Caracterização citológica dos hemócitos de Anticarsia gemmatalis (Lepidoptera, Noctuidae) em larvas resistentes ao vírus AgMNPV

A ocorrência de larvas de Anticarsia gemmatalis (Hübner, 1932) resistentes ao vírus AgMNPV em laboratório levou ao estudo dos hemócitos deste inseto para avaliar sua participação nos mecanismos que possibilitam a resistência ao vírus. As larvas resistentes com 6 - 11 dias de desenvolvimento (3º a 5º instar) foram anestesiadas por resfriamento e rapidamente limpas em álcool 70%. A hemolinfa foi coletada através de punção abdominal, a análise morfológica foi realizada em contraste de fase e esfregaços corados com solução de Seller. A contagem total de hemócitos (CTH) foi realizada em câmara de Neubauer com hemolinfa não diluída. Para a contagem diferencial de hemócitos (CDH), utilizou-se hemolinfa diluída em solução anticoagulante para insetos. Foram identificados seis tipos de hemócitos: plasmatócitos (38,5%), granulócitos (22,6%), oenocitóides (20,4%), esferulócitos (14,5%), prohemócitos (2,3%) e vermiformes (1,5%). O número total de hemócitos mostrou um aumento significativo durante o período larval estudado.

Nymphal development of Podisus nigrispinus (Heteroptera, Pentatomidae) preying on larvae of Anticarsia gemmatalis (Lepidoptera, Noctuidae) fed with resistant and susceptible soybeans

Nymphal development of the predator Podisus nigrispinus (Dallas) fed with a susceptible (UFV 16) or an insect resistant soybean genotype (IAC 17) and with larvae of the prey Anticarsia gemmatalis Hübner (Lepidoptera, Noctuidae) reared on these genotypes, was evaluated. Survival and duration of each instar and of total nymphal stage, besides weight of nymphs at the beginning of each instar and of adults of P. nigrispinus soon after emergence, were also evaluated. Nymphal survival of this predator was similar with both genotypes (64.41% for the UFV 16 and 72.88% for the IAC 17). Duration of second and fourth instars for nymphs that originated females, of fourth instar for those that originated males, of the nymphal period for males (20.21 and 17.94 days) and females (19.76 and 18.19 days) was longer on the IAC 17 than on the UFV 16. Weight of third instar nymphs (3.12 mg and 2.42 mg) for those that originated males and of fifth instar (26.20 mg and 23.86 mg) for those that originated females and female weight after emergence (65.76 mg and 58.68 mg) was lower with the IAC 17 than with the UFV 16. Sex ratio of P. nigrispinus was not affected by the resistant soybean IAC 17.

Incidência natural e biologia de Trichogramma atopovirilia Oatman & Platner, 1983 (Hymenoptera, Trichogrammatidae) em ovos de Anticarsia gemmatalis Hübner, 1818 (Lepidoptera, Noctuidae)

Trichogramma atopovirilia Oatman & Platner is an egg parasitoid of the corn earworm Helicoverpa zea (Boddie) (Lepidoptera, Noctuidae), and has recently been collected from eggs of Anticarsia gemmatalis Hübner on soybeans. In order to evaluate the suitability of A. gemmatalis eggs as hosts of T. atopovirilia, field surveys were conducted in 1999 and 2000 on corn and soybeans, and a colony of the parasitoid was established in laboratory. At 25 ºC, development from oviposition to emergence lasted nine days and a sex-ratio of 0.58 (females:males) was obtained. Females lived significantly longer (11.4 days) when kept in ovipositional activity, than in the absence of host eggs (6.6 days). Total fecundity averaged 104.5 parasitized eggs, resulting in the emergence of 138.3 descendents. Mean daily fecundity was highest (30 eggs/female) on the first day. Oviposition continued until one day before the death of the females, however 70% of the eggs were laid during the first four days after emergence. A female-biased progeny was produced during the first three days of oviposition, whereas further ovipositions were male-biased. Females lived significantly longer when exposed to host eggs in comparison to females deprived of eggs. The results show that eggs of A. gemmatalis are suitable for the development of T. atopovirilia, and this parasitoid should be considered in future programs of biological control of the velvetbean caterpillar.

