Functional response and egg distribution among hosts by Pseudapanteles dignus,a larval endoparasitoid of Tuta absoluta

The functional response of a biocontrol agent has been classically pointed out as a quantitative evaluation criterion to understand its killing capacity to an arthropod pest. In this paper, we revisited the functional response of the internal larval parasitoid Pseudapanteles dignus (Muesebeck) (Hymenoptera: Braconidae), a candidate for biocontrol of the South American tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), measured as the daily egg oviposition of single parasitoid females at increasing densities of T. absoluta larvae through dissection of hosts. The functional response curve of the number of parasitized hosts was fitted out taking into account the number of eggs laid and their distribution among hosts at each T. absoluta larval density. The data also allowed us to discuss the self-superparasitism strategy of this parasitoid as an adaptive trait. Pseudapanteles dignus showed a sigmoid shape functional response and a contagious distribution of eggs among hosts, favouring self-superparasitism and laying a similar number of eggs in each superparasitized host at each T. absoluta density. This research is firstly intended to ascertain about the oviposition behaviour of P. dignus and additionally to provide information on its reproduction to be applied in mass rearing procedures and augmentative releases against T. absoluta.     

Efficacy of some biorational insecticides against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under laboratory and greenhouse conditions in Kuwait

The tomato leafminer, Tuta absoluta, is one of the most destructive pests of tomato worldwide. Management of the pest is mainly based on chemical insecticides. Reliance on insecticides is difficult to sustain because of unintended long‐term adverse effects on the environment and human health. Consequently, there is a need to develop pest management strategies that ensure the production of high‐quality products, while at the same time ensuring environmental sustainability and maximum consumer protection. We evaluated the efficacy the biopesticides: Azadirachtin, Bacillus thuringiensis, Steinernema feltiae and Beauveria bassiana individually and in combination against T. absoluta under laboratory and greenhouse conditions. When second instar larvae were exposed to tomato leaf discs treated with Azadirachtin (3 g / L), B. thuringiensis (0.5 g/L) or B. bassiana (1.5 g/L), 70%–86%, 55%–65%, and 45.5%–58.5% mortality was observed, respectively. Steinernema feltiae (1,000 IJs/ml) was the least effective biopesticide, with 26%–42% mortality. In the greenhouse trials on tomato, pest infestation (mines/10 leaves/plant) and fruits damaged were significantly lower on plants treated with Azadirachtin  +  B. thuringiensis or Azadirachtin  +  B. bassiana compared to plants treated with Azadirachtin, B. thuringiensi, B. bassiana or S. feltiae alone. Azadirachtin  +  B. thuringiensis and Azadirachtin  +  B. bassiana resulted in 90% and 81% reduction in fruits damaged in the summer experiments, respectively, and 96% and 91% in winter. The most severe pest infestation was observed on plants treated with S. feltia. The results indicate that the biopesticides, except S. feltia, can contribute to T. absoluta control in greenhouse tomato crops. In particular, the combined use of Azadirachtin with B. thuringiensis or B. bassiana provided the highest level of control of the pest. The potential for including these biopesticides in an overall sustainable integrated pest management programme for T. absoluta is discussed.     

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.     

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.     

Biological studies on Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae), egg parasitoid of Tuta absoluta Meyrick (Lepidoptera: Gelechiidae)

The tomato moth, Tuta absoluta Meyrick, is one of the most important tomato pests in South America. In Argentina, management strategies include only chemical control. In this work, the parasitoid wasp Trichogrammatoidea bactrae Nagaraja was evaluated as a potential natural enemy against this pest. Biological and population parameters were estimated by developing a life table under laboratory conditions at 25 ± 1oC, 14:10 photoperiod and 60 ± 10% RH. Three cohorts of 26-30 T. bactrae females each were placed with one of the three following treatments: 1 - Sitotroga cerealella (Olivier) eggs on a piece of cardboard; 2 - S. cerealella eggs on a piece of tomato leaf, and 3- T. absoluta eggs on a piece on tomato leaf. The following parameters were estimated for each cohort: survival (egg to adult), longevity, fecundity and oviposition period of females, sex proportion of the F1, net rate of reproduction (Ro), mean generation time (T) and intrinsic rate of population increase (r m). Survival of the T. bactrae immatures was higher than 90% on both, S. cerealella and T. absoluta eggs. The female survival curves corresponded to type III and showed no significant differences among treatments. The three cohorts did not show significant differences between sex ratio, female longevity, oviposition period, fecundity and the population parameters studied. These results indicate that T. bactrae would be a potential biological control agent of T. absoluta.     

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.     

