Characterization of a Costa Rican granulovirus strain highly pathogenic against its indigenous hosts,Phthorimaea operculella and Tecia solanivora

A granulovirus isolate collected from diseased Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) larvae in Costa Rican potato [Solanum tuberosum L. (Solanaceae)] crops was characterized at the molecular and biological level. Restriction endonuclease analysis identified this isolate as a novel P. operculella granulovirus (PhopGV) (Baculoviridae: Betabaculovirus) strain and was designated as PhopGV‐CR1. In addition, PCR amplification of four specific variable genomic regions yielded multiple amplicons for two open reading frames, revealing the presence of different genotypic variants within the virus population. Biologically, PhopGV‐CR1 was highly pathogenic for its two indigenous hosts, although significant differences of up to four‐fold were detected against P. operculella [LD₅₀ = 17.9 occlusion bodies (OBs) mm^?2] and Tecia solanivora (Povolny) (Lepidoptera: Gelechiidae) (LD₅₀ = 69.1 OBs mm^?2). The two P. operculella colonies, from Costa Rica and France, were equally susceptible to PhopGV‐CR1. Serial passage of PhopGV‐CR1 over four generations in T. solanivora increased its pathogenicity by five‐fold in three generations, suggesting an ongoing adaptation to its alternate host.     

Responses of different geographic populations of two potato tuber moth species to genetic variants of Phthorimaea operculella granulovirus

Phthorimaea operculella granulovirus (PhopGV) belongs to the genus Betabaculovirus of the arthropod‐infecting Baculoviridae. PhopGV is able to infect several gelechiid species. Among them are the potato tuber moths Phthorimaea operculella Zeller and Tecia solanivora Povolny (both Lepidoptera: Gelechiidae). In various South American countries, PhopGV‐based biopesticides are used to control either P. operculella or T. solanivora. Many trials have indicated that a particular viral isolate can exhibit very distinct pathogenicity when infecting different host species or different populations of one host species. In this study, we compared host–pathogen interactions using various PhopGV isolates and various populations of P. operculella and T. solanivora. Virus isolates from P. operculella were more pathogenic against their original host species than against T. solanivora. A PhopGV isolated from T. solanivora was less efficient against P. operculella. In addition, virus isolates differed in pathogenicity toward their hosts (i.e., lethal concentrations of isolates ranged from low to high). Unexpectedly, we also found that host populations of one species from distinct geographic origins did not differ significantly in susceptibility to the same PhopGV isolate. This was the case for both host species and for five PhopGV isolates. Comparative restriction fragment length polymorphism (RFLP) analyses of 11 isolates including those used in bio‐assays indicated three main regions of variation in the genome of PhopGV, corresponding to the regions of open reading frame PhopGV046, gene PhopGV129 (egt), and repeat 9 (located between open reading frames PhopGV083 and PhopGV084). Comparison of the nucleotide sequences of the insertions/deletions present in these regions were carried out for the most variable isolate, JLZ9f. The results are discussed in the context of the production and use of PhopGV as a biological agent against these two pest species.     

Potential of a granulovirus isolate to control <Emphasis Type="Italic">Phthorimaea operculella</Emphasis> (Lepidoptera: Gelechiidae)

In this study a Brazilian granulovirus strain, PhopGV, isolated from the potato tuber moth (PTM) Phthorimaea operculella, was investigated regarding its potential for biological control and in vivo production. The relationship between mortality of P. operculella larvae and virus concentration was determined at different temperatures on potato tubers and susceptibility of P. operculella to PhopGV was also determined on potato leaves. Virulence of PhopGV to P. operculella was not affected by temperatures from 18 to 30°C. The median lethal concentration (LC₅₀) of larvae fed on potato foliage treated with PhopGV was not higher than that verified with larvae fed on treated tubers. Optimal conditions for production of virus-infected larvae were obtained by using the virus suspensions of 41 × 10⁵, 6.3 × 10⁵ and 62 × 10⁵ OBs ml⁻¹ at 18, 24 and 30°C, which resulted in 32.0, 31.4 and 34.8% of infected larvae collected, respectively. The maximum percentage of infected larvae recovered from tubers was not affected by temperature. However, time for production of virus-infected larvae was longer at 18°C and shorter at 30°C. Persistence of PhopGV was determined on stored tubers and we observed that the virus remained effective for at least two months, causing up to 84.2% mortality of P. operculella at 1 × 10⁷ OBs ml⁻¹. The pathogen was also highly virulent to tomato pinworm, Tuta absoluta, inflicting high percentage of mortality, delaying larval growth and inhibiting pupation. This Brazilian PhopGV strain has potential to control PTM larvae on potato tubers at a broad range of temperature and can be produced in vivo using virus-treated tubers.     

