Larvicidal activities of limonoids from Turraea abyssinica (Meliaceae) on Tuta absoluta (Meyrick)

Preliminary screening of extracts of the leaves and stems of four Turraea plant species (Meliaceae) on second instar larvae of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) showed that the methanolic extract of Turraea abyssinica leaves possess good toxic potential with LD₅₀ of 270.7 ppm. Fractionation of this extract led to isolation of a new limonoid derivative, 12α‐diacetoxywalsuranolide (1) and three other known limonoids [1α,7α,12α‐triacetoxy‐4α‐carbomethoxy‐11β‐hydroxy‐14β,15β‐epoxyhavanensin (2), 11‐epi‐21‐hydroxytoonacilide (3), 11β,12α‐diacetoxycedrelone (4)]. The structures of the compounds were established by IR, UV, mass spectrometry and 1D/2D NMR analyses, and in the case of the known compounds, also by comparison with reported data. All the isolates were tested for their larvicidal activities at different dose range against second instar larvae of T. absoluta. They were found to be more active (with LD₅₀ < 7.0 ppm) compared to the reference compound azadirachtin (LD₅₀ value of 7.8 ppm).     

Biology and performance of two indigenous larval parasitoids on Tuta absoluta (Lepidoptera: Gelechiidae) in Sudan

Tuta absoluta is an alien invasive pest in Sudan. Since it was detected in the country, the pest continues to cause major tomato losses. Alarmed by its devastating nature and the speed of spread, tomato growers resorted to the indiscriminate use of broad-spectrum insecticides. Promising indigenous parasitoid(s) may contribute to suppression of this pest. The biology and performance of the native parasitoids, Bracon nigricans Szépligeti (Braconidae) and Dolichogenidea appellator (Telenga) (Braconidae), was therefore evaluated against different immature stages of T. absoluta under laboratory conditions. A significantly higher number of fourth instar larvae was accepted for oviposition by B. nigricans. Similarly, fourth instar larvae yielded a considerably higher number of parasitoid offspring compared to third instar larvae. The male ratio of B. nigricans offspring which emerged from both larval instars was high, 0.96 and 0.66 for third and fourth instar larvae of T. absoluta, respectively. There was, however, no significant difference in the number of males and females that emerged from fourth instar larvae. Conversely, the number of hosts killed by stinging behaviour or host feeding was significantly higher on third instar larvae. B. nigricans potential fecundity varied with the age of the wasp with the lowest fecundity on the day of eclosion. The performance of D. appellator in terms of the total number of offspring produced and female progeny was similar for second and third instar larvae of T. absoluta. The preimaginal developmental time for both parasitoid species did not vary with either host stage or sex of the parasitoid. B. nigricans adult longevity was similar for both sexes, while that of D. appellator significantly varied with females living longer than males. Prospects for conservative biological control of T. absoluta are discussed in the light of the results of this study.     

Variability of Lycopersicon hirsutum f. typicum and possible compounds involved in its resistance to Tuta absoluta

1 The resistance of Lycopersicon hirsutum f. typicum and L. esculentum to the leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) was investigated in two experiments. The first experiment assessed the resistance of L. hirsutum f. typicum (accession LA 1777) to T. absoluta, the second assessed the variability of the resistance among plants of this accession. 2 It was found that L. hirsutum f. typicum was resistant to the leafminer, which showed longer larval phase, higher larval mortality, smaller numbers of large mines and greater numbers of small mines/leaf than on L. esculentum. Seven plants of the accession LA 1777 showed lower number of small mines/leaf, but their results of larval mortality and length of larval and pupal phase were similar. Twenty-two peaks were observed in total ion chromatograms of L. hirsutum f. typicum hexane extracts of leaves subjected to a gas chromatographic-mass spectrometric analysis (CG-MS). However, the matches obtained between the peak spectra and the MS database were too low to justify even preliminary identification of the compounds.     

