Potato Beetle Leptinotarsa Decemlineata Research Articles

Purification and characterization of Stenotrophomonas maltophilia chitinase with antifungal and insecticidal properties

This study aimed to determine the ability of bacteria to produce the chitinase enzyme, purify, and characterize the enzyme from the isolate with the best activity, and determine the use of this purified enzyme as a biocontrol agent. The chitinolytic bacterium was identified as Stenotrophomonas maltophilia. The chitinase enzyme was purified 1.4 times at a 30% ammonium sulfate concentration with a yield of 40.7%. Following partial purification, the enzyme was purified by ion-exchange chromatography using HiPrep Q XL 16/10 column and HiPrep™ 26/10 desalting column with 25.34% and 18.12% yields, respectively. It was calculated that the purified enzyme had a molecular weight of 52 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. The optimum activity of the enzyme was determined at 50 °C and pH 7.0. Enzyme activity was most induced by Fe2+, while it was most inhibited by Zn2+ at 5 mM concentration. Km and V max values of the enzyme for colloidal chitin were calculated as 1.6419 mg/mL and 16.129 U/mg, respectively. The purified chitinase was used as a biocontrol agent against the fungus Fusarium oxysporum and potato beetle Leptinotarsa decemlineata. The enzyme was shown to be effective in reducing the growth of fungus and causing disruption of the chitin structure of potato beetle.

Efficacy of single and combined applications of entomopathogenic fungi and nematodes against the pupae of colorado potato beetle (Leptinotarsa decemlineata [Say]), (Coleoptera: Chrysomelidae)

BackgroundThe lethal effects of different entomopathogenic fungi (EPF) and nematodes (EPN) on the pupae of the Colorado Potato Beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) were investigated in a two-step study when used separately or together. In the first step, Nostalgist (Beauveria bassiana strain Bb-1, Agrobest Co.), Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae), Heterorhabditis bacteriophora Poinar, 1976 (Rhabditida: Heterorhabditidae) (Bioglobal Co.), 2 Turkish isolates of Beauveria bassiana BIM-001 and BY2 were applied separately to the pupal stage of pest in the soil. In the experiments, 3 different concentrations (150, 200, and 250 million infective juveniles (IJs)/100 l water) of EPN and a single concentration (1x108 spores/ml for and maximum recommended field dose 1 × 108 CFU/ml) of EPF were used. In the second step, BIM-001 and BY2 isolates of B. bassiana were combined with both EPN species; S. feltiae + B. bassiana BIM-001, S. feltiae + B. bassiana BY2, H. bacteriophora + B. bassiana BIM-001, H. bacteriophora +B. bassiana BY2 were applied to pupae. At this stage, 150 million IJs/100 l water which was the maximum recommended field concentration for EPN and 1 × 108 spores/ml for local EPF isolates were used.ResultsAccording to the study results, pupae deaths were significantly higher in Nostalgist (74%) than those of B. bassiana BIM-001, B. bassiana BY2, S. feltiae, and H. bacteriophora (P<0.05). While both EPN caused higher mortality than B. bassiana BY2, B. bassiana BIM-001 had the highest mortality rates. The combination of S. feltiae + B. bassiana BIM-001 at the highest mortality rate (80%) was found statistically different and significant from other EPF + EPN treatments on pupae. Moreover, there were non-statistical differences between the other EPF and EPN combinations.ConclusionIt was found that the combined use of EPF and EPN was more effective on the pupae of L. decemlineata than a single application. According to the results of the study, it may be promising to use EPN and EPF together for the control of the Colorado Potato Beetle pupae.

Effects of Artemisia dracunculus L. Water Extracts on Selected Pests and Aphid Predator Coccinella septempunctata L.

