Spodoptera Cosmioides Research Articles

Biology ofSpodoptera eridaniaandSpodoptera cosmioides(Lepidoptera: Noctuidae) on Different Host Plants

The moths Spodoptera eridania (Stoll) and Spodoptera cosmioides (Walker) are pests of increasing importance in various grain production systems, causing defoliation and damage to reproductive structures of plants. This fact underscores the need for studies that analyze the nutrition and development of pests on different hosts. The objective of this study was to evaluate the development of S. eridania and S. cosmioides feeding on different host species. To this end, newly hatched larvae were separated individually into waxed cups and fed soybean, cotton, maize, wheat, oat leaves, or an artificial diet as control. The evaluated parameters were: duration of larval, pre-pupal, and pupal development (days), pupal weight (g), sex ratio (%), larvae-adult survival (%), oviposition preference, larval feeding performance, and weight gain on different hosts. Soybean and cotton were found to be more suitable hosts for development and oviposition of S. eridania and S. cosmioides than oat, wheat, and maize, all of which negatively affected larval development and survival. The maize cultivar ‘DKB 390’ did not allow for larvae to develop to adults and therefore proved to be inadequate for both studied Spodoptera species.

Toxicidade de extratos de Anadenanthera macrocarpa (Fabaceae: Mimosoideae) e Bougainvillea buttiana (Nyctaginaceae) para lepidópteros-praga

http://dx.doi.org/10.5007/2175-7925.2017v30n2p15O uso de extratos vegetais apresenta grande eficiência no manejo de pragas, destinados a produções agrícolas de pequeno e médio porte, por controlar uma gama muito grande de artrópodes. O objetivo desta pesquisa consiste em avaliar os efeitos tóxicos dos extratos de Anadenanthera macrocarpa (Fabaceae: Mimosoideae) e Bougainvillea buttiana (Nyctaginaceae) em Helicoverpa armigera (Hübner), Spodoptera cosmioides (Walker) e Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae). Lagartas de H. armigera e S. cosmioides foram mantidas em discos foliares de soja, enquanto S. frugiperda foi mantida em discos foliares de milho, tratados com os extratos aquoso diluídos nas concentrações de: 0, 500, 1.000, 2.500, 4.000, 5.000, 10.000 e 15.000 mg.L-1. Foram mensurados os efeitos letais e subletais dos extratos sobre os insetos. De acordo com os resultados obtidos, a concentração de 500 mg.L-1 do extrato de A. macrocarpa causou o maior percentual de mortalidade (93,33%) em H. armigera. O extrato de B. buttiana causou 86,67% e 60% de mortalidade em H. armigera (1.000 mg.L-1) e S. cosmioides (4.000 mg.L-1), respectivamente. A redução da emergência dos adultos foi o principal efeito subletal constatado em S. cosmioides e S. frugiperda. Considerando os resultados obtidos, destaca-se que os extratos vegetais utilizados apresentam-se como uma alternativa em potencial para o manejo de lepidópteros-praga.

Efficacy of Soybean's Event DAS-81419-2 Expressing Cry1F and Cry1Ac to Manage Key Tropical Lepidopteran Pests Under Field Conditions in Brazil.

Bacillus thuringiensis (Bt) event DAS-81419-2 (Conkesta technology) in soybean, Glycine max (L.) Merrill, expresses Cry1F and Cry1Ac proteins to provide protection from feeding by several lepidopteran pests. A total of 27 field experiments across nine locations were conducted from 2011 to 2015 in southern and central Brazil to characterize the efficacy of DAS-81419-2 soybean infested with Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae), Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), Heliothis virescens (F.) (Lepidoptera: Noctuidae), and Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) during vegetative (V4) and reproductive (R2 and R4) crop developmental stages. The efficacy of DAS-81419-2 was compared to that of a non-Bt isogenic variety managed with or without applications of commercial foliar insecticides for lepidopteran control. DAS-81419-2 soybean consistently experienced defoliation levels of 0.5% or less (compared with 20.05–56.74% in the non-Bt, nonsprayed treatment) and larval survival of < 0.1% in all four species across the vegetative and reproductive plant stages evaluated. The efficacy of DAS-81419-2 was significantly higher than commercial foliar insecticides applied to the non-Bt variety. DAS-81419-2 soybeans containing two highly effective Bt proteins are expected to be a more robust IRM tool compared to single-trait Bt technologies. The consistent efficacy of DAS-81419-2 soybeans across years, locations, and crop stages suggests that it will be a valuable product for management of hard-to-control key lepidopteran pests in South American soybean production.

