Beatriz S. Corrêa-Ferreira

Soybean seed damage by different species of stink bugs

Abstract 1  Damage caused by the three main species of stink bugs occurring on soybean Nezara viridula (Linnaeus), Piezodorus guildinii (Westwood) and Euschistus heros (Fabricius) was compared in field cages and in greenhouses. Infestation levels of 4 stink bugs/m row of plants (field cages) and 2 stink bug/plant (greenhouse) for 15 days during the pod filling stage are reported. At harvest, the yield and seed quality were evaluated. 2  In the field, there was no difference in yield between infested and insect‐free plants, but damage to seed quality varied with stink bug species. Plants damaged by P. guildinii had the lowest quality seeds. From 50 g seed samples harvested in the field, the mean weight of seeds classified as ‘good’ was 37.3 g in plants infested with P. guildinii, compared to 41.8, 44.2 and 46.6 g in plants infested with E. heros, N. viridula and the control, respectively. 3  Plants infested with P. guildinii showed the highest number of seeds damaged by stink bugs, whereas those infested with E. heros showed the lowest damage. 4  Plants infested with P. guildinii had 18.5% damaged seeds, higher than the 3.6% and 3.4% damaged seeds from plants infested with the two other species and 0.1% in control plants. The percentage of non‐viable seeds due to stink bug damage was 5.7% for P. guildinii but lower for the other two species.

Methodology of mass multiplication of Telenomus podisi Ash. and Trissolcus basalis (Woll.) (Hymenoptera: Scelionidae) on eggs of Euschistus heros (Fab.) (Hemiptera: Pentatomidae)

Laboratory studies were carried out to develop a methodology for the mass production of Telenomus podisi Ash. and Trissolcus basalis (Woll.) on eggs of Euschistus heros (Fabr.) and to compare it with the methodology presently used in the biological control program of soybean stink bugs in Brazil [T. basalis reared on Nezara viridula (L.) eggs]. In a first experiment, egg masses randomly distributed were shown the most adequate method of exposure of E. heros to parasitism. In a second experiment, egg masses of E. heros were randomly glued on cardboard cards and exposed to parasitism by T. podisi and T. basalis. The parasitoids multiplied on E. heros eggs showed parasitism (ca. 99%) similar to that observed with T. basalis reared on N. viridula eggs (99.7%). Emergence rates were higher than 80% for T. podisi and T. basalis multiplied on E. heros eggs and 95% for T. basalis reared on N. viridula eggs. Later, similar emergence rates (> 78%) were observed on cardboard cards tied on soybean plants. No differences were detected between courtship behavior of T. podisi and T. basalis emerged from E. heros eggs compared to T. basalis emerged from N. viridula eggs. The sex ratios in the offspring of T. podisi and T. basalis emerged from E. heros eggs were similar to that exhibited by the offspring of T. basalis emerged from N. viridula eggs. The results suggest that the developed methodology is simple, efficient and can be an important tool in biological control program of soybean stink bugs.

Parasitismo de Telenomus podisi Ashmead (Hymenoptera: Scelionidae) em populações de percevejos pragas da soja

The parasitism of Telenomus podisi Ashmead, on some pentatomid pests of soybean [Glycine max (L.) Merrill] was studied. The tests were conducted during soybean crop (1996/97) on two areas, cultivated with BR-48 and BR-37 (area 1 and 2, respectively), at Embrapa Soja, in Londrina, PR. Euschistus heros (Fabricius), Piezodorus guildinii (Westwood) and Nezara viridula (Linnaeus) were the most abundant species on this crop. The highest populational density occurred at the end of the crop cycle (5.3, 3.3, 3.6 - area 1 and 5.2, 14.5, 7.5 stink bugs / 2 m - area 2, respectively). On both areas, the parasitoid T. podisi had better interaction, with the population of E. heros, with increasing parasitism on the area 1, reaching 100% in the end of the cycle, and showing above 80% during all sample period on area 2. The parasitism obtained on eggs of E. heros, in cages with isolate population of this insect, was statistically similar, when compared with eggs of the same pentatomid in cages with mixed population containing the three species (31.7 ± 7.51 and 20.1 ± 6.67, respectively). P. guildinii and N. viridula, however, had consistently more parasitism in cages with mixed population.

