Compuestos cuticulares de Euschisthus heros (F.) (Heteroptera: pentatomidae) y su papel en las etapas inciales de la infección por hongos entomopatógenos.

2015

Species from the Heliothinae complex (Lepidoptera: noctuidae) in Tucuman, Argentina, an update of geographical distribution of Helicoverpa armigera.

The Heliothinae complex in Argentina encompasses Helicoverpa gelotopoeon (Dyar), Helicoverpa zea (Boddie), Helicoverpa armigera (Hu ̈ bner), and Chloridea virescens (Fabricius). In Tucum an, the native species H. gelotopoeon is one of the most voracious soybean pests and also affects cotton and chickpea, even more in soybean-chickpea succession cropping systems. Differentiation of the Heliothinae complex in the egg, larva, and pupa stages is difficult. Therefore, the observation of the adult wing pattern design and male genitalia is useful to differentiate species. The objective of this study was to identify the species of the Heliothinae complex, determine population fluctuations of the Heliothinae complex in soybean and chickpea crops using male moths collected in pheromone traps in Tucuman province, and update the geographical distribution of H. armigera in Argentina. The species found were H. gelotopoeon, H. armigera, H. zea , and C. virescens. Regardless of province, county, crop, and year, the predominant species was H. gelotopoeon . Considering the population dynamics of H. gelotopoeon and H. armigera in chickpea and soybean crops, H. gelotopoeon was the most abundant species in both crops, in all years sampled, and the differences registered were significant. On the other hand, according to the Sistema Nacional Argentino de Vigilancia y Monitoreo de Plagas (SINAVIMO) database and our collections, H. armigera was recorded in eight provinces and 20 counties of Argentina, and its larvae were found on soybean, chickpea, sunflower crops and spiny plumeless thistle (Carduus acanthoides). This is the first report of H. armigera in sunflower and spiny plumeless thistle in Argentina.

Biological characteristics of black armyworm Spodoptera cosmioides on genetically modified soybean and corn crops that express insecticide Cry proteins.

This study aimed to evaluate the development and reproduction of the black armyworm, Spodoptera cosmioides when larvae fed on leaves of Bt-corn hybrids, expressing a single Cry1F and also Cry1F, Cry1A.105 and Cry2Ab2 in pyramided corn and their non-Bt-isoline (hybrid 2B688), as well as on leaves of two soybean isolines expressing the Cry1Ac protein and its non-Bt isoline (A5547-227). We also assessed the effect of these Bt and non-Bt plants on the leaf consumption rate of S. cosmioides larvae. This pest was unable to develop when fed on any of the corn isolines (Bt and non-Bt). When both 1st and 3rd instar larvae were fed on corn leaf, mortality was 100% in both Bt and non-Bt corn. In contrast, when corn leaves were offered to 5th instar larvae, there were survivors. Defoliation and leaf consumption was higher with non-Bt corn than with both of the Bt corn isolines. There was no negative effect of Bt soybean leaves on the development and reproduction of S. cosmioides with respect to all evaluated parameters. Our study indicates that both Bt and non-Bt corn adversely affect the development of S. cosmioides while Bt soybean did not affect its biology, suggesting that this lepidopteran has major potential to become an important pest in Bt soybean crops.

Controle de Helicoverpa armigera (Lepidoptera: Noctuidae) em soja com inseticidas químicos e biológicos.

