Effect of cropping season and possible compounds involved in the resistance of Lycopersicon hirsutum f. typicum to Tuta absoluta (Meyrick) (Lep., Gelechiidae)

The effect of cropping season on the resistance of the accession LA 1777 of Lycopersicon hirsutum f. typicum to the tomato leafminer Tuta absoluta (Meyrick) and the preliminary identification of the possible compounds involved in this trait were the objectives of this study. Two experiments were carried out with the accession LA1777 and the commercial cultivar Santa Clara of Lycopersicon esculentum . The first experiment was carried out during the summer season (January to April 1997) and the second was carried out during the autumn–winter season (May to September 1997). The accession LA 1777 was significantly more resistant to T. absoluta than the commercial cultivar, especially during the autumn–winter cropping season. Either antibiosis or antixenosis was probably responsible for the higher larvae mortality (54.2 and 91.2% for the summer and autumn–winter seasons, respectively) and longer larval development of T. absoluta (14.2 and 25.9 days for summer and autumn–winter seasons, respectively) on L. hirsutum f. typicum as compared with L. esculentum (11.0 and 19.6 days for summer and autumn–winter seasons, respectively). Insect fecundity parameters such as oviposition period, number of eggs/female, and rate of larvae eclosion were also negatively affected by L. hirsutum f. typicum . Fourteen main peaks were observed in total ion chromatograms of both tomato species. Eleven of these were present only in chromatograms of the accession, one was only present in chromatograms of the commercial cultivar, and two peaks were present in chromatograms from both when hexane extracts of leaves were subjected to a gas chromatographic–mass spectrometric analysis (GC–MS). However, the matches obtained between the peak spectra and the MS database were too low to justify even preliminary identification of the compounds.     

Cartap resistance and synergism in populations of Tuta absoluta (Lep., Gelechiidae)

Abstract: Control failures of cartap when used against the tomato leafminer Tuta absoluta (Meyrick) in Brazil and a recent report of cartap resistance in Brazilian populations of this pest species led to the investigation of the possible involvement of detoxification enzymes on this phenomenon using insecticide synergists. The insect populations were collected from seven different sites in the states of Minas Gerais, Rio de Janeiro and São Paulo. These populations were subjected to insecticide-impregnated filter paper assays. The concentration–mortality assays were carried out for cartap alone and in a mixture (1 cartap : 10 synergist) with the synergists diethyl maleate, piperonyl butoxide and triphenylphosphate which, respectively, inhibit the enzymes glutathion-S-transferases, cytochrome P450-dependent monooxygenases and esterases. Resistance to cartap was observed in all populations when compared with the standard susceptible population, with resistance ratios ranging from 2.3- to 21.9-fold. Piperonyl butoxide was the most efficient synergist with cartap synergism ratios ranging from 1.3- to 21.0-fold and nearly completely suppressing the resistance to cartap in all of the populations studied, suggesting a major involvement of cytochrome P450-dependent monooxygenases as a cartap resistance mechanism in these populations of T. absoluta . Diethyl maleate and triphenylphosphate also synergized cartap in nearly every population, and they still provided partial suppression of cartap resistance in the leafminer populations studied. Therefore, glutathion-S-transferases and esterases seem to play a secondary role in cartap resistance in Brazilian populations of T. absoluta .     

Susceptibility of Tuta absoluta (Meyrick) (Lep., Gelechiidae) reared on two species of Lycopersicon to Bacillus thuringiensis var. kurstaki

The mortality of Tuta absoluta (Meyrick) larvae that were fed on leaves of Lycopersicon hirsutum f. glabratum (PI 134417, insect resistant) and Lycopersicon esculentum (cultivar Santa Clara, susceptible) treated with Bacillus thuringiensis var. kurstaki (Btk) was evaluated. Feeding on untreated PI 134417 was detrimental to the survival of T. absoluta larvae. When Btk was applied to the two Lycopersicon plants, mortality occurred in all T. absoluta instars. Application of Btk on tomato leaves had synergistic or additive effects with the resistant genotype on larval survival. This effect was dependent on the instar at which the larvae were fed Btk-treated leaves. Delayed Btk application may cause higher insect mortality if the insects become more susceptible to the pathogen after a longer period of feeding on the resistant crop.     