Natural parasitism in eggs of Anticarsia gemmatalis Hübner (Lepidoptera, Noctuidae) by Trichogramma spp. (Hymenoptera, Trichogrammatidae) in Brazil

Field surveys were carried during four soybean seasons in Southern Brazil to evaluate the occurrence of parasitoids in eggs of Anticarsia gemmatalis Hübner, 1818 and their incidence along the crop season. Eggs were collected by visual search on soybean leaves and from plants kept inside cages where A. gemmatalis moths were allowed to lay eggs. Trichogramma acacioi Brun, Moraes & Soares, 1984 was recorded for the first time in eggs of A. gemmatalis and the citations in the literature of Trichogramma lasallei Pinto, 1998 in Brazil where based on the material collected in this survey. Apart from these species, Trichogramma pretiosum Riley, 1879, Trichogramma rojasi Nagaraja & Nagarkatti, 1973 and Trichogramma atopovirilia Oatman & Platner, 1983 were also collected, all of which have been previously recorded in this host. Parasitized eggs were collected all over the period of occurrence of A. gemmatalis, from January to April each year. Total parasitism ranged from 4.8% in 2000 and 2002, 23.3% in 2001 and 28.9% in 2003. T. pretiosum and T. acacioi accounted for more than 80% of the parasitoids emerged each year, followed by T. atopovirilia, T. rojasi and T. lasallei, with less than 20% of incidence. Both the sex ratio and the mean number of parasitoids/egg did not differ among the species. Searching for A. gemmatalis eggs proved to be time consuming in comparison to the collection of eggs laid by moths inside the cages, which showed to be a useful method to provide qualitative estimates of parasitism in eggs of A. gemmatalis.

Fitness cost of resistance to Bacillus thuringiensis in velvetbean caterpillar Anticarsia gemmatalis Hübner (Lepidoptera, Noctuidae)

Selection pressure to obtain resistant genotypes can result in fitness cost. In this study, we report the effects of the selection pressure of a commercial formulation of Bacillus thuringiensis on biological aspects of a Dipel-resistant strain of velvetbean caterpillar, Anticarsia gemmatalis Hübner. Comparisons of Dipel-resistant and susceptible individuals revealed significant differences in pupal weight and larval development time. Both strains (Dipel-resistant and susceptible) were susceptible to Cry1Ac toxin expressed in foliar cotton tissues. Resistant and susceptible strains showed low survival rates of 22.5% and 51.2%, respectively, when fed with Greene diet containing Bt-cotton. Larvae bioassayed after three laboratory generations presented lower survival and less instar numbers than individuals maintained in the laboratory for more than 144 generations. Pupal weight was 9.4% lower and larval development time was 1.9 days longer in the resistant population than in the susceptible strain. Other parameters, such as duration of pupal stage, adult longevity, number of eggs per female, oviposition period, and egg fertility, remained unaffected.

Simulação do impacto do fungo Nomuraea rileyi em populações da lagarta da soja, Anticarsia gemmatalis

O fungo entomopatogênico Nomuraea rileyi (Farlow) Samson produz epizootias em populações de lagarta da soja, Anticarsia gemmatalis (Huebner), controlando naturalmente a praga em determinadas condições. No entanto, a epizootia nem sempre ocorre a tempo de evitar que as populações desta praga causem dano econômico à cultura. Foi criado um modelo matemático para simular a ocorrência de N. rileyi em populações de A. gemmatalis nas lavouras de soja da Flórida, EUA. O objetivo deste trabalho foi desenvolver um sistema que integrasse esse modelo a outros modelos (fenologia da soja e da praga, interações inseto-planta e dinâmica populacional da praga), a fim de gerar simulações mais precisas no manejo da praga. Estes modelos foram construídos a partir de estudos ecológicos dos organismos envolvidos, conduzidos nas áreas de soja no Brasil. O sistema integrado foi desenvolvido com base em equações de diferenças que são processadas pelo programa STELLA, versão 5.0 Research. A avaliação do modelo em Planaltina, DF, e Londrina, PR, demonstraram que o sistema é capaz de simular a ocorrência de epizootias ou explosões populacionais da lagarta da soja.