Host instar suitability and life-history parameters under different temperature regimes of Necremnus artynes on Tuta absoluta

Necremnus artynes is native to the Mediterranean region where it has been observed in greenhouses parasitising Tuta absoluta on tomato. In this study, we evaluated the suitability of the different instars of T. absoluta as hosts for N. artynes and the life-history traits of N. artynes at three different temperature regimes (20, 25 and 30°C) on third instar T. absoluta larvae infesting tomato. N. artynes females preferred third instar T. absoluta larvae for oviposition, whereas host-feeding was significantly higher on the second instar larvae. Duration of life stages was no different between sexes but was affected by temperature, being significantly reduced as temperature increased. Pre-imaginal survival also decreased with temperature and the percentage of females was ca. 70% under all temperature regimes. Adult longevity was 1.5-fold significantly greater at 25°C compared to 30°C with no differences between 20 and 25°C. Fecundity was estimated at 36.3±7.80, 51.8±10.65 and 52.1±10.03 eggs/female and host-feeding at 59.5±8.50, 71.6±12.07, 51.4±7.89 hosts/female at 20, 25 and 30°C, respectively, although these differences among temperatures were not significant. However, oviposition and feeding rate were significantly higher at 30 and 20°C, respectively. The estimated intrinsic rate of increase (r _m) was significantly higher as temperature increased from 20 to 30°C and it was greater than those reported for T. absoluta on tomato, indicating the potential of N. artynes to control this pest.     

Efficacy of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> (Berliner) in controlling the tomato borer, <Emphasis Type="Italic">Tuta absoluta</Emphasis> (Meyrick) (Lepidoptera: Gelechiidae)

The tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is considered to be one of the most devastating pests affecting tomato crops in South America, where crop losses range from 60 to 100%. After its detection in the Spanish tomato-growing area at the end of 2006, it spread quickly to other European and northern African countries. Currently, T. absoluta management in these countries is mainly based on chemical treatments. Nonetheless, special emphasis is being placed on implementing environmentally safe strategies. Commercial formulates based on Bacillus thuringiensis may be a good alternative, as they have been used to control other insect pests successfully. The laboratory, greenhouse, and open-field experiments presented in this work are evidence that B. thuringiensis is highly efficient in controlling T. absoluta. First instar larvae were the most susceptible, while susceptibility was lower in second and third instar larvae. Our results have shown that the impact of T. absoluta can be greatly reduced by spraying only B. thuringiensis-based formulates, with no need for chemical insecticides. Furthermore, the integration of this technology with other biological control methods focused on T. absoluta eggs, such as the use of mirid predators or parasitoids, could reduce the number of B. thuringiensis treatments and the use of chemicals, with the consequent reduction of residues on fruits.     

Towards using of new and safety material against tomato leafminer,Tuta absoluta (Mayrick)

New silica formulations offer expanded possibilities for use in horticultural crops. However, many crop pests are found on the leaf underside, and this is especially challenging when using silica because the substance must have direct contact with the insect to be effective. Silica a new and safety material was used against the second instar larvae of tomato leafminer, Tuta absoluta (Mayrick) alone and combined with other pesticides (chlorfenapyr, spinetoram and chlorantraniliprole). The results showed that when silica was used alone, the percents of mortalities were 51.7, 26.7 and 13.3%. The results showed also chlorantraniliprole was the most toxic compared with the other compounds. The per cents of mortalities were 90, 65 and 30% with the first, second and third concentrations, respectively. When silica was used in a combination with the tested pesticides, the mixture of silica and chlorfenapyr was the most toxic against the second instar larvae of T. absoluta, the percents of mortalities were 100, 76.7 and 60% with the first, second and third concentrations, respectively. The results recommended that silica was moderate toxic to the second instar larvae of T. absoluta when it used alone, so it can be used when this pest under the economic threshold or with integrated pest management programme. Silica has an activation action on the tested pesticides. Although silica was combined with one-fifth of the field rate of the tested pesticides, the toxicity of these pesticides was increased.     

Suitability of the tomato borer Tuta absoluta as prey for Macrolophus pygmaeus and Nesidiocoris tenuis

The tomato borer, Tuta absoluta (Meyrick) (Lep.: Gelechiidae), is an important tomato pest native to South America, which appeared in eastern Spain at the end of 2006. Prey suitability of T. absoluta eggs and larval instars was examined under laboratory conditions to evaluate whether two indigenous predators, Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hem.: Miridae), can adapt to this invasive pest. Both predators preyed actively on T. absoluta eggs and all larval stages, although they preferred first‐instar larvae. Our results demonstrate that both mirids can adapt to this invasive pest, contributing to their value as biological control agents in tomato crops.     