Mortality of second-instar larvae of Tuta absoluta produced by the hexane extract of Lycopersicon hirsutum f. glabratum (PI 134417) leaves

1 The mortality resulting from exposure of second‐instar larvae of Tuta absoluta to a hexane extract of Lycopersicon hirsutum f. glabratum (PI 134417) leaves was evaluated in the laboratory. 2 A crude hexane extract was fractionated on a silica gel column to produce 17 fractions. The toxicity of the fractions was evaluated on T. absoluta larvae at 2 and/or 6 mg/10 larvae/Petri dish along with a control. 3 Only two fractions, 4.50 and 10.18% of the total hexane extract, were found to result in very high mortality of second‐instar T. absoluta. 4 All the 17 fractions were analysed by capillary gas chromatography/mass spectrometry (GC/MS). The two most toxic fractions were virtually identical and contained mainly undeca‐2‐one (2‐UD) and trideca‐2‐one (2‐TD). 5 A third major sub‐fraction 13 (50.73% of the total hexane extract) was further fractionated on a silica gel column to obtain five additional sub‐fractions. The toxicity of all the five sub‐fractions was evaluated using second‐instar T. absoluta at 2 mg/10 larvae/Petri dish and also analysed by GC/MS. The most toxic sub‐fractions contained mostly 2‐UD and 2‐TD. 6 The results suggest that 2‐UD and 2‐TD could be related to resistance of L. hirsutum to T. absoluta.     

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.     

Insecticide resistance in populations of Tuta absoluta (Lepidoptera: Gelechiidae)

1 Control failures of insecticides used against the tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in Brazil led to the investigation of the possible occurrence of resistance of this insect pest to abamectin, cartap, methamidophos and permethrin. 2 The insect populations were collected from seven sites in the states of Minas Gerais, Rio de Janeiro, and São Paulo. These populations were subjected to concentration–mortality bioassays using insecticide‐impregnated filter papers. 3 We were unable to obtain a single population which provided a susceptibility standard for all insecticides tested. Therefore, the resistance levels were estimated in relation to the most susceptible population to each insecticide. Resistance to abamectin and cartap were observed in all populations when compared with the susceptible standard population, with resistance ratios ranging from 5.2‐ to 9.4‐fold and from 2.2‐ to 21.9‐fold for abamectin and cartap, respectively. Resistance to permethrin was observed in five populations with resistance ratios ranging from 1.9‐ to 6.6‐fold, whereas resistance to methamidophos was observed in four populations with resistance ratios ranging from 2.6‐ to 4.2‐fold. 4 The long period and high frequency of use of these insecticides against this insect pest suggest that the evolution of insecticide resistance on them has been relatively slow. Alternatively, the phenomenon might be widespread among Brazilian populations of T. absoluta making the finding of suitable standard susceptible populations difficult and leading to an underestimation of the insecticide resistance levels in this pest. 5 Higher levels of resistance to abamectin, cartap and permethrin are correlated with greater use of these compounds by growers. This finding suggests that local variation in insecticide use was an important cause of variation in susceptibility.     

Fertility life table of Trichogramma pretiosum (Hym., Trichogrammatidae) in eggs of Tuta absoluta and Phthorimaea operculella (Lep., Gelechiidae) at different temperatures

Abstract: The aim of this work was to study the reproductive potential of Trichogramma pretiosum reared on Tuta absoluta and Phthorimaea operculella eggs through fertility life tables at different temperatures. The development cycle and the parasitization capacity of this parasitoid was determined in order to calculate the net reproductive rate ( R _o), the infinitesimal increase ratio ( r _m), the finite increase rate ( λ ) and the mean duration of the generation ( T ). The mean duration of one generation of T. pretiosum kept on both eggs was observed to show an inverse relation with the increase of temperature. The net reproduction rate varied according to the temperature variation for both species. The maximum increase in capacity of T. pretiosum on the first host ( T. absoluta ) was reached at 22°C and on the second host ( P. operculella ) between 22 and 25°C. The infinitesimal increase rate and the finite increase rate for both moths had a relationship with the increase of temperature ranging from 18 to 30°C. The highest value of λ for both moths occurred at 30 and 32°C according to the lesser duration of a generation.     

