Genetic improvement of the desiccation tolerance and host-seeking ability of the entomopathogenic nematode <Emphasis Type="Italic">Steinernema feltiae</Emphasis>

Entomopathogenic nematodes (EPNs) from the genus Steinernema (Steinernematidae) are used for biological control of insect pests. The infective stages of these nematodes are intolerant of extreme environmental conditions. Genetic improvement has been suggested as an approach for improving their ability to overcome these limitations. In this study, we bred a heterogeneous population of the EPN Steinernema feltiae Filipjev for desiccation tolerance (both rapid and slow) and enhanced host-seeking ability. We selected for tolerance of rapid desiccation by exposing infective juveniles (IJs) to ambient conditions (22–25°C; 50–65% r.h.) for 100 min. A survival rate of 80–90% was reached after ten selection cycles. To select for tolerance of slow desiccation, we exposed IJs to 97% r.h. for 72 h, followed by further exposure to 85% r.h. for an additional 72 h. A high survival rate (>85%) was obtained after 20 selection cycles. We selected for enhanced downward dispersal by forcing IJs to move through a sand column to reach larvae of last-instar Galleria mellonella placed at the bottom of the column. After 25 selection cycles, the majority (>75%) of these nematodes were found at the layer close to the insects. No reduction in fitness was detected in the selected populations. Nevertheless, the nematode population selected for enhanced downward dispersal displayed significantly higher infectivity than the foundation population. The population selected for slow desiccation was more tolerant of heat stress than the foundation population. These findings establish the basis for improvement of this nematode for use as a biological control agent under field conditions.     

Genetic engineering of insect viruses for insect biological control

Insect viruses can be exploited for the biological control of insect pests and serve as well as vehicles for the introduction of ‘foreign genes’ into insect cells and insects. The present work describes some of the molecular events that take place during the replication of theGalleria mellonella densonucleosis virus in the insect host. Viral RNA and protein synthesis were monitored. An understanding of the virus biology is essential for further implementation of these viruses for biological control purposes.     

Genetic engineering of insect viruses for insect biological control

Insect viruses can be exploited for the biological control of insect pests and serve as well as vehicles for the introduction of ‘foreign genes’ into insect cells and insects. The present work describes some of the molecular events that take place during the replication of theGalleria mellonella densonucleosis virus in the insect host. Viral RNA and protein synthesis were monitored. An understanding of the virus biology is essential for further implementation of these viruses for biological control purposes.     

Sensitivity of caterpillars of the pine tree lappet moth Dendrolimus pini to native isolates of entomopathogenic nematodes

Abstract

The pine tree lappet moth Dendrolimus pini (Lasiocampidae) is one of the most dangerous pests of pine Pinus sylvestris stands in Central Europe. To develop biological control method of this pest, the bioassay was made to assess the sensitivity of D. pini caterpillars to native EPMs strains representing two species: Steinernema feltiae and Heterorhabditis megidis in laboratory conditions. The results showed higher activity of S. feltiae strains which parasitized 86.7 - 100% of D. pini caterpillars, compared to the 20-100% of insects parasitized by H. megidis strain. Most nematodes were found in caterpillars treated with S. feltiae (in average 40 IJs/caterpillar), the least – in individuals parasitized by H. megidis (in average IJs/caterpillar). No effect of dose and temperature on parasitizm was found with S. feltiae strains while in H. megidis increased doses resulted in higher extensity of parasitism. The results indicate higher biological activity of S. feltiae strains and advisability of their further studies in field experiments.     

Status of pesticide resistance in arthropod pests in Israel

A complex of events and factors, pertinent to a specific insect and insecticide, governs the development of resistance to insecticides. In Israel, resistance to conventional and novel insecticides occurred in insect pests such asBemisia tabaci andSpodoptera littoralis (that damage agricultural crops),Tribolium castaneum and other flour beetles (that contaminate stored products), andPediculus humanus spp., house flies and mosquitoes (that threaten public health). In the mid-1980s an insecticide resistance management (IRM) strategy was established for all cotton grown in Israel and is being adjusted on a yearly basis as needed. At present, insect pest management and IRM strategies are being developed and implemented area-wide for three regions in Israel: Bet She’an Valley, western Galilee, and western Negev. There are several research groups now working in Israel on various aspects of resistance including occurrence, mechanisms, and management practices. This paper offers a tentative review of the status of insecticide and acaricide resistance in pests in Israel.     

