Efficacy of two predatory mirid bugs as candidates for the control of tomato pests


Abstract: In this study, we evaluated two predatory mirid species, Dicyphus errans and D. bolivari, present in the Mediterranean region, for the control of T. absoluta. We tested them in the presence of B. tabaci because both pests simultaneously infest the crop in most of the greenhouses. We evaluated consumption rate of different developmental stages of the two predator species on both pests in laboratory tests; predator's control capacity of the two pests in a full crop cycle in walk-in cages inside a greenhouse; and the prey consumption of D. errans when the two prey species were offered in single or mixed diets in small cages with individual plants.Based on results of laboratory experiments, both predatory species could be similarly efficient in the suppression of both pests, and more specifically in the control of T. absoluta.From greenhouse walk-in cages experiments, the main results indicated that there was a statistical significant higher number of nymphs and adults, almost four times more, of D. bolivari than of D. errans, indicating that the first species was more successful in establishing and developing its populations in our crop conditions. Regarding B. tabaci, there was a lower population in D. bolivari treatment than in the control treatment, with an intermediate population of whiteflies in D. errans treatment. When examining the total weight of fruits collected, a significantly higher yield was obtained in D. bolivari treatment than in D. errans or in the control treatment. As to Tomato leaf miner, a similar number of tomato leaflets containing T. absoluta mines were found in both predators’ treatments and these numbers were significantly lower than those registered in the control treatment, showing that the two predators are able to suppress T. absoluta populations. We could conclude that both predators were similarly efficient in reducing populations of B. tabaci while D. errans was more efficient in reducing populations of T. absoluta.Results from semi-field experiments showed that when only B. tabaci was offered to the predator, a statistical significant lower number of adult whiteflies (56% of population reduction) was observed in the predator than in the control treatment at the end of the test. In addition, plants were statistical significant taller in the predator treatment than in the control. When only T. absoluta was available for the predator, a statistically similar moth population was observed in the predator than in the control treatment, and plants were all of the same height. When both preys were offered together, a statistical significant lower number of both prey (83% reduction of B. tabaci adults and 77% T. absoluta eggs), was observed in the predator treatment in comparison with the control treatment. Population growth of D. errans was statistical significant higher in the treatment with B. tabaci + T. absoluta than in that with only T. absoluta, and intermediate numbers were observed in the treatment with only B. tabaci.The common situation in Mediterranean greenhouses in which B. tabaci and T. absoluta coexist is a good combination for the development of D. errans populations and therefore for their impact in the control of both pests. In conclusion, D. errans could be a good candidate for biological control of tomato pests in Mediterranean greenhouses.

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