Heteropteran Bugs Assemblage Associated to Organic Tomato Farms: Knowledge for Pest Management.

The suborder Heteroptera (Hemiptera) includes zoophagous and zoophytophagous species which conform diverse natural enemies' systems with potential to control several horticultural pests. In this study, we report the assemblage structure of heteropteran bugs species inhabiting open-field and greenhouse organic tomato crops and one common adjacent non-crop solanaceous plant, Solanum sisymbriifolium, in North Buenos Aires province, Argentina, aimed to select promissory biocontrol species. Biweekly direct inspection of selected plants was carried out during a 3-year period (2017-2019) to collect hemipteran nymphs and adults. As a result, nine species and morphospecies belonging to Berytidae (zoophytophagous), Lygaeidae (phytophagous), and Miridae (phytophagous and zoophytophagous) were found, with ≥ 75% of species belonging to the latter family. The zoophytophagous mirid Tupiocoris cucurbitaceus (Spinola) was the most frequent and dominant species in all sites studied. Among the phytophagous species, Nysius simulans Stål was mostly present in greenhouse crops. The community found in greenhouse tomato crops was more diverse than that registered in open-field crops. The characterization of the heteropteran complex in organic tomato farms provides basic knowledge necessary to design pest control strategies in the region studied.

Performance of Pseudapanteles dignus (Hymenoptera: Braconidae), a Natural Enemy of Tuta absoluta (Lepidoptera: Gelechiidae) in Eggplant.

Pseudapanteles dignus (Muesebeck; Hymenoptera: Braconidae) is an American endoparasitoid that attacks the South American tomato leafminer Tuta absoluta (Meyrick; Lepidoptera: Gelechiidae). The interaction between P. dignus and T. absoluta in tomato (Solanum lycopersicum L.; Solanales: Solanaceae) crops has demonstrated that this enemy exhibits some desirable ecological traits as an effective biological control agent of this pest. With the aim of extending the use of P. dignus to other solanaceous crops, laboratory experiments were carried out to assess some life history traits and the parasitism efficiency when parasitizing T. absoluta larvae fed on eggplant (Solanum melongena L.; Solanales: Solanaceae). Rearings and experiments were conducted at 25 ± 2°C, ≈70% RH, and 14:10 (L:D) h photoperiod, and T. absoluta was fed with eggplant. P. dignus developmental times of immature stages were lower (~ 5 d) on S. melongena than on S. lycopersicum. The female did not exhibit a pre-reproductive period, and its oviposition period lasted longer (~ 4 d) than that determined in tomato plants. Adult longevity was ca. 24 d for both sexes. Females produced ca. 61 cocoons during their lives and the maximum daily percentage of parasitism was 50% at the first day of adult emergence. Functional response of P. dignus on eggplant was density-independent of the host density offered, as in tomato plant, and the instantaneous attack rate (a') was 0.24 attacked larvae/ available larvae, in 24 h. Our results indicate that although there are differences, P. dignus would have a similar performance in eggplant and tomato in terms of its efficacy in the control of T. absoluta.

Intraguild predation and competitive displacement between Nesidiocoris tenuis and Dicyphus maroccanus, two biological control agents in tomato pests.

Dicyphus maroccanus Wagner and Nesidiocoris tenuis Reuter (Hemiptera: Miridae) are 2 biological control agents in tomatoes. Through the crop seasons, a natural shift in the occurrence of both mirids in favor of N. tenuis has been observed at the end of the cropping cycle in eastern Spain. To better optimize their conservation, the reasons for the observed change, such as intraguild interactions (IGP) or the influence of environmental conditions, are worth elucidating. To do this, we first studied the IGP of adult females on heterospecific nymphs in the laboratory. We next studied exploitative competition between adults and nymphs of each species when feeding on Ephestia kueniella Zeller (Lepidoptera: Pyralidae) eggs in the laboratory. Finally, to analyze the competitive displacement between both mirids, we conducted a semifield experiment in which both predators were released together. All experiments were conducted at 2 temperature regimes (20 and 25°C). Adult-to-nymph intraguild interactions occurred only at 25 ºC at very low levels, showing that N. tenuis attacked and consumed a greater proportion of heterospecific nymphs. Nesidiocoris tenuis was a better competitor than D. maroccanus when feeding on the shared prey in the presence of its heterospecific nymph at 25 ºC. In semifield conditions, N. tenuis showed a competitive advantage over D. maroccanus at both temperatures. We conclude that there is not direct interference between both species, however, N. tenuis has a greater ability to outcompete, since it is best adapted to higher temperatures and it is able to remove food sources for D. maroccanus.