RESUMO: O objetivo deste trabalho foi avaliar o desempenho de inseticidas autorizados emergencialmente para o controle de Helicoverpa armigera (Lepidoptera: Noctuidae) em soja. Sete inseticidas foram pulverizados em campo e, após 24 horas, folhas do ponteiro foram coletadas e oferecidas para lagartas de 2o instar em laboratório. Lagartas do 4o instar receberam a última folha trifoliolada que se encontrava completamente expandida no momento da pulverização. Outro grupo foi exposto a folhas coletadas a partir de 72 horas da pulverização. Em campo, seis inseticidas foram pulverizados e, em seguida, as plantas foram infestadas com lagartas de 2o e 3o instar. No primeiro estudo, flubendiamida, clorantraniliprole, clorfenapir, indoxacarbe e metoxifenozida causaram 100% de mortalidade do 4o instar aos oito dias após o início da exposição, enquanto baculovírus e Bacillus thuringiensis (Bt) propiciaram mortalidade de 60-75%, que evoluiu para 88?90% ao final da fase de pupa. Para o 2o instar, apenas flubendiamida e clorantraniliprole proporcionaram mortalidade de 100%. Flubendiamida, clorantraniliprole e clorfenapir apresentaram o menor tempo letal para o 4o instar, e flubendiamida e clorantraniliprole, para o 2o instar. Após 72 horas da pulverização, o desempenho dos inseticidas foi insatisfatório. Em campo, houve eficiência satisfatória de flubendiamida, espinosade, baculovírus e Bt sobre lagartas de 2o e 3o instar. ABSTRACT:The objective of this work was to evaluate the performance of insecticides authorized on an emergency basis to control of Helicoverpa armigera (Lepidoptera: Noctuidae) in soybean. Seven insecticides were sprayed on the field and, 24 hours after that, soybean pointer leaves were collected and offered to 2nd instar larvae in the laboratory. Fourth instar larvae received the last trifoliate leaf that was fully expanded at the time of spraying. Another larvae group was exposed to leaves collected from 72 hours onwards after spraying. In the field, six insecticides were sprayed, and then the plants were infested with 2nd and 3rd instar larvae. In the first study, flubendiamide, chlorantraniliprole, chlorfenapyr, indoxacarb, and methoxyfenozide caused 100% mortality of the 4th instar, eight days after the beginning of exposure, while baculovirus and Bacillus thuringiensis (Bt) caused 60?75% mortality, which reached 88?90% at the end of the pupal stage. For 2nd instar larvae, only flubendiamide and chlorantraniliprole caused 100% mortality. Flubendiamide, chlorantraniliprole, and chlorfenapyr showed the lowest lethal time for the 4th instar, and flubendiamide and chlorantraniliprole for the 2nd instar. Seventy-two hours after spraying, the performance of insecticides was not satisfactory. In the field, there was satisfactory efficiency of flubendiamide, spinosad, baculovirus, and Bt on 2nd and 3rd instar larvae.

Analysis of long-term light-trap data for Helicoverpa spp. (Lepidoptera : Noctuidae) in Australia: the effect of climate and crop host plants

Regression analyses of a long series of light-trap catches at Narrabri, Australia, were used to describe the seasonal dynamics of Helicoverpa armigera (Hubner). The size of the second generation was significantly related to the size of the first generation, to winter rainfall, which had a positive effect, and to spring rainfall which had a negative effect. These variables accounted for up to 96% of the variation in size of the second generation from year to year. Rainfall and crop hosts were also important for the size of the third generation. The area and tonnage of many potential host crops were significantly correlated with winter rain. When winter rain was omitted from the analysis, the sizes of both the second and third generations could be expressed as a function of the size of the previous generation and of the areas planted to lucerne, sorghum and maize. Lucerne and maize always had positive coefficients and sorghum a negative one. We extended our analysis to catches of H. punctigera (Wallengren), which declines in abundance after the second generation. Winter rain had a positive effect on the sizes of the second and third generations, and rain in spring or early summer had a negative effect. Only the area grown to lucerne had a positive effect on abundance. Forecasts of pest levels from a few months to a few weeks in advance are discussed, along with the improved understanding of the seasonal dynamics of both species and the significance of crops in the management of insecticide resistance for H. armigera.

Establishment of Nilaparvata Iugens Stl in rice crop nurseries: a possible source of outbreaks

We tested the hypothesis that early-planted seedbeds of rioe are mere heavily infested with brown planthopper (BPH) than later seedbeds, and that transplanted plants with lBPH are a source of subsequent population increase and possible outbreaks. The experiments were conducted at CARDI and Takeo province in wet season 2000 and early wet 2 season 200 I. BPH at O. 25. 50, 100, 200 1m were infested onto plants with low and high fertilizer treatments. Rice seeds of varieties moderately and highly susceptible to BPH were sown 3 weeks early, 2 weeks early, at the normal time, and later than normal (5 weeks) and treated with low and high fertilizer rates. At Takeo, the 3< weeks early seedbeds were infested by BPH migration, and both varieties with high fertilizer caught more immigrant insects and subsequently had damaging outbreaks of BPH in the third generation. At CARDl, no seedbeds were infested with immigrant BPH. Seedbeds in areas with continuous cropping of rice have a high risk of BPH attack, Seedlings infested with 200, 100, and 50 BPI[/m2 resulted in death of the plant. Plants with 100 and 200 BPH/m'! were kj[Jed sooner. With 25 BPIVm2 plants were not kllled, but subsequent population increase caused yi eld reduction. Yield loss was high ill higlh fertilizer treated plants. Key words , ,

Towards the on-farm conservation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera : Reduviidae) during winter using crop plants as refuges