The aim of this study was to determine the effects of water extracts of tarragon (Artemisia dracunculus L.) on the feeding intensity, mortality, and weight gain of selected pests, i.e., adult pea leaf weevils (Sitona lineatus L.), nymphs, wingless females of black bean aphids (Aphis fabae Scop.), and L2 and L4 larvae of Colorado potato beetle (Leptinotarsa decemlineata Say). In addition, the effect of the tarragon extracts on the voracity of the non-target organism Coccinella septempunctata L. L3 larvae was examined. To reduce S. lineatus feeding, at least 10% dry matter (DM) extract and 20% fresh matter (FM) should be used. Tarragon water extract has strong aphicidal potential against A. fabae, with 84% mortality of nymphs at 30% FM and 78% mortality of wingless females at 10% DM after 108 h of exposure. Aphid nymphs turned out to be more sensitive to the extracts prepared from fresh tarragon than from its dry matter. They were also more sensitive than wingless females. The body weight gain of L2 and L4 larvae of Colorado potato beetle was significantly reduced through the application of 10% and 5% extracts prepared from dry matters, respectively, while extracts prepared from fresh matter turned out to be ineffective. L2 larvae were more susceptible to extracts than L4 larvae, which suggests that they should be used as early as possible in the pest season. No negative influence of the extracts used on the voraciousness of C. septempunctata L3 larvae was found.

Detection of sex in adults and larvae of Leptinotarsa decemlineata on principle of copy number variation

The identification of sex in larvae of insects is usually challenging or even impossible, while in adults the sexual dimorphism is usually evident. Here, we used copy number analysis to develop a method of sex detection in Colorado potato beetle (Leptinotarsa decemlineata), which has an X0 sex determination system. The X linked gene LdVssc and autosomal gene LdUBE3B were identified as appropriate target and reference loci, respectively. The copy numbers (CNV) of LdVssc in males and females were estimated using standard droplet digital PCR (ddPCR) and real-time PCR (qPCR). With both methods, CNVs were bimodally distributed (BAddPCR = 0.709 and BAqPCR = 0.683) with 100% ability to distinguish females from males. The use of qPCR-based sex detection in a broad collection of 448 random CPB adults showed a perfect association (Phi = 1.0, p < 0.05) with the true sexes of adults, with mean CNV in females of 2.032 (SD = 0.227) and 0.989 in males (SD = 0.147). In the collection of 50 random 4th instar larvae, 27 females and 23 males were identified, consistent with the expected 1:1 sex ratio (p = 0.689). The method is suitable for sexing in all stages of ontogenesis. The optimal cost-effective application of the method in large populations requires the DNA extraction using CTAB, the qPCR assay in one biological replicate and three technical replicates of each marker, and the use of one randomly chosen male per run to calibrate calculation of CNV.

Exposure to Temperature and Insecticides Modulates the Expression of Small Noncoding RNA-Associated Transcripts in the Colorado Potato Beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae).

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) is an insect that can adapt to various challenges, including temperature fluctuations or select insecticide treatments. This pest is also an ongoing threat to the potato industry. Small noncoding RNAs such as miRNAs, which can control posttranscriptionally the expression of various genes, and piRNAs, which can notably impact mRNA turnover, are modulated in insects under different conditions. Unfortunately, information regarding the expression status of key players involved in their synthesis and function is for the most part lacking. The current study thus aims at assessing the levels of such targets in L. decemlineata exposed to hot and cold temperatures as well as treated to the insecticides chlorantraniliprole, clothianidin, imidacloprid, and spinosad. Transcript expression levels of Ago1, Ago2, Ago3, Dcr2a, Dcr2b, Expo-5, Siwi-1, and Siwi-2, components of pathways associated with small noncoding RNA production or function, were measured by qRT-PCR and revealed modulation of select transcripts in response to temperature challenges and to select insecticides. RNAi-mediated reduction of Ago2 transcript levels in L. decemlineata injected with Ago2-targeting dsRNA and exposed to cold and warm temperatures was also conducted. Changes in survival rates were observed for the latter condition in dsRNA- versus saline-injected insects. These results showcase the differential expression of select targets involved in small noncoding RNA homeostasis and provide leads for the subsequent assessment of their involvement during stress response in L. decemlineata using RNAi-based approaches.

