Comparative susceptibility of Ostrinia furnacalis, Ostrinia nubilalis and Diatraea saccharalis (Lepidoptera: Crambidae) to Bacillus thuringiensis Cry1 toxins

Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) are highly effective against the European corn borer, Ostrinia nubilalis (Hübner), and the closely related Asian corn borer, Ostrinia furnacalis (Guenée). Since the registration of Bt corn hybrids in the U.S. in 1996, there has been a great deal of information generated on O. nubilalis. However, relatively little information exists for O. furnacalis. To help determine whether the information generated for O. nubilalis can be leveraged for decisions regarding the use of transgenic Bt corn against O. furnacalis, experiments were designed to determine whether the pattern of sensitivity to various Bt Cry1 toxins is similar between the two species. Test insects included laboratory-reared O. furnacalis originating from Malaysia, a Bt-susceptible laboratory colony of O. nubilalis maintained at the University of Nebraska-Lincoln (UNL) and an out-group consisting of the sugarcane borer, Diatraea saccharalis (F.), from Louisiana which represents a different genus from the same family. O. furnacalis and O. nubilalis exhibited a similar pattern of susceptibility to all the Cry1 toxins and were highly susceptible to the range of Bt toxins tested including Cry1Aa, Cry1Ab, Cry1Ac and Cry1F. Both of the Ostrinia species were more tolerant to Cry1Ba compared with D. saccharalis, although sensitivity of O. furnacalis was intermediate and did not differ significantly from that of O. nubilalis and D. saccharalis. D. saccharalis was also susceptible to the range of toxins tested but unlike the two Ostrinia species, was more tolerant to Cry1F and more susceptible to Cry1Ba. These results indicate that both of the Ostrinia corn borer species are similar in sensitivity to the Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba and Cry1F toxins, thus suggesting shared toxin receptors and mechanisms of toxicity for the two species.     

Efficacy of entomopathogenic nematodes (Nematoda: Rhabditida) and insecticide mixtures to control Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) in corn crops

The main insect pest in Brazilian corn is fall armyworm, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae). Entomopathogenic nematodes (EPNs) can be used to control this pest, and can be applied together with various insecticides. Thus, the objective of this work was to evaluate the efficacy of mixtures of EPNs and insecticides to control S. frugiperda in corn crops. In laboratory bioassays three species of EPNs were tested (Heterorhabditis indica, Steinernema carpocapsae and Steinernema glaseri) together with 18 registered insecticides to control S. frugiperda in corn. Efficacy of association between insecticides and EPNs on S. frugiperda larvae was evaluated against the insect's third instar, 2 and 4 days after applications in laboratory. Experiments in the field were performed in two consecutive years, with located application of H. indica and S. carpocapsae (250 IJs/cm²) mixed with chlorpyrifos (0.3 L/ha) and lufenuron (0.15 L/ha) on the corn husk. In laboratory, after two days exposure the interaction between chlorpyrifos and H. indica was synergistic, while interaction with cypermethrin, spinosad, methoxyfenozide and deltamethrin + triazofos was additive, as was interaction between lufenuron, chlorpyrifos and cypermethrin with S. carpocapsae. In contrast, the interaction between chlorpyrifos (Vexter™ and Lorsban™) and lufenuron with S. glaseri was synergistic. In the field, the best treatment was the mixture of H. indica with lufenuron (0.15 L/ha), with 62.5% and 57.5% larval mortality in the two evaluation years in the field, respectively.     

Potential of extracts of the tropical plant Balanites aegyptiaca (L) Del. (Balanitaceae) to control the mealy bug, Maconellicoccus hirsutus (Homoptera: Pseudococcidae)