Suscetibilidade da soja a percevejos na fase anterior ao desenvolvimento das vagens

The objective of this work was to evaluate the damages caused by stink bug populations of Euschistus heros (F.) and Piezodorus guildinii (West.) to soybean crop on november/december, prior to pod set. Greenhouse and field experiments were carried out comparing infestations at vegetative-flowering and pod development stages. Soybean plants at vegetative and flowering growth stages, even under severe bugs infestation (8 per plant) did not show significant yield reduction. Seed quality, was similar among population levels and bug species. At R4 stage, the number of seedless pods increased proportionally to the number of bugs per plant. In field experiment, yield and seed quality of soybean plants infested with up to four E. heros or P. guildinii adults per meter, at the end of the vegetative-flowering stage, were similar to bug-free plants. The number of bug- punctured and inviable seeds increased and the average yield decreased with the increase of population levels of both bug species, at the pod filling stage (R5-R6) infestation. In relation to the soybean quality, the damage caused by P. guildinii was twice bigger than that caused by the brown stink bug. Infestations of these stink bugs on the vegetative-flowering stage do not cause reduction on yield and quality of soybean seeds.

Potencial reprodutivo e longevidade do parasitóide Telenomus podisi Ashmead, em ovos de diferentes espécies de percevejos

The reproductive potential and the longevity of Telenomus podisi Ashmead egg parasitoid was studied in the laboratory. The parasitoid was reared in eggs of the stink bug hosts Euschistus heros (F.), Piezodorus guildinii (West.) and Nezara viriula (L.). The reproductive capacity and longevity of the T. podisi females was significantly different on the three species. The higher production of progeny occurred on the first 10 d of female´s life in eggs of E. heros and P. guildinii. The parasitism on N. viridula eggs was very low (8.1%), with only 5 parasitoids completing their development. In the progeny, young females produced higher number of females than males, while the opposite occurred with older females. The parasitoid sex ratio in E. heros and P. guildinii hosts was 0.67 and 0.61, respectively, and the mean fertility per females was of 211.0 and 76.1 descendents, respectively. The longevity of T. podisi females was different on each host species, with an average of 19.9, 30.9 and 40.6 d when they parasitized eggs of P. guildinii, E. heros and N. viridula, respectively. The longevity of males was longer than females, and it was similar in the three hosts, with mean time of 32.0, 34.5 and 43.5 d, respectively. The results suggest that E. heros and P. guildinii are more adequate hosts to T. podisi development.

Ocorrência do parasitóide Hexacladia smithii Ashmead em adultos de Euschistus heros (F.) no Brasil

Parasitism of Euschistus heros (F.) adults was studied in Londrina, PR. Twenty males and 20 females were collected each week from November 1996 to December 1997. In the laboratory, adults were sexed and maintained in plastic box (12 x 12 cm) with humidity and soybean pods as food, and observed daily during 30 days. The encyrtid Hexacladia smithii Ash. was observed attacking the bugs, being the first register of parasitism by Hexacladia in this host. The natural incidence of parasitism varied from 0.6% to 39.5%. Higher abundance of the parasitoid occurred during December and January and it was drastically reduced (<1%) from May to September. Males and females were equally attacked by the parasitoid (14.7% and 11.9%, respectively). H. smithii is a gregarious endoparasitoid that completed its development inside the host body. Adults emerged through a hole in the ventral or dorsal surface of the abdomen. From 2 up to 39 parasitoids were observed to emerge from a single adult E. heros.

Nymphal and Adult Performance of Euschistus heros (Fabr.) (Hemiptera: Pentatomidae), as a Potential Alternative Host for Egg Parasitoids Multiplication

This research aimed to evaluate the potential of Euschistus heros (Fabr.) (Hemiptera: Pentatomidae) as host for multiplication of egg parasitoids, by determining the nymphal and adult performance of E. heros from laboratory and the field, comparing with Nezara viridula (L.) (Hemiptera: Pentatomidae), under mass conditions. One hundred eggs of E. heros and N. viridula were placed among the leaves of soybean plants contained in cages (50x50x70 cm) and observation were made until adult emergence. The nymphs fed on soybean pods, dry soybean and peanuts seeds. The number of nymphs that reached adulthood and the development time were calculated. The survivorship and reproduction performance of laboratory and field populations of E. heros and N. viridula were evaluated during 13 weeks in February-May 1999. The number of eggs produced by 100 pairs of stink bugs per cage containing the same diet was recorded. Nymphal development time of E. heros and N. viridula was 33.0 and 34.0 days and 65.0% and 71.3% of nymphs reached adulthood, respectively. Adults of E. heros reared under laboratory conditions produced 2.5 times more eggs (5547.0 eggs/cage) than those collected in the field (2262.7 eggs/cage). The adult field population of E. heros had reduced reproduction and longevity due to parasitism by Hexacladia smithii Ash. (Hymenoptera: Encyrtidae). The N. viridula adults collected in the field produced 1.7 times more eggs (6304.9 eggs/cage) than those reared in the laboratory (3609.2 eggs/cage). E. heros laboratory reared is a promising host for egg parasitoids multiplication when compared with N. viridula collected in the field.

