Skip to content

Author: admin

Published on

Galimberti A, Alyokhin A. J Econ Entomol. 2018;111(3):1261-1267. doi: 10.1093/jee/toy046.

Mineral oil is a product used to reduce Potato Virus Y transmission in potato fields. However, there is little information available about other effects that oil may have on insect pests of potato. To better understand how mineral oil affects potato pests, we performed a series of experiments testing the effects of oil on mortality, behavior, and development of potato aphids, Macrosiphum euphorbiae (Thomas) (Hemiptera: Aphididae), green peach aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), and Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae). All three species showed negative behavioral responses to oil-treated potato foliage. Oil treatment also increased aphid mortality. Colorado potato beetle mortality was not affected, but developing on oil-treated potato plants resulted in prolonged development and smaller adults. Additionally, oil acted synergistically with the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae); Colorado potato beetle larvae were killed more rapidly when sprayed with both products compared with when sprayed with B. bassiana alone. Based on these results, mineral oil has the potential for expanded use in potato IPM programs.

Published on

Wetzel WC, Aflitto NC, Thaler JS. 2018. Ecology. 99(10):2338-2347. doi: 10.1002/ecy.2472.

A growing number of studies have manipulated intraspecific plant diversity and found dramatic changes in the densities of associated insect herbivores and their predators. While these studies have been essential for quantifying the net ecological consequences of intraspecific plant diversity, they have been less effective at uncovering the ways in which plant diversity alters trophic interactions within arthropod communities. We manipulated intraspecific plant diversity and predation risk in the field in a factorial design to reveal how a mixture of plant genotypes changes the response of an herbivorous beetle (Leptinotarsa decemlineata) to a common stink bug predator (Podisus maculiventris). We repeated the manipulations twice across the ontogeny of the beetle to examine how the effects of diversity on the predator-prey interaction differ between larval and adult stages. We found that intraspecific plant diversity, mixtures of susceptible and resistant varieties of potato (Solanum tuberosum), reduced larval survival by 20% and adult oviposition by 34%, which surprisingly put survival and oviposition lower in the mixed-genotype plots than in the resistant monocultures. Moreover, we found that predation risk reduced larval survival 25% and 11% in resistant and susceptible monocultures, respectively, but had no effect in the mixture. This result indicated that our genotypic mixing treatment interacted nonadditively with predation risk such that plant diversity altered the predator-prey interaction by changing the responses of the beetles to their stink bug predators. In addition, even though predation risk reduced larval survival, it increased adult overwintering survival by 9%, independently of plant treatment, suggesting that these interactions change through ontogeny. A key implication of our study is that plant diversity influences arthropod communities not only by changing resource quality, as past studies have suggested, but also by changing interactions between species within the arthropod community.

Published on

Wraight SP, Ramos ME. 2017. J Invertebr Pathol. 144:47-57. doi: 10.1016/j.jip.2017.01.007.

Studies were undertaken to further characterize the previously identified synergistic activity of Bacillus thuringiensis- and Beauveria bassiana-based biopesticides against Colorado potato beetle (CPB). A flowable concentrate of B. thuringiensis morrisoni strain tenebrionis (Bt) (Novodor® FC) and a wettable powder of B. bassiana strain GHA (Bb) (Mycotrol® 22WP) were applied against CPB larval populations infesting potato in field plots. Novodor FC and an oil-dispersion formulation of Bb (Mycotrol ES) were applied against second-instar CPB larvae on potted potato plants in greenhouse tests under low relative humidity (RH), variable-temperature conditions. Each pathogen was applied alone and in combination (tank-mixed) with the other pathogen. In the field tests, each biopesticide was also combined with the spray-carrier (formulation without active ingredient) of the other pathogen. Results from the greenhouse tests showed that under warm, dry conditions, low activity of Mycotrol was counterbalanced by high activity of the Novodor, and under cool, somewhat more humid conditions, low Novodor activity was balanced by high activity of Mycotrol, with the result being a constant level of synergism (CPB mortality ca. 20 percentage points higher than predicted by independent action). Similar levels of synergism were observed under the markedly different conditions of the field and greenhouse environments, and the synergism was confirmed as arising from interaction of the two microbes, as the Bt spray carrier had no significant effect on efficacy of the Mycotrol product and the Bb spray carrier had no effect on the efficacy of Novodor. The great capacity of these two control agents to act in concert to control CPB is well documented (the fast-acting, toxic Bt acting to protect potato crops from defoliation and the slow-acting Bb reducing survival to the adult stage). These finding further underscore the strong complementary action of these agents applied jointly against CPB.