The effects of extracts of different parts of the perennial tropical plant Balanites aegyptiaca (L) Del., including various solvent extracts of roots, methanol extracts from leaves, fruits, flowers and roots, partially purified saponins obtained from its roots and a standard saponin were studied on the life cycle (adult longevity, number of eggs, crawlers, adults, weight of adults and % wax content) of a laboratory-reared parthenogenic line of the mealy bug, Maconellicoccus hirsutus (Homoptera: Pseudococcidae). Extracts derived from various parts of B. aegyptiaca (leaves, fruits, flowers, and roots in methanol) affected the life cycle of M. hirsutus with a methanol root extract being the most effective at a concentration of 500 μg ml⁻¹. Partially purified saponin of B. aegyptiaca and the commercial bark saponin extract (Sigma) from Quillaja saponaria at a concentration of 500 μg ml⁻¹ were effective in reducing the longevity of M. hirsutus. Significant reductions in oviposition by M. hirsutus were found for all the extracts at a concentration of 500 μg ml⁻¹. Extracts also affected the number of emerging crawlers, number of adults as well as the weight and wax content of emerging adults. These studies suggest that B. aegyptiaca plant extracts and saponins can be useful botanical insecticides for the protection of crops from mealy bugs.     

Characterization of Solanum chomatophilum resistance to 2 aphid potato pests, Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer)

The aphids Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer) (Hemiptera: Aphididae) are responsible for yield reduction in potato (Solanum tuberosum) production by direct phloem feeding and by spreading viruses. Breeding resistant traits from Solanum chomatophilum into the potato germplasm provides alternative means to control aphid infestations. Integrated pest management strategy, using plant resistance, benefits from the characterization of the resistance and of its impact on aphid biology. Our objective was to characterize the resistance of S. chomatophilum by assessing the effects of accessions, plant parts on aphid performance, and by assessing the impact of the resistance factors on different aphid developmental stages and on alate morph production. Detailed aphid performance was obtained by measuring fecundity, survival, percentage of nymphs that reached adult moult, and population growth using whole plant and clip cage experimental designs. Accession and plant physiological age, but not aphid developmental stage, influenced all life-history parameters, except for alate morph production which was not induced on the resistant accessions. Plant part influence was independent of plant species and accession. Both experimental designs resulted in congruent resistance levels at the accession level for each of the two aphid species, supporting the use of any of them in S. chomatophilum resistance screening. PI243340 was resistant to both aphid species, while PI365324 and PI310990 were also resistant to M. euphorbiae and M. persicae, respectively.     

Efficacy of entomopathogenic nematodes (Nemata: Rhabditida) to control Brazilian apple leafroller Bonagota salubricola (Meyrick, 1937) (Lepidoptera: Tortricidae)

The Brazilian apple leafroller, Bonagota salubricola (Meyrick, 1937) (Bonagota cranaodes) (Lepidoptera: Tortricidae), is one of the main pest problems in apple orchards is Brazil. The purpose of this work was to evaluate B. salubricola larval and pupal susceptibility to different species of entomopathogenic nematodes, isolated in Rio Grande do Sul state in Brazil, under laboratory and field (apple orchard) conditions. Bioassays for isolates selection and determination of lethal concentration were performed in tubes of 1.5 ml (eppendorf), each containing one B. salubricola third instar larvae and filter paper. Field experiments were performed in commercial orchard, with application of 100 infecting juveniles (IJs)/cm² for each apple plant previously infected with five B. salubricola larvae covered with plastic trays containing thin cloth. Nematodes H. bacteriophora RS107 and H. bacteriophora RS57 had LC₅₀ of 13 and 4.5 IJs/larvae (4.3 and 1.5 IJs/cm²), respectively. In the field, H. bacteriophora RS107 and H. bacteriophora RS57, applied with sorbitol as an adjuvant, reached 70.2 and 61.1% larval mortality, respectively. The results showed that both isolates had biological activity against B. salubricola under laboratory and field conditions.     

Differential response of pea (Pisum sativum) to Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca

Several broomrape species including Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca are reported to infect various grain and forage legumes in the Mediterranean and West Asia. Pea (Pisum sativum) is severely damaged by O. crenata, but there are no reports on O. foetida or P. aegyptiaca infection. We report here that pea can induce high germination of seeds of O. crenata, O. foetida and P. aegyptiaca but only O. crenata success infecting pea roots and developing further. Some differences in levels of infection by O. crenata were observed among pea accessions what can be exploited in pea resistance breeding programmes. On the contrary, all pea accessions studied were highly resistant to infection by both O. foetida and P. aegyptiaca, preventing any tubercle attachment and development. This makes pea a promising candidate as trap crop for O. foetida and P. aegyptiaca seed bank demise in infested soils.     