Efficient production of long double-stranded RNAs applicable to agricultural pest control by Corynebacterium glutamicum equipped with coliphage T7-expression system

RNA-based pesticides exert their function by suppressing the expression of an essential gene in the target pest through RNA interference caused by double-stranded RNA (dsRNA). Here, we selected target genes for growth suppression of the solanaceous crop pests ladybird beetle (Henosepilachna vigintioctopunctata) and Colorado potato beetle (Leptinotarsa decemlineata)-the death-associated inhibitor of apoptosis protein 1 gene (diap1), and an orthologous gene of the COPI coatomer protein complex (copI), respectively. We constructed a cost-competitive overproduction system for dsRNA using Corynebacterium glutamicum as a host bacterium. The dsRNA expression unit was equipped with two sets of promoters and terminators derived from coliphage T7, and the convergent expression system was designed to be selectively transcribed by T7 RNA polymerase. This expression system efficiently overproduced both target dsRNAs. On culture in a jar fermentor, the yield of diap1-targeting dsRNA (approximately 360 bp) was > 1 g per liter of culture. Long-chain diap1-targeting dsRNAs (up to around 1 kbp) could be produced without a substantial loss of efficiency. dsRNA accumulated in C. glutamicum significantly suppressed larval growth of H. vigintioctopunctata. The dsRNA expression technology developed here is expected to substantially reduce dsRNA production costs. Our method can be applied for a wide range of industrial uses, including agricultural pest control.Key points• Overexpression of dsRNA was achieved in C. glutamicum using a coliphage T7 system.• The best strain produced > 1 g/L of the target dsRNA species, for use as an insecticide.• The developed system efficiently produced long dsRNA species, up to ~ 1 kbp.

Field Testing of Efficacy of Three Environmentally Friendly Insecticides Against Colorado Potato Beetle (Leptinotarsa Decemlineata [Say], Coleoptera, Chrysomelidae) on Potato-Evaluation of the Effect on Yield

In 2007 and 2008 the field experiment was conducted to test the efficacy of three environmentally friendly insecticides against the Colorado potato beetle (Leptinotarsa decemlineata), with the aim of evaluating their effect on the yield of potato. 0.25 % water emulsion of Neem-Azal (active ingredient azadirachtin) was applied twice, while 3 % water emulsion of Aktiv (a.i. potassium salt of fatty acids) and 1 % water emulsion of Prima (a.i. refined rape oil) were applied eight times. In 2007, the potato yield was higher (25.3±3.2 t ha-1) than in 2008 (8.2 ± 0.8 t ha-1). In 2007 there were no significant differences in potato yield at different control measures and the yield ranged from 7.5 ± 1.3 t ha-1 (Aktiv) to 9.4 ± 1.8 t ha-1 (Prima). In 2008, the highest potato yield was recorded in Neem-Azal treatment (3.5 ± 0.7 t ha-1), while in two other insecticide treatments the potato yield did not differ significantly with control treatment neither with the Neem-Azal treatment. Potato tubers were classified into three fractions: fraction 1 (tubers &lt;4 cm), fraction 2 (tubers between 4 and 5 cm), and fraction 3 (tubers &gt; 5 cm). On average we produce 2.11 ± 0.06 t ha-1, 9.93 ± 0.53 t ha-1, and 13.17 ± 0.70 t ha-1 of potato in 2007, and 2.11 ± 0.20 t ha-1, 4.68 ± 0.37 t ha-1, 0.84 ± 0.29 t ha-1 of potato in 2008, respectivelly.

Response of adult Colorado potato beetles (Coleoptera: Chrysomelidae) to water in the landscape

AbstractThis laboratory study confirmed that the strategy of adult terrestrial Colorado potato beetle (Leptinotarsa decemlineata(Say); Coleoptera Chrysomelidae) to survive the threat of drowning in water is based on avoidance of water crossings. It also showed that beetles at the surface of a body of water after failing to avoid it, long considered limited to passive floating and phoretic transport were in fact likely to rely on a complex fight or flee response. Beetles showed capacity to swim in a pattern similar to land foraging beetles. Beetles also tolerated submergence and walked underwater. These active behaviours should improve their probability of finding shore or refuge for longer survival. Results confirmed that Colorado potato beetles are likely to accumulate near water features in the potato agro-ecosystem landscape but suggest that successful crossings and colonisation of crops on the other side are more likely than previously expected. On a larger scale, new information provided by this study combined with our knowledge of dominant winds and currents should make it possible for future research to better predict the probability of surviving encounters with water and the orientation of invasive Colorado potato beetle colonisers dispersing at the surface of bodies of water.

