Egg parasitism of Piezodorus guildinii and Nezara viridula (Hemiptera: Pentatomidae) in soybean, alfalfa and red clover

Piezodorus guildinii Westwood and Nezara viridula (L.) (Hemiptera: Pentatomidae) are important soybean pests. P. guildinii causes more injury and is less susceptible to insecticides compared to N. viridula. N. viridula egg parasitoids are well studied; however, little is known about parasitoids of P. guildinii. Alfalfa, soybean and red clover were sampled during several seasons to characterize the abundance of both stink bugs, to determine their egg parasitoids, and to estimate parasitoids impact. In the field, Telenomus podisi (Ashmead),Trissolcus urichi (Crawford) and Trissolcus basalis (Wollaston) (Hymenoptera: Platygastridae) emerged from P. guildinii, while only T. basalis (Wollaston) (Hymenoptera: Platygastridae) emerged from N. viridula. The proportions of parasitized eggs (i. e., the parasitoid impact) and egg masses, as well as the number of parasitized eggs/total number of eggs of the parasitized egg masses, were similar for alfalfa and soybean. Parasitism was not observed in red pclover. Parasitoid impact was lower during the dry growing seasons. Although P. guildinii field parasitism by T. urichi was less significant, laboratory experiments from the bibliography indicate that this wasp species performs well on this host. Trissolcus urichi would be an important biological control agent against P. guildinii, principally when the stink bug is more abundant.

Trichogramma pretiosum parasitism of Pseudoplusia includens and Anticarsia gemmatalis eggs at different temperatures

Egg parasitism of Trichogramma pretiosum strain RV when presented with eggs of Anticarsia gemmatalis and Pseudoplusia includens was investigated at 18, 20, 22, 25, 28, 30 and 32 degrees C. The number of eggs parasitized per day decreased for both hosts as a function of the age of parasitoids, reaching 80% of lifetime parasitism more rapidly as temperature increased; on the 4th day at 32 degrees C and on the 12th day at 18 degrees C. The lifetime number of parasitized P. includens eggs achieved by the parasitoid maintained at 20 degrees C (44.95 +/- 3.94) differed from the results recorded at 32 degrees C (28.5 +/- 1.33). Differently, the lifetime number of A. gemmatalis parasitized eggs did not differ among the temperatures. When T. pretiosum reached 100% of lifetime parasitism, each adult female had parasitized from 28.5 +/- 1.33 to 44.95 +/- 3.94 and from 29.58 +/- 2.80 to 45.36 +/- 4.50 P. includens and A. gemmatalis eggs, respectively. Also, the longevity of these adult T. pretiosum females, for which P. includens or A. gemmatalis eggs were offered, was inversely correlated with temperature. Not only were the survival curves of those adult T. pretiosum females of type I when they were presented with eggs of A. gemmatalis but also with eggs of P. includens, i.e., there was an increase in the mortality rate with time as the temperature increased. In conclusion, T. pretiosum strain RV parasitism was impacted by temperature when on both host eggs; however, the parasitoid still exhibited high survival and, more importantly, high number of parasitized A. gemmatalis and P. includens eggs even at the extremes tested temperatures of 18 and 32 degrees C. Those results indicate that T. pretiosum strain RV might be well adapted to this studied temperature range and, thus, be potentially suitable for use in biological control programs of P. includens and A. gemmatalis in different geographical areas that fits in this range. It is important to emphasize the results here presented are from laboratory studies and, therefore, field trials still need to be carried out in the future with this strain in order to support the full development of the technology intend to use this egg parasitoid in soybean fields worldwide. (C) 2011 Elsevier Inc. All rights reserved.

