The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest of tomato originating from South America. After its initial detection in eastern Spain in 2006, it rapidly invaded various other European countries and spread throughout the Mediterranean basin. If no control measures are taken, then the pest can cause up to 80–100% yield losses in tomato crops in recently invaded areas and may pose a threat to both greenhouse and open-field tomato production. The exceptional speed and extent of T. absoluta invasion have called for studies documenting its biology and ecology, while indicating an urgent need for efficient and sustainable management methods. The development of approaches to manage T. absoluta would be facilitated through a detailed revision of information on this pest in its area of origin. This review combines information on the invasion by T. absoluta, its ecology, and potential management strategies, including data that may help the implementation of efficient biological control programs. These programs, together with a variety of other management tactics, may allow efficient integrated pest management of T. absoluta in Europe and Mediterranean Basin countries.

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Biological invasion of European tomato crops by Tuta absoluta: ecology, geographic expansion and prospects for biological control

BACKGROUND: Insecticide resistance is a likely cause of field control failures of Tuta absoluta, but the subject has been little studied. Therefore, resistance to ten insecticides was surveyed in seven representative field populations of this species. The likelihood of control failures was assessed, as well as weather influence and the spatial dependence of insecticide resistance.

RESULTS: No resistance or only low resistance levels were observed for pyrethroids (bifenthrin and permethrin), abamectin, spinosad, Bacillus thuringiensis and the mixture deltamethrin + triazophos (<12.5-fold). In contrast, indoxacarb exhibited moderate levels of resistance (up to 27.5-fold), and chitin synthesis inhibitors exhibited moderate to high levels of resistance (up to 222.3-fold). Evidence of control failures was obtained for bifenthrin, permethrin, diflubenzuron, teflubenzuron, triflumuron and B. thuringiensis. Weather conditions favour resistance to some insecticides, and spatial dependence was observed only for bifenthrin and permethrin.

CONCLUSION: Insecticide resistance in field populations of the tomato pinworm prevails for the insecticides nowadays most frequently used against them—the chitin synthesis inhibitors (diflubenzuron, triflumuron and teflubenzuron). Local selection favoured by weather conditions and dispersal seem important for pyrethroid resistance evolution among Brazilian populations of T. absoluta and should be considered in designing pest management programmes. Copyright © 2011 Society of Chemical Industry

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Control failure likelihood and spatial dependence of insecticide resistance in the tomato pinworm, Tuta absoluta

Since its detection in the Mediterranean basin at the end of 2006 and later in other European countries, the South American tomato pinworm, Tuta absoluta (Meyrick), has become a serious threat to tomato crops. In newly infested areas, it is especially problematic during the first years of its presence. Nevertheless, after 2-3 years, the incidence of T. absoluta has become less severe in certain areas. There are several factors contributing to this decline, such as the increase in growers' knowledge of pest behaviour and biology and the correct application of integrated pest control strategies. The impact of opportunistic native natural enemies (fortuitous biological control) should be considered as one of the key factors in this decline. In this review, available information on indigenous natural enemies is updated, and the current pest management approaches used against T. absoluta are addressed. Finally, future scenarios for biological control of this pest are discussed.

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Prospects for the biological control of Tuta absoluta in tomatoes of the Mediterranean basin

Tuta absoluta (Meyrick) is an important tomato pest that also feeds on other host-plants from the Solanceae family. We studied the effect of two cultivated plants, tomato (Lycopersicum esculentum Mill.) and potato Solanum tuberosum L. on the development and populational parameters of T. absoluta related with host-plant suitability. Larval developmental time, pupal weight, mean fecundity and an index of host-plant quality (IPQ = pupal weight / frass weight) were estimated. Age-specific survivorship and fecundity life tables were constructed in the laboratory to evaluate the following populational parameters: net reproductive rate (Ro), intrinsic rate of increase (r) and generation time (T). Larval developmental time was shorter and pupal weight was higher (P < 0.0001) for larvae reared on tomato (P < 0.0001). Mean fecundity was not significantly different on both plants (P = 0.07) and food quality of host-plant was higher for tomato (P = 0.02). Mean population parameters on tomato were: Ro = 48.92; T = 27.98, r = 0.14; and on potato: Ro = 14.43; T = 32.35, r = 0.08. Although results showed that tomato was a more suitable host-plant and had a better nutritional quality than potato, when T. absoluta fed on potato the potential population increase requires attention. Under appropriate climatic conditions, spatial and temporal coincidence between crop and pest, T. absoluta could become a pest for the potato crop.

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Effect of two solanaceous plants on developmental and population parameters of the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato borer Tuta absoluta (Lepidoptera: Gelechiidae) is an invasive pest of tomato crops that is rapidly expanding around the world. It is considered a devastating pest and its control heavily relies on application of insecticides. Diamides are a novel class of insecticides acting on insect ryanodine receptors and are highly effective against lepidopteran pests. To date, chlorantraniliprole and flubendiamide have been registered in the market and they have been extensively used to manage T. absoluta. In this study, a survey was conducted in Greece and Italy monitoring diamide resistance. The populations originating from Sicily (Italy) exhibited LC50s that ranged between 47.6–435 for chlorantraniliprole and 993–1.376 for flubendiamide, while for Crete (Greece) LC50s ranged between 0.14–2.45 for chlorantraniliprole and 1.7–8.4 for flubendiamide (LC50s in mg L−1). Comparing this result to the susceptible reference strain, high resistance levels for the Italian populations were detected, i.e., up to 2,414- and 1,742-fold for chlorantraniliprole and flubendiamide, respectively. Resistance ratios for Greek populations were found up to 14-fold for chlorantraniliprole and 11-fold for flubendiamide, suggesting that diamide resistance is low but increasing considering monitoring data over time. Hereby, we report for the first time, cases of resistance development to diamide insecticides in T. absoluta. These findings underline the importance of committing to the resistance management strategies for diamide insecticides.