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.

Identification and field evaluation of the sex pheromone of a Brazilian population of Spodoptera cosmioides

Abstract: The objective of this work was to identify the sex pheromone of Spodoptera cosmioides and to evaluate whether there is pheromone cross-attraction in Spodoptera sp. (Lepidoptera: Noctuidae). Spodoptera cosmioides gland extracts were analyzed by GC-FID and GC-MS. Wind tunnel and electrophysiology experiments were conducted to evaluate the role of gland compounds. In the field, different pheromone traps were tested: S. frugiperda commercial lure; (9Z)-9-tetradecenyl acetate (Z9-14:OAc) and (9Z,12E)-9,12-tetradecadienyl acetate (Z9,E12-14:OAc) trap; two females of S. cosmioides trap; and hexane control trap. Four acetates were identified in the S. cosmioides female gland extracts as Z9-14:OAc, Z9,E12-14:OAc, (11Z)-11-hexadecenyl acetate (Z11-16:OAc) and hexadecyl acetate (16:OAc), but only the first two acetates induced electrophysiological responses from S. cosmioides male antennae. In wind tunnel experiments, S. cosmioides and S. frugiperda males responded more strongly to conspecific blends; however, there was some cross-attraction, as 47% males of S. frugiperda and 25% males of S. cosmioides responded to heterospecific blends. In field experiments, S. frugiperda and S. cosmioides showed the same response pattern as observed in the wind tunnel bioassays. In summary, the sex pheromone components of S. cosmioides are Z9-14:OAc and Z9,E12-14OAc; they are important for conferring species specificity, and there is pheromone-mediated cross attraction between S. frugiperda and S. cosmioides.

Immature stages of Spodoptera cosmioides (Lepidoptera: Noctuidae): developmental parameters and host plants

The goal of this study was to detail the temporal and morphological parameters of the immature stages of Spodoptera cosmioides (Walker, 1858) and to gather information about their larval host plants. Larvae were reared on artificial diet and under controlled conditions (25 ± 1°C, 70 ± 10% RH and 14 hour photophase). The viability of eggs, larvae (pre-pupae period inclusive) and pupae were 98.97, 97.33, 97.95 and 94.76%, respectively. The average duration of egg, larval, pre-pupal and pupal stages was 3.82, 19.24, 3.20 and 14.81 days, respectively. A small proportion of females (9.48%) passed through seven instars, and female development was significantly slower than male development. The female larvae that developed through six and seven instars exhibited a mean growth rate of 1.63 and 1.49, respectively. Overall, female pupae were significantly larger, exhibiting slower development than males. One hundred and twenty six plants belonging to 40 families are listed as hosts of S. cosmioides , mainly including Solanaceae, Fabaceae, Asteraceae and Poaceae.

Biological Parameters ofPodisus nigrispinus(Hemiptera: Pentatomidae) Fed with Different Soybean Insect Pests

AbstractBiological parameters of Podisus nigrispinus (Dallas) fed with third-instar Lepidoptera larvae of Spodoptera frugiperda J.E. Smith, Spodoptera cosmioides (Walker, 1858), and Anticarsiagemmatalis (Hübner, 1818), as well as eggs of Euschistus heros (F., 1798), the brown stink bug, were evaluated. Experiments were performed under controlled conditions (25 ± 1°C; 70 ± 10% relative humidity, and a photoperiod of 16:8 [L:D] h). P. nigrispinus had good nymphal development with &amp;gt;87% larval survival (viability), as well as high fecundity in adults, when fed with A. gemmatalis, S.frugiperda, and S. cosmioides larvae. Differently, adults of P. nigrispinus originating from nymphs fed with eggs of E. heros completed their life cycle; however, larval survival (viability) was reduced to 45.7%. Furthermore, these adults did not oviposit, and their body mass was from 50 to 73% lower than in individuals originating from nymphs fed with other tested prey. Taking into consideration that neither E. heros nor Spodoptera spp. are controlled by Bt soybean varieties expressing the Cry 1Ac protein, it can be assumed that the predator P. nigrispinus will still find prey species to feed in soybean fields even after the adoption of this pest control technology. This might help lower any potential negative impact of Bt soybean adoption above this insect predator. Moreover, the studied caterpillars proved to be potential prey for the predator's mass rearing, similarly to what is presently being done with coleopteran larvae.