The potential of novel African isolates of Phthorimaea operculella granulovirus for the control of Tuta absoluta

Phthorimaea operculella granulovirus (PhopGV) is infectious for larvae of different Gelechiidae insect species, including Tuta absoluta and Phthorimaea operculella. As these are major economic pests in North and sub‐Saharan Africa as well as in the Mediterranean area, the development of locally suitable biocontrol agents is essential. We have studied five isolates of PhopGV from Tunisia (Tns16, Tu1.11 and Tu2.11), Kenya (Ken13) and Yemen (Ym14) for their biological activity and the sequence polymorphism of their granulin and ecdysteroid UDP‐glucosyltransferase (egt) genes and allocated the isolates to two different egt types. Infection experiments with neonate larvae of T. absoluta and P. operculella demonstrated their pathogenicity to both host species. The isolate PhopGV Tu1.11 was the most virulent one for T. absoluta but had a relatively low infectivity to two P. operculella populations originating from Italy and Tunisia.     

Pheromone-mediated communication disruption in Guatemalan potato moth, Tecia solanivora

Chemical analysis of pheromone gland extracts followed by behavioural studies in the wind tunnel and by field trapping tests show that the sex pheromone of the Guatemalan potato moth, Tecia (Scrobipalpopsis) solanivora Povolny (Lepidoptera: Gelechiidae), is a blend of (E)‐3‐dodecenyl acetate, (Z)‐3‐dodecenyl acetate, and dodecyl acetate. A 100 : 1 : 20 blend of these compounds, formulated at 1000 µg on rubber septa, captured more males than the main compound alone. This lure was species‐specific and did not capture the potato tubermoth, Phthorimaea operculella. A potato field was treated with a blend of these three compounds at a rate of 28 g ha^?1. Male T. solanivora attraction to synthetic pheromone traps was almost completely suppressed for 2 months, demonstrating the potential use of pheromones for control of this economically important insect pest of potato in Central and Southern America.     

Developing a biocontrol strategy to protect stored potato tubers from infestation with potato tuber moth species in the Andean region

Heavy infestations of stored potato (Solanum tuberosum L.) tubers by the two potato tuber moth species Symmetrischema tangolias (Gyen) and Tecia solanivora (Povolny) frequently occur in Andean potato‐growing regions of Ecuador. The aim of the study was to develop a biological control strategy for both species using powder formulations made of inert substances, Phthorimaea operculella (Zeller) granulovirus (PhopGV) and Bacillus thuringiensis Berliner subsp. kurstaki (Btk). The LC₅₀ of PhopGV on T. solanivora was 0.33 LE/L, and Btk caused 82.7% mortality at a concentration of 100 g/L in bioassays. The efficacy of talcum, kaolin, calcium carbonate and sand ranged between 76.2% and 98.7%. Calcium carbonate was highly effective to control both species; however, its efficacy was affected by the relative humidity and dropped to 55.4% at relative humidity of 100%. PhopGV at concentrations of five larvae equivalents (LE) per kg kaolin and Btk at a concentration of 60 g Btk/kg talcum caused 95.7% and 88.1% mortality of T. solanivora, respectively. In storage experiments, the efficacy of calcium carbonate alone and in combination with PhopGV (20 LE/kg) and Btk (15 g/kg) caused 95.0–99.8% mortality of T. solanivora in all treatments and reduced infestation on potato tubers by 83.6%–91.0%. In the case of S. tangolias, Btk significantly increased mortality to 96.5% compared with calcium carbonate alone and reduced tuber infestation by 83.4%. Storage of potato tubers in thin layers enhanced the efficacy of the calcium carbonate treatment compared with storage in bags. It was concluded that calcium carbonate alone seems to be appropriate for the control of T. solanivora, and an addition of 15 g Btk/kg would improve the control of S. tangolias. It is suggested to test these new formulations under on‐farm storage conditions.     

