Bruna Magda Favetti

Natural parasitism of Hexacladia smithii Ashmead (Hymenoptera: Encyrtidae) on Euschistus heros (F.) (Hemiptera: Pentatomidae): new record from Mato Grosso State, Brazil

The neotropical stink brown bug, Euschistus heros (F.) (Hemiptera: Pentatomidae), is an insect pest to soybean crops in Mato Grosso State, Brazil. In this region, synthetic insecticides are frequently used for insect control. An alternative to the indiscriminate use of insecticides is the biological control with parasitoids. Thus, the objective of this study was to conduct the survey of parasitoids that use E. heros adults as hosts. Random samples were conducted during the harvests of 2009/10 and 2010/11 in two farms that produce soybean (conventional system) in Tangara da Serra, Mato Grosso State, Brazil. The total number of collected E. heros was: 297 (Field 1) and 293 (Field 2) in 2009/10 and 295 (Field 1) and 376 (Field 2) in 2010/11. Of these, 1.50 (Field 1) and 13.99% (Field 2) were parasitized in 2009/10 and 8.47 (Field 1) and 7.45% (Field 2) in 2010/11. The parasitoids found were Hexacladia smithii Ashmead (Hymenoptera: Encyrtidae) in both fields. This is the first record of parasitism in E. heros adults in the state of Mato Grosso, Brazil.

Oviposition preference of the neotropical brown stink bug "Euschistus heros" on artificial substrates of different colors

This study aimed to evaluate the oviposition preference of the Neotropical brown stink bug, Euschistus heros (F.) on artificial substrates of different colors (felt woven). For this, ten pairs of stink bugs were transferred into plastic pots. Each pot contained seven felts of 6x20 cm (100% polyester-atoxic) of different colors (white, black, blue, green, red, yellow and brown). The pots were evaluated daily for three weeks (21 days) being counted the number of eggs, clutches and eggs per clutch for each color of felt. The choice test was set in a completely randomized design. Data obtained was submitted to the analysis of variance and means were compared by Scott-Knott test at 5% probability. During the evaluation were produced 7074 eggs distributed in 977 clutches, accounting a mean of 7.06±0.67 eggs per clutch. Results indicated that females laid a significantly greater number of eggs (2380 and 1686) and a greater number of clutches (319 and 233) on the yellow and white felts, respectively, than on the remaining substrates. The substrates in color red, black and brown were the least preferred, and the colors blue and green were intermediate when compared with others. Therefore, the substrates colored yellow and white are suggested to be used in rearing E. heros in the laboratory.

Dispersal capacity of the egg parasitoid Telenomus remus Nixon (Hymenoptera: Platygastridae) in maize and soybean crops

Abstract This study examined the dispersal capacity of the parasitoid Telenomus remus Nixon (Hymenoptera: Platygastridae) in soybean and maize crops. Knowledge on mobility and dispersal capacity of parasitoids is crucial for the implementation of successful biological control strategies using this biological control agent. Experiments were conducted at the experimental farm of Embrapa Soja located in Londrina, PR (−51°11′0.54″ Long.; −23°11′58.94″ Lat.) in the crop seasons of 2012, 2012/13 and 2013 at different plant phenological stages. Experimental plots consisted of six concentric circles with radii of 5, 10, 15, 20, 25, and 30 m, with 8, 24, 40, 56, 72 and 88 parasitoid traps per circle, respectively. Host eggs were placed on each plant as parasitoid traps. Approximately 150,000 newly emerged (up to 24 h old) adults of T. remus reared on eggs of Corcyra cephalonica Stainton (Lepidoptera: Pyralidae) or Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) were released at the central point of each circle. Parasitism by T. remus decreased with increasing distance to the release points regardless of host, phenological stage, crop or season. Our findings allow the conclusion that T. remus should be released at a minimum density of 35 points/hectare in soybean crops and 34 points/hectare in maize crops to ensure T. remus dispersal over 100% of the area in the worst case scenario. Since wind direction influences the dispersal pattern of T. remus, the release methodology should be determined according to wind conditions, possibly with preference for a perimetric distribution of the released insects.

Use of artificial substrates of different colors for oviposition by the brown stink bug Euschistus heros (Hemiptera, Pentatomidae)

Aiming to contribute to a rearing methodology for the brown stink bug, Euschistus heros, in the laboratory, we evaluated oviposition on artificial substrates of different colors. During six days, oviposition was evaluated daily, by counting the total number of eggs, number of clutches, and eggs/clutch. Females laid 12,463 eggs, in 1,677 clutches, resulting in an average of 7.28 ± 0.44 eggs/clutch. Black, brown, and green felt had the most eggs and clutches. The results demonstrated that many colors are suitable as oviposition substrate for E. heros, providing information for the mass rearing of this insect.