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 zeaoccur 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.

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Tuta absoluta (Meyrick), a key pest of tomato, is quickly spreading over the world and biological control is considered as one of the control options. Worldwide more than 160 species of natural enemies are associated with this pest, and an important challenge is to quickly find an effective biocontrol agent from this pool of candidate species. Evaluation criteria for control agents are presented, with the advantages they offer for separating potentially useful natural enemies from less promising ones. Next, an aggregate parameter for ranking agents is proposed: the pest kill rate km. We explain why the predator's intrinsic rate of increase cannot be used for comparing the control potential of predators or parasitoids, while km can be used to compare both types of natural enemies. As an example, kill rates for males, females and both sexes combined of three Neotropical mirid species (Campyloneuropsis infumatus (Carvalho), Engytatus varians (Distant) and Macrolophus basicornis (Stål)) were determined, taking all life-history data (developmental times, survival rates, total nymphal and adult predation, sex ratios and adult lifespan) into account. Based on the value for the intrinsic rate of increase (rm) for T. absoluta and for the kill rate km of the predators, we predict that all three predators are potentially able to control the pest, because their km values are all higher than the rm of the pest. Using only km values, we conclude that E. varians is the best candidate for control of T. absoluta on tomato, with C. infumatus ranking second and M. basicornis last.

Knowledge of the optimal temperatures for development and survival of biological control agents is essential for efficient mass-rearing and introduction of natural enemies in augmentative biological control programs. We studied the effect of constant and alternating temperatures on development and survival of immature stages and the sex ratio at emergence of adults of the Nearctic generalist predator Geocoris punctipes (Say). We also determined its thermal requirements. They were reared in climatic chambers at alternating (21/11°C, 24/18°C, 27/21°C and 30/26°C ± 1°C) and constant temperatures (16.8°C, 21.5°C, 24.5°C and 28.3°C ± 1°C), RH 70 ± 10% and a 14 h photophase. Survival and development of G. punctipes were the same when reared at constant and alternating temperatures. Five instars were recorded in all temperature regimes. The duration of the egg stage and each instar, as well as that of total larval development were longer, and larval survival lower when reared at 16.8°C, 21/11°C, 21.5°C and 24/18°C than at 24.5°C, 27/21°C, 28.3°C and 30/26°C. The optimal temperature range for development and survival of G. punctipes is 24.5°C to 30°C, its lower development threshold temperature is 13.5°C and its thermal constant 295.9 DD. Sex ratios were not significantly different from 1 : 1 male : female ratio in all temperature regimes. There is an excellent match between the temperature regimes at which the prey Tuta absoluta (Meyrick) and predator G. punctipes are active, which indicates that this predator will function well in crops where this pest is present.

Ecologists study how populations are regulated, while scientists studying biological pest control apply population regulation processes to reduce numbers of harmful organisms: an organism (a natural enemy) is used to reduce the population density of another organism (a pest). Finding an effective biological control agent among the tens to hundreds of natural enemies of a pest is a daunting task. Evaluation criteria help in a first selection to remove clearly ineffective or risky species from the list of candidates. Next, we propose to use an aggregate evaluation criterion, the pest kill rate, to compare the pest population reduction capacity of species not eliminated during the first selection. The pest kill rate is the average daily lifetime killing of the pest by the natural enemy under consideration. Pest kill rates of six species of predators and seven species of parasitoids of Tuta absoluta were calculated and compared. Several natural enemies had pest kill rates that were too low to be able to theoretically reduce the pest population below crop damaging densities. Other species showed a high pest reduction capacity and their potential for practical application can now be tested under commercial crop production conditions.

Tuta absoluta (Meyrick; Lepidoptera: Gelechiidae) is a key pest of tomato and is quickly spreading over the world. We conducted an experiment aimed at evaluating the control capacity and risk for plant damage of three Neotropical mirid species, Campyloneuropsis infumatus (Carvalho; Hemiptera: Miridae), Engytatus varians (Distant; Hemiptera: Miridae) and Macrolophus basicornis (Stal; Hemiptera: Miridae) on T. absoluta infested tomato plants in large cages in an experimental greenhouse. During three successive periods of 9 wk each, we followed population development of the three mirids when exposed to T. absoluta, and of T. absoluta alone in separate cages in the greenhouse. We determined weekly the numbers of T. absoluta eggs and larvae per leaf, the number of mirid predators per leaf, the percentage of damaged leaves and fruits by T. absoluta, and the weight of fruits. Two of the mirid predators, C. infumatus and M. basicornis, successfully established on T. absoluta infested tomato plants and significantly reduced T. absoluta numbers, which ultimately resulted in an increased yield. These two mirid species hardly injured tomato plants or fruits as a result of plant feeding. Surprisingly, the species E. varians, which showed high predation rates in laboratory experiments, did not establish and reduce pest populations in any of the tests.

During the past decade, the use of predatory mirids alone or combined with releases of egg parasitoids of the genus Trichogramma have been tested in Europe for biological control of the worldwide invasive pest, Tuta absoluta (Meyrick). Here, we evaluated the control of this pest by the release of the Neotropical mirid Macrolophus basicornis (Stal), the Neotropic/Nearctic parasitoid Trichogramma pretiosum Riley, and by combined releases of the predator and the parasitoid. Tests were conducted in greenhouse compartments during the summer and fall season. Each compartment contained 10 tomato plants in which only the pest was released or the pest with 1 or 2 natural enemies. Plant damage, and pest and natural enemy densities were checked weekly on one apical, medium, and bottom leaf of 5 plants. Both M. basicornis and T. pretiosum significantly reduced T. absoluta density when released alone. Combined releases resulted in a 10% higher reduction during the summer season, but not during the fall season. The damage caused by T. absoluta was significantly higher in control treatments than in all natural enemy treatments: at the end of the summer trial leaves were completely damaged in the control treatment, whereas only up to 25% leaf damage occurred in the natural enemy treatments. Combined releases did not result in lower damage than with releases of either M. basicornis or T. pretiosum. Practical aspects of single and combined releases are discussed.