Histopathology and effect on development of the PhopGV on larvae of the potato tubermoth, Phthorimaea operculella (Lepidoptera: Gelechiidae)

Larvae of the potato tubermoth (PTM), Phthorimaea operculella, feed on potato plants and tubers and are a major pest in the tropics and subtropics worldwide, causing up to 100% damage. The PTM granulovirus (PhopGV) provides significant potato protection, but little is known about its effect on larval development or its histopathology. Here we show that only 10% of larvae exited from PhopGV-treated tubers (1.4 × 10⁸ granule/ml), lagging significantly behind controls, and most of these died by 72 h after emergence. Histopathology studies showed the fat body and epidermis were the principal tissues infected. PhopGV morphogenesis was similar to other GVs, the exception being small vesicles between mature granules.     

Establishment of Beauveria bassiana as a fungal endophyte in potato plants and its virulence against potato tuber moth,Phthorimaea operculella (Lepidoptera: Gelechiidae)

The potato tuber moth, Phthorimaea operculella, is the most damaging potato pest in the world and is difficult to control as the larvae are internal feeders in the foliage and tubers. Entomopathogenic fungi that colonize plants as endophytes have lethal and sublethal pathological effects on insect pests. We show that Beauveria bassiana colonizes the aerial parts of potato plants endophytically after inoculation through soil drenching. Endophytic B. bassiana persisted in potato foliage for more than 50 days postinoculation. Bioassays indicated that foliage of B. bassiana-inoculated potato plants were pathogenic against larvae of P. operculella. Sublethal experiments indicated that B. bassiana negatively affected the growth, development, and reproduction of P. operculella. Development experiments showed that the weight of P. operculella pupae reared on B. bassiana-colonized potato plants (4.25 mg) was significantly less than that of those reared on uninoculated control plants (8.89 mg). Compared with newly eclosed larvae fed on control plants, those fed on B. bassiana-inoculated plants had significantly lower survivorship, with only 17.8% developing to the adult stage. Oviposition of P. operculella females reared on B. bassiana endophytically colonized plants was significantly lower (35 eggs/female) than of those reared on uninoculated plants (115 eggs/female). This study demonstrates that endophytic B. bassiana can be a potential biological control agent for the control and management of P. operculella. Comparing pupal weights of P. operculella reared on potato plants inoculated with the B. bassiana strain GZGY-1-3 and on untreated control plants, pupae from the control plants were significantly heavier than those from treated plants.     

Isolation and characterization of halotolerant Streptomyces radiopugnans from Antarctica soil

An actinomycete wild strain PM0626271 (= MTCC 5447), producing novel antibacterial compounds, was isolated from soil collected from Antarctica. The taxonomic status of the isolate was established by polyphasic approach. Scanning electron microscopy observations and the presence of LL‐Diaminopimelic acid in the cell wall hydrolysate confirmed the genus Streptomyces. Analysis of 16S rRNA gene sequence showed highest sequence similarity to Streptomyces radiopugnans (99%). The phylogenetic tree constructed using near complete 16S rRNA gene sequences of the isolate and closely related strains revealed that although the isolate fell within the S. radiopugnans gene subclade, it was allocated a different branch in the phylogenetic tree, separating it from the majority of the radiopugnans strains. Similar to type strain, S. radiopugnans R97^T, the Antarctica isolate displayed thermo tolerance as well as resistance to ⁶⁰Co gamma radiation, up to the dose of 15 kGy. However, media and salt tolerance studies revealed that, unlike the type strain, this isolate needed higher salinity for its growth. This is the first report of S. radiopugnans isolated from the Antarctica region. The GenBank/EMBL/DDBJ accession number for the 16S rRNA gene sequence of Streptomyces radiopugnans MTCC 5447 is JQ723477 .