Chitosan enhances parasitism of Meloidogyne javanica eggs by the nematophagous fungus Pochonia chlamydosporia

Pochonia chlamydosporia (Pc), a nematophagous fungus and root endophyte, uses appressoria and extracellular enzymes, principally proteases, to infect the eggs of plant parasitic nematodes (PPN). Unlike other fungi, Pc is resistant to chitosan, a deacetylated form of chitin, used in agriculture as a biopesticide to control plant pathogens. In the present work, we show that chitosan increases Meloidogyne javanica egg parasitism by P. chlamydosporia. Using antibodies specific to the Pc enzymes VCP1 (a subtilisin), and SCP1 (a serine carboxypeptidase), we demonstrate chitosan elicitation of the fungal proteases during the parasitic process. Chitosan increases VCP1 immuno-labelling in the cell wall of Pc conidia, hyphal tips of germinating spores, and in appressoria on infected M. javanica eggs. These results support the role of proteases in egg parasitism by the fungus and their activation by chitosan. Phylogenetic analysis of the Pc genome reveals a large diversity of subtilisins (S8) and serine carboxypeptidases (S10). The VCP1 group in the S8 tree shows evidence of gene duplication indicating recent adaptations to nutrient sources. Our results demonstrate that chitosan enhances Pc infectivity of nematode eggs through increased proteolytic activities and appressoria formation and might be used to improve the efficacy of M. javanica biocontrol.

Egg parasitoids of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), from south-east Queensland

Field surveys of egg parasitoids of the diamondback moth, Plutella xylostella, were conducted at Redlands and Gatton, south-east Queensland. Eggs of P. xylostella were present all year round in both localities, and parasitized eggs were consistently found between late spring and early winter. Percent parasitism in the range 30-75% was recorded on many occasions, although rates less than 10% were more common. The major parasitoids included Trichogrammatoidea bactrae Nagaraja and Trichogramma pretiosum Riley. Laboratory evaluation showed that the T. pretiosum from Gatton has a high capacity to parasitize P. xylostella eggs under suitable conditions. This study represents the first record of egg parasitoids of P. xylostella from Australia.

SELECTION OF TRICHOGRAMMA PRETIOSUM LINEAGES FOR CONTROL OF GRAPHOLITA MOLESTA IN PEACH

Grapholita molesta (Lepidoptera: Tortricidae) is one of the main pests of peach trees in Brazil, causing fruit losses of 3-5%. Among possible biological control agents, Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) has been found in peach orchards. Our objectives were to study the rearing of T pretiosum in eggs of G. molesta and Anagasta kuehniella (Lepidoptera: Pyralidae), and select lineages of this parasitoid that have the potential to control G. molesta. Selection of best lineages was made from 5 populations of T pretiosum collected from organically-cultivated peach orchards. The study was done under controlled temperature (25 +/- 2 degrees C), relative humidity (70 +/- 10%) and 14:10 h (light:dark) photoperiod conditions. Grapholita molesta eggs were found to be adequate hosts for the development of T pretiosum, and the parameters for number of parasitized eggs, percent parasitized eggs, and sex ratio were similar to those for A. kuehniella eggs. The highest rate of parasitism of G. molesta eggs occurred in eggs with up to 48 h of embryonic development. Among the lineages of T pretiosum that were collected, HO8, PO8, PEL, and L3M showed the best biological performance and are therefore indicated for semi-field and field studies for biological control of oriental fruit moth.

An evaluation of selective Helicoverpa armigera control options in sweet corn

Helicoverpa armigera is a serious insect pest of sweet corn in Australia and is becoming increasingly difficult to manage with conventional chemical insecticides due to resistance problems. A number of alternative H. armigera control options were evaluated in sweet corn and compared with deltamethrin and no action (control). The alternative tactics evaluated were: heliothis nuclear polyhedrosis virus plus Trichogramma nr. brassicae releases; Bacillus thuringiensis; and Trichogramma alone. The H. tea nuclear polyhedrosis virus + Trichogramma plots had the lowest cob damage (6.0%), followed by the B. thuringiensis plots (12.0%), Trichogramma alone plots (20.2%), control plots (23.2%) and deltamethrin plots (53.5%). There was no evidence to suggest that the Trichogramma nr. brassicae releases had any impact on H. armigera egg mortality. However, there was a large natural population of Trichogramma pretiosum in all plots. The application of deltamethrin reduced the action of these wasps and predators, resulting in higher larval infestation and significantly more cob damage. The findings indicate that the pathogens heliothis nuclear polyhedrosis virus and B. thuringiensis can effectively control H. armigera when their action complements high natural levels of egg parasitism, and that they have potential for use in integrated pest management programs in sweet corn.