Seasonal variation in natural mortality factors of Tuta absoluta (Lepidoptera: Gelechiidae) in open‐field tomato cultivation

The seasonal variation in natural mortality of phytophagous insects is determined by the relative importance of biotic and abiotic factors in agroecosystems. Knowledge regarding these factors throughout the year represents a key concern for IPM programmes. Seasonal population fluctuations of tomato pinworm, Tuta absoluta, led to an investigation of its natural mortality factors during the rainy season when the population level is low and during the dry season when population peaks occur. The aim of this study was to verify the seasonal variation in T. absoluta mortality factors in tomato crops. Immature stages of T. absoluta were obtained from laboratory‐rearing in the laboratory. These were taken to the field and monitored over two years. The mortality causes for each stage of insect development from egg to adult were assessed daily. Multiple biotic and abiotic mortality factors affected the immature T. absoluta stages such as rainfall, physiological disturbances, diseases, parasitoids and predators. The key T. absoluta mortality factor during summer–spring was predation. In addition, larvae predation correlated positively with temperature, wind velocity, photoperiod and rainfall. Nevertheless, during winter–fall, the key mortality factor was parasitism. Therefore, the critical stage for mortality was 3rd‐ and 4th‐instar larvae, being more vulnerable to natural control factors. Finally, the results showed the importance of vertical and horizontal action on natural mortality factors.     

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.     

Extracts from the bark of Fagara heitzii (Aubr. et Pel.) (Rutaceae) tree are toxic to two weevils and the American cockroach

The bark of the Fagara heitzii tree in the west‐central African Republic of Congo (Congo–Brazzaville) is known anecdotally to provide protection for human residents against fleas and to be of use as a narcotic in fishing (similar to rotenone). We found that powder and hexane extracts from the bark of the Fagara heitzii tree contain insecticidal compounds. Dried powder (14.5 mg) on the bottom of a Petri dish is the residue at 14.494 mg per dish (LD₅₀) for 20 adult maize weevils Sitophilus zeamays after four days. The LD₅₀ of the same material to 20 adult cowpea weevils Callosobruchus maculatus was slightly higher at 16.144 mg/dish (after 48 h). These weevils cause significant economic damage to cowpea and maize in Congo–Brazzaville. Hexane extracts of the bark of Fagara heitzii were also toxic to these weevils. Symptoms of toxicity suggested the extracts were slow‐acting nerve poisons or respiratory inhibitors or both. The time needed to develop full toxicity suggested a respiratory poison. The hexane extract was also toxic to the American cockroach Periplaneta americana. The symptoms in the cockroach were similar, but cockroaches also exhibited apparent escape attempts suggesting they could detect the compounds. Signs of apparent irritation or exaggerated locomotion in all three insects also suggested irritation or nerve effects.     

Repellent,antifeedant and toxic effects of Ageratum conyzoides (Linnaeus) (Asteraceae) extract against Helicovepra armigera (Hübner) (Lepidoptera: Noctuidae)

Repellent, antifeedant and toxic effect of crude hexane extract of Ageratum conyzoides were investigated against Helicoverpa armigera. In orientation bioassay, the extract exhibited dose-dependent repellency against neonates. Extract significantly increased the mortality and decreased growth of different larval stages when administrated orally in artificial diet. EC₅₀ value was at 0.11% for larval growth inhibition. Toxicity of the extract was manifested by high mortality of first instar larvae after 7 days of feeding on diet containing 0.05–0.4% of extract with LC₅₀ of 0.17%. Under choice bioassay, extract showed strong antifeedant activity against fifth instar larvae with DI₅₀ of 0.21%. In nutritional bioassay, extract significantly reduced RCR, RGR, ECI and ECD of fifth instar larvae with increased AD. When RGR were plotted against RCR, the growth efficiency of larvae fed on treated diet was significantly lower than the control fed larvae suggesting the antifeedant and toxic effect of extract.     