Low susceptibility of Spodoptera cosmioides, Spodoptera eridania and Spodoptera frugiperda (Lepidoptera: Noctuidae) to genetically-modified soybean expressing Cry1Ac protein

Spodoptera cosmioides (Walker), Spodoptera eridania (Stoll) and Spodoptera frugiperda (J. E. Smith) have caused significant damage on soybean Glycine max (L.) Merrill in Brazil. Genetically-modified MON 87701 × MON 89788 soybean that expresses the Cry1Ac protein is potentially an alternative tool for the management of these species. Purified protein bioassays were done to evaluate the susceptibility of S. cosmioides, S. eridania and S. frugiperda to Cry1Ac protein. The level of efficacy of the Bt soybean plants in controlling these species was measured through laboratory and greenhouse trials under high artificial insect infestations. The biology of these insects was evaluated over their development cycles to understand their life history when fed on Bt soybean. Purified Cry1Ac protein at the maximum concentration tested (100 μg Cry1Ac mL−1 diet) resulted in low mortality of S. cosmioides and S. eridania (<13%) and intermediate mortality of S. frugiperda (50%). No significant effects of the Bt soybean plants were observed in the life table parameters of S. cosmioides and S. eridania. However, S. frugiperda fed on Bt soybean plants had a prolonged larval stage (by 5 days), reduced larvae viability, increased mean generation time (by 8 days) and reduced intrinsic rate of increase. In general, the Bt soybean plants showed poor control of Spodoptera species when evaluated by leaf-disc bioassay and greenhouse trials. Consequently, other control tactics must be used in combination with MON 87701 × MON 89788 soybean in the field for the efficient management of S. cosmioides, S. eridania and S. frugiperda.

Parasitism of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) on Spodoptera cosmioides (Lepidoptera: Noctuidae) at different temperatures

Spodoptera cosmioides (Lepidoptera: Noctuidae) is a polyphagous pest that causes damage to various crops including those used in the production of biodiesel, such as castor bean (Ricinus communis), Barbados nut (Jatropha curcas), and Tung-oil tree (Aleurites fordii). One of the main biological control agents of lepidopteran pests are egg parasitoids of the genus Trichogramma. The influence of temperature on the performance of three strains (TRS13, TRS65 and TRS81) of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) on eggs of S. cosmioides and thermal requirements were studied. The experiments were carried out at constant temperatures (18, 20, 22, 25 and 28) and 30 ºC, 70 ± 10% relative humidity and photoperiod of 14:10 (light: dark) hours. The development time of the three strains of T. pretiosum was inversely related to temperature rise. The temperatures affected the parasitoid emergency, being higher than 74% for each of the strains at 25 ºC. However, the temperatures tested did not affect the number of adults per egg and sex ratio. The lower temperature threshold (Tb) and thermal constant (K) were 11.21 ºC and 131.41 DD (degree-days) for strain TRS13, 10.73 ºC and 137.70 DD for TRS65 and 10.68 ºC and 138.70 DD for TRS81.

Development and Leaf Consumption by Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) Reared on Leaves of Agroenergy Crops.

Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) is a polyphagous pest that threatens more than 24 species of crop plants including those used for biodiesel production such as Ricinus communis (castor bean), Jatropha curcas (Barbados nut), and Aleurites fordii (tung oil tree). The development and leaf consumption by S. cosmioides reared on leaves of these three species were studied under controlled laboratory conditions. The egg-to-adult development time of S. cosmioides was shortest when reared on castor bean leaves and longest when reared on tung oil tree leaves. Larvae reared on castor bean and Barbados nut leaves had seven instars, whereas those reared on tung oil tree leaves had eight. Females originating from larvae reared on castor bean and Barbados nut leaves showed greater fecundity than did females originating from larvae reared on tung oil tree leaves. Insects fed on castor bean leaves had shorter life spans than those fed on tung oil tree and Barbados nut leaves although the oviposition period did not differ significantly. The intrinsic and finite rates of increase were highest for females reared on castor bean leaves. Total leaf consumption was highest for larvae reared on tung oil tree leaves and lowest for those reared on Barbados nut leaves. We conclude that castor bean is a more appropriate host plant for the development of S. cosmioides than are Barbados nut and tung oil tree.