Detrimental effect of rutin on Anticarsia gemmatalis

Behavioral and nutritional effect of rutin (quercetin 3-O-rutinosídeo) on Anticarsia gemmatalis Hübner (Lep.: Noctuidae), a major soybean defoliator in Brazil, was evaluated from the third instar to pupation. Rutin is one of the flavonol glycosides identified in the leaves of the wild soybean PI 227687. Larval weight and amount of ingested food decreased as rutin concentration in the diet increase. An interactive effect between feeding time and diet (treatment) was observed on insect growth; when larvae fed on pure-diet, feeding time elongation resulted in heavier pupae. Differently, the weight of larvae fed on rutin-diet remained almost stable, in spite of eating for longer. A. gemmatalis growth was negatively influenced by rutin-diet not only by feeding deterrence but also by post-ingestive effect on insect growth, since after adjustment of pupal weight by the amount of ingested food (covariate), the effect of diet remained significant. Rutin negatively influenced A. gemmatalis growth as result of pre-ingestive effect, indicated by reduction in food consumption, and post-ingestive effect, indicated by lower conversion of ingested food into body mass and food assimilation.

Perspectives of digestive pest control with proteinase inhibitors that mainly affect the trypsin-like activity of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)

The present study describes the main characteristics of the proteolytic activities of the velvetbean caterpillar, Anticarsia gemmatalis Hübner, and their sensitivity to proteinase inhibitors and activators. Midguts of last instar larvae reared on an artificial diet were homogenized in 0.15 M NaCl and centrifuged at 14,000 g for 10 min at 4ºC and the supernatants were used in enzymatic assays at 30ºC, pH 10.0. Basal total proteolytic activity (azocasein hydrolysis) was 1.14 ± 0.15 absorbance variation min-1 mg protein-1, at 420 nm; basal trypsin-like activity (N-benzoyl-L-arginine-p-nitroanilide, BApNA, hydrolysis) was 0.217 ± 0.02 mmol p-nitroaniline min-1 mg protein-1. The maximum proteolytic activities were observed at pH 10.5 using azocasein and at pH 10.0 using BApNA, this pH being identical to the midgut pH of 10.0. The maximum trypsin-like activity occurred at 50ºC, a temperature that reduces enzyme stability to 80 and 60% of the original, when pre-incubated for 5 and 30 min, respectively. Phenylmethylsulfonyl fluoride inhibited the proteolytic activities with an IC50 of 0.39 mM for azocasein hydrolysis and of 1.35 mM for BApNA hydrolysis. Benzamidine inhibited the hydrolysis with an IC50 of 0.69 and 0.076 mM for azocasein and BApNA, respectively. The absence of cysteine-proteinases is indicated by the fact that 2-mercaptoethanol and L-cysteine did not increase the rate of azocasein hydrolysis. These results demonstrate the presence of serine-proteinases and the predominance of trypsin-like activity in the midgut of Lepidoptera insects, now also detected in A. gemmatalis, and suggest this enzyme as a major target for pest control based on disruption of protein metabolism using proteinase inhibitors.

Molecular biology of baculovirus and its use in biological control in Brazil

Baculoviruses are insect viruses found mainly in Lepidoptera. The family Baculoviridae is taxonomically divided in two genera, Nucleopolyhedrovirus and Granulovirus, which differ by occlusion body morphology. NPVs (Nucleopolyhedroviruses) have polyhedrical inclusion bodies (PIBs) containing multiple viral particles, while GVs (Granuloviruses) appear to be generally single particles occluded in oval shaped occlusion bodies. During the life cycle, two different viral progenies are produced: BV (Budded Virus) and PDV (Polyhedra Derived Virus), which are essential for the infectious process and virus propagation in host cells. Baculoviruses are being used for pest control and they are especially safe due to their specificity and invertebrate-restricted host range. Baculoviruses have been used as vectors for high level protein expression ofheterologous genes from prokaryotic and eukaryotic organisms. Also, recombinant DNA techniques have allowed the production of genetically modified viral insecticides. This study is a review on the taxonomy, structure, replication and molecular biology of baculoviruses, as well as their use as bioinsecticides in Brazil.