Significance and Impact of the Study

The study presents the first report of isolation of Streptomyces radiopugnans from Antarctica. To date, there is only one publication regarding S. radiopugnans R97^T isolated from radiation‐polluted soil. Like the type strain, Antarctica isolate was thermotolerant and radiotolerant, but in addition, it required salts for growth and did not degrade phenol. We envisaged that metabolic pattern of the same species varies based on acclimatization in its native ecological habitat. Additionally, Antarctica isolate had produced novel antibacterial compounds (patent‐US2012/0156295). The study highlighted that least explored extreme regions like Antarctica are rich resources of novel microbial strains producing novel bioactive compounds.     

Granulovirus formulations efficiently protect stored and field potatoes from Phthorimaea operculella and Tecia solanivora in Costa Rica

The control efficiency of a Phthorimaea operculella granulovirus isolate from Costa Rica (PhopGV-CR1) against the concurrent insect pests P. operculella (Zeller) and Tecia solanivora (Povolny) (Lepidoptera: Gelechiidae) was evaluated. In warehouses, the best control efficiency was achieved with a powder formulate applied inside bags, which reduced injury over 70 % compared with the untreated controls. In the field, liquid and powder virus formulations significantly reduced injury between 56.2 and 81.7 % compared with the untreated controls, and were as efficient as chemical treatments. The efficiency of formulations stored at ?20 °C for six months (liquid) or at ambient temperature for three months (powder) was maintained, but higher temperatures and/or longer exposure times resulted in loss of pathogenicity. The data presented here favor the inclusion of granulovirus formulations of PhopGV-CR1 in Integrated Pest Management programs against tuberworms in Costa Rica and give clues on storage conditions for the growers in this country.     

Tuber production,dormancy and resistance against Phthorimaea operculella (Zeller) in wild potato species

The diversification of resistant potato varieties at a landscape level could slow adaptation by Phthorimaea operculella to potato resistance and promote sustainable crop protection. In this study, we assessed wild potato species as novel sources of foliage and tuber resistance against P. operculella. Tuber resistance was quantified for 136 and foliage resistance for 54 potato accessions representing 14 and nine potato species, respectively. Several accessions were highly resistant to moth damage in tubers and/or foliage. In particular, Solanum chiquidenum and Solanum sandemanii were highly resistant to damage in tubers. Several accessions of Solanum multiinterruptum and a small number of accessions of Solanum bukasovii, Solanum berthaultii, Solanum sparsipilum and Solanum wittmackii also had highly resistant tubers. Larval survival on foliage of S. bukasovii and S. chiquidenum was generally low. New resistance sources are listed, and insect performance on the plants is described with possible resistance mechanisms. The study also examined potential trade‐offs associated with resistance. Tuber resistance was negatively correlated with the number and weight of tubers produced per plant, but positively correlated with the length of dormancy across accessions, indicating that, although long dormancy is not a prerequisite for resistance, species and accessions with extended dormancy will have more resistant tubers. Tuber and foliage resistance were generally positively correlated across all accessions; however, among accessions from within a potato species, there were negative (S. berthaultii), positive (S. chiquidenum) and non‐significant (S. bukasovii) relations. These results indicate that, besides identifying novel resistance sources, an improved understanding of the mechanisms and inherent trade‐offs associated with tuber and foliage resistance will improve the efficiency of potato breeding programmes aimed at enhancing resistance against P. operculella.     