Published on

Gabaston J, El-Khawand T, Waffo-Teguo P, et al. Journal of Pest Science. 2018;91(2):897-906. doi: 10.1007/s10340-018-0956-2.

Stilbenes are phenolic compounds which are produced in large amounts in vine and are involved in plant defence as phytoalexins. Oligomeric forms have recently proven to be the most active compounds against a wide range of parasites such as fungi, bacteria or algae. The aim of this study was to investigate the activity of a grapevine root extract which is a stilbene oligomer pool against Leptinotarsa decemlineata, a major pest of Solanaceae crops. Analysis by UHPLC-DAD-MS of the stilbene-enriched extract obtained from grapevine root (Riparia Gloire de Montpellier rootstock) highlighted twelve stilbenes at 25% (w/w). The major stilbenes found in root extract were isolated such as the tetramers vitisin B, vitisin A and hopeaphenol; the dimers ampelopsin A and E-ε-viniferin and the monomer E-resveratrol. The insecticidal effects of this extract as well as the main compounds were investigated against L. decemlineata larvae. The extract caused chronic toxicity, inhibited larval development and, to a lesser extent, inhibited food intake. The high concentrations of vitisin A and vitisin B in grapevine root contributed to this effect as they are the most toxic compounds. Outdoor pot experiments revealed the efficacy of stilbene-enriched extract with high mortality of L. decemlineata and protection of potato plants. The extract also revealed an absence of toxicity against non-targeted organisms such as earthworms (Eisenia fetida). Thus, these results strongly suggest that grapevine roots are a promising source of bioactive stilbenes for the development of natural insecticides.

Published on

Kryukov V, Yaroslavtseva O, Tyurin M, et al. J Invertebr Pathol. 2017;149:1-7. doi: 10.1016/j.jip.2017.07.001.

Thirty-four isolates of Metarhizium spp. from Russian collections were genotyped using 5′ EF-1α gene sequence analysis. Four species were identified, of which M. robertsii and M. brunneum were the most frequent, whereas M. anisopliae and M. pemphigum were sporadic. Radial growth studies in the temperature range of 10-40°C revealed that growth at high temperatures (35-37.5°C) was inherent for M. robertsii isolates but not for M. brunneum isolates. In contrast, M. brunneum isolates were more active at cold temperatures (10°C) compared to M. robertsii. Virulence was evaluated against larvae of the Colorado potato beetle (CPB), Leptinotarsa decemlineata Say, under two regimes: humid (21°C, 80% relative humidity (RH)) and arid (31°C, 55% RH). M. brunneum isolates were less virulent compared to M. robertsii under both regimes. M. robertsii activity did not differ under the two regimes, but M. brunneum was less virulent under the arid regime compared to the humid one. A field experiment under natural conditions (steppe zone of Western Siberia) with daily ranges of 10-43°C and 13-98% RH showed that M. robertsii was significantly more active than M. brunneum against CPB larvae.

Published on

Ahmed HAA, Onarıcı S, Bakhsh A, et al. Plant Biotechnology Reports. 2017;11(5):315-329. doi: 10.1007/s11816-017-0453-8.