Ecological Life Table of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

An ecological life table was constructed, aiming to determine the critical stages and key mortality factors of Tuta absoluta (Lepidoptera: Gelechiidae). The total population mortality of this tomato leafminer was 92.3%. During the egg stage the mortality was 58.7%, mainly due to egg inviability. A total of 8.6% egg parasitism by Trichogramma pretiosum (Riley) (Hymenoptera: Trichogrammatidae) and 5.0% egg predation by Xylocoris sp. (Heteroptera: Anthocoridae), Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) and members of the family Phlaeothripidae (Thysanoptera) was observed. The mortality of the larval stage was 33.0%. This was considered to be the critical stage as it showed the highest apparent mortality (79.8%). Larval parasitism was low (0.1%), and was only found with Goniozus nigrifemur Ashmead (Hymenoptera: Bethylidae). Predators were responsible for 79.4% of larval mortality. Therefore, their attraction to and maintenance in the target area are important management tactics to be considered for T. absoluta control. The first and second instars were considered to be the most critical, and predation by the above mentioned species was the key mortality factor. The mortality at the pupal stage was low (0.6%) and was due to malformation.     

Adaptation of indigenous larval parasitoids to Tuta absoluta (Lepidoptera: Gelechiidae) in Italy

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious threat to tomato (Solanum lycopersicum L.) crops in South America. In Europe, after its first detection in Spain in 2006, it rapidly spread through the Mediterranean basin, reaching Italy 2 yr later. The aim of our work was to find indigenous effective biological control agents and to evaluate their potential role in the control of larval populations of T. absoluta in controlled conditions. Nine species of larval parasitoids emerged from field-collected tomato leaves infested by T. absoluta. The most abundant, Necremnus near artynes (Walker) and Necremnus near tidius (Walker) (Hymenoptera: Eulophidae), were tested in laboratory parasitism trials. Furthermore, because the species N. artynes and N. tidius are each reported in literature as an ectoparasitoid of Cosmopterix pulchrimella Chambers (Lepidoptera: Cosmopterigidae) on upright pellitory plants, olfactometer bioassays were performed to assess the response of our parasitoids to the odors of tomato and pellitory leaves infested by T absoluta and C. pulchrimella, respectively, compared with healthy ones. Both Necremnus species showed good adaptation to the invasive pest, and we observed a high larval mortality of T. absoluta because of host feeding and parasitism. Even olfactory responses highlighted a preference of both wasps for tomato plants infested by the exotic pest. These preliminary results demonstrated a high suitability of these indigenous natural enemies for controlling T. absoluta. Further investigations are needed to confirm their role as potential biological agents in commercial tomato plantations.     

Resistance to the pink potato aphid, Macrosiphum euphorbiae, in two accessions of Lycopersicon hirsutum f. glabratum

An integrated programme of pheromone-mediated mating disruption using Isomate-C®, post-harvest removal of fruit, and trapping overwintering larvae with cardboard tree bands, was used to control codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in four commercial organic apple orchards in Cawston, British Columbia during 1989–1992. One application of 1000 dispensers ^{– 1} on May 1 delivered estimated seasonal totals of 16.6, 16.5 and 19.9 g of E,E-8,10-dodecadien-1-ol [=codlemone] ^{– 1}in 1990, 1991 and 1992, respectively, at median rates of 8.4, 8.3, and 13.3 mg · < ha^–1 · ha^–1 during dusk flight periods of first brood and 5.3, 4.7 and 4.6 mg · ^{– 1}· ha^–1 in second brood, respectively. Over this 3-year period damage from codling moth at harvest ranged from 0.08 to 2.4%, and averaged 60.7% in these four organic orchards, while damage in five conventional orchards receiving sprays of azinphosmethyl ranged from 0.02 to 1.85%, and averaged 0.5%. Damage in an experimental orchard that was banded only, ranged from 43.5 to 56.7%, and averaged 48.9%. Between 1990 and 1992 cumulative male catches in Pherocon 1-CP wing traps baited with 10 mg of codlemone declined by 52% and densities of overwintering codling moth larvae declined an average of 49.5% in all organic orchards. Overwintering populations in the banded experimental orchard showed an increase of 57.7% during this study period. We conclude that an integrated programme of pheromone-mediated mating disruption, post-harvest fruit removal and tree banding, controls codling moth effectively enough to make organic apple production viable in British Columbia.     