Flutuação populacional de Pragas e seus inimigos naturais em Soja no projeto Rio Formoso - Formoso do Araguaia - TO, Brasil

Neste estudo, desenvolvido na entressafra do arroz (Julho-Outubro) de 1995, no Projeto Rio Formoso, município de Formoso do Araguaia - TO, com o objetivo de verificar o comportamento da população das pragas e seus inimigos naturais em soja, foram realizados levantamentos semanais com o método do pano de batida, em três cultivares de soja de ciclo médio: EMGOPA 308, DOKO RC e EMBRAPA 31 (BR 81). Entre os percevejos fitófagos somente foi constatada a ocorrência de Piezodorus guildinii, com picos populacionais no período de enchimento de grãos, porém não atingindo o nível de controle. As lagartas desfolhadoras encontradas foram Anticarsia gemmatalis, Hedylepta indicata e Chrysodeixis íncludens, em ordem decrescente de abundância. Dos coleópteros desfolhadores, a espécie encontrada em maior abundância foi Cerotoma sp. com picos populacionais próximos ao período reprodutivo, diferindo significativamente entre as cultivares. Dentre os inimigos naturais, foi verificada a ocorrência, em maior abundância de Cycloneda sanguínea (Coleoptera, Coccinellidae), Geocoris sp. (Heteroptera, Lygaeidae) e Lebia sp. (Coleoptera, Carabidae).

An evaluation of natural infestation by leaf pests on soybean (Glycine max (L.) Merrill) cultivars

Damage caused by leaf pests of soybean on five cultivars was evaluated. Afield experiment was carried out at the Piracicaba region, cultivars Davis, IAC 73-228, PI 227.687,PI 171.451, and PI 229.358 having been compared. Leaf damage was produced by natural infestation of Anticarsia gemmatalis and Plusia sp. Cultivar PI 171.451 showed lower comsumption of leaves in relation to control ('Davis') and other cultivars. Damage was more serious on IAC 73-228 than on PI 227.687 and PI 229.358.

Exigências térmicas para o desenvolvimento de Palmistichus elaeisis (Hymenoptera, Eulophidae) em pupas de cinco espécies de lepidópteros

The thermal requirements of Palmistichus elaeisis Delvare & LaSalle, 1993 were determined by rearing this pupal parasitoid in the following lepidopteran hosts: Diatraea saccharalis (Fabricius, 1794) (Crambidae), Anticarsia gemmatalis (Hübner, 1818), Heliothis virescens (Fabricius, 1777), Spodoptera frugiperda (J.E. Smith, 1797) (Noctuidae) and Thyrinteina arnobia (Stoll, 1782) (Geometridae). The experiment was set in laboratory conditions (temperatures between 18ºC and 30ºC, RH=70 ± 10% and 14-hour photoperiod). The life cycle (egg-adult) ranged from 40.4 ± 0.63 days (18ºC, H. virescens) to 18.1 ± 0.13 days (28ºC, D. saccharalis). The thermal constant of the egg-adult period ranged from 353.1 (D. saccharalis) to 407.7 degree-days (S. frugiperda). The lowest thermal threshold ranged from 5.0ºC (A. gemmatalis) to 7.5ºC (D. saccharalis). At 30ºC, all prepupae died. These results suggest that P. elaeisis can be reared in laboratory on all the hosts tested.

Desenvolvimento dos estágios imaturos de Palmistichus elaeisis Delvare & LaSalle (Hymenoptera, Eulophidae) em pupas de Lepidoptera

Palmistichus elaeisis Delvare & LaSalle, 1993 é um endoparasitóide coletado de pupas de Sabulodes sp. (Lepidoptera, Geometridae). Os estágios imaturos deste parasitóide foram estudados em laboratório (25 ± 1ºC; 70 ± 10% UR; fotofase 14 h) em pupas dos seguintes lepidópteros: Diatraea saccharalis (Fabricius, 1794) (Crambidae), Anticarsia gemmatalis Hübner, 1818, Heliothis virescens (Fabricius, 1781), Spodoptera frugiperda (J. E. Smith, 1797) (Noctuidae) e Thyrinteina arnobia (Stoll, 1782) (Geometridae). Observou-se que os ovos e as larvas de 1º ínstar são hialinas e himenopteriformes; as larvas dos 2º, 3º e 4º ínstares são esbranquiçadas e 12 segmentadas. A espécie de hospedeiro não influenciou o número de ínstares.