Economic injury level and crop loss assessment for Tuta absoluta (Lepidoptera: Gelechiidae) on different tomato cultivars

Specifying the relationship between pests and their host plants in terms of damage is one of the basic concepts of integrated pest management (IPM) programmes. The crop loss and economic injury level (EIL) of Tuta absoluta (Lepidoptera: Gelechiidae) were determined on different tomato cultivars using gain threshold (field experiment) and regression (semi‐field experiment) methods. By assessing the crop loss in 2015 and 2016, four out of seven infested tomato cultivars had a significant yield loss in terms of weight of total fruits versus the control under the open‐field conditions. However, the total number of tomato cultivars had no significant difference to control treatment. The semi‐field experiment included six treatments (0, 2, 4, 6, 8 and 10 gravid females/plant) and examined two tomato cultivars. The tomato cages with between 6 and 10 gravid females/plant showed the highest number and weight of damaged fruits. Based on pesticide control costs, the market value of tomato and the control efficacy, we determined the EIL for T. absoluta. In the field experiment, the EIL value for T. absoluta on “Petomech,” “Cal JN3,” “Rio Grande” and “Early Urbana Y” cultivars was 4.15, 4.47, 4.70 and 5.04 larvae per plant, respectively. Based on regression equations, we calculated the EIL values for T. absoluta on “Cal JN3” and “Early Urbana Y” to be 4.75 and 5.44 larvae/plant, respectively. Crop loss assessment and EIL are necessary components of cost‐effective IPM programs and can be effective tools for making decisions about the application of pesticides against T. absoluta.     

The entomopathogen Beauveria bassiana has epiphytic and endophytic activity against the tomato leaf miner Tuta absoluta

The recent introduction and rapid spread of the tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) throughout Europe, Africa and the Middle East poses a severe threat to future cultivation of tomato and other Solanaceae. Among the best practicable means for effective and sustainable control of this invasive insect pest are entomopathogenic fungi, which can either prevent a further spread of this insect to new areas or keep population densities below an economic threshold level. Here, we report on the efficacy of a commercially available mycoinsecticide based on the entomopathogen Beauveria bassiana (Bals.) Vuill. (Ascomycota: Hypocreales) against all four larval stages of T. absoluta. In bioassays, high mortality rates and significantly reduced longevity of larvae were obvious when larvae had fed for a period of around 15 days on leaves with B. bassiana propagules present on the surface as an epiphyte with mortality values corrected for variance in control mortality of 90–100%. In addition, a second mode of action of B. bassiana against T. absoluta larvae was evident in bioassays in the form of an endophytic establishment of this fungus in treated tomato plants. Longevity of T. absoluta L4 larvae was significantly lower in individuals which had fed on surface‐sterilized tomato leaves obtained from plants treated 18 days before the bioassay with a B. bassiana suspension compared to larvae feeding on control plants treated with water. Corrected mortality reached values between 30% and 50% for all larval instars. Growth of tomato plants was not inhibited due to colonization by endophytic B. bassiana and a weak systemic translocation of fungal propagules in non‐treated leaves was evident in the assays. Accordingly, entomopathogenic fungi like B. bassiana express different modes of action again target insect pests, which is of particular relevance for the design of efficient management strategies for invasive pests like T. absoluta.     

Investigations on the efficacy of entomopathogenic nematodes against Spodoptera littoralis (Biosd.) and Galleria mellonella (L.)

Abstract

The infectivity of seven entomopathogenic nematode strains of the families Steinernematidae and Heterorhabditidae were tested against the last instar larvae of the cotton leafworm, Spodoptera littoralis (Biosd.) and the greater wax moth, Galleria mellonella (L.) in a Petri dish and sand column assay. Exposure of the insect species was done at a dose of 100 IJ/ ml. Heterorhabditis sp. ELG., H. indica, Heterorhabditis sp. ELB. were the highest in activity, they gave a 100% mortality to S. littoralis larvae in a Petri dish assay 24 h postexposure. The rest of the strains tested gave mortalities ranged between 50 and 90% at 24 h then 100% after 48 h postexposure . In the sand-column assay strains, Heterorhabditis sp. ELB., S. riobravae and S. carpocapsae were the highest in activity against S. littoralis with 100% mortality within 24 h postexposure. The results of infectivity against G. mellonella showed that H. indica was the highest in the Petri dish assay and H. egyptii was the highest in the sand column assay with 100% mortality after 24 h of exposure. The penetration rate as an indicator of entomopathogenic nematode infection was also evaluated. The highest value was recorded for Heterorhabditis sp. ELB. (62.3%) and S. carpocapsae (61.4%) against S. littoralis in both the Petri dish and sand-column assay, respectively. In the case of G. mellonella, the highest value of penetration was recorded for Heterorhabditis sp. ELG. (68.3%) and S. riobravae (65.00%) in both the Petri dish and sand-column assay, respectively.     