Life tables of the processionary caterpillar Ochrogaster lunifer Herrich-Schaffer (Lepidoptera : Thaumetopoeidae) at local and regional scales

A major ongoing debate in population ecology has surrounded the causative factors underlying the abundance of phytophagous insects and whether or not these factors limit or regulate herbivore populations. However, it is often difficult to identify mortality agents in census data, and their distribution and relative importance across large spatial scales are rarely understood. Were, we present life tables for egg batches and larval cohorts of the processionary caterpillar Ochrogaster lunifer Herrich-Schaffer, using intensive local sampling combined with extensive regional monitoring to ascertain the relative importance of different mortality factors at different localities. Extinction of entire cohorts (representing the entire reproductive output of one female) at natural localities was high, with 82% of the initial 492 cohorts going extinct. Mortality was highest in the egg and early instar stages due to predation from dermestid beetles, and while different mortality factors (e.g. hatching failure, egg parasitism and failure to establish on the host) were present at many localities, dermestid predation, either directly observed or inferred from indirect evidence, was the dominant mortality factor at 89% of localities surveyed. Predation was significantly higher in plantations than in natural habitats. The second most important mortality factor was resource depletion, with 14 cohorts defoliating their hosts. Egg and larval parasitism were not major mortality agents. A combination of predation and resource depletion consistently accounted for the majority of mortality across localities, suggesting that both factors are important in limiting population abundance. This evidence shows that O. lunifer is not regulated by natural enemies alone, but that resource patches (Acacia trees) ultimately, and frequently, act together to limit population growth.

Effect of sorghum resistant to Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) on oviposition and development of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae)

Helicoverpa armigera oviposition preference for, and larval development on sorghum hybrids with differing resistance to sorghum midge, Stenodiplosis sorghicola, were investigated. When H. armigera larvae were fed seed of resistant and susceptible hybrids in the laboratory there were no differences in larval and pupal sizes or the rate of development. The same result was recorded when larvae fed on panicles on plants in a glasshouse. On some sampling occasions, significantly more eggs were laid on panicles of resistant hybrids in the field. This occurred when plants were in plots and also in a mixed planting. Midge-resistance status did not affect levels of egg parasitism. In a field study using recombinant inbred lines between a midge-resistant and a midge-susceptible line, no relationship was found between level of resistance and oviposition of H. armigera. We conclude that, although midge-resistant hybrids are sometimes preferred for oviposition by H. armigera, the resistance per se does not determine this preference. Egg survival, larval survival, development and resultant damage are not significantly affected by the midge-resistance status of the host.

Influência da competição intra-específica entre fêmeas e da ausência de hospedeiro no parasitismo de Telenomus remus Nixon (Hymenoptera, Scelionidae) sobre ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae)

A competição intraespecífica e a ausência de hospedeiros podem comprometer o sucesso de programas de controle biológico. Assim, este trabalho objetivou avaliar o efeito de diferentes densidades de fêmeas (1, 3, 6 e 9 fêmeas/ 100 ovos) e da ausência de hospedeiro no parasitismo de Telenomus remus Nixon (Hymenoptera, Scelionidae) em ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae). Observou-se aumento no parasitismo de ovos de S. frugiperda por T. remus a partir da densidade 3 fêmeas/ 100 ovos tanto em condições de laboratório (18%) quanto em campo (32%), embora o parasitismo causado por densidades maiores que 1 fêmea/100 ovos não foi significativamente diferente. Todavia, isso não causou superparasitismo. Por outro lado, o número de fêmeas produzidas na progênie diminuiu (39%) com a maior densidade de fêmeas sob condições de laboratório. Contudo, não verificou-se diferença significativa sob condições de campo. Mesmo após 9 dias de ausência de hospedeiro não houve redução nos índices de parasitismo, permanecendo em torno de 95 ovos parasitados/fêmea/dia. Todavia, no décimo dia pode-se observar redução (40%) no número médio de ovos parasitados. Desse modo, a liberação de três fêmeas por 100 ovos é adequada para se obter elevados níveis de parasitismo.