Evaluation of augmentative release of Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) for biological control of Parthenium hysterophorus L.

Augmentative release of biocontrol agents has been largely successful for the management of insect pests but it has not been a common approach for weed management. Augmentation methods need to be developed for weed management, especially for pernicious weeds like Parthenium hysterophorus L., commonly known as pathenium or carrot weed. The leaf beetle Zygogramma bicolorata is a potential biocontrol agent of P. hysterophorus. Initial release of biocontrol agents is subject to uncertainties as to whether timely population built-up will take place in sufficient numbers. Several augmentative releases may be required to ensure early establishment of the biocontrol agents, for successful biological control of noxious weeds including pathenium. We made augmentative releases of larvae or adults of Z. bicolorata each to three sites, severely infested with pathenium at Jabalpur, India consecutively for a period of three years. Initially 10 larvae or adults per sq m were released in each plot, followed by a second, third and fourth release of 3, 1.5 and 1.5 larvae or adults per sq m at an intervals of 3, 7 and 14 days after the first augmentation. The pathenium at augmented sites were completely defoliated in 45 and 60 days by larvae and adults respectively. There was also a reduction in the pathenium density and plant height in the augmented sites as compared to the non-augmented sites. Over a period of 3 years augmentation resulted in a noteworthy negative effect on the weed.     

Comparative overwintering host range of three Adelphocoris species (Hemiptera: Miridae) in northern China

In northern China, Adelphocoris suturalis, Adelphocoris lineolatus and Adelphocoris fasciaticollis (Hemiptera: Miridae) are common pests of cotton and several other crops. These species have vastly diverse geographic distribution, seasonal dynamics and abundance, the underlying causal factors of which are poorly understood. In this study, the importance of a broad range of plant species as overwintering hosts for each Adelphocoris sp. was compared. Nymphal emergence from a total of 126 plant species was monitored at two distinct locations. The eggs of A. suturalis successfully eclosed from un-plowed cotton field soil and 115 plant species, primarily pastures, weeds and agricultural crops. The eggs of A. lineolatus successfully eclosed from 40 plant species, mainly pastures and weeds. Finally, A. fasciaticollis overwintered on 35 plant species, primarily tree species, weeds and agricultural crops. In conclusion, the most common and widely distributed mirid species, A. suturalis, overwintered on a comparatively broader range of plants compared to the other two species. These observations help to understand the differences in geographical distribution and abundance of the three Adelphocoris species, and constitute the basis for forecasting and pest management protocols for Adelphocoris spp. in China.     

Insecticidal effects of Ungernia severtzovii bulb extracts against the grain aphid Schizaphis graminum (Rondani)

Insecticidal effect of Ungernia severtzovii bulbs extract has been investigated against the grain aphid Schizaphis graminum. LC₅₀ value of the ethanolic extract of U. severtzovii against the female aphids was 0.235% (2.35 g/l). There was 100% mortality of the subsequent nymphs of the treated females at 0.25-1.0%. The extract was equally active against the nymphs at the highest concentrations. Hexane and ethanolic extracts were the most active against the aphids of all the extracts. Fractionation of the hexane extract by TLC yielded three fractions. Fraction II was the most active (>90% mortality) against the aphids. Xanthoxylin was identified as the major constituent in fraction II of the hexane extract and may be responsible for the insecticidal effect of U. severtzovii.     

