Pest Of Tomato Crops Research Articles

Evaluation of the effectiveness of some protection products against the Tuta absoluta pest in tomato crops from southern Romania

Evaluation of the effectiveness of some protection products against the <i>Tuta absoluta</i> pest in tomato crops from southern Romania

Decision-making systems for controlling L. huidobrensis in tomato crops using principles of precision agriculture

Decision-making systems are key components in integrated pest management (IPM). Tomato (Solanum lycopersicum) is the second most cultivated vegetable worldwide. The leaf miner L. huidobrensis (Diptera: Agromyzidae) is one of the main pests in tomato crops around the world and can causes up to 15% of yield losses. Decision-making in precision agriculture is performed on management zones. This approach enables cost reducing, yield enhancement, and reduction of environmental harm. Our research proposes a decision-making system to manage L. huidobrensis in tomato crops, using a precision agriculture management zone approach. We compared the decision-making systems: CI (periodic application calendar), IPM-CS (conventional sampling plan and economic injury level of 3.24 mines. leaf−1), IPM-SS (sequential sampling plan), and IPM-MZ (management zone). Systems IPM-CS, IPM-SS and IPM-MZ reduced 66% of application indications compared to systems CI. Systems IPM-CS and IPM-SS generated errors of 5% and 3% in the decisions of control and no control, respectively. System IPM-MZ had the utmost economic performance, followed by IPM-SS and IPM-CS. Therefore, the IPM-MZ is a promising system to be incorporated into the IPM tomato program for L. huidobrensis control decision-making on zones in which the pest can reach the economic threshold, enhancing crop yield.

Modelling the interaction between a pest (Aculops lycopersici), two predators (Pronematus ubiquitus and Macrolophus pygmaeus) and climate variables: a 3-year greenhouse study in a tomato crop.

The tomato russet mite, Aculops lycopersici, is a major pest in tomato crops, causing damage through leaf and stem browning, defoliation and russeting of fruit. Biological control of this mite on tomato plants is difficult. While several phytoseiid mites feed on the pest, they cannot survive, move, or reproduce on tomato plants due to the presence of glandular trichomes. Pronematus ubiquitus has recently been identified as a biocontrol agent of A. lycopersici in tomato crops, but the predator-prey interaction between these two species is not well studied. In this paper, we present a validated logistic regression predator-prey model based on a 3-year study supplemented with additional datasets. Besides the predator and the prey, this model takes into account an extra generalist predator, Macrolophus pygmaeus, and various climate parameters. The population trend of A. lycopersici is best explained by the presence of the predator P. ubiquitus, the relative humidity and the fact that the crop was lit or unlit using artificial light. P. ubiquitus has proved to be an efficient biocontrol agent of A. lycopersici. For P. ubiquitus the presence of M. pygmaeus, the vapour pressure deficit, the number of light hours and radiation explained the population trend best. For both the predator and the prey density-dependent interactions were identified. Model outcomes are discussed in detail. Our study provides insights into the potential use of P. ubiquitus as a biocontrol agent for A. lycopersici in tomato crops in combination with M. pygmaeus. However, we highlight the importance of considering the presence of other predators and environmental conditions when developing integrated pest management strategies. © 2023 Society of Chemical Industry.

Predatorska stenica Nesidiocoris tenuis (Heteroptera: Miridae), prirodni neprijatelj štetnih insekta u plasteničkoj proizvodnji paradajza

Species of zoophytophagous genus Dicyphina, plant bugs (Hemiptera: Miridae: Bryocorinae) are among the most abundant and effective predators of tomato pests. Nesidiocoris tenuis Reuter, 1895 (Hemiptera: Miridae) is the predominant species of Dicyphina sp. and it is considered to be a major natural enemy of insect pests in tomato crops in the Mediterranean region. This predatory bug is proved to be particularly successful in suppressing Tuta absoluta Meadow, 1917 (Lepidoptera: Gelechiidae), a major pest of tomato in greenhouse production. Aims of the study were to 1) investigate the efficiency of the mirid predatory bug N. tenuis in greenhouse tomato production and 2) to estimate the possibilities of its application in commercial vegetable production in Western Balkan countries of Europe. The significance of the study results relies on the possibility of commercialisation and general promotion of biological agent N. tenuis in tomato production in South East part of Europe, where the usage of pesticides still dominates the field of plant protection, both in vegetables and other agricultural sectors. According to the obtained results, the biological agent N. tenuis represents a reliable tool for controlling the level of the tomato leaf miner population by keeping the pest below its economic and intervention threshold.