A survey of entomopathogenic nematodes (rhabditida) in the negev desert

The aim of the present survey was to isolate entomopathogenic rhabditids in an arid region. The survey was conducted in the Negev desert, located in the southern part of Israel. Soil samples were collected from 21 sites and the presence of entomopathogenic nematodes in the soil samples was determined by usingGalleria mellonella larvae as bait. Entomopathogenic nematodes, identified as heterorhabditids, were isolated only from soil samples obtained from under the canopy of irrigated fruit trees, planted in sandy soils. The nematodes from the new isolated populations were subjected to low relative humidity (75%) for 3 days after preconditioning for 72 h at 97% RH. Under these conditions, fewer than 10% survived for 48 h.     

PGPR and entomopathogenic fungus bioformulation for the synchronous management of leaffolder pest and sheath blight disease of rice

BACKGROUND: The biological control of plant pests and diseases using a single organism has been reported to give inconsistent and poor performance. To improve the efficacy, bioformulations were developed possessing mixtures of bioagents. RESULTS: Bioformulations combining Pseudomonas fluorescens Migula strains Pf1 and AH1 and Beauveria bassiana (Balsamo) Vuill. isolate B2 were developed and tested for their efficacy against leaffolder pest and sheath blight disease on rice under glasshouse and field conditions. The combination of Pf1, AH1 and B2 effectively reduced the incidence of leaffolder insect and sheath blight disease on rice compared with other treatments. An in vitro assay of leaffolder preference to rice leaf tissues treated with Pf1 + AH1 + B2 biformulation showed variation from normal growth and development of leaffolder larvae. Plants treated with the Pf1 + AH1 + B2 combination showed a greater accumulation of enzymes, lipoxygenase and chitinase activity against leaffolder insect compared with other treatments. Similarly, the plants showed a higher accumulation of defence enzymes, peroxidase and polyphenol oxidase activity against sheath blight pathogen in Pf1 + AH1 + B2 treatment compared with the untreated control. The bioformulation mixture attracted the natural enemy population of leaffolder under field conditions. In addition, a significant increase in rice grain yield was observed in Pf1 + AH1 + B2 treatment compared with the untreated control. CONCLUSION: The combination of P. fluorescens strains and B. bassiana isolate effectively reduced the incidence of leaffolder insect and sheath blight disease on rice plants and showed the possibility of controlling both pest and disease using a single bioformulation. Copyright © 2010 Society of Chemical Industry     

Biological control of Lycoriella ingenua (Diptera: Sciaridae) in commercial mushroom (Agaricus bisporus) cultivation: a comparison between Hypoaspis miles and Steinernema feltiae

BACKGROUND: Mushroom cultivation may be adversely affected by insect pests, including sciarids (Lycoriella spp.), which were previously controlled by application of chemical pesticides. However, owing to food safety and environmental concerns, availability of pesticides for use during mushroom cultivation has diminished. Consequently, it is imperative to investigate alternative control strategies, not reliant on chemical pesticides, which may be used in an integrated pest management system. RESULTS: Application of the predatory mite Hypoaspis miles Berlese to commercial mushroom‐growing beds at the beginning of spawn run or just prior to casing (830 mites m^?2) significantly reduced immature sciarids, Lycoriella ingenua (Dufour), in the growing substrate and also adult activity towards the conclusion of cropping. A trend towards lower sciarid emergence from substrates and reduced adult sciarid activity was observed following the application of Steinernema feltiae (Filipjev) (1.5 × 10⁶ nematodes m^?2) at casing. No significant treatment effects on mushroom yield were observed. However, contamination of the mushroom crop by adult sciarids increased in untreated controls. Application of H. miles required a 12‐fold increase in labour when compared with application of S. feltiae. CONCLUSION: Contingent upon the development of an effective application system, H. miles has potential for the biological control of sciarids in commercial mushroom production. Copyright © 2009 Society of Chemical Industry     

Entomopathogenic nematodes (Nematoda: Steinernematidae, heterorhabditidae) as control agents forParahypopta caestrum, a pest in the culture ofAsparagus officinalis