Compatibility of entomopathogenic nematodes (Nematoda: Rhabditida) with registered insecticides for Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) under laboratory conditions

The fall armyworm, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) is considered the main key pest of corn crops in Brazil. Entomopathogenic nematodes (EPNs) may be used to control this pest, applied together with other different entomopathogen agents or phytosanity products in the spraying mixture. Thus, the objective of work was to evaluate the compatibility of EPNs with different insecticides used of S. frugiperda control in laboratory conditions. Three species of EPNs (Heterorhabditis indica, Steinernema carpocapsae and Steinernema glaseri) and 18 insecticides registered to control of S. frugiperda in corn crops were tested. Compatibility of the insecticides with EPNs was evaluated by observing mortality and infectivity of infecting juveniles (IJs) 48 h after immersion in solution of the insecticide formulations. Among all insecticides tested, Lorsban™ (chlorpyrifos), Decis™ (deltamethrin), Match™ (lufenuron), Deltaphos™ (deltramethrin + triazophos), Dimilin™ (diflubenzuron), Stallion™ (gamacyhalothrin), Karate Zeon™ (lambdacyhalothrin) Tracer™ (spinosad), Vexter™ (chlorpyrifos), Galgotrin™ (cypermethrin), Certero™ (triflumuron), and Talcord™ (permethrin) were compatible (class 1) with the three nematode species tested under laboratory conditions.     

Manihot flabellifolia Pohl,wild source of resistance to the whitefly Aleurotrachelus socialis Bondar (Hemiptera: Aleyrodidae)

Aleurotrachelus socialis is one of the most important pests of cassava (Manihot esculenta Crantz) in the Neotropics. In Colombia, high whitefly populations can reduce crop yields by 79%; and although the farmers intensify the use of insecticides, this practice is highly contaminating, costly and leads to the development of resistance in the insect. An alternative for managing whitefly populations is to develop genetically resistant varieties. Wild parents of Manihot are a useful source of genes against pests for the cultivated species of cassava. Based on prior research that showed the existence of moderate-to-high levels of resistance to A. socialis in Manihot flabellifolia, a wild species of cassava, this study was proposed to characterize this new source of resistance, evaluating the biology and demographics of A. socialis on eight accessions of M. flabellifolia, a susceptible check (CMC-40) and a resistant (MEcu72) check. The averages of A. socialis longevity and fecundity on the accessions were not significantly different to MEcu72, but different from CMC-40 (P < 0.05). Development time was not significantly different, ranging from 35–40 days on accessions and MEcu72 and 33.5 days on CMC-40 (P < 0.05). In contrast, the population growth rate (r_m) was significantly lower on the M. flabellifolia accessions, with Fla 61 standing out with a growth rate 98 and 99% less than that obtained on MEcu72 and CMC-40, respectively. Once the resistant levels have been identified to A. socialis on the M. flabellifolia accessions, interspecific crosses of M. esculenta subsp. M. flabellifolia and backcross programs could be developed to incorporate the desirable characteristics from the wild relatives into elite progenitors of M. esculenta.     

Actinomycetes mediated biochemical responses in tomato (Solanum lycopersicum) enhances bioprotection against Rhizoctonia solani

Six actinomycetes isolates, namely Streptomyces toxytricini vh6, Streptomyces flavotricini vh8, S. toxytricini vh22, Streptomyces avidinii vh32, Streptomyces tricolor vh85 and vh41, an isolate of an unknown species of Actinomycetales, were tested for their efficacy in protecting tomato (Solanum lycopersicum) against Rhizoctonia solani under green house conditions. Actinomycetes treated plants showed better growth in terms of high chlorophyll content, higher phenylalanine ammonia lyase (PAL) activity and high total phenolic content. Qualitative and quantitative estimation of phenolic compounds from tomato leaves showed significant accumulation of six phenolic acids, gallic (29.02 μg g⁻¹ fresh leaf wt), ferulic (11.44 μg g⁻¹ fresh wt), cinnamic (56.84 μg g⁻¹ fresh wt), gentisic (24.19 μg g⁻¹ fresh wt), chlorogenic acid (1.72 μg g⁻¹ fresh wt) and salicylic (0.39 μg g⁻¹ fresh wt) acid, in actinomycetes treated plants. Biochemical profiling, when correlated with plant mortality in actinomycetes treated and untreated plants, indicated that isolates vh6 and vh8 offered 44.55% and 40.14% disease reductions, respectively compared to the control. These results established that these organisms have the potential to act as biocontrol agents.     

