Interactions between two mirid predators and their efficacy on whitefly control

Abstract: Mirid bugs are important zoophytophagous predators in protected cultures in the
Mediterranean. Dicyphus cerastii (Dc) and Nesidiocoris tenuis (Nt) occur naturally in
greenhouses in the Oeste region in Portugal. In addition, N. tenuis is extensively released for
the control of whiteflies and Tuta absoluta eggs. Plant damage caused by N. tenuis is more
severe than that caused by D. cerastii and can be of economic importance. Two different assays were performed in greenhouse simulating concrete scenarios to study the interaction between these mirid species and to compare their efficacy as biological control agents. For the first objective, different numbers of adult mirids (6 treatments) were placed inside cages with two potted tomato plants: 12 Dc; 8 Dc + 4 Nt; 6 Dc + 6 Nt; 4 Dc + 8 Nt; 12 Nt; control without
mirids. In all cases, equal numbers of females and males were used. This assay was repeated
twice, in autumn and late spring, for 6 or 7 weeks, respectively. Mirids were fed with eggs of
Ephestia kuehniella and Artemia sp. cysts. No differences were found between treatments. The highest means of total number of mirids at the end of the trial were observed in the 12 Nt
treatment in spring and 4 Dc + 8 Nt in autumn. To study their efficacy, 5 potted tomato plants infested with Bemisia tabaci were placed inside cages and 5 pairs (female: male) of Dc or Nt were released inside. Weekly, one plant was removed and observed. At the end, B. tabaci population was significantly lower in Nt cages.