First report of Tuta absoluta resistance to diamide insecticides

PALAVRAS-CHAVE: Traca-do-tomateiro, deltametrina, abamectina, metamidofos, resistencia a inseticidas ABSTRACT - The tomato leafminer, Tuta absoluta (Meyrick), is one of the key pests of tomato in Argentina. Since its dispersal in the 1970s, chemical control has been the main method of controlling it. However, reduced efficacy of some of the recommended insecticides has been observed since the 1980s. The aim of this work was to study the toxicity of three insecticides widely used in chemical control of T. absoluta (abamectin, deltamethrin and methamidophos) on larvae from a laboratory susceptible population (CASTELAR) and two greenhouse populations (ROSARIO and BELLA VISTA). Insecticides were dissolved in acetone and topically applied to the mid-dorsal abdominal region of two- day old 4 th instar larvae. LD 50 values were estimated and the Resistance Ratio (RR) for each insecticide was calculated (RR = LD 50 value of each greenhouse population/LD 50 value of the susceptible population). ROSARIO and BELLA VISTA populations showed the following RRs values: > 68.38 for deltamethrin; 2.48 and 3.49 for abamectin, respectively; and 0.79 and 0.86 for metamidophos, respectively. Deltamethrin resistance observed in ROSARIO could be due to the high selective pressure exerted by pyrethroids in this location. Deltamethrin resistance in BELLA VISTA is more difficult to explain, because pyrethroids were scarcely used in the greenhouse where the insects were sampled. The incipient abamectin resistance detected in the BELLA VISTA population could result from the frequent use of this insecticide in this location, although natural variation can not be discarded.

CROP PROTECTION Insecticide Resistance in Argentine Populations of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato leafminer, Tuta absoluta (Meyrick), is one of the key pests of tomato in Argentina. Since its dispersal in the 1970s, chemical control has been the main method of controlling it. However, reduced efficacy of some of the recommended insecticides has been observed since the 1980s. The aim of this work was to study the toxicity of three insecticides widely used in chemical control of T. absoluta (abamectin, deltamethrin and methamidophos) on larvae from a laboratory susceptible population (CASTELAR) and two greenhouse populations (ROSARIO and BELLA VISTA). Insecticides were dissolved in acetone and topically applied to the mid-dorsal abdominal region of two-day old 4th instar larvae. LD50 values were estimated and the Resistance Ratio (RR) for each insecticide was calculated (RR = LD50 value of each greenhouse population/LD50 value of the susceptible population). ROSARIO and BELLA VISTA populations showed the following RRs values: > 68.38 for deltamethrin; 2.48 and 3.49 for abamectin, respectively; and 0.79 and 0.86 for metamidophos, respectively. Deltamethrin resistance observed in ROSARIO could be due to the high selective pressure exerted by pyrethroids in this location. Deltamethrin resistance in BELLA VISTA is more difficult to explain, because pyrethroids were scarcely used in the greenhouse where the insects were sampled. The incipient abamectin resistance detected in the BELLA VISTA population could result from the frequent use of this insecticide in this location, although natural variation can not be discarded.

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

Resumen en: Whiteflies of economic importance are polyphagous, being able to develop on a large number of cultivated and spontaneous plants. We recorded the whitefly...

Whitefl y species (Hemiptera: Aleyrodidae) on wild and cultivated plants in the horticultural region of Rosario, Santa Fe, Argentina

Many animals lay their eggs in clusters. Eggs on the periphery of clusters can be at higher risk of mortality. We asked whether the most commonly occurring clutch sizes in pentatomid bugs could result from geometrical arrangements that maximize the proportion of eggs in the cluster’s interior. Although the most common clutch sizes do not correspond with geometric optimality, stink bugs do tend to lay clusters of eggs in shapes that protect increasing proportions of their offspring as clutch sizes increase. We also considered whether ovariole number, an aspect of reproductive anatomy that may be a fixed trait across many pentatomids, could explain observed distributions of clutch sizes. The most common clutch sizes across many species correspond with multiples of ovariole number. However, there are species with the same number of ovarioles that lay clutches of widely varying size, among which multiples of ovariole number are not over-represented. In pentatomid bugs, reproductive anatomy appears to be more important than egg mass geometry in determining clutch size uniformity. In addition, within this group of animals that has lost most of its variation in ovariole number, clutches with a broad range of shapes and sizes may still be laid.

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Marcela M. Lietti

Papers

CROP PROTECTION Insecticide Resistance in Argentine Populations of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

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

Whitefl y species (Hemiptera: Aleyrodidae) on wild and cultivated plants in the horticultural region of Rosario, Santa Fe, Argentina

Protective geometry and reproductive anatomy as candidate determinants of clutch size variation in pentatomid bugs