Bypassing a plant's defense for pest defense

Pest Control![Figure][1] The Colorado potato beetle ( Leptinotarsa decemlineata ) IMAGE: © DANIEL BORZYNSKI/ALAMY Colorado potato beetles can skeletonize the leaves on a potato plant, devastating crop yields. Insecticides are increasingly useless as the beetle evolves resistance. Zhang et

Factors affecting development and overwintering of second generation Colorado Potato Beetle (Coleoptera: Chrysomelidae) in Estonia in 2010

We have established for the first time that Colorado potato beetle (CPB) (Leptinotarsa decemlineata Say) (Coleoptera: Chrysomelidae) produced a distinct second generation in 2010 in Estonia. This species has a history, in Estonia, of less than 50 years. Due to their great ability to adapt to variable environmental conditions, the beetles spread very quickly throughout the country and established a permanent population in the 1980s. Before 2010, CPB has been predominantly univoltine. The occurrence of the second generation was the result of rare coincidence of extremely favourable weather as the cumulative degree days (DD) of 927 exceeded the sum needed for two full generations. Constantly high temperatures from the beginning of May caused the formation of summer generation adults already by the end of July and the long day photoperiod, as well the availability of fresh food, kept the beetles in reproductive mode preventing the onset of diapause. Summer beetles continued to oviposit up to the second half of September, but a large proportion of the second generation was eliminated from the population in the pre-adult or adult stages as they failed to end their development in the favourable period. Successful overwintering with about 50% survivors occurred only in association with completed development which was restricted to August and the beginning of September. An abundant second generation has potential to reduce primarily the yield of late potato cultivars. However, the unpredictable weather conditions in Estonia does not allow exact prediction of the appearance of a second generation.

Characterization of two unrelated satellite DNA families in the Colorado potato beetleLeptinotarsa decemlineata(Coleoptera, Chrysomelidae)

The Colorado potato beetle (Leptinotarsa decemlineata, family Chrysomelidae),a phytophagous insect, which feeds preferably on potatoes, constitutes a serious pest of this crop and causes extensive damage to tomatoes and egg plants. It has a remarkable ability to develop resistance quickly against insecticides and shows a diversified and flexible life history. Consequently, the control of this pest has become difficult, requiring the development of new alternative biotechnology-based strategies. Such strategies require a thorough knowledge of the beetle’s genome,including the repetitive DNA. Satellite DNA (stDNA), composed of long arrays of tandemly arranged repeat units, constitutes the major component of heterochromatin and is located mainly in centromeric and telomeric chromosomal regions. We have studied two different unrelated satellite-DNA families of which the consensus sequences were 295 and 109bp in length, named LEDE-I and LEDE-II, respectively.Both were AT-rich (70.8% and 71.6%, respectively). Predictive models of sequence-dependent DNA bending and the study of electrophoretic mobility on non-denaturing polyacrylamide gels have shown that the DNA was curved in both satellite-DNA families. Among other features, the chromosome localization of both stDNAs has been studied. In situ hybridization performed on meiotic and mitoticnuclei showed chromosomes, including the X chromosome, with zero, one, or two stDNAs. In recent years, it has been proposed that the repetitive DNA may play a key role in biological diversification processes. This is the first molecular and cytogenetic study conducted on L. decemlineata repetitive DNA and specifically on stDNA, which is one of the important constituents of eukaryotic genomes.

Forecasting the influence of temperature increase on the development of the Colorado potato beetle [Leptinotarsa decemlineata (Say)] in the Wielkopolska region of Poland

The Colorado potato beetle (Leptinotarsa decemlineata) is probably the most dangerous pest species of potatoes. This study assessed the influence of expected climate warming on the number of Colorado potato beetle generations in the Wielkopolska region of Poland using two simulation models, SimLep 1 and NumoGen 1. Two types of data sets were utilised in the simulations: real meteorological data recorded in Winna Góra (52.2N; 17.4E) in the period 2002–2011 and virtual data obtained after transformation of the real data to include an increase in the recorded temperature values between 1 and 6°C. The threat to potato crops from Colorado potato beetle was found to increase in response to expected climate change. A temperature increase of 2°C above that recorded during the last few years would allow the development of two full generations of the beetle, and further temperature increases may even permit the occurrence of three generations.