The expression of insecticidal genes must be induced at appropriate time and in sufficient amount to confer protection against targeted pests. However, the increased scientific reports of resistance development in insect pest against insecticidal delta-endotoxins, produced by Bacillus thuringiensis, provide impetus for the development of alternative insect management strategies. The present study was conducted to investigate the importance of targeted expression of a hybrid insecticidal gene (SN19) in potatoes. For this purpose, two plant expression vectors were constructed by cloning hybrid SN19 gene (cry1Ba-domain I-III and cry1Ia-domain II) under the control of a wound-inducible promoter isolated from Asparagus officinalis (AoPR1) and CaMV 35S promoter, and were transferred to Agrobacterium tumefaciens strain EHA 105. Four potato genotypes (Marabel, Innovator, Tokat 10/1 and Tokat 6/24) were transformed with EHA 105 strain harboring pTF101.1 35S-SN19 and pTF101.1 AoPR1-SN19 constructs. Phosphinothricin (PPT) was used at concentration of 1 mg/l for selection of primary transformants. PCR results showed the presence of both introduced SN19 and bar genes in 43 plants out of total 154 putative transgenics. Expression of SN19 protein in primary transformants was confirmed by Western blot assays. The mechanical wounding of transgenic plants exhibited more accumulated levels of SN19 proteins during post wounding period. Leaf biotoxicity assays with Colorado potato beetle (Coleoptera) and tomato leafminer (Lepidoptera) exhibited 100% mortality of the pests in primary transformants. Based on our mortality results with both constructs, we concluded that the potato transgenic lines exhibited targeted expression of insecticidal gene under the control of AoPR1 promoter upon insect wounding with eliminated toxicity of Cry protein and hence can be further used effectively in potato breeding programme.

Published on

Clements J, Schoville S, Peterson N, Huseth AS, Que L, Groves RL. Pestic Biochem Physiol. 2017;135:35-40. doi: 10.1016/j.pestbp.2016.07.001.

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a major agricultural pest of potatoes in the Central Sands production region of Wisconsin. Previous studies have shown that populations of L. decemlineata have become resistant to many classes of insecticides, including the neonicotinoid insecticide, imidacloprid. Furthermore, L. decemlineata has multiple mechanisms of resistance to deal with a pesticide insult, including enhanced metabolic detoxification by cytochrome p450s and glutathione S-transferases. With recent advances in the transcriptomic analysis of imidacloprid susceptible and resistant L. decemlineata populations, it is possible to investigate the role of candidate genes involved in imidacloprid resistance. A recently annotated transcriptome analysis of L. decemlineata was obtained from select populations of L. decemlineata collected in the Central Sands potato production region, which revealed a subset of mRNA transcripts constitutively up-regulated in resistant populations. We hypothesize that a portion of the up-regulated transcripts encoding for genes within the resistant populations also encode for pesticide resistance and can be suppressed to re-establish a susceptible phenotype. In this study, a discrete set of three up-regulated targets were selected for RNA interference experiments using a resistant L. decemlineata population. Following the successful suppression of transcripts encoding for a cytochrome p450, a cuticular protein, and a glutathione synthetase protein in a select L. decemlineata population, we observed reductions in measured resistance to imidacloprid that strongly suggest these genes control essential steps in imidacloprid metabolism in these field populations.

Published on

Rainio MJ, Margus A, Lehmann P, Helander M, Lindström L. Comparative Biochemistry and Physiology C, Toxicology & Pharmacology. 2019;215:47-55. doi: 10.1016/j.cbpc.2018.09.005.