Entomopathogenic fungus isolates for adult Tuta absoluta (Lepidoptera: Gelechiidae) management and their compatibility with Tuta pheromone

Tomato, Solanum lycopersicum, is a widely consumed and economically important vegetable in the tropics. However, its production and productivity have been recently hampered by the invasive Tuta absoluta (Meyrick), a key pest of tomato causing extensive economic damage in Africa. Currently, the commonly used management strategy is synthetic insecticides with hazardous effects on humans and environment. The application of entomopathogenic fungal and viral-based biopesticides is promising alternatives. To identify potent strains, pathogenicity of dry conidia of 12 Metarhizium anisopliae isolates was evaluated against adult T. absoluta. Further effects of the most potent isolates on pupation through the late 4th instar larval infection, adult emergence and horizontal transmission of inoculum were assessed. Metarhizium anisopliae ICIPE 18, ICIPE 20 and ICIPE 665 outperformed the other isolates causing adult mortality of 95.0%, 87.5% and 86.25%, respectively. The three potent isolates differed significantly for LT₅₀ values of 5.13, 3.17 and 2.38 days for ICIPE 18, ICIPE 20 and ICIPE 665, respectively. Pupation and adult emergence were significantly reduced by these potent isolates, which were also compatible with Tuta pheromone (TUA-Optima^®) with ≥90% conidial germination 24 hr post-exposure. These potent isolates could be developed as effective biopesticides and used in combination with TUA-Optima^® for mass trapping and autodissemination for T. absoluta management in solanaceous crop production systems.     

Population growth potential of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) on tomato,potato, and eggplant

The influence of host plant on population dynamics of an invasive pest, Tuta absoluta was studied on three economically important solanaceous crops. Experiments were conducted in laboratory (29 ± 0.5°C, 75 ± 5% RH and a photoperiod of 14:10 hr [L:D]) using tomato (Solanum lycopersicum L.), potato (Solanum tuberosum L.) and eggplant (Solanum melongena L.). Results indicated that intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R₀) were higher, and mean generation time (T) was the shortest on tomato. Results suggested that T. absoluta developed on all the three plants, and tomato plant was most preferred one. Results suggested that T. absoluta has a potential to become a serious pest on potato and even on eggplant under favourable conditions. We used the life tables of 0.025th and 0.975th percentiles of bootstraps to project the uncertainty of population growth, a new concept.     

Evaluating the damage of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) on some cultivars of tomato under greenhouse condition

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is the major pest of tomato plant. Since using relatively resistant cultivars may reduce the number of sprayings as well as postpone the development of the resistance to pesticides, the present study focused on evaluating the damage of T. absoluta on eleven 45-day-old tomato cultivars under greenhouse condition. Larval mines on the leaves as well as the terminal bud damage were considered. Damaged leaves, active mines and damaged terminal buds were significantly different among the cultivars. Cluster analysis using SPSS software resulted in grouping the cultivars into four categories as relatively resistant, partially resistant, partially susceptible and susceptible. The host plant’s growing characteristics (height and leaflet number) were assessed and likewise the weight of the resulted pupae. Differences in vulnerability of the cultivars showed that tomato cultivars possess resistant traits and the identification and utilisation of these traits can give rise to resistant varieties.     

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.     

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.     

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.     

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.     

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.     

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.     

Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae), a newly recorded parasitoid of the tomato moth, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in Argentina

We report the first record of Neochrysocharis formosa (Westwood) parasitizing larvae of the tomato moth, Tuta absoluta (Meyrick), in tomato crops in Northern Buenos Aires Province, Argentina. Tomato moth larvae were sampled during four consecutive growing cycles, between 2003 and 2005, in 10 sites. Neochrysocharis formosa was present only in organic outdoor and protected crops, and predominantly during the late season. Parasitism rates varied from 1.5% to 5%. The finding of this species is a new record for Argentina and South America, and T. absoluta is a new host record.     

Efficacy of mating disruption compared with chemical insecticides for controlling Tuta absoluta (Lepidoptera: Gelechiidae) in Kuwait

Applied Entomology and Zoology - The efficacy of mating disruption with Isonet®-T at the rate of 30, 45 or 60 g a.i. ha –1 of sex pheromone to control Tuta absoluta (Meyrick)...     

Life table parameters of the tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae) on different tomato cultivars

The tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato plants originating from South America. In this study, the effect of three tomato cultivars on the life table parameters of T. absoluta was investigated. Data were analysed based on age‐stage, two‐sex life table theory. The net reproduction rate (R₀) of T. absoluta on Falkato, Isabella and Grandella cultivars was determined as 15.73 ± 3.35, 17.66 ± 3.33 and 10.03 ± 4.10 eggs, respectively. The intrinsic rate of increase (r) value on those cultivars was 0.09 ± 0.007, 0.095 ± 0.006 and 0.074 ± 0.017 day^?1, respectively. Finite population rates of increase (λ) were 1.095 ± 0.008, 1.099 ± 0.007 and 1.076 ± 0.018 day^?1, and mean generation times (T) on the three cultivars were 30.09 ± 0.29, 30.22 ± 0.27 and 31.12 ± 0.65 days, respectively. The egg incubation period, pre‐adult duration and fecundity on these tomato cultivars was also calculated. The results showed no significant differences between r, R₀, and T on the three tested tomato cultivars. These findings can be useful for developing an integrated pest management strategy against this noxious pest.     

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.