Efficacy of endosulfan and fipronil and joint toxic action of endosulfan mixtures against Leptinotarsa decemlineata (Say)

The Colorado potato beetle (Leptinotarsa decemlineata [Say]) in the north Xinjiang Uygur autonomous region in China has evolved resistance to pyrethroids and carbamates. Mutations resulting in target site insensitivity, namely L1014F in LdVssc1 voltage-sensitive sodium channel and S291G in acetylcholine esterase, confer, at least partially, the resistance. Insecticides with different modes of action may serve as likely replacements. Endosulfan and fipronil are GABA-gated chloride channel-blocking insecticides. In this article, we found that the contact toxicities of the two compounds were among the highest ever estimated to the 4th-instar larvae and the adults and affirmed that they were useful for L. decemlineata control in north Xinjiang. Regarding stomach toxicities of the two compounds, adult beetles were less sensitive than 2nd-, 3rd-, and 4th-instar larvae, suggesting that the appropriate timing for spraying is the early larval stage. Mixtures of endosulfan and α-cypermethrin at 1:160, 1:80, and 1:40 ratios, of endosulfan and phoxim at 1:24 ratio, and of endosulfan and isocarbophos at 1:72 and 1:288 ratios, significantly increased toxicity in a field population. The combination indices were significantly below 1 at both LD50 and LD90 levels, revealing synergistic effects. Our results demonstrated that endosulfan and fipronil could be applied alone and endosulfan may also be used in binary mixtures to restore pyrethroid susceptibility. These findings may have considerable practical implications for L. decemlineata resistance management.

Morphology and ultrastructure of the chemosensory sensilla of larval antennae in the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae)

The allocation, external morphology, and ultrastructure of various types of sensilla on the antennae have been studied in the larvae of the Colorado potato beetle (Leptinotarsa decemlineata Say) using scanning and transmission electron microscopy. It has been found that the larval antenna bears 11 sensilla of four morphological types: trichoid (five), basiconic (four), styloconic (one), and antennal cone (one). It has been shown that the sensilla are innervated by 2–7 receptor cells: trichoid, by 2–4 receptor cells; basiconic, by 4–7 receptor cells; and styloconic, by 6 receptor cells. Judging by the specifics of their ultrastructural organization, the function of these sensilla is gustatory. The antennal cone is innervated by two receptor cells, and its function is olfactory.

ISOLATION AND IDENTIFICATION OF NOVEL LOCAL ISOLATES OF Bacillus thuringiensis ACTIVE AGAINST RED PALM WEEVIL (RPW)

The gram-positive bacterium B. thuringiensis is well-known as sources of insecticidal proteins, most of which accumulate in crystalline inclusions during sporulation, these parasporal inclusions contain various types of insecticidal crystal protein (ICP). The crystal proteins from B. thuringiensis are among the most successful biological control agents for the suppression of agriculturally and medically important insect pests (Roh et al., 2007), being toxic to the larvae of lepidopteron, dipteran, and coleopteran insects (Johnson et al., 1998), as well as certain hymenoptera, homoptera, and mallophaga, in addition to many nematodes, flatworms, and Sarcomastigophora (Walters and English, 1995; Horak et al., 1996). At present, more than 130 B. thuringiensis crystal proteins have been described based on their gene sequences and amino acid homologies (Crickmore et al., 1998). Recently, all crystal proteins show some relatedness is grouped into four main groups. B. thuringiensis isolates are distributed worldwide, and more than 60,000 have already been collected by various industries in an effort to obtain novel crystal proteins (Martin and Travers 1989; Li et al., 2007). In addition, B. thuringiensis isolates showing different crystal protein gene patterns from the reference strains have also been reported (Li et al., 2002). The red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier), a concealed tissue borer, is a lethal pest of palms and is reported to attack 17 palm species worldwide. Although the weevil was first reported on coconut (Cocos nucifera) in South Asia during the last two decades it has gained a foothold on date palm Phoenix dactylifera in several Middle Eastern countries from where it has moved to Africa and Europe, mainly due to the movement of infested planting material. In the Mediterranean region, RPW also severely damages Phoenix canariensis. Infested palms, if not early detected and treated, often declined and die. However, palms in the early stages of infestation usually respond to chemical insecticide treatments. RPW has been managed in several countries through an integrated pest management (IPM) program (Faleiro, 2006). The search for effective natural enemies (biological control) for RPW still continues. A novel Bacillus thuringiensis strain, NCIMB 40152, was isolated from dead Tenebrio molitor L. Larvae. The isolate is endowed with specific insecticide activity against the Colorado potato beetle (Leptinotarsa decemlineata (Say), Coleoptera, Crysomelidae), but has no effect against lepidopteran or dipteran insects (Cidaria et al., 1991). Bacillus thuringiensis strains C-4, C-9, GM-7, and GM-10, with high toxicity against lepidopteran and coleopteran pests have been isolated from Northeast Mexico (Tamez-Guerra et al., 2004). Bacillus thuringiensis soil isolates A21, A51 and C17 isolated from different regions of the Cuban archipelago showed higher larvicide activity than Bactivec's isolated reference strain, against both Aedes aegypti and Culex quinquefasciatus (Gonzalez et al., 2011). Accordingly, This study describe the isolation and identification of novel isolates of B. thuringiensis, in order to study insecticidal activity of isolates produced proteins against Red Palm Weevil insect.