Parasitismo em ovos de percevejos da soja Euschistus heros (Fabricius) e Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae) em São Gabriel do Oeste, MS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Parasitismo natural de ovos do curuquerê-do-algodoeiro por Trichogramma pretiosum em diferentes estágios fenológicos de variedades de algodoeiros em Ipameri, GO

The cotton can be damaged by many pests, standing out among them cotton leafworm, responsible for major losses in production, if not controlled properly. A group of natural enemies is the most studied of the family Trichogrammatidae, mainly species of the genus Trichogramma, because of its importance in biological control at the initial stage of development of their hosts. In order to study the natural egg parasitism of Alabama argillacea (Hubner, 1818) (Lepidoptera: Noctuidae) by Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) in different phenological stages of transgenic and conventional varieties of cotton (Gossypium hirsutum L.) in the region of Ipameri, GO, it was carried out this experiment from december 2007 to april 2008, in the UEG, State of Goias. The experimental design was in randomized blocks with five treatments consisting of the conventional varieties DeltaOPAL, FMX 966, FMX 993, FMX 910 and NuOPAL transgenic variety, in four replications. In the beginning of oviposition of the A. argillacea it was started the 27 old days plant and the parasitism increased as the availability of eggs of the host, regardless of variety. It was found that the varieties over the vegetative cycle did not show statistical differences on the preference for oviposition by the moth neither on the parasitism. The level of parasitism of eggs of A. argillacea by T. pretiosum varied depending on the density of eggs on plants, not in terms of varieties and phenological stages.

Dinâmica populacional de ovos e lagartas e parasitismo de ovos de Curuquerê-do-algodoeiro por Trichogramma pretiosum em cultivares convencionais e transgênica de algodoeiro

The introduction of new cotton cultivars in the Midwest region of Brazil resulted in a significant increase in productivity, but the use of inappropriate farming techniques brought many problems to field, as the higher incidence of pests, diseases and weeds. The aim of this work was to study the population dynamics of eggs and larvae of cotton leafworm and natural egg parasitism of the pest by Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) at different phenological stages of conventional and transgenic cultivars (Bollgard I) of cotton was carried out this experiment from December 2007 to April 2008 in Ipameri, Goias State, Brazil. The experimental design was a randomized blocks with five trataments and four replications. The treatments consisting of the conventional cotton cultivars DeltaOPAL, FMX 966, FMX 993, FMX 910 and the cultivar transgenic NuOPAL. Allabama argillacea Hubner (Lepidoptera: Noctuidae) oviposited on all cultivars, not presented differences in relation to oviposition preference. Compared to the average number of eggs of A. argillacea parasitized by T. pretiosum, there were no differences between cultivars. In conventional cultivars, small, medium and large larvae occurred from 34 days after plant emergence until the end of the cycle, while in the transgenic cultivar were found only small caterpillars. Cultivar NuOPAL control cotton leafworm since the first larval stage, and does not interfere in egg parasitism by T. pretiosum compared with other cultivars.

Capacidade de parasitismo de Trichogramma exiguum Pinto & Platner, 1978 (Hymenoptera: Trichogrammatidae) em ovos de Plutella xylostella (L., 1758) (Lepidoptera: Plutellidae) em diferentes temperaturas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Short-term assessment of bt maize on non-target arthropods in Brazil

Embora não haja cultivos comerciais de milho geneticamente modificado no Brasil, o efeito de híbridos de milho Bt sobre inimigos naturais e artrópodos de solo deve ser avaliado antes da liberação aos produtores. Assim, ensaios foram conduzidos durante uma safra em duas localidades. Os híbridos de milho modificado geneticamente 7590-Bt11 e Avant-ICP4 foram comparados com seus respectivos isogênicos não transgênicos. Os artrópodes foram avaliados através de observação direta nas plantas e armadilhas de alçapão. de modo geral, não se observaram diferenças entre as populações de tesourinha (Dermaptera: Forficulidae), joaninhas (Coleptera: Coccinellidae), percevejo-pirata (Coleoptera: Anthocoridae), carabídeos (Carabidae), cicindelídeos (Cicindelidae) e aranhas (Araneae). Também não houve diferença no parasitismo de ovos de Helicoverpa zea (Boddie) por Trichogramma sp. (Hymenoptera: Trichogrammatidae). Assim, milho geneticamente modificado expressando as proteínas inseticidas Cry1A(b) e VIP 3A não causa redução nas populações dos principais predadores e parasitóides.

Flutuação populacional de Meloidogyne mayaguensis em pomar de goiabeira e estudo do controle biológico com fungos nematófagos associado a culturas de cobertura

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)