ASPECTS REGARDING THE APPEARANCE AND EVOLUTION OF THE PEST TUTA ABSOLUTA (LEPIDOPTERA: GELECHIIDAE) IN TOMATO CROPS IN GREENHOUSES

The most important vegetable crop in the world in greenhouses is tomato (Solanum lycopersicum L.) with an yield of 182 MT per year. Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) commonly known as ”tomato leafminer” or ”South American tomato moth” is the main pest in tomato crops in greenhouses, that can cause economic losses of up to 80-100%, if appropriate control measures are not taken. The experience was carried out during 2 years (2020-2021), between July and September, in greenhouse conditions (second cycle) in Vărăști village (Giurgiu county). The pest population was dynamically monitored by placing pheromone traps in the tomato crops in the high plastic tunnels, the average of the captured adults being 3367.5. In both years, the climatic conditions were favorable for the appearance and evolution of the pest attack. To prevent the spread of the attack, chemical treatments were applied at intervals of 7-10 days. In 2021, the yield obtained was with 4.76% higher than in 2020.

Trial of the use of aqueous extracts based on Artemisia annua L in the protection of soilless tomato crop (Solanum lycopersicum L. 1753) in Daloa (Central-Western Côte d'Ivoire)

Tomato (Solanum lycopercicum L) is one of the most cultivated crops in Côte d'Ivoire. However, its production is confronted with enormous constraints, especially the damage caused by pathogens and vectors of certain diseases. Faced with this damage, most growers resort to chemical products that are harmful to the environment, the user and consumers. Therefore, it becomes necessary to use the extract of Artemisia annua as a biopesticide in the control of diseases and pests of tomato crop in the field. The trial consisted in setting up an above ground tomato crop and then formulating a biopesticide based on Artemisia annua L at different doses (100% pure filtrate; 75% diluted filtrate; 50% and 25%) and applying it on the crop. It appears from this test that the biological extract based on Artemisia annua L , proved to be an insecticide or an insect repellent and biostimulator. Moreover, the dose of 100% of the pure extract of Artemisia annua L was the best on the agromorphological parameters and on the pathogenicity parameters.

The hunt for beneficial fungi for tomato crop improvement – Advantages and perspectives

Beneficial fungi with antagonistic and entomopathogenic properties have shown promising effect in the biological control of diseases and pests in a variety of commercially significant crops, including tomato, in recent years. Despite the fact that such treatments are environmentally safe, their risk on non-target species in tomato fields remains unknown. Beneficial fungi that have been commercialised for field use have had little effects on the population of arthropod pests and the incidence of diseases in tomato fields due to various reasons. The use of fungal antagonists and entomopathogenic fungi-based products for the management of diseases and pests of tomato crop has been done all over the world. The investigated reports, however, are scattered throughout the research papers, so they need to be compiled and discussed. Therefore, efficiency of antagonistic and entomopathogenic fungi against important pests and pathogens of tomato crop, as well as their practical use as biofungicides and bioinsecticides to reduce the use of synthetic pesticides, are discussed in this review paper. Besides, plant growth promotion activity of beneficial fungi, their appropriateness as an alternative of synthetic pesticides, and future prospects are also discussed.

Occurrence, biology, natural enemies and management of Tuta absoluta in Africa

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a devastating invasive pest of tomato crops in several areas around the world including Africa. Here, we comprehensively review and discuss the relevant scientific knowledge on its occurrence, biological and ecological aspects, fortuitous insect natural enemies, and potential advantages and constraints of pest management scenarios adopted against this pest in tomato crops in both Northern and Sub-Saharan Africa. We conclude the manuscript with a comprehensive research agenda providing future priorities towards sustainable control of this important tomato pest.