The effect of soil depth and exposure to winter conditions on survival of the potato tuberworm,Phthorimaea operculella

The potato tuberworm, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), is an important pest of solanaceous crops including potato [Solanum tuberosum L. (Solanaceae)]. Recent evidence of survival of the pest in the Columbia Basin of Oregon and Washington, USA, is surprising as potato tuberworm is most commonly a pest in tropical and subtropical regions. Potato tuberworm was studied in a manipulative experiment to determine how stage (egg, larva, and pupa) and soil depth affected the potential for winter survival. In early January 2007, eggs, tubers infested with larvae, and pupae were placed in the soil at 6, 10, and 20 cm depths, or left on the soil surface. Each potato tuberworm life stage was sampled at 7–17‐day intervals for 90 days and survival was estimated at each time period. Eggs survived up to 54 days with the greatest survival observed at 6‐cm soil depth and the lowest survival on the soil surface. However, egg survival was significantly reduced after 1 month of exposure to winter conditions. Larvae were able to survive up to 30 days with the greatest survival observed at 20‐cm soil depth. Tubers at the surface and buried at 6 cm were frozen; thus, no larval survival was recorded. The pupal stage showed a greater tolerance to winter conditions than the egg or larval stages, surviving up to 91 days of exposure. These results suggest that the pupal stage is probably the stage most likely to survive winter conditions in the northwestern USA.     

Metastasis‐specific patterns of response and progression with anti‐PD‐1 treatment in metastatic melanoma

This study evaluated patterns of response as discerned by comprehensive metastasis‐specific analysis in metastatic melanoma patients receiving anti‐PD‐1 antibodies. Bi‐dimensional measurements of every metastasis in patients enrolled in the KEYNOTE‐001 trial at a single institution were obtained at baseline and throughout treatment. Twenty‐seven evaluable patients had 399 baseline metastases measurable on CT imaging. Complete response (CR) which occurred in 52.6% of metastases was smaller (mean 223 mm² versus 760 mm², p < .01) and occurred more frequently in the lungs (65% versus 39.4%, p < .01). Response was heterogenous (new/progressing metastases alongside CR metastases) at first assessment in 4/14 patients with objective response (OR) as opposed to 7/13 patients with non‐OR. CR of individual metastases is common and influenced by site and size. Most patients with OR demonstrate homogenous regression in all metastases at the first assessment. In contrast, patients with early heterogeneity had a poor outcome.     

Forest bolsters bird abundance,pest control and coffee yield

Efforts to maximise crop yields are fuelling agricultural intensification, exacerbating the biodiversity crisis. Low‐intensity agricultural practices, however, may not sacrifice yields if they support biodiversity‐driven ecosystem services. We quantified the value native predators provide to farmers by consuming coffee's most damaging insect pest, the coffee berry borer beetle (Hypothenemus hampei). Our experiments in Costa Rica showed birds reduced infestation by ~ 50%, bats played a marginal role, and farmland forest cover increased pest removal. We identified borer‐consuming bird species by assaying faeces for borer DNA and found higher borer‐predator abundances on more forested plantations. Our coarse estimate is that forest patches doubled pest control over 230 km² by providing habitat for ~ 55 000 borer‐consuming birds. These pest‐control services prevented US$75–US$310 ha‐year⁻¹ in damage, a benefit per plantation on par with the average annual income of a Costa Rican citizen. Retaining forest and accounting for pest control demonstrates a win–win for biodiversity and coffee farmers.     

Insecticidal Activity of the Granulosis Virus in Combination with Neem Products and Talc Powder Against the Potato Tuberworm Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)

The potato tuberworm Phthorimaea operculella (Zeller) is an important agricultural pest that causes significant economic losses to potato growers worldwide. The addition of an effective method of biological control for the potato tuberworm is greatly needed, and is currently unavailable in Brazil. The granulosis virus (Baculoviridae) is a promising biological control agent to protect post-harvest potatoes and in storage from the potato tuberworm. However, the control measure must be economically feasible. Liquid suspensions of a granulosis virus applied alone or in mixture with two commercial neem oil-based products (DalNeem? and NeemAzal?), and a dry powder formulation of viral granules were evaluated for control of potato tuberworm larvae by treating potato tubers under laboratory conditions. High larval mortality (86.7%) was achieved when DalNeem and virus were applied together at 4?mg of azadirachtin/L and 10⁴ occlusion bodies (OBs)/mL, respectively. This combination resulted in ??50% efficacy in relation to their counterparts alone. Conversely, NeemAzal did not enhance virus effectiveness against larvae of the potato tuberworm. The talc-based virus formulation was used for dusting seed tubers at different concentrations and resulted in 100% larval mortality at 5?×?10⁸ OBs/g. Formulated and unformulated virus provided 50% mortality at 166 OBs/g and at 5.0?×?10⁵ OBs/mL, respectively. As a result, talc-based virus formulation had a better control efficiency on potato tuberworm than the aqueous virus suspension. The granulosis virus combined with DalNeem at low rates or formulated with talc powder is a viable option to control the potato tuberworm under storage conditions.     