Biological activity of maize leaf extracts against the African armyworm,Spodoptera exempta

Maize (Zea mays L.) leaf tissue of cv Bastille and cv Michoacan 12 was extracted with n-hexane. The extracts were bioassayed against 5th instar African armyworm,Spodoptera exempta (Walker)(Lepidoptera: Noctuidae), by feeding the larvae on agar based media or sucrose impregnated glass fibre discs. The hexane extract of the ‘resistant’ cv Bastille exhibited feeding deterrency and toxicity which were not shown by the ‘susceptible’ cv Michoacan 12. The hexane extract of cv Bastille was adsorbed onto silica gel, the solution filtered off and the adsorbed component taken up into ethyl acetate. Bioassay of these fractions indicated that the toxic and deterrent action was retained in the ethyl acetate fraction. Preparative thin layer chromatography of the ethyl acetate fraction isolated two biologically active constituents. These were both growth inhibitors and lethal by ingestion to the 5th instar African armyworm. Implications for resistance in maize varieties to insect pests are discussed.     

Comparative damage and digestive enzyme activity of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) on 12 tomato cultivars

The damage caused by the tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) to 12 tomato cultivars was investigated under greenhouse conditions. The 2 cultivars Korral and CH Falat experienced lower damage in terms of all parameters investigated, whereas the cultivars Valouro and Cal JN3 were categorized as the most susceptible host plants. The larvae feeding on CH Falat and Korral cultivars reached the lowest final weight (1.82 and 1.93 mg, respectively), whereas those reared on the Valouro and Cal JN3 cultivars reached the highest body weight (3.42 and 3.33 mg, respectively). The highest proteolytic and amylolytic activity was detected in larvae feeding on the Korral cultivar, whereas larvae reared on the Valouro cultivar had the lowest enzyme activity for both third and fourth instar larvae. Altogether, the Korral and CH Falat cultivars were classified as relatively resistant cultivars, whereas the 2 cultivars Valouro and Cal JN3 were categorized as highly susceptible to infection by T. absoluta. Therefore, the resistant cultivars can be considered as candidates for use in integrated management programs of the tomato leaf miner in Iran.     

Interrelated responses of tomato plants and the leaf miner Tuta absoluta to nitrogen supply

Plant–insect interactions are strongly modified by environmental factors. This study evaluates the influence of nitrogen fertilisation on the tomato (Solanum lycopersicum L.) cv. Santa clara and the leafminer (Tuta absoluta (Meyrick), Lepidoptera: Gelechiidae). Greenhouse‐grown tomato plants were fed hydroponically on a complete nutrient solution containing either a high nitrogen concentration (HN) sustaining maximum growth or a low nitrogen concentration (LN) limiting plant growth. Insect‐free plants were compared with plants attacked by T. absoluta. Seven and 14 days after artificial oviposition leading to efficacious hatching and larvae development, we measured total carbon, nitrogen and soluble protein as well as defence compounds (phenolics, glycoalkaloids, polyphenol oxidase activity) in the HN versus LN plants. Only in the HN treatment did T. absoluta infestation slightly impair leaf growth and induce polyphenol oxidase (PPO) activity in the foliage. Neither the concentration of phenolic compounds and proteins nor the distribution of nitrogen within the plant was affected by T. absoluta infestation. In contrast, LN nutrition impaired T. absoluta‐induced PPO activity. It decreased protein and total nitrogen concentration of plant organs and enhanced the accumulation of constitutive phenolics and tomatine. Moreover, LN nutrition impaired T. absoluta development by notably decreasing pupal weight and lengthening the development period from egg to adult. Adjusting the level of nitrogen nutrition may thus be a means of altering the life cycle of T. absoluta. This study provides a comprehensive dataset concerning interrelated responses of tomato plants and T. absoluta to nitrogen nutrition.     