How Safe Is It to Rely on Macrolophus pygmaeus (Hemiptera: Miridae) as a Biocontrol Agent in Tomato Crops?

Omnivorous mirids (Hemiptera: Miridae) are unusual as biocontrol agents, as they feed on both plants and pests. Therefore, extensive knowledge of their ecological behavior is required to maximize their predatory side and to minimise crop damage. Macrolophus pygmaeus is a known predator of small arthropods, used in European tomato crops for more than 20 years. This mirid is currently considered harmless to tomato, although some controversy remains in relation to the status of the species. The aim of this work was to investigate the benefits that M. pygmaeus provides as a predator and the likely damage as a plant feeder. The experiment was carried out in 6 experimental greenhouses in southern Spain. Two treatments, low and high M. pygmaeus populations, were assayed in a complete factorial randomized design with three replicates. Low and high M. pygmaeus populations were achieved by direct and pre-plant release methods, respectively. Tomato plants with a lower number of M. pygmaeus had a significantly higher number of whiteflies and Tuta absoluta galleries than those with a higher number of the mirid, and vice versa. A significantly higher proportion of aborted flowers and fruits was registered in greenhouses with higher M. pygmaeus numbers. Yield was also lower in greenhouses with higher mirid populations. The number of fruits harvested did not differ between treatments, but average fruit weight was significantly lower in the greenhouses with higher mirid numbers. The number of punctures attributed to M. pygmaeus on fruits were low in general and slightly higher in the treatment with more mirids. This work shows that M. pygmaeus provides both services, as an efficient biocontrol agent of key pests in tomato crops, and disservices, as it feeds on the reproductive organs of tomato plants, reducing yield. A deeper understanding of the factors that modulate the zoophytophagous response of this economically important species is needed.

Impact of Feeding on Contaminated Prey on the Life Parameters of Nesidiocoris Tenuis (Hemiptera: Miridae) Adults.

Insecticide selectivity to natural enemies is an important concern in integrated pest management programs. Although there is a wide range of information concerning pesticide lethal and sublethal effects on contaminated surfaces, little is known when the route of exposure occurs at a trophic level. This study evaluates this route of pesticide intake on the omnivorous predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) for the first time. Under laboratory conditions, prey treated with six insecticides (flubendiamide, spirotetramat, deltamethrin, flonicamid, metaflumizone, and sulfoxaflor) were offered to N. tenuis adults for 3 days. Mortality (24, 48, and 72 h after treatment), offspring production (third until eighth day) and longevity were documented. Metaflumizone and sulfoxaflor were classified as moderately harmful products because although the percentage of mortality was only 28 and 36%, respectively, both products caused a severe decrease in offspring production and longevity. Flonicamid and flubendiamide were classified as slightly harmful products; although they did not have a lethal effect, sublethal impact was important on the parameters studied. Spirotetramat and deltamethrin were insecticides categorized as harmless. This information could be useful for selecting the most appropriate insecticides to control pests in tomato crops in which N. tenuis is a relevant biological control agent.

Generating Within-Plant Spatial Distributions of an Insect Herbivore Based on Aggregation Patterns and Per-Node Infestation Probabilities.

Most predator-prey models extrapolate functional responses from small-scale experiments assuming spatially uniform within-plant predator-prey interactions. However, some predators focus their search in certain plant regions, and herbivores tend to select leaves to balance their nutrient uptake and exposure to plant defenses. Individual-based models that account for heterogeneous within-plant predator-prey interactions can be used to scale-up functional responses, but they would require the generation of explicit prey spatial distributions within-plant architecture models. The silverleaf whitefly, Bemisia tabaci biotype B (Gennadius) (Hemiptera: Aleyrodidae), is a significant pest of tomato crops worldwide that exhibits highly aggregated populations at several spatial scales, including within the plant. As part of an analytical framework to understand predator-silverleaf whitefly interactions, the objective of this research was to develop an algorithm to generate explicit spatial counts of silverleaf whitefly nymphs within tomato plants. The algorithm requires the plant size and the number of silverleaf whitefly individuals to distribute as inputs, and includes models that describe infestation probabilities per leaf nodal position and the aggregation pattern of the silverleaf whitefly within tomato plants and leaves. The output is a simulated number of silverleaf whitefly individuals for each leaf and leaflet on one or more plants. Parameter estimation was performed using nymph counts per leaflet censused from 30 artificially infested tomato plants. Validation revealed a substantial agreement between algorithm outputs and independent data that included the distribution of counts of both eggs and nymphs. This algorithm can be used in simulation models that explore the effect of local heterogeneity on whitefly-predator dynamics.

