approach on biological material coming from short experimental evolution, and encourage the use of a high coverage genome scan by whole genome resequencing.

Broad-scale suppression of cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae), associated with Bt cotton crops in Northern New South Wales, Australia.

The cotton bollworm, Helicoverpa armigera, is a major pest of many agricultural crops in several countries, including Australia. Transgenic cotton, expressing a single Bt toxin, was first used in the 1990s to control H. armigera and other lepidopteran pests. Landscape scale or greater pest suppression has been reported in some countries using this technology. However, a long-term, broad-scale pheromone trapping program for H. armigera in a mixed cropping region in eastern Australia caught more moths during the deployment of single Bt toxin cotton (Ingard®) (1996-2004) than in previous years. This response can be attributed, at least in part, to (1) a precautionary cap (30% of total cotton grown, by area) being applied to Ingard® to restrict the development of Bt resistance in the pest, and (2) during the Ingard® era, cotton production greatly increased (as did that of another host plant, sorghum) and H. armigera (in particular the 3rd and older generations) responded in concert with this increase in host plant availability. However, with the replacement of Ingard® with Bollgard II® cotton (containing two different Bt toxins) in 2005, and recovery of the cotton industry from prevailing drought, H. armigera failed to track increased host-plant supply and moth numbers decreased. Greater toxicity of the two gene product, introduction of no cap on Bt cotton proportion, and an increase in natural enemy abundance are suggested as the most likely mechanisms responsible for the suppression observed.

Forecast of phytosanitary condition of grain crops

The influence of climate change on expanding the species distribution area of pests, and their harmfulness. Analyzes phytosanitary situation in recent years and developed a prediction on major pests of grain crops: еurygaster integriceps Put., zabrus tenebrioides Gz., and cereal beetles (Anisoplia).

Synergistic and compensatory effects of two point mutations conferring target-site resistance to fipronil in the insect GABA receptor RDL.

Insecticide resistance can arise from a variety of mechanisms, including changes to the target site, but is often associated with substantial fitness costs to insects. Here we describe two resistance-associated target-site mutations that have synergistic and compensatory effects that combine to produce high and persistent levels of resistance to fipronil, an insecticide targeting on γ-aminobytyric acid (GABA) receptors. In Nilaparvata lugens, a major pest of rice crops in many parts of Asia, we have identified a single point mutation (A302S) in the GABA receptor RDL that has been identified previously in other species and which confers low levels of resistance to fipronil (23-fold) in N. lugans. In addition, we have identified a second resistance-associated RDL mutation (R300Q) that, in combination with A302S, is associated with much higher levels of resistance (237-fold). The R300Q mutation has not been detected in the absence of A302S in either laboratory-selected or field populations, presumably due to the high fitness cost associated with this mutation. Significantly, it appears that the A302S mutation is able to compensate for deleterious effects of R300Q mutation on fitness cost. These findings identify a novel resistance mechanism and may have important implications for the spread of insecticide resistance.

Pesticide resistance in Plutella xylostella (Lepidoptera: Plutellidae) populations from Togo and Benin

AbstractThe diamondback moth,Plutella xylostella(L.) is the major insect pest of cabbage crops in Togo and Benin. For control, farmers very often resort to spraying chemical insecticides at high dosages with frequent applications. Bioassays were carried out on three populations ofP. xylostella, two from Togo (Kara and Dapaong) and one from Benin (Cotonou), to assess their level of susceptibility to currently used insecticides. A reference strain ofP. xylostellafrom Matuu in Kenya was used as a control. In the laboratory, three insecticide representatives of different chemical families (deltamethrin, chlorpyrifos ethyl and spinosad) were assayed against third instar larvae ofP. xylostella. Results revealed thatP. xylostellapopulations from Dapaong, Kara and Cotonou were more resistant to deltamethrin (13 to 59-fold at LC50level, 149 to 1772-fold at LC90level) and chlorpyrifos ethyl (5 to 15-fold at LC50level, 9 to 885-fold at LC90level) than the reference strain. Spinosad was more toxic toP. xylostellapopulations than the other insecticides with LC50and LC90values less than 1 µg/ml and 15 µg/ml, respectively. However, the population from Cotonou appeared significantly more resistant to spinosad compared to the reference strain. These results are discussed in the light of developing an integrated pest management strategy for reducing the selection pressure of spinosad.