Effect of talc-formulated entomopathogenic fungus Beauveria against leaffolder (Cnaphalocrosis medinalis) in rice

Thirteen Beauveria strains were isolated from the soil and infected insects. Among the various isolates, B₂ isolate (Arachalore) showed a higher percentage of mortality against C. medinalis (73.3%) under in vitro conditions. Conidial concentration of 1 × 10⁸ of the B2 strain registered maximum mortality of 76.7%. The least LT₅₀ value of 4.4 days was registered in B2 isolate with the spore concentration of 1 × 10⁸ and the LC₅₀ value was 3.4 × 10⁴. Beauveria strains altered the feeding behavior of C. medinalis, reduced the pupal weight, prolonged the pupation period, malformed the pupa and adult under in vitro. The efficacy of the talc-based bioformulation of Beauveria (B2) strain was tested as seed treatment + seedling dip + soil application + foliar spray against rice leaffolder under in vitro and greenhouse conditions. The percentage damage was significantly less (5.5) in B2 as compared to untreated healthy control (25.8). In addition, the same treatment increased the activities of defense-related enzymes, namely peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, chitinase, and phenolics in rice.     

Molecular and Morphological characterization of multiple nucleopolyhedrovirus from Mexico and their insecticidal activity against Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), is the most important pest of maize in many countries. Entomopathogenic viruses mainly Baculoviruses family are excellent biological control agents and therefore a viable alternative for managing this pest. The aim of this study was to determine the biological activity of eight native nucleopolyhedrovirus (NPVs) against FAW larvae. Additionally, two of the most virulent isolates (SfCH32 and SfCH15) were characterized biologically by bioassays to estimate their median lethal dose (LD₅₀) and median lethal time (LT₅₀), morphologically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and molecularly by restriction enzymes. Three (SfCH15, SfCH18 and SfCH32) of the eight tested native nucleopolyhedrovirus isolates caused mortalities ˃98% at 168-hr post-inoculation (hpi) with a dose of 9.2 × 10⁴ OBs/larva. SfCH15 and SfCH32 isolates showed occlusion bodies (OBs) of irregular shape and size (1.02–2.24 μm). The SfCH15 and SfCH32 isolates showed similar median lethal dose (5.6 × 10²–6.4 × 10² OBs/larva). The lowest median lethal time (114.5 hpi) was observed with the SfCH15 isolate at the highest concentration (2.5 × 10⁶ OBs/larva). The DNA restriction profiles for SfCH15 and SfCH32 were different, with their genome size being ~128,000 bp and 132,000 bp, respectively. SfCH15 and SfCH32 isolates showed similar morphological characteristics and the highest virulence against fall armyworm. This study showed that native isolates were highly virulent against S. frugiperda larvae, being similar to other reported strains; however, field studies are required to confirm their insecticidal effect.     

Spiroplasma species in the Costa Rican highlands: implications for biogeography and biodiversity