Contributions of visual cues to cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), resistance in novel host genotypes

Herbivorous insects can demonstrate great selectivity among visual cues. The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) (syn. Ceutorhynchus assimilis (Paykull)) is also influenced by visual cues. Here, we present results of a study examining the attractiveness of flowers and foliage of Sinapis alba (a suboptimal host for larval development), Brassica napus (an excellent host for larval development) and novel lines derived from S. alba x B. napus; several of these have been demonstrated to be resistant in field and laboratory tests. Attractiveness, reflectance properties and resistance demonstrated in field trials were related. Responses to host plants differed among plant genotypes and were related to the amounts of UV and yellow reflected from flowers. Moderate UV reflectance greatly increased the attractive effects of yellow. Fewer weevils responded to test plants with greater or lesser floral UV reflectance.     

High level of resistance to Sclerotinia sclerotiorum in introgression lines derived from hybridization between wild crucifers and the crop Brassica species B. napus and B. juncea

Sclerotinia rot caused by the fungus Sclerotinia sclerotiorum is one of the most serious and damaging diseases of oilseed rape and there is keen worldwide interest to identify Brassica genotypes with resistance to this pathogen. Complete resistance against this pathogen has not been reported in the field, with only partial resistance being observed in some Brassica genotypes. Introgression lines were developed following hybridization of three wild crucifers (viz. Erucastrum cardaminoides, Diplotaxis tenuisiliqua and E. abyssinicum) with B. napus or B. juncea. Their resistance responses were characterized by using a stem inoculation test. Seed of 54 lines of B. napus and B. juncea obtained from Australia, India and China through an Australian Centre for International Agricultural Research (ACIAR) collaboration programme were used as susceptible check comparisons. Introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum had much higher levels (P < 0.001) of resistance compared with the ACIAR germplasm. Median values of stem lesion length of introgression lines derived from the wild species were 1.2, 1.7 and 2.0 cm, respectively, as compared with the ACIAR germplasm where the median value for stem lesion length was 8.7 cm. This is the first report of high levels of resistance against S. sclerotiorum in introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum. The novel sources of resistance identified in this study are a highly valuable resource that can be used in oilseed Brassica breeding programmes to enhance resistance in future B. napus and B. juncea cultivars against Sclerotinia stem rot.     

Validation of tuber blight (Phytophthora infestans) prediction model

Potato tuber blight caused by Phytophthora infestans accounts for significant losses of tubers in storage. Despite research on infection and management of tuber blight, there is paucity of information on the prediction of the occurrence tuber blight or modelling of tuber infection by P. infestans under field conditions. A tuber blight prediction model was developed in New York in experiments conducted using cultivars Allegany, NY101, and Katahdin in 1998 and 1999. This model was validated using data collected from the potato cultivar Snowden in field experiments in Laingsburg, Michigan from 2000 to 2009. In both New York and Michigan experiments, disease was initiated by artificial inoculation of cultivars with a US-8 isolate of P. infestans. Mean leaf area affected ranged from 0 to 94% at New York, and 0 to 93% at Michigan. At New York and Michigan, mean tuber blight incidences ranged from 1 to 40% and 0 to 15%, respectively. In the validation of the model using data collected at Laingsburg, Michigan, the model correctly predicted tuber blight incidence in 7 out of 9 years. Comparison of observed with predicted values indicated that slopes of the regression line between observed and predicted germination and infection data were not significantly different (P > 0.3547). Correlation coefficient between observed and predicted values was high (r² > 0.65) and the coefficient of variation of the residuals of error was about 12%. Although inoculum availability is assumed in the model, incorporation of relationships of inoculum density, propagule survival in soil, and tuber blight incidence would greatly improve the prediction of tuber blight under field conditions.     