Habitat instability associated with seasonal crop succession in broad-acre farming systems presents a problem for the conservation and utilisation of beneficial insects in annual field crops. The present paper describes two experiments used to measure the potential of seven plant species to be utilised as winter refuges to support and conserve the predatory bug Pristhesancus plagipennis (Walker). In the first experiment, replicated plots of canola (Brassica napus ), red salvia (Salvia coccinea ), niger (Guizotia abyssinica ), linseed (Linum usitatissimum ), lupins (Lupinus angustifolius ), and lucerne (Medicago falcata ) were planted in a randomized experiment during Autumn 1998. Upon crop establishment, adults and nymphs of P. plagipennis were released into treatment plots and their numbers were assessed, along with those of their potential prey, throughout the ensuing winter months. Post-release sampling suggested that canola and niger retained a proportion of adult P. plagipennis , while niger, lucerne and canola retained some nymphs. The other plant species failed to support P. plagipennis nymphs and adults postrelease. In the second experiment, niger was compared with two lines of sunflower (Helianthus annus ). Both sunflower lines harboured significantly higher (P < 0.05) densities of P. plagipennis nymphs than did niger. The more successful refuge treatments (sunflower, niger and canola) had an abundance of yellow flowers that were attractive to pollinating insects, which served as supplementary prey on which P. plagipennis were observed to feed. Sunflower and niger also supported high densities of the prey insect Creontiades dilutus (Stal) and provided protective leafy canopies which supplied shelter during the winter months. The potential and limitations for using each plant species as a winter refuge to retain P. plagipennis during winter are discussed.

Distribution and abundance of ladybirds (Coleoptera : Coccinellidae) in non-crop habitats

The abundance and distribution of coccinellids in non-crop habitats was studied using removal sampling and visual observation. Coccinellids were most frequently found on grassland habitats. Coccinellid abundance appeared to be most strongly correlated with the percentage ground cover of thistle, grasses and nettles. The most commonly collected coccinellids were Coccinella septempunctata and Adalia bipunctata comprising 60% and 35% of the catches respectively. Most coccinellids were found on Rubus spp. with nettles (Urtica dioica) and grasses being the next most favoured plant species. Adalia bipunctata was the most commonly found coccinellid species on nettles and birch (Betula spp.) whereas C. septempunctata was the most commonly found species on grasses, Rubus spp, and oak (Quercus spp.). These results are discussed in light of current thinking on the importance of "island" habitats as pali of an integrated pest management programme.

Behavioural responses of the seven-spot ladybird Coccinella septempunctata to plant headspace chemicals collected from four crop Brassicas and Arabidopsis thaliana, infested with Myzus persicae

1 Insects using olfactory stimuli to forage for prey/hosts are proposed to encounter a ‘reliability–detectability problem’, where the usability of a stimulus depends on its reliability as an indicator of herbivore presence and its detectability. 2 We investigated this theory using the responses of female seven-spot ladybirds Coccinella septempunctata (Coleoptera: Coccinellidae) to plant headspace chemicals collected from the peach-potato aphid Myzus persicae and four commercially available Brassica cultivars; Brassica rapa L. cultivar ‘turnip purple top’, Brassica juncea L. cultivar ‘red giant mustard’, Brassica napus L. cultivar ‘Apex’, Brassica napus L. cultivar ‘Courage’ and Arabidopsis thaliana. For each cultivar/species, responses to plants that were undamaged, previously infested by M. persicae and infested with M. persicae, were investigated using dual-choice Petri dish bioassays and circular arenas. 3 There was no evidence that ladybirds responded to headspace chemicals from aphids alone. Ladybirds significantly preferred headspace chemicals from B. napus cv. Apex that were undamaged compared with those from plants infested with aphids. For the other four species/cultivars, there was a consistent trend of the predators being recorded more often in the half of the Petri dish containing plant headspace chemicals from previously damaged and infested plants compared with those from undamaged ones. Furthermore, the mean distance ladybirds walked to reach aphid-infested A. thaliana was significantly shorter than to reach undamaged plants. These results suggest that aphid-induced plant chemicals could act as an arrestment or possibly an attractant stimulus to C. septempunctata. However, it is also possible that C. septempunctata could have been responding to aphid products, such as honeydew, transferred to the previously damaged and infested plants. 4 The results provide evidence to support the ‘reliability–detectability’ theory and suggest that the effectiveness of C. septempunctata as a natural enemy of aphids may be strongly affected by which species and cultivar of Brassica are being grown.