The entomopathogenic nematodes (EPNs)Steinernema feltiae (under the trade name Entonem) andHeterorhabditis bacteriophora (under the trade name Larvanem) were evaluated as potential control agents ofParahypopta caestrum, the major pest of the asparagus crop in Greece. In laboratory experiments the two nematodes provided equal insect suppression, but significant differences were found in the time it took them to kill the larvae.S. feltiae caused high levels of mortality within 24 h and the highest level at 48 h. In contrast,H. bacteriophora required 96 h to achieve the highest level of mortality. In field experiments, the nematodes provided equal insect suppression as compared with the insecticide cadusaphos and the mixture teflubenzuron +Bacillus thuringiensis var.kurstaki. No significant differences were found in the effectiveness of the insecticides used, but there were significant differences between the control and treatments. The findings showed thatS. feltiae andH. bacteriophora could be used to control the insectP. caestrum in asparagus culture. http://www.phytoparasitica.org posting Jan. 10, 2007.     

Benefits of a maize–bean–weeds mixed cropping system in Urubamba Valley,Peruvian Andes

Abstract

In the Urubamba Valley, Peruvian Andes, we evaluated the abundance of insect pests and natural enemies in experimental plots where maize was grown either as monoculture, intercropped with beans, or intercropped with beans plus associated weeds. We also assessed the consequences of the cropping system for maize yield. The main insect pests recorded were Diabrotica spp. (Coleoptera: Chrysomelidae), Carpophilus sp. (Coleoptera: Nitidulidae) and Pagiocerus frontalis (Coleoptera: Scolytidae), and their overall abundance did not differ among crop diversity treatments. However, there was a significant adverse effect of crop diversity on the maximum abundance of both Carpophilus and Pagiocerus. The main beneficial arthropods were Paratriphleps sp. (Hemiptera: Anthocoridae), ladybirds and spiders, and their density did not differ among treatments. Maize yield did not decrease with increasing plant diversity. The reported benefits of intercropping, together with the associated efficiency in land use, make this traditional agricultural practice a valuable alternative to the use of pesticides, particularly for resource-poor Andean farmers.     

高毒力金龟子绿僵菌的筛选及其胞外蛋白酶产量测定

以大蜡螟Galleria mellonella L.幼虫为供试昆虫,对从果园土壤中筛选出的金龟子绿僵菌Metarhizium anisopliae的生物活性进行了测定,共获得4株高毒力菌株,其LT50值在1.85～2.56 d之间,LD50值在6.11×102～1.55×104 spores之间。利用明胶-琼脂平板分析法对筛选出的高毒力绿僵菌菌株产胞外蛋白酶的水平进行了测定,结果显示,各菌株间产酶水平差异较大,且菌株产酶水平的高低与其对大蜡螟幼虫的毒力之间存在明显的线性相关性。     

基于转录组数据的害虫抗药性综合检测方法

为建立基于转录组数据的害虫抗药性检测方法,以3种重要害虫家蝇Musca domestica、白纹伊蚊Aedes albopictus和小菜蛾Plutella xylostella的8个抗性/敏感种群的转录组数据为对象,使用已开发的乙酰胆碱酯酶抗性突变检测程序ACE检测不同种群中的乙酰胆碱酯酶抗药性突变,并使用Bowtie 2软件和R程序包DESeq2检测其解毒酶基因的表达量变化,分析这3种害虫对有机磷类和氨基甲酸酯类杀虫剂的抗性分子基础。结果显示,在家蝇2个抗性种群KS8S3和ALHF中检测到ace2基因上发生了G227A抗药性突变,突变频率分别为0.318和1.000;在白纹伊蚊抗性种群Tem-GR中检测到CCEae3a基因的表达量较敏感种群Par-GR上调了7.175倍;在小菜蛾抗性种群ZZ中检测到ace1基因上发生A201S和G227A抗药性突变,突变频率分别为0.656和0.692。根据上述突变频率和解毒酶基因表达量变化评估的3种害虫种群抗药性情况与其之前的报道基本相符,表明基于转录组数据同时对靶标抗性机制和代谢抗性机制进行检测的害虫抗药性综合检测方法可以很好地反映害虫种群的抗药性状况。     

Biological control potential of Turkish entomopathogenic nematodes against the Mediterranean fruit fly <Emphasis Type="Italic">Ceratitis capitata</Emphasis>