Effect of fertilization levels, age and canopy height of Lycopersicon hirsutum on the resistance to Myzus persicae

The effects of different levels of fertilization with nitrogen and potassium (NK), height within the canopy and plant age of Lycopersicon hirsutum f. glabratum (PI 134417) C. H. Mull and L. esculentum on the density of foliar cristalliferous idioblasts and trichomes, and on the levels of 2- tridecanone (2-TD) and 2-undecanone (2-UD) and their influence on the resistance to Myzus persicae (Sulzer) were investigated. NK levels were inversely related to densities of trichomes and cristalliferous idioblasts in L. esculentum, but only to densities of cristalliferous idioblasts in L. hirsutum. Trichome density increased with increasing height within the canopy and with plant age in L. esculentum and L. hirsutum. Density of cristalliferous idioblasts in L. hirsutum increased with canopy height reaching a maximum at mid-height within the canopy in opposition to L. esculentum in which a small decrease in density with height within the canopy was found. There was also a small decrease of idioblast density with increasing plant age for L. esculentum, while a greater and opposite variation took place in L. hirsutum. L. esculentum has mainly non- glandular leaf trichomes (90%), while L. hirsutum has mainly glandular trichomes (97%). The main glandular trichomes of L. hirsutum are producers of 2-TD and 2-UD, whose leaf content increases with increase of trichome density. A negative effect of 2-TD concentration and cristalliferous idioblast density on the survival and longevity of M. persicae was observed. Since L. hirsutum presented much higher levels of 2-TD and cristalliferous idioblast density than L. esculentum, L. hirsutum seems a promising source of resistance to M. persicae for tomato breeding programs.     

Molecular tagging of the Am gene from Lycopersicon hirsutum f. glabratum PI 134417 using AFLP markers

Recently important epidemics caused by Alfalfa Mosaic Virus (AMV) have been reported in field grown canning tomatoes in southern Italy. The Am resistance gene identified in Lycopersicon hirsutum PI 134417 confers a complete resistance to several isolates of AMV with different geographical and botanical origins. In order to identify linked molecular markers, a segregant back-cross population of 120 individuals was obtained from the intraspecific cross between the resistant L. hirsutum accession PI 134417 and the susceptible accession L. hirsutum PI 247087. Using bulked segregant analysis combined with AFLP technology, four AFLP markers were found to be linked to the Am resistance gene. This gene will be assigned to a tomato chromosome using L. pennellii introgression lines.     

Ryanodine receptor point mutations confer diamide insecticide resistance in tomato leafminer,Tuta absoluta (Lepidoptera: Gelechiidae)

Insect ryanodine receptors (RyR) are the molecular target-site for the recently introduced diamide insecticides. Diamides are particularly active on Lepidoptera pests, including tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae). High levels of diamide resistance were recently described in some European populations of T. absoluta, however, the mechanisms of resistance remained unknown. In this study the molecular basis of diamide resistance was investigated in a diamide resistant strain from Italy (IT-GELA-SD4), and additional resistant field populations collected in Greece, Spain and Brazil. The genetics of resistance was investigated by reciprocally crossing strain IT-GELA-SD4 with a susceptible strain and revealed an autosomal incompletely recessive mode of inheritance. To investigate the possible role of target-site mutations as known from diamondback moth (Plutella xylostella), we sequenced respective domains of the RyR gene of T. absoluta. Genotyping of individuals of IT-GELA-SD4 and field-collected strains showing different levels of diamide resistance revealed the presence of G4903E and I4746M RyR target-site mutations. These amino acid substitutions correspond to those recently described for diamide resistant diamondback moth, i.e. G4946E and I4790M. We also detected two novel mutations, G4903V and I4746T, in some of the resistant T. absoluta strains. Radioligand binding studies with thoracic membrane preparations of the IT-GELA-SD4 strain provided functional evidence that these mutations alter the affinity of the RyR to diamides. In combination with previous work on P. xylostella our study highlights the importance of position G4903 (G4946 in P. xylostella) of the insect RyR in defining sensitivity to diamides. The discovery of diamide resistance mutations in T. absoluta populations of diverse geographic origin has serious implications for the efficacy of diamides under applied conditions. The implementation of appropriate resistance management strategies is strongly advised to delay the further spread of resistance.     