Effectiveness of entomopathogenic nematodes Steinernema feltiae and Heterorhabditis bacteriophora on the Colorado potato beetle Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) under laboratory and greenhouse conditions

In laboratory and greenhouse studies, the invading ability, virulence, and mortality caused by Stinernema feltiae and Heterorhabditis bacteriophora were compared. After one and two days of exposure to either nematode species, the mortality of Colordo potato beetle (CPB) Leptinotarsa decemlineata larvae at different instars, third and fourth, was recorded and the number of nematodes invading cadavers was more than the number of nematodes inside the larvae at the late last instar (one day before pre-pupa). Two concentrations, 250 and 500 IJs/dish, infective juvenile nematodes/0.5 ml were tested on different CPB larval instar. S. feltiae was more effective, with fourth instar rather than third and late last instar. On the other hand, H. bacteriophora showed a very weak effect with L. decemlineata. Also it was clear that S. feltiae was more effective and faster than H. bacteriophora: more than 70% of larvae were killed within 24 hours compared with H. bacteriophora which killed 40% of larvae within 48–72 hours. A significant difference in invading efficiency was observed with concentration 2500 IJs/pot in the greenhouse test. The number of adult females found in the cadavers of L. decemlineata larvae was always higher than the number of males. Foliage application of S. feltiae and H. bacteriophora resulted in a significant reduction of the number of damaged leaves and a lower index of damage compared with that in the control. We conclude that S. feltiae has significant potential and can help in the management of the Colorado potato beetle.

Is there a role for stripes of adults and colour of larvae in determining the avoidance of the Colorado potato beetle by the American toad?

It has been suggested that the stripes on the elytra of the adult Colorado potato beetle ( Leptinotarsa decemlineata (Say, 1824); Coleoptera: Chrysomelidae) and the red colouration of the larvae are aposematic characters warning predators of their distastefulness as prey. The role of stripes and red colour in determining the avoidance behaviour of the American Toad ( Bufo americanus Holbrook, 1836 = Anaxyrus americanus (Holbrook, 1836); Anura: Bufonidae) for the Colorado potato beetle was investigated in a series of laboratory tests. The behaviour of toads exposed to wild Colorado potato beetles was compared with that of toads exposed to genetic mutant Colorado potato beetles without elytral stripes. Tests confirmed the distastefulness of adult and larval stages and demonstrated the development of prey avoidance (cessation of feeding in spite of hunger) combined or not to behavioural displays where the toad plants down, crouches, and turns away or shows wincing, prey dropping, and mouth gaping after snapping at the beetle. However, toads showed the same response to mutant adult beetles without stripes and to mutant larval beetles without the red colour as to wild adult beetles with stripes and to wild red larvae. Results indicate that the stripes and the red colouration of the Colorado potato beetle do not constitute aposematic characters for the toad.