The entomopathogenic nematodes Steinernema weiseri, S. feltiae, S. carpocapsae and two strains of Heterorhabditis bacteriophora, isolated from Turkish soils, were evaluated against larvae of the Mediterranean fruit fly (medfly) Ceratitis capitata in plastic cups under laboratory conditions with sandy loam soil and 10% moisture level. At a rate of 100 infective juveniles (IJs)/cm², the last instar larvae of C. capitata were susceptible to the entomopathogenic nematodes: the S. feltiae 09-31 strain recovered from Aydin provided 78% mortality, whereas S. weiseri and S. carpocapsae killed 50% and 56% of the larvae, respectively. Both strains of H. bacteriophora species caused less than 50% mortality. Except for S. feltiae, the majority of infected medflies died as prepupae or pupae within the puparia. More than 90% larval mortality was recorded at 200 and 400 IJs/cm² for S. feltiae. None of the nematode isolates infected the medfly pupae within the puparia. In pot experiments containing soil, S. feltiae caused 96% and 97% mortality at 100 and 200 IJs/cm², respectively. In pot experiments with grass present, more than 94% mortality was obtained in the presence of grass roots.     

Field trial measuring the compatibility of methoxyfenozide and flonicamid with Orius laevigatus Fieber (Hemiptera: Anthocoridae) and Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) in a commercial pepper greenhouse

BACKGROUND: Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) and Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) are among the most serious pests of sweet peppers in greenhouses. Chemical control is difficult because of their high reproductive rates and insecticide resistance, and seasonal inoculative releases of Orius laevigatus (Fieber) and Amblyseius swirskii (Athias‐Henriot) are commonly used to reduce their populations. As chemical treatments are often needed in the crop against other pests, the side effects of methoxyfenozide (an insect growth regulator against lepidopteran pests) and flonicamid (a selective feeding inhibitor against sucking insects) were studied in both beneficial organisms in a commercial greenhouse. RESULTS: Orius laevigatus and A. swirskii were released at commercial rates (4–5 and 100 m^?2), and a strong establishment and a very homogeneous distribution were reached. One pesticide treatment with the maximum field recommended concentration of methoxyfenozide and flonicamid (96 and 100 mg AI L^?1) was done when they were well established, and their population levels were not affected either immediately or up to 30 days after treatment. CONCLUSION: The results are indicative of no impact of methoxyfenozide and flonicamid on the two natural enemies in the field, and both can be considered as potential alternatives to be included in IPM programmes in sweet pepper. Copyright © 2011 Society of Chemical Industry     

Genotypic diversity of soybean in mixed cropping can affect the populations of insect pests and their natural enemies

In order to determine the potential benefits of soybean genotypic diversity for the population densities of major insect pests and their natural enemies, the field treatments were compared in monocultures and mixed cropping systems that included five soybean cultivars. The results indicate that monocultures tended to have similar density of aphids, Aphid glycines Matsumura, but a higher density of leafhoppers, Empoasca flavescens (Fab.), than mixed cropping systems. The mixed cropping array significantly increased the population density of some generalist natural enemies, including ladybeetles, lacewings and hoverflies, to varying degrees. These findings suggest that mixed cropping systems may be more effective to control insect pests than monocultures in soybean fields, and these findings offer a practical implication in modern soybean agricultural industry.     

Occurrence of Harmonia axyridis in Tunisia

In a study on the population dynamics of insect pests on Pinus halepensis in Chott Mariem, two specimens of the harlequin ladybird, Harmonia axyridis, were found. This is the first record of this species in Tunisia.     

大螟与寄主植物关系的研究

大螟成虫产卵对寄主植物种类和生育期有明显选择性。寄主植物种类和理化性状影响幼虫的成活率,蛹体重量和性比,从而影响成虫产卵量,表明寄主植物对大螟种群数量有明显的影响。幼虫在田间的分布状况主要也是由于田边寄主植物更适合其生长发育之故。     

Current Status of Integrated Control of Citrus Pests in Israel1)

Following the spectacular biological control of the Florida ted scale, an effective program of integrated control was developed on citrus in Israel. In recent years, a gradual increase of various pests has brought about a marked increase in the amounts of non-selective pesticides applied on citrus, which has in turn triggered still heavier pest resurgences. Intensive efforts are now being made to break that vicious cycle and restore the upset natural balance in the citrus eco-system. A vigorous biological control program has been embarked upon. The prospects for successful integrated control are very good, especially if more realistic tolerances for insect damage on citrus fruit are adopted.