Desempenho alimentar e sobrevivência de Euschistus heros parasitado por Hexacladia smithii em sementes de soja

(3) Resumo – Avaliou-se, em laboratorio, a influencia do parasitoide Hexacladia smithii Ashmead (Hymenoptera: Encyrtidae) na atividade alimentar e sobrevivencia de Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), aos 10, 20, 30 e 40 dias apos o inicio do parasitismo. A atividade alimentar foi avaliada pelo numero de bainhas constatadas nas sementes de soja, Glycine max (L.) Merrill (Fabaceae), em 48 horas de alimentacao. O teste foi mantido sob condicoes controladas de temperatura (25±2°C), umidade (65±10%) e fotoperiodo (14L:10E). No inicio do desenvolvimento de H. smithii a atividade alimentar dos percevejos nao-parasitados e parasitados foi semelhante, obtendo-se, entretanto, duas vezes mais bainhas alimentares depositadas/grao pelos machos e femeas, apos 30 dias de parasitismo. A sobrevivencia dos percevejos parasitados foi menor que a dos percevejos nao-parasitados, alcancando 100% de mortalidade 40 a 50 dias apos o inicio do parasitismo. A reducao na sobrevivencia dos percevejos parasitados por H. smithii e a atividade alimentar, semelhante a dos percevejos nao-parasitados durante quase todo o periodo de desenvolvimento do parasitoide, destacam a contribuicao desse parasitismo na reducao da populacao do percevejo-marrom E. heros. Termos para indexacao: Glycine max, controle biologico, percevejo-marrom, parasitoide, bainhas alimentares. Feeding activity and survival of the Euschistus heros parasitized by Hexacladia smithii

Danos causados à soja por adultos de Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), sadios e parasitados por Hexacladia smithii ashmead (Hymenoptera: Encyrtidae)

Damage on soybean [Glycine max (L.) Merrill] caused by Euschistus heros (Fabricius) parasitized by Hexacladia smithii Ashmead was studied in greenhouse. Soybean plants, cultivar BR-37, were covered with nylon screen net and artificially infested with two bugs/plant, for a 15-day period, from the stage corresponding to the end of pod development (R4) up to filled seeds (R5-R6). Plants infested by non-parasitized bugs were compared with plants infested by bugs parasitized by H. smithii and with non-infested plants (control), with 20 replicates per treatment. The yield (g/plant), total number of pods and number of failed pods per plant did not differ between plants attacked by non-parasitized as well as by parasitized bugs, but they both differed from the control. Similarly, the qualitative analysis of seeds (good, medium and bad) and the tetrazolium test (punctured seeds, damaged seeds and vigor) demonstrated the same effect. However, the germination potentiality of the seeds attacked by parasitized bugs was higher than those seeds attacked by non-parasitized ones, indicating that a lower damage was caused by parasitized bugs.

Diagnóstico exploratório na análise de dados entomológicos:: efeito do diflubenzurom no consumo alimentar de Anticarsia gemmatalis (Hübner)

Different statistical methods of data analysis were performed on the effect of different dosages of Diflubenzurom in the consumption of velvetbean caterpillar, Anticarsia gemmatalis (Hubner). The best descriptives statistics to visualize the lack of normality were skewness and kurtosis suggesting the necessity of data transformation. When data without transformation were analyzed no statistical differences were observed among consumption of larvae maintained on leaves treated with Diflubenzurom. However, analysis of transformed data showed that larval feeding was lower on leaves treated with 15 g a.i. of Diflubenzurom, differing from 7.5 g a.i. treatment. It was observed a reduction coefficient of variation from 47.8 % to 2.7 % of foliar consumption one day after treatment, reducing the experimental variability.