Morphological and Molecular Characterization of the Eggs of Some Noctuid Species Associated with Soybean in Brazil

AbstractThe most important species of Lepidoptera that attack soybean, in descending order of importance, are Chrysodeixis includens (Walker), Anticarsia gemmatalis Hübner, Spodoptera cosmioides (Walker), Spodoptera eridania (Stoll), and Spodoptera albula (Walker). In addition, Rachiplusia nu ( Guenée ) is one of the most common Plusiinae in the southern region of Brazil, encompassing the states of Paraná, Santa Catalina, and Rio Grande do Sul. The correct identification of these species is essential for choosing the appropriate control measures, as they differ in their susceptibility to insecticides and biological control agents. To distinguish Lepidoptera species commonly found in Brazil, the eggshells of all these species were morphologically characterized by scanning electron microscopy. Diagnostic characters for differentiating species include shape of rosette petals, number of primary cells, number of secondary cells, number of ribs, and rosette diameter. Also, a molecular diagnostic method using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis was developed to distinguish noctuid species commonly found in Brazil. A 658-bp region of the mitochondrial DNA cytochrome oxidase subunit I gene was amplified using PCR and then sequenced. The five Lepidoptera species were distinguished by restriction enzymes Bpm I and Mbol. RFLPs produced by Bpm I endonuclease were useful to discriminate species from within Spodoptera (S. cosmioides, S. eridania, and S. albula) and R. nu from C. includens. However, Bpm I did not digest the amplicons from S. eridania and C. includens, which were discriminated by RFLP patterns produced by the restriction enzyme MboI. PCR-RFLP can be performed in a short period, and it is useful to distinguish the most important Brazilian Lepidoptera soybean pests.

Telenomus remus Nixon Egg Parasitization of Three Species of Spodoptera Under Different Temperatures

Telenomus remus Nixon is a promising biocontrol agent as an egg parasitoid of Spodoptera spp., but the lack of information on the host-parasitoid interactions in this system precludes its applied use in agriculture. Therefore, we studied the parasitism capacity of T. remus on eggs of Spodoptera cosmioides (Walker), Spodoptera eridania (Cramer), and Spodoptera frugiperda (Smith) in a range of temperatures (19, 22, 25, 28, 31, and 34 ± 1°C) under controlled conditions (70 ± 10% RH and 12h photophase). Egg masses of Spodoptera spp. were offered to a single-mated T. remus female on a daily basis. More than 80% lifetime parasitism on eggs of S. cosmioides, S. frugiperda, and S. eridania was reached from 1 to 5, 1 to 7, and 1 to 9 days, respectively, at temperatures from 19 to 34°C. More than 80% parasitization was obtained at extreme temperatures for all hosts studied. Lifetime parasitization of S. frugiperda, S. cosmioides, and S. eridania was affected by temperature, with the lowest values for S. frugiperda (34°C) and S. cosmioides (19 and 34°C). Parasitization of S. eridania eggs was reduced around 18% at 28 and 31°C, but dropped more severely at 34°C. Parasitoid longevity was reduced as temperature increased. Thus, our data indicated that T. remus might be suitable as a biocontrol agent against S. eridania, S. cosmioides, and S. frugiperda in geographical areas that fit the temperature range studied here, even though T. remus parasitism was reduced at 34°C.

Identification of α-tocopherol and α-tocopheryl acetate from the cuticle of soybean pods armyworm (Spodoptera cosmioides)

The chemical composition of the soybean pods armyworm Spodoptera cosmioides (Walker, 1858) (Lepidoptera: Noctuidae) and Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Erebidae) larval cuticles was evaluated using gas chromatography coupled to a mass detector (GC-MS). Among the usual lipids found in the insect cuticle, α-tocopherol and α-tocopheryl acetate were also isolated from S. cosmioides. On the other hand, no vitamin E derivative was found in A. gemmatalis exuvia. This is the first report of vitamin E occurrence in the insect's cuticle.