Glyphosate is the globally most used herbicide against a wide range of weeds. Glyphosate has been considered safe to animals as it mainly targets physiological pathways in plants. However, recent toxicological studies have revealed that glyphosate can cause various toxic effects also on animals. In this study, we investigated the direct toxic effects of a glyphosate-based herbicide (GBH, Roundup® Bio) on (1) survival and (2) oxidative status of a non-target herbivore by using Colorado potato beetles (Leptinotarsa decemlineata), originating from Poland and USA, as model species. Larvae were randomly divided into three groups: (1) high concentration (100% Roundup Bio, 360 g/l), (2) low concentration (1.5% Roundup Bio) and (3) control group (water). Larvae were exposed to Roundup for different time periods: 2 h, 24 h, 48 h, 72 h and 96 h. Larval survival decreased in the group treated with high concentration of GBH compared to controls, whereas the low concentration group did not differ from the control group. GBH treatment had no association with oxidative status biomarkers (i.e. catalase, superoxide dismutase, glutathione-S-transferase, glutathione and glutathione related enzymes), but increased lipid hydroperoxide levels after 2 h exposure, suggesting increased oxidative damage soon after the exposure. Larvae of different origin also differed in their oxidative status, indicating population-dependent differences in antioxidant defence system. Environmentally relevant concentrations of GBH are not likely to affect larval survival, but high concentrations can reduce survival and increase oxidative damage of non-target herbivores. Also, populations of different origin and pesticide usage history can differ in their tolerance to GBH.

Published on

Yaroslavtseva ON, Dubovskiy IM, Khodyrev VP, Duisembekov BA, Kryukov VY, Glupov VV. J Insect Physiol. 2017;96:14-20. doi: 10.1016/j.jinsphys.2016.10.004.

The synergistic effect between the entomopathogenic fungus Metarhizium robertsii and a sublethal dose of the bacterium Bacillus thuringiensis ssp. morrisoni var. tenebrionis was studied in terms of immune defense reactions and detoxification system activity of the Colorado potato beetle, Leptinotarsa decemlineata, fourth instar larvae. Bacterial infection led to more rapid germination of fungal conidia on integuments. We found a significant decrease of cellular immunity parameters, including total hemocyte count and encapsulation response, under the influence of bacteria. Phenoloxidase activity in integuments was increased under bacteriosis, mycosis and combined infection compared to controls. However, phenoloxidase activity in the hemolymph was enhanced under bacteriosis alone, and it was decreased under combined infection. Activation of both nonspecific esterases and glutathione-S-transferases in the hemolymph was shown at the first day of mycosis and third day of bacteriosis. However, inhibition of detoxification enzymes was detected under combined infection. The suppression of cellular immunity and detoxification reactions in Colorado potato beetle larvae with a sublethal dose of bacteria is discussed as a reason for synergy between B. thuringiensis and M. robertsii.

Published on

Hussain T, Aksoy E, Çalișkan ME, Bakhsh A. Transgenic Res. 2019;28(1):151-164. doi: 10.1007/s11248-018-0109-7.

Most of the commercialized insect resistant transgenic crops express cry gene(s) isolated from Bacillus thuringiensis; however, intensive cultivation of Bt crops over almost two decades has been questioned regarding its sustainability and durability in pest management. The present study focused on silencing of highly specific molting-associated Ecdysone receptor (EcR) gene of Colorado potato beetle (CPB) using RNA interference (RNAi) approach. The partial cDNA of EcR gene of CPB was amplified using specific primers in sense and anti-sense orientations, and cloned in pRNAi-GG vector flanked by an intronic sequence (pdk). Leaf and internodal explants of Agria and Lady Olympia potato cultivars were infected with Agrobacterium strain LBA4404 harboring constructs under the control of CaMV 35S promoter. Standard molecular analysis of primary transformants showed proper integration of T-DNA in plant genome. The transgenic plants of both cultivars were evaluated for their efficacy against first, second and third instar CPB larvae. The leaf biotoxicity assays revealed 15-80% of CPB mortality. A significantly lower fold-change (0.87-4.14×) in larval weight was observed in insects fed on transgenic plants compared to the ones fed on control plants (1.87-6.53×). Furthermore, CPB larvae fed on transgenic plants exhibited reduced EcR transcripts, indicating the functionality of dsRNA EcR in silencing EcR gene expression. This study is an excellent example of the integration of an alternative, effective and reliable method to cope with potato insect pests that incur significant losses to potato production in the world.