Population growth, phytophagy and olfactory response of three brazilian mirid predatory bugs (Hem.: Miridae) and herbivoreinduced plant volatiles from either Tuta absoluta or Bemisia tabaci on tomato

Abstract

Tomato borer Tuta absoluta (Meyrick) and silverleaf whitefly Bemisia tabaci (Gennadius) are key pests for tomato and cause considerable losses in crops when control measures are not adopted. The use of pesticides is the main control strategy of both pests in Brazil. However, alternative control methods are needed. Mirid predatory bugs Macrolophus basicornis (Stal), Engytatus varians (Distant) and Campyloneuropsis infumatus (Carvalho) present high capacity for preying tomato pests such as B. tabaci and T. absoluta, and are now being evaluated as biological control agents. The objectives of this work were to evaluate the population growth of these three mirid species feeding on T. absoluta eggs and larvae, as well as to assess the type and risk of damage caused by nymphs and adults on tomato seedlings and fruits in the absence of prey and at high population density. Subsequently, the response of these three mirids to herbivory caused by T. absoluta and B. tabaci were investigated using Y-tube olfactometer experiments. Finally, a comparative analysis of volatile blends released by tomato plants infested with T. absoluta, with B. tabaci and with both pests was conducted. Nymphs and adults successfully used T. absoluta as prey, although significant differences in the biology of the species were observed. They were able to survive and their populations increased having T. absoluta as prey. Both nymphs and adults of the three mirid predators caused feeding rings on the leaflets of tomato seedlings. The injuries consisted of blemishes characterized by feeding punctures surrounded by a yellowish, bleached area. The nymphs of all three mirid species caused injuries to tomato fruit. The type of damage was similar to that occurred on tomato seedling, however, in less quantity. At the end of the evaluations the number of feeding rings on tomato seedling and fruit did not exceed one per individual, and tomato seedlings developed normally. Results of the Y-tube experiments revealed that T. absoluta egg deposition did not cause plants to be more attractive to the predators than uninfested plants. Macrolophus basicornis is attracted to plants infested with either T. absoluta larvae or B. tabaci nymphs. Engytatus varians and C. infumatus responded only to tomato plants infested with T. absoluta larvae over uninfested plants. In addition, plants simultaneously infested with both prey species were as attractive to the predators as plants infested with one only of the prey species. A total of 80 volatiles organic compounds (VOCs) was recorded. The difference in VOC composition among the treatments was largely influenced by herbivory, enhancing the emission rate of several compounds. Plants damaged by T. absoluta emitted higher levels of many compounds when compared to plants damaged by the phloem-feeder B. tabaci and intact plants. In conclusion, M. basicornis, E. varians and C. infumatus populations increased feeding on T. absoluta; they do not cause damage on tomato seedlings/fruits and respond to tomato infested with key pests. Thus, they are good candidates for the biological control of T. absoluta and other tomato crop pests.