Bioefficacy of Ceasalpinea bonduc (L.) Roxb. against Spodoptera litura Fab. (Lepidoptera: Noctuidae)

Bioefficacy of hexane, chloroform and ethyl acetate extracts of the seeds of Ceasalpinea bonduc (L.) Roxb. was studied against third instar larvae of Spodoptera litura at 0.25, 0.5, 1, 2.5 and 5.0% concentrations. Significant antifeedant, larvicidal and pupicidal activities and least LC₅₀ values were observed in chloroform extract. The chloroform extract was subjected to fractionation using silica gel column chromatography. Six fractions were obtained; among these, the third fraction showed high antifeedant, larvicidal and pupicidal activities at 1000 ppm concentration. Abnormalities in adults were also observed. All the activities were concentration dependent. C. bonduc could be useful in integrated pest management programme.     

First record of an entomopathogenic fungus of tomato leafminer,Tuta absoluta (Meyrick) in Tanzania

Tuta absoluta (Meyrick) is a destructive pest causing adverse environmental and economic effects globally. Management of T. absoluta by synthetic chemicals is of diminutive achievement due to resistance trick of the pest. Harnessing of biocontrols is currently fascinating and efficient for management of the tremendous pests. This study isolated an entomopathogenic fungus from dead larvae of T. absoluta on tomato leaves from farmer’s field Tanzania. Two Aspergillus fungal isolates were isolated and tested against larvae and adults of T. absoluta under conditions of 19.5°C and 50%RH, 30.4°C and 70% RH, respectively, in the laboratory. Sequence analysis of Aspergillus isolates that we referred as A-Tz1 and A-Tz2 were analysed with the BLAST program available at the National Center for Biological Information (NCBI). The two isolates (A-Tz1 and A-Tz2) showed 100% similarity with Aspergillus oryzae of GeneBank accession numbers EF121337.1 and MG519722.1. Such similarity implied that both A-Tz1 and A-Tz2 isolates were A. oryzae. To confirm pathogenicity, bioassays were conducted against the larvae, pupa and adults of T. absoluta. Results showed that at 1.0?×?10⁸?conidia/mL, fungal isolates caused up to 70% larval mortality 3 days post inoculation and consequently inhibited pupation by 84.5% and adult emergence by 74.4%. The identified A. oryzae reduced the life span of adult T. absoluta up to 5 days post inoculation at 1.0?×?10⁸?conidia/mL whereas in control T. absoluta survived up to 25 days. This study found that isolates of Aspegillus species have the potential to be used as active ingrediennt for the formulation of a new bioinjections for application by farmers to control the pest in fields.     

Molecular and biological characterization of native <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> strains for controlling tomato leafminer (<Emphasis Type="Italic">Tuta absoluta</Emphasis> Meyrick) (Lepidoptera: Gelechiidae) in Colombia

Twenty-eight soil samples were obtained from open fields and greenhouses used for tomato cultivation in various regions of Colombia. For functional characterization, 99 Bacillus thuringiensis (Bt) strains were isolated and characterized by abundance and morphology of microscopic crystals, SDS–PAGE of protein extracts and M-PCR analyses of genes of the cry1 family, as well as for their insecticidal activity against Tuta absoluta second instar larvae. Native Bt strains had amorphous (5%), bi-pyramidal (27%), square (8%), spherical (38%) and triangular (22%) crystal forms. Based on the presence of 1–4 different crystal forms, 18 different profiles were established. The SDS–PAGE analyses of protein extracts established ten different strain groups based on their protein band weight and potential biological activity. The M-PCR technique identified 35 native Bt strains based on the presence of the 6 genes cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C and cry1D, whose frequency of occurrence was 76, 26, 21, 35, 32 and 8.8%, respectively. Thirteen different PCR profiles were found in native Bt strains. Several gene combinations tended to co-occur with elevated frequency, such as the pairs cry1Ac/cry1C, cry1Ab/cry1Ac and cry1Ab/cry1B, for which Pearson correlation coefficients were 0.69, 0.52 and 0.54, respectively. Native strains ZBUJTL39 and ZCUJTL11 had up to three times higher biological activity against T. absoluta second instar larvae than the reference strain Bt var. kurstaki HD1, with an LD₅₀ of 2.4 μg/ml (P < 0.05) for native Bt strain ZCUJTL11. This study suggests a high biodiversity of native Bt strains from tomato growing regions in Colombia, which has important implications for designing biological control strategies for T. absoluta.