Overwintering potential of the invasive leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) as a pest in greenhouse tomato production in Western Europe

The South American tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest in tomato crops. After having spread rapidly in the Mediterranean area since its first detection in 2006, it has recently become established in greenhouses in Western Europe. It was assumed that the low temperatures commonly associated with the winters in this area would prevent this exotic species from successful overwintering. However, the observed presence of T. absoluta at the start of the growing season in Belgium sparked a study on its potential to overwinter in Western Europe. In this study, the insect’s cold hardiness and overwintering potential was assessed by determining: (1) the supercooling point (SCP) of larvae, pupae, and adults, (2) the lower lethal time (LT) for these stages at 0 and 5 °C, and (3) the reproductive diapause incidence, as indicated by the reproductive performance of females reared at two temperatures (18 and 25 °C) and two photoperiods [16:8 and 8:16 (L:D) h]. The mean SCP recorded for pupae (−16.7 °C) was significantly higher than for adults (−17.8 °C) and larvae (−18.2 °C). Based on estimates of the LT adults demonstrated better cold hardiness than larvae and pupae at both 0 and 5 °C with the median LT of adults averaging 17.9 and 27.2 days, respectively. No reproductive diapause was observed under the tested regimes. The results of this study indicate that T. absoluta is likely to successfully overwinter between two successive tomato crops in commercial greenhouses in Western Europe.

Suitability of the Pest-Plant System &lt;I&gt;Tuta absoluta&lt;/I&gt; (Lepidoptera: Gelechiidae)-Tomato for &lt;I&gt;Trichogramma&lt;/I&gt; (Hymenoptera: Trichogrammatidae) Parasitoids and Insights for Biological Control

The South American tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is a major pest that has recently invaded Afro-Eurasia. Biological control, especially by Trichogramma parasitoids, is considered to be promising as a management tool for this pest. However, further development of Trichogramma-based biocontrol strategies would benefit from assessing the impact of released parasitoid offspring on the pest. Under laboratory conditions, we 1) compared the parasitism of five Trichogramma species-strains on the pest-plant system T. absoluta-tomato, and 2) assessed various biological traits of parasitoids, mass-reared on a factitious host (Ephestia kuehniella Zeller), when developing on T. absoluta. In addition, we evaluated the overall efficiency of two specific Trichogramma species when released under greenhouse conditions in combination with a common natural enemy in tomato crop, the predator Macrolophus pygmaeus Rambur. Parasitoids emerging from T. absoluta on tomato showed lower parasitism rates and poor biological traits, for example, wing deformations, reduced longevity, when compared with the control reared on the factitious host. Under greenhouse conditions, the parasitoids that developed on T. absoluta after initial releases contributed little to biological control of T. absoluta, and parasitism tended to be lower when the predator was present. However, a slightly higher T. absoluta control level was achieved by combining the predator and release of the parasitoid Trichogramma achaeae Nagaraja and Nagarkatti. This study shows that Trichogramma parasitoids may not build up populations on the T. absoluta-tomato system, but that Trichogramma parasitoids can be used in combination with M. pygmaeus to enhance biological control of the pest in tomato crops.