Impact of intercropping of medicinal and aromatic plants with organic farming approach on resource use efficiency in arecanut (Areca catechu L.) plantation in India

The present investigation was conducted at Vittal, Karnataka, India during 2004-2007 to study the feasibility of intercropping of medicinal and aromatic plants (MAPs) in arecanut plantation. The results revealed that MAPs can be successfully grown as intercrops in arecanut plantation with increased productivity and net income per unit area. Kernel equivalent yield of MAPs varied between 272 kg ha⁻¹ in case of Piper longum to 1218 kg ha⁻¹ in Cymbopogon flexuosus. Pooled data indicated that Asparagus racemosus produced fresh root yield of 10,666 kg ha⁻¹ of arecanut plantation and contributed to maximum kernel equivalent yield of 1524 kg ha⁻¹ among all medicinal and aromatic plants. Intercropping of MAPs in arecanut was found economical. The net return per rupee investment was highest in C. flexuosus (4.25) followed by Bacopa monnieri (3.64), Ocimum basilicum (3.46) and Artemisia pallens (3.12). The total system productivity of arecanut + MAPs intercropping system varied from 2990 to 4144 kg ha⁻¹. Arecanut + O. basilicum intercropping system registered significantly higher production efficiency 8.2 kg ha⁻¹ day⁻¹ than other systems. Intercropping of MAPs had more positive effect on soil pH in arecanut based cropping system. The soil pH was 5.6 in 2004 and it was 0.3-0.9 units higher in 2007. Soil organic carbon (SOC) content varied significantly due to intercropping of MAPs at the end of experiment. The SOC content increased in Aloe vera, A. pallens, P. longum and B. monnieri, while it depleted in grasses and rhizomatic MAPs. Based on demand and marketing opportunities for MAPs, farmers are advised to grow aromatic plants in large areas on a community basis to meet huge industrial demand and variety of medicinal crops in small areas to meet the requirement of traditional systems of medicine.     

A comparison of monitoring systems used for Ceratitis species (Diptera: Tephritidae) in South Africa

For 16 years a bucket-type trap known as the Sensus fruit fly trap has been used to monitor three fruit fly pest species Ceratitis capitata, Ceratitis rosa and Ceratitis cosyra in South African fruit industries. The relative efficiencies of lures sold for monitoring fruit flies with the Sensus trap in South Africa were determined in field experiments where laboratory-reared C. capitata, C. rosa and C. cosyra were released in a mango orchard within a few metres of Sensus traps containing either Capilure (trimedlure or tert-butyl 4 (or 5) -chloro-2-methylcyclohexane carboxylate), Ceratitislure (protein hydrolysate plus β-caryophyllene) or Questlure (protein hydrolysate plus plant extracts). When using 12-day-old flies, Capilure caught 3 times more C. capitata males than C. rosa males and this difference was more extreme when 3-day-old flies were released. Ceratitislure caught significantly more 12-day-old C. cosyra males than 12-day-old C. capitata males, but the difference was reversed when 3-day-old flies were compared. Questlure showed the least differences between species and age but recovered the lowest proportion of released species. Further comparisons were conducted in an orchard with wild flies using other known attractants in larger yellow Probodelt bucket traps. Capilure caught more male C. capitata than BioLure Fruit Fly 3-component, but BioLure 2-component (trimethylamine and ammonium acetate) was more effective than Questlure for C. capitata females. The 3-component lure was also more effective than both Capilure and Questlure for male and female C. rosa, respectively. Ceratitislure was the most effective lure for male C. cosyra flies and BioLure 3-component was more effective than Ceratitislure and Questlure for female C. cosyra flies. The intervention threshold of 4 flies/trap/week previously used in citrus with Capilure for C. rosa was lowered to 2 C. rosa/trap/week when using the Sensus trap due to the lower sensitivity of this trap-lure combination found for C. rosa in this study. The 3-component lure, or the 2-component combination of trimethylamine and ammonium acetate in a ratio of 1:8 in the Sensus trap capsule, would be more effective for both sexes of all three Ceratitis species than the Questlure that is currently being used.     