Spatial analysis of the distribution of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) and losses in maize crop productivity using geostatistics

A lagarta-do-cartucho, Spodoptera frugiperda (J.E. Smith), é uma das principais pragas do milho nas Américas. O estudo de sua distribuição espacial é fundamental para a utilização de estratégias de controle, otimização de técnicas de amostragens, determinação de danos econômicos e incorporação de um programa de agricultura de precisão. em uma área cultivada com milho foram realizadas amostragens com intervalo semanal, correspondendo ao estádio vegetativo que compreende desde a germinação até o pendoamento. Foram amostradas 10 plantas ao acaso por parcela, no total de 2000 plantas em cada amostragem. A produtividade foi obtida através da colheita de todas as parcelas que eram pesadas separadamente no campo e em cada parcela foram coletadas 15 espigas aleatoriamente para estimar o comprimento e o diâmetro médio. As análises espaciais, utilizando geoestatística, mostraram que o modelo esférico apresentou o melhor ajuste às lagartas pequenas. À medida que as lagartas foram se desenvolvendo sua distribuição foi tornando aleatória, representada por um modelo ajustado por uma reta, não tendo sido detectado nenhum tipo de dependência espacial nos pontos de amostragem. A produtividade e o diâmetro e comprimento da espiga foram descritos por modelos esféricos, indicando uma variabilidade espacial nos parâmetros de produtividade na área cultivada. A geoestatística mostrou-se promissora para a aplicação de métodos precisos no controle integrado de pragas.

Green lacewings (Neuroptera: Chrysopidae) associated with Melon Crop in Mossoró, Rio Grande do Norte State, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Weekly report on insects, diseases, and crop development to cooperative extension agents.

Mode of access: Internet.

Forage crop insect investigations; report.

Mode of access: Internet.

Foraging behaviour of Helicoverpa armigera first instar larvae on crop plants of different developmental stages

Understanding how insect pests forage on their food plants can help optimize management strategies. Helicoverpa armigera (Hubner) (Lep., Noctuidae) is a major polyphagous pest of agricultural crops worldwide. The immature stages feed and forage on crops at all stages of plant development, damaging fruiting and non-fruiting structures, yet very little is known about the influence of host type or stage on the location and behaviour of larvae. Through semi-continuous observation, we evaluated the foraging (movement and feeding) behaviours of H. armigera first instar larvae as well as the proportion of time spent at key locations on mungbean [Vigna radiata (L.) Wilczek] and pigeon pea [Cajanus cajan (L.) Millspaugh] of differing developmental stages: seedling- and mature (flowering/pod fill)-stage plants. Both host type and age affected the behaviour of larvae. Larvae spent more time in the upper parts of mature plants than on seedlings and tended to stay at the top of mature plants if they moved there. This difference was greater in pigeon pea than in mungbean. The proportion of time allocated to feeding on different parts of a plant differed with host and age. More feeding occurred in the top of mature pigeon pea plants but did not differ between mature and seedling mungbean plants. The duration of key behaviours did not differ between plant ages in either crop type and was similar between hosts although resting bouts were substantially longer on mungbeans. Thus a polyphagous species such as H. armigera does not forage in equivalent ways on different hosts in the first instar stage.

Does the cutting of lucerne (Medicago sativa) encourage the movement of arthropod pests and predators into the adjacent crop?

Lucerne (Medicago sativa) has been suggested as an ideal refuge habitat as part of an integrated pest management (IPM) program because it harbours high numbers of beneficial arthropods. Whether or not cutting of lucerne encourages the movement of these beneficials into adjacent target crops is unknown. Vacuum samples were used to determine the effects of cutting lucerne on arthropod abundance (pests and predators) within lucerne and adjacent soybean (Glycine max) crops. Vacuum-sample collections of arthropods were conducted before and after lucerne cutting on seven occasions in four fields over two seasons. In the lucerne, 10 m by 1 m strips parallel to the crop interface were sampled at 5, 10, 15, 20 and 30 m from the interface. In the soybean, 10 m of row were sampled at the same distances from the crop interface. The abundance of predators in lucerne was reduced immediately after cutting at all distances from the interface. Predator abundance in soybean did not show any change. The cutting of lucerne significantly reduced pest numbers within the lucerne but had little effect on pest abundance in the adjacent soybean. The temporal pattern in pest and predator abundance was very different for each field sampled. Generally, arthropods decreased in abundance after cutting and gradually increased as the lucerne grew back. In soybeans, arthropod numbers fluctuated regardless of the cutting of the lucerne. Cutting of lucerne alone does not guarantee movement of predators into the adjacent target crop. The presence of lucerne fields within a cropping area may have some impact on regional predator populations, and so still be useful for IPM programs, but this has yet to be tested critically.