Researches Concerning the Spreading of Tuta Absoluta Species into Greenhouses from West of Romania

Tuta absoluta - the tomato leafminer originated from South America was signaled for the first time in the South of Spain in 2006. In Romania Tuta absoluta was detected for the first time in the Western part of the country, into a grange from Satu Mare county in 2009. A year later, in the spring of 2010 its attack was signaled into greenhouses from Curtici, situated in Arad county. We studied the phytosanitary spreading area of Tuta absoluta, into solariums and greenhouses. Observations were made in the greenhouse from west of Romania. The tomatoes crops from greenhouse were verified to establish the frequency of pest attack. There were found insignificant pest attacks of Tuta absoluta in the first months, but in the last weeks we found major attack of this pest in tomato crops. Tuta absoluta is a specie whose area of distributions is expanding. Specialists in the field of plant protection should give special attention to monitoring this invasive pest.

Do the interactions among natural enemies compromise the biological control of the whitefly Bemisia tabaci?

The whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a worldwide pest which has become one of the main pests in tomato crops. The predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae) and the parasitoid Eretmocerus mundus (Mercet) (Hymenoptera: Aphelinidae) have shown their efficacy at controlling B. tabaci populations when used as biological control agents. Intraguild predation (IGP) between natural enemies can affect their effectiveness at controlling pests. In the present study, the interaction of these three natural enemies and their effect on B. tabaci was studied on tomato plants by combining morphological observations and molecular analysis of trophic interactions. Under the conditions used in the present study, no IGP was detected between M. pygmaeus and N. tenuis by either counting dead predators or by PCR using prey-specific cytochrome c oxidase I primers. However, predation on B. tabaci decreased when they coexisted on the same plant, which could compromise the biological control of this pest. Although PCR analyses using E. mundus-specific primers showed predation on B. tabaci-parasitized nymphs in 27 % of M. pygmaeus and 17 % of N. tenuis, B. tabaci control was improved when both predators coexisted on the same plant with the parasitoid. The combined use of E. mundus and M. pygmaeus/N. tenuis is therefore recommended in order to improve B. tabaci control in conservation biological control strategies.

Potential for combined use of parasitoids and generalist predators for biological control of the key invasive tomato pest Tuta absoluta

The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has recently invaded Mediterranean countries and is a major pest in tomato crops. Trichogrammatid oophagous parasitoids have shown promising potential for controlling the pest before the yield decreases in the greenhouse. In protected tomato crops (greenhouse), mirid predators are commonly used for biological control of whiteflies and they also prey on T. absoluta. These predators do not attack Trichogramma adults but they may partially decrease the overall impact of parasitoids on T. absoluta if intraguild predation (IGP) occurs on parasitized eggs. Under laboratory conditions, we tested if the mirid predator Macrolophus pygmaeus shows preference between parasitized and unparasitized T. absoluta eggs. We also tested if the predator reduces the number of parasitized eggs on caged tomato plants (microcosms) and assessed the efficacy of natural enemies used alone or together in limiting T. absoluta populations. We found that IGP is inflicted on the parasitoid Trichogramma achaeae by M. pygmaeus and that the risk of IGP depends on the developmental stage of T. achaeae inside the egg because the larva is at risk mostly early in its development (when parasitized egg is still yellow). In addition, we observed that non-consumptive events, likely probing of the predator on parasitized eggs, may induce mortality in parasitoid offspring without actual feeding on parasitized eggs. However, both IGP and non-consumptive events decreased when the predator was not confined with parasitized eggs in small arenas. Despite negative effects of the predator to the parasitoid, results demonstrate that adding Trichogramma parasitoids may significantly increase the level of control of the pest over what could be attained when only the mirid predator M. pygmaeus is present on tomato. Implications of results are discussed regarding potential of these natural enemies for biological control of T. absoluta in greenhouse tomato crops.

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

AbstractThe 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.

Trophic relationships between predators, whiteflies and their parasitoids in tomato greenhouses: a molecular approach