More than 1,000 Spiroplasma isolates have been obtained from horse flies and deer flies (Diptera:Tabanidae) in the United States and Canada. However, the spiroplasma biota of Central America is poorly known. In August of 1995 and 1998, 13 isolates were obtained in 14 attempts from horse flies of a single species, Poeciloderas quadripunctatus, taken in the Costa Rican highlands (1,100–2,000 m). The majority of the “isolates” proved to be mixtures of two or more Spiroplasma species, but after filter cloning, single strains emerged that were designated as representatives of the 13 accessions. Six distinct spiroplasma serogroups were identified from these isolations. Three of the strains are putative new species with no serological relationship to any other Spiroplasma species. A fourth strain is a putative new species that may be distantly related to S. helicoides, a southeastern U.S. species. These four strains are accorded herein status as representatives of new serogroups: strain BARC 4886 (group XXXV); strain BARC 4900 (group XXXVI); strain BARC 4908 (group XXXVII); and GSU5450 (group XXXVIII). A fifth Spiroplasma species was very closely related to S. lineolae, known previously only from the Georgia (U.S.) coast. The sixth was most closely related to subgroup VIII-3, known from Texas and the southeastern U.S. Discovery of six spiroplasma species in only 13 attempted isolations reflects diversity seldom equaled in southeast Georgia, and never elsewhere in the U.S. These results are consistent with a hypothesis that spiroplasma diversity increases from north (Nova Scotia) to south (Georgia and Costa Rica). The discovery of significant affinity between some spiroplasmas of the southeastern U.S. and the Costa Rican highlands was unexpected, but may reflect a climatically complex Pleistocene history.

Efficacy of entomopathogenic nematodes against potato tuber moth,Phthorimaea operculella (Lepidoptera: Gelechiidae) under laboratory conditions

The susceptibility of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) to native and commercial strains of entomopathogenic nematodes (EPNs) was studied under laboratory conditions. Native strains of EPNs were collected from northeastern Iran and characterised as Steinernema feltiae and Heterorhabditis bacteriophora (FUM 7) using classic methods as well as analysis of internal transcribed spacer (ITS) and D2/D3 sequences of 28S genes. Plate assays were performed to evaluate the efficiency of five EPN strains belonging to four species including Steinernema carpocapsae (commercial strain), S. feltiae, Steinernem glaseri and H. bacteriophora (FUM 7 and commercial strains). This initial assessment with 0, 75, 150, 250, 375 and 500 IJs/ml concentrations showed that S. carpocapsae and H. bacteriophora caused the highest mortality in both larval and prepupal stages of P. operculella, PTM. Thereafter, these three strains (i.e. S. carpocapsae, H. bacteriophora FUM 7 and the commercial strains) were selected for complementary assays to determine the effects of soil type (loamy, loamy–sandy and sandy) on the virulence of EPNs against the second (L2) and fourth instar (L4) larvae as well as prepupa. A soil column assay was conducted using 500 and 2000 IJs in 2-ml distilled water. Mortality in the L2 larvae was not affected by the EPN strain or soil type, while there was a significant interactive effect of nematode strains and soil type on larval mortality. The results also showed that EPN strains have higher efficiency in lighter soils and caused higher mortality on early larvae than that in loamy soil. In L4 larvae, mortality of PTM was significantly influenced by nematode strain and applied concentrations of infective juveniles. The larval mortality induced by S. carpocapsae was higher than those caused either by a commercial or the FUM 7 strain of H. bacteriophora. Prepupa were the most susceptible stage.     

Potential of betabaculoviruses to control the tomato leafminer Tuta absoluta (Meyrick)

The tomato leafminer Tuta absoluta (Meyrick 1917) (Lepidoptera:Gelechiidae) is a devastating pest, causing losses of up to 100%. An interesting tool for its control is the use of the insect specific viruses of Baculoviridae family. Despite its high potential, its use on T. absoluta larvae has been poorly studied. In this work, Colombian granuloviruses VG013 and VG003 isolated from T. absoluta and Tecia solanivora (Lepidoptera:Gelechiidae) larvae sampled in tomato and potato crops, respectively, were morphologically, biologically and molecularly characterized. Occlusion bodies showed ovoid shape containing one nucleocapsid. Restriction endonuclease analysis revealed a pattern similar to Phthorimaea operculella granulovirus and bioinformatics studies showed that both isolates are variants of that baculovirus specie. Similar mean lethal concentrations (LC₅₀) on T. absoluta larvae were estimated for both viruses, although VG013 exhibited shorter mean time to death than VG003. The latter reached a higher OBs yield in comparison with VG013. These results demonstrated an interesting potential of evaluated betabaculoviruses to control T. absoluta populations and pointed key features to its use under field conditions.