Oviposition of the Colorado potato beetle (Leptinotarsa decemlineata) and natural predation on its egg masses in Bt-expressing fields

Generalist predators are relevant natural enemies of the Colorado potato beetle (CPB) in Europe. In fields of insect resistant genetically modified plants (GMPs), predators could be exposed to toxins either directly (e.g., via pollen), or indirectly through feeding on herbivorous prey. Hence, they represent an important functional group to consider when studying environmental impacts of GMPs. CPB females show a ‘bet-hedging’ strategy in spatial and temporal distribution of eggs, through which the species tries to minimize the risks of progeny loss due to adverse conditions. Experimental fields of GM eggplants expressing Cry3Bb toxin and potatoes expressing Cry1Ab toxin were set up. CPB egg masses were counted on naturally infested plants at four time points during the field season of each crop. To assess predation, newly deposited egg masses were marked at the same dates. Daily visual observations were conducted recording the numbers of intact or preyed eggs and neonate larvae. In both cases, oviposition was similar between GM and control plots, as the number of egg masses per plant and the number of eggs per mass did not differ significantly between treatments. A statistical analysis of the spatial distribution of egg masses revealed a similar aggregation in the potato field, whereas in the eggplant field, the variance of the number of egg masses per plant was smaller than expected in GMP plots. The predation rate was similar between treatments. These results suggest that the ecological function of natural predation on CPB eggs in GM plots was not impaired.

Level and genetic variability of resistance to the colorado potato beetle (leptinotarsa decemlineata (say)) in wild solarium species

Crop resistance to insects is a preferred approach of the agriculture industry and could play an important role in the development of an integrated pest management strategy, having a reduced environmental footprint. The resistance to the Colorado potato beetle for six accessions of wild Solanum species [S. acroglossum (PI 498204), 5. chomatophilum (PI 310991 and PI 365325), S. paucissectum (PI 365340), S. piurae (PI 473501), and 5. tarnii (PI 498044)] was evaluated using a field test. The population density of the Colorado potato beetle was lower on the Solanum accessions compared to potato, and highest on S. piurae where defoliation reached 20%, compared to less than 10% with the other Solanum species and 80% with potato. Factor analysis was used to extract information from the field data on the mode of resistance and the genetic variability within accessions. All accessions had a low score for the “colonisation” factor, an indication of the presence of a factor deterring the adults and interfering with colonisation. The score for the “large larvae” factor was also low and could be due to the presence of factors reducing the development of the larvae. The analysis of the genotypic variance for each accession indicated the absence of variability for resistance to the Colorado potato beetle within an accession. This study provided the first information on the level of resistance to the Colorado potato beetle for three of the wild Solanum accessions studied. It demonstrated that all the accessions except S. piurae (PI 473501) were highly resistant to the Colorado potato beetle. It provided some indication that the mode of resistance involves interference with colonisation of the plant by adults. Finally, it demonstrated the general lack of genetic variability within accessions for resistance to the Colorado potato beetle.

Antifeedant effects of several plant extracts on Colorado potato beetle larvae

The antifeedant activities of methanolic extracts made from seven plant species (Abutilon theophrasti Medic., Ajuga chamaepitys (L.) Schreb., Amorpha fruticosa L., Matricaria chamomilla L., Matricaria inodora L., Tanacetum vulgare L. and Tilia cordata Mill.) were assessed in the laboratory at 0.5% and 5% dosages against Colorado potato beetle (Leptinotarsa decemlineata Say) larvae. Three h and 24 h dual-choice and 3 h no-choice feeding bioassays were carried out with potato (Solanum tuberosum L.) leaf discs. Furthermore, during the no-choice test direct observations on larval behaviour were performed to help to distinguish the mode of action which underlies inhibition of feeding. At a dosage of 0.5% no plant extract deterred feeding of larvae. At 5% Matricaria inodora (and our standard Ajuga chamaepitys with well-known antifeedant properties) was the most potent antifeedant of the seven extracts tested. Antifeedant indexes and results of the behavioural observations suggest that M. inodora acts as a sensory mediated feeding deterrent, rather than as a toxin.