Hybanthus parviflorus (Violaceae): Insecticidal activity of a South American plant

Hybanthus parviflorus is a perennial shrub, widely distributed in the tropical and subtropical regions of America, and is known as ‘violetilla’ in Argentina. Previous phytochemical studies of this species led us to the isolation and determination of the primary structure of a novel macrocyclic polypeptide, the cyclotide hypa A. Here the insecticidal activities of extracts of H. parviflorus were determined against Ceratitis capitata Wied., the Mediterranean fruit fly or ‘Medfly’. Mortality in the different life stages of Medfly, total mortality and modifications of the insect’s physiology caused by 50% EtOH and CH₂Cl₂ extracts of H. parviflorus were evaluated. In addition, we determined the occurrence of ursolic acid, β-sitosterol and the polyphenols quercetin, quercetin-3-methyl ether, apigenin, luteolin, kaempferol, rutin, caffeic acid and chlorogenic acid. The promising insecticidal activity of 50% EtOH extracts of H. parviflorus and its purified fractions was related to the presence of cyclotides. The insecticidal activity of CH₂Cl₂ extracts could be related to the presence of polyphenols, ursolic acid and β-sitosterol.     

Toxicity, inheritance of fenpyroximate resistance, and detoxification-enzyme levels in a laboratory-selected fenpyroximate-resistant strain of Tetranychus urticae Koch (Acari: Tetranychidae)

A strain (BEYO 2) of Tetranychus urticae was selected with fenpyroximate for 14 selections. The resulting strain (named FPY 14) became resistant to fenpyroximate. The present study examines the inheritance of fenpyroximate resistance, the toxicity of some insecticides and acaricides, detoxification enzymes [esterase, glutathione S-transferase (GST), and monooxygenase (P450)], and the synergistic ratios of certain synergists [piperonyl butoxide (PBO), S-benzyl-O,O-diisopropyl phosphorothioate (IBP), and triphenyl phosphate (TPP)] in the FPY 14 strain of T. urticae. A spray tower-Petri dish method was used in the selection and toxicity studies. The level of fenpyroximate resistance was 64.43-fold higher in the FPY 14 strain and 1.06-fold higher in the BEYO 2 strain compared to the GSS (German susceptible strain) strain. The FPY 14 strain was 7.80-, 6.90-, 6.43-, 4.78- and 2.78-fold more resistant to abamectin, chlorpyrifos, propargite, clofentezine and amitraz, respectively. Fenpyroximate resistance is inherited as an incompletely dominant trait with no sex linkage. None of the synergists showed a significant synergistic effect. In the FPY 14 strain, the activities of esterase, GST and P450 enzymes were 1.92-, 1.06- and 3.96-fold higher, respectively, when compared to the susceptible GSS strain. The P450 and esterase enzymes might play a role in the mechanism of resistance to fenpyroximate.     

Overwintering hosts of Apolygus lucorum (Hemiptera: Miridae) in northern China

During the past decade, Apolygus lucorum Meyer-Dür (Heteroptera: Miridae) has become a key pest of cotton in northern China, due to widespread planting of Bt cotton and an associated drop in the use of broad-spectrum insecticides. Because of a lack of management alternatives, A. lucorum outbreaks are presently exclusively controlled with insecticides. In this study, we determined A. lucorum overwintering locations and host plants during the 2006–2009 winter seasons. A total of 126 plant species were screened and nymphal emergence of A. lucorum was monitored over time. Eggs of A. lucorum successfully overwintered in cotton field soils and on 86 plant species, including weeds, fruit trees, pastures and agricultural crops. More specifically, Vitis vinifera L., Ricinus communis L., Momordica charantia L., Artemisia argyi Levl. et Vant., Artemisia annua L., Artemisia lavandulaefolia DC., Isatis indigotica Fort., Artemisia scoparia Waldst. et Kit., Vigna radiate (L.) Wilczek, Ziziphus jujuba Mill., Vigna angularis (Willd.) Ohwi et, Ocimum basilicum L., Onobrychi viciifolia Scop., Pyrus bretschneideri Rehd., Malus domestica Borkh. and Brassica juncea (L.) Czern. et Coss proved optimal overwintering hosts of A. lucorum. Based upon plant species occurrence and distribution in Chinese cotton-growing regions, several weeds and fruit trees, such as V. vinifera, Z. jujuba, P. bretschneideri and M. domestica can be termed key overwintering hosts of A. lucorum. Our findings can form the basis for future formulation of targeted management actions to lower A. lucorum overwintering populations in cotton-growing landscapes of northern China.