Thermal plasticity in the invasive south American tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating invasive global insect pest of tomato, Solanum lycopersicum (Solanaceae). In nature, pests face multiple overlapping environmental stressors, which may significantly influence survival. To cope with rapidly changing environments, insects often employ a suite of mechanisms at both acute and chronic time-scales, thereby improving fitness at sub-optimal thermal environments. For T. absoluta, physiological responses to transient thermal variability remain under explored. Moreso, environmental effects and physiological responses may differ across insect life stages and this can have implications for population dynamics. Against this background, we investigated short and long term plastic responses to temperature of T. absoluta larvae (4th instar) and adults (24–48 h old) from field populations. We measured traits of temperature tolerance vis critical thermal limits [critical thermal minima (CT_min) and maxima (CT_max)], heat knockdown time (HKDT), chill coma recovery time (CCRT) and supercooling points (SCP). Our results showed that at the larval stage, Rapid Cold Hardening (RCH) significantly improved CT_min and HKDT but impaired SCP and CCRT. Heat hardening in larvae impaired CT_min, CCRT, SCP, CT_max but not HKDT. In adults, both heat and cold hardening generally impaired CT_min and CT_max, but had no effects on HKDT, SCP and CCRT. Low temperature acclimation significantly improved CT_min and HKDT while marginally compromising CCRT and CT_max, whereas high temperature acclimation had no significant effects on any traits except for HKDT in larvae. Similarly, low and high temperature acclimation had no effects on CT_min, SCPs and CT_max, while high temperature acclimation significantly compromised adult CCRT. Our results show that larvae are more thermally plastic than adults and can shift their thermal tolerance in short and long timescales. The larval plasticity reported here could be advantageous in new envirnments, suggesting an asymmetrical ecological role of larva relative to adults in facilitating T. absoluta invasion.     

Relationship of leaf lamellar-based resistance toLeptinotarsa decemlineata andHeliothis zea in a wild tomato,Lycopersicon hirsutum f.glabratum, PI 134417

Segregating populations of hybrids of the insect-resistant wild tomato,Lycopersicon hirsutum f.glabratum, C.H. Mull, PI 134417, and the susceptible tomato cultivar ofL. esculentum Mill, Walter, were screened by bioassays with the Colorado potato beetle,Leptinotarsa decemlineata (Say) and tomato fruitwormHeliothis zea (Boddie). Plant lines with a range of levels of resistance toH. zea were selected from one group of hybrids; plants with a range of resistance levels toL. decemlineata, from another group. The response of both insect species to both groups of plants was evaluated. Resistance to each of these species is under separate genetic control and apparently involves distinct mechanistic components, although it remains possible that at least some factors are important in conditioning resistance to both species.

---

Résumé La tomate sauvage,L. hirsutum f.glabratum C.H. Mull, n⁰ PI134417, présente des lamelles foliaires qui lui confèrent une résistance au doryphore,L. decemlineata Say et àH. zea Bodie. Cette étude a voulu préciser si ces résistances étaient héritées ensemble dans des populations d'hybrides entre PI 134417 et la tomate cultivée,L. esculentum Mill. Des lignées de plantes présentant une gamme de résistance àH. zea ont été sélectionnées à partir d'une population hyrbide. De même, des lignées de plantes ayant une gamme de résistance àL. decemlineata ont été sélectionnées à partir d'un second groupe d'hybrides. Les réactions des 2 insectes aux 2 groupes de plantes ont été estimées.Les résistances àH. zea et àL. decemlineata n'étaient pas corrélées nettement. Certaines lignées sont résistantes aux 2 espèces, mais d'autres ne sont résistantes qu'à une espèce. Ainsi, les résistances à chacune de ces espèces ont probablement des déterminismes génétiques différents. Différentes composantes mécaniques sont vraisemblablement impliquées dans ces résistances, bien qu'il soit possible qu'au moins quelques facteurs aient un rôle important dans le conditionnement de la résistance. La création de cultivars de tomates avec une résistance liée aux lamelles foliaires sera compliquée par le besoin d'une sélection en fonction des réponses aux 2 espèces..

     

Role of larval host plant experience and solanaceous plant volatile emissions in Tuta absoluta (Lepidoptera: Gelechiidae) host finding behavior

The tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), is considered to be a major pest that damages tomato (Solanum lycopersicum L; Solanaceae) crops in South American, European, and Mediterranean countries. This insect species is polyphagous (i.e., feeds on many types of food); hence, it could also develop on other cultivated host plants, principally solanaceous plants, such as potato (S. tuberosum L.; Solanaceae) and eggplant (S. melongena L.; Solanaceae). Therefore, we tested the hypothesis that host plant choice by adult T. absoluta is influenced by plant volatile organic compounds and larval host plant experience. One tomato cultivar (cv.) ‘Moneymaker’ and three potato cv. ‘Charlotte’ ‘Bintje,’ and ‘Nicola’ were tested. Using a flying tunnel, we observed that females reared on tomato preferred flying toward tomato and, to a lesser extent, potato cv. ‘Charlotte.’ These preferences might be explained by the high release of terpenes by these two plants. When conducting oviposition choice assays, we found no preference between tomato and potato in the number of eggs laid by females that had been previously reared on either host plant. This study indicates that the host finding behavior of T. absoluta is mediated by solanaceous volatiles, while oviposition behavior appears to depend on additional stimuli. These results provide baseline information for use in the development of new control strategies against T. absoluta using semiochemicals and plant breeding.     