The whiteflies Bemisia tabaci Gennadius and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are two of the main pests in tomato crops. Their biological control in Mediterranean IPM systems is based on the predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae), as well as on the parasitoids Eretmocerus mundus (Mercet) and Encarsia pergandiella Howard (Hymenoptera: Aphelinidae). These natural enemies may interact with each other and their joint use could interfere with the biological control of those whitefly pests. Analysis of predator-prey interactions under field conditions is therefore essential in order to optimize whitefly control. Species-specific polymerase chain reaction (PCR)-primers were designed to detect DNA fragments of these whiteflies and parasitoids within both predator species in tomato greenhouses. We demonstrated that both predators feed on both whitefly species, as well as on both parasitoids under greenhouse conditions. Prey molecular detection was possible where prey abundance was very low or even where predation was not observed under a microscope. Whitefly DNA detection was positively correlated with adult whitefly abundance in the crop. However, a significant relationship was not observed between parasitoid DNA detection and the abundance of parasitoid pupae, even though the predation rate on parasitoids was high. This unidirectional intraguild predation (predators on parasitoids) could potentially reduce their combined impact on their joint prey/host. Prey molecular detection provided improved detection of prey consumption in greenhouse crops, as well as the possibility to identify which prey species were consumed by each predator species present in the greenhouse, offering a blueprint with wider applicability to other food webs.

Impact of the Zoophytophagous Plant Bug &lt;I&gt;Nesidiocoris tenuis&lt;/I&gt; (Heteroptera: Miridae) on Tomato Yield

Nesidiocoris tenuis Reuter (Heteroptera: Miridae) is one of the most controversial dicyphines because of the injuries it causes to tomato (Solanum esculentum) crops. The aim of this study was to quantify the impact of N. tenuis on fruit yield. Tomato plants were exposed to an average of 0.53 +/- 0.26, 3.4 +/- 1.1, 12.0 +/- 1.4, and 35.2 +/- 7.7 N. tenuis per plant for 3 wk. When fruit were exposed to N. tenuis as flowers, the percentage of aborted fruit was higher in compartments infested with N. tenuis, and this was related directly to the cumulative number of N. tenuis (CNN). However, compartments with the highest abortion rates had heavier and bigger fruit and were not significantly different from the controls. The variation in fruit weight was satisfactorily explained with a logistic equation in relation to the proportion of aborted fruit. To estimate the density thresholds, the variation in truss weight was predicted as a function of fruit weight and aborted fruit. The two latter variables were expressed as a function of the CNN. A maximum of 15% truss weight overcompensation was predicted at 15.8% of fruit abortion. Yield reduction was predicted at fruit abortion rates > or = 27.7%, which corresponded to 566 CNN per plant or 32.11 CNN per leaf. N. tenuis may be considered a useful predator of small pests in tomato crops if kept under these thresholds. Mathematical models predict a yield increase and fruit upgrade that overcompensates for the reduction in the number of fruit below the density threshold.

Colonisation of tomato fields by predatory mirid bugs (Hemiptera: Heteroptera) in northern Spain

Dicyphus tamaninii and Macrolophus caliginosus are predatory bugs that significantly contribute to control of pests in tomato crops following early colonisation in spring from winter refuges. This paper aimed to determine the influence of the richness of nearby potential predator sources at the time of arrival, amount and establishment of the mirid bugs in tomato fields. For this, six tomato fields were selected that showed a gradient of vegetational settings in the landscape. Crops and non-crop vegetation were sampled with a vacuum suction sampler and abundance of potential colonising predators was estimated. Soon after transplantation of tomatoes, weekly visual counts on the crop were initiated and continued for 8 weeks to estimate densities of Trialeurodes vaporariorum adults, the most abundant pest, and predator adults and nymphs. Time of predator arrival in each field, which varied between 6 and 8 weeks after seedling transplantation, was not related to the respective predator abundance in the surrounding vegetation. Eleven weeks after transplantation, fields differed in their cumulative numbers of insect-days (greenhouse whitefly, predator adults and nymphs). Differences in predator-days were not related to densities of greenhouse whitefly-days but to predator abundance in field surroundings. Fields were also colonised by predators coming from distant sources. Mirid bugs were more abundant in outer rows, particularly in fields with close predator sources and were concentrated on plants with higher whitefly densities. Predator nymphs were detected soon after adult arrival and distributed in the field mostly according to adult predator or prey spatial pattern. Presence of winter refuges for predators in nearby habitats increases the amount of colonisation. However, in order to rely on predator colonisation into fields, the stimuli involved in the predator movement from winter refuges to crops and the predator dispersal capacity should be further investigated.