Organophosphate and pyrethroid resistances in the tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae) from Iran

The tomato leafminer, Tuta absoluta (Meyrich) (Lepidoptera: Gelechiidae), is a serious pest of tomato crops worldwide. The intensive use of chemical pesticides to control it has led to the selection of resistant populations. This study investigated the resistance of T. absoluta populations to pyrethroid and the organophosphate insecticides from ten regions of Iran. The resistance ratios at LC₅₀ for chlorpyrifos and diazinon varied among populations from 4.3 to 12 and from 1.4 to 9.0, respectively. The resistance ratios of the pyrethroids cypermethrin, deltamethrin and permethrin varied from 1.3 to 3.7, 2.7 to 13 and 1.2 to 4.3, respectively. Inclusion of synergists in toxicological bioassays and the variation observed in the activity of esterases, glutathione S‐transferase and cytochrome P450‐dependent monooxygenase suggest the existence of metabolically based resistance. Esterase and P450 biochemical assays were positively correlated with deltamethrin, and cypermethrin tolerance and diazinon tolerance correlated with esterase activity. The genes encoding the organophosphate and pyrethroid target sites acetylcholinesterase (ace1) and sodium channel (kdr) were partly sequenced. The genotyping revealed mutations in high frequencies in all populations leading to an A201S substitution in ace1 and three substitutions in the sodium channel gene L1014F, M918T, T929I. In summary, our results indicate the presence of organophosphate and pyrethroid resistance in Iranian T. absoluta populations with involvement of both detoxification enzymes and target site alterations. Most likely the populations of T. absoluta imported to Iran were resistant upon arrival.     

New records of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) predation by Brazilian Hemipteran predatory bugs

The tomato borer Tuta absoluta, native to western South America, is an extremely devastating pest in tomato crops in most of South America, Europe and Africa North of the Sahel, causes yield losses up to 100% and decreases fruit quality in open field and greenhouse crops if control methods are not applied. In Brazil two other important lepidopteran pests – Neoleucinodes elegantalis and Helicoverpa zea – occur in tomato, as well as thrips, whiteflies and aphids. For control of these pests, frequent applications of pesticides of up to 5 times per week are needed, and these resulted in the appearance of resistant populations to a number of active ingredients and decimation of natural enemies. Biological control may offer a better, safer and more sustainable opportunity for pest management. Mirid predatory bugs are currently used with success in southern Europe to control T. absoluta and other pests. In Brazil, four Hemipteran predatory bugs, not yet known to attack T. absoluta, were found to successfully prey on eggs and larvae of this pest. The first results on their predation capacity, development, survival and reproduction on T. absoluta on tomato plants are presented.     

Control of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in greenhouse tomato crops using the mating disruption technique

The effectiveness of mating disruption to control the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in greenhouse tomato crops was evaluated in four trials carried out in winter–spring and summer–winter growing seasons in Southwestern Sardinia (Italy). Pheromone dispensers loaded with 60 mg of the natural blend of the major and minor sex pheromone component (rate 90 : 10) were applied in disrupted greenhouses at a rate of 1000/ha (60 g of active ingredient/ha). Male captures in monitoring pheromone traps, percentage of tomato plants infested by T. absoluta and damage on leaves and fruits were monitored weekly and compared in disrupted and untreated (control) greenhouses. In greenhouses disrupted with 1000 dispensers/ha, a reduction of 93–97% in male trap captures was observed, compared with control. Leaf damage was significantly lower in greenhouses disrupted with 1000 dispensers/ha than in control ones, with a reduction of infestation throughout the growing season ranging from 57% to 85%. Pheromone dispensers applied at the density of 1000/ha significantly reduced the percentage of damaged fruits by 62–89%. In control greenhouses, the highest damage on leaves and fruits was generally observed in edge plants, while leaf and fruit infestation was uniformly distributed in pheromone‐treated greenhouses, indicating an even distribution of the pheromone cloud inside the greenhouse. Mating disruption showed to be an efficient strategy to control in greenhouse the tomato leafminer and can be included in the overall tomato integrated pest management programs.     

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.