Bacillus thuringiensis Cry1Ia10 and Vip3Aa protein interactions and their toxicity in Spodoptera spp. (Lepidoptera)

The polyphagous pests belonging to the genus Spodoptera are considered to be among the most important causes of damage and are widely distributed throughout the Americas’. Due to the extensive use of genetically modified plants containing Bacillus thuringiensis genes that code for insecticidal proteins, resistant insects may arise. To prevent the development of resistance, pyramided plants, which express multiple insecticidal proteins that act through distinct mode of actions, can be used. This study analyzed the mechanisms of action for the proteins Cry1Ia10 and Vip3Aa on neonatal Spodoptera frugiperda, Spodoptera albula, Spodoptera eridania and Spodoptera cosmioides larvae. The interactions of these toxins with receptors on the intestinal epithelial membrane were also analyzed by binding biotinylated toxins to brush border membrane vesicles (BBMVs) from the intestines of these insects. A putative receptor of approximately 65kDa was found by ligand blotting in all of these species. In vitro competition assays using biotinylated proteins have indicated that Vip3Aa and Cry1Ia10 do not compete for the same receptor for S. frugiperda, S. albula and S. cosmioides and that Vip3Aa was more efficient than Cry1Ia10 when tested individually, by bioassays. A synergistic effect of the toxins in S. frugiperda, S. albula and S. cosmioides was observed when they were combined. However, in S. eridania, Cry1Ia10 and Vip3Aa might compete for the same receptor and through bioassays Cry1Ia10 was more efficient than Vip3Aa and showed an antagonistic effect when the proteins were combined. These results suggest that using these genes to develop pyramided plants may not prove effective in preventing the development of resistance in S. eridiana.

Novo registro de Trichospilus diatraeae Cherian &amp; Margabandhu, 1942 (Hymenoptera: Eulophidae), como parasitóide de Spodoptera cosmioides Walker, 1858 (Lepidoptera: Noctuidae) no Brasil

Spodoptera cosmioides (Lepidoptera: Noctuidae)é uma espécie polífaga e alimenta-se de grande número de plantas cultivadas e espontâneas. No Brasil, as culturas do abacaxi, algodoeiro, arroz, berinjela, cebola, eucalipto, pimentão e tomateiro, entre outras hortaliças, são consideradas hospedeiras da praga. Entretanto, apesar da ampla gama de hospedeiros, sua ocorrência como praga é relatada relacionada a desequilíbrios provocados pelo uso excessivo de inseticidas de amplo espectro, o que vem causando a resistência da praga a inseticidas. Devido a essa complexidade, métodos alternativos de controle têm sido propostos, por exemplo, o controle biológico através da utilização de parasitóides. Trichospilus diatraeae (Hymenptera: Eulophidae) é um parasitóide gregário pupal preferencialmente de espécies da ordem Lepidoptera. Este é o primeiro relato de T. diatraeae parasitando pupas de S. cosmioides, parasitóide que oferece novas perspectivas para os programas de controle biológico.

Interaction between Telenomus remus and Trichogramma pretiosum in the management of Spodoptera spp.

Interaction betweeen Telenomus remus and Trichogramma pretiosum in the management of Spodoptera spp. The use of egg parasitoids is a promising strategy for Integrated Pest Management (IPM), but different species of parasitoids have greater or lesser control efficiency, depending on the pest species. Recently, not only Anticarsia gemmatalis and Pseudoplusia includens but also Spodoptera cosmioides and S. eridania have been among the key Lepidoptera larvae attacking soybeans. This study evaluated the combination of Telenomus remus and Trichogramma pretiosum for parasitism of eggs of the Spodoptera complex, for better control efficiency and broader spectrum of action among the key pests of soybeans. The experiment was carried out under controlled environmental conditions (25 ± 2oC; 70 ± 10% RH; and 14 h photophase) in a completely randomized experimental design with seven treatments and 10 replicates with S. frugiperda, S. cosmioides and S. eridania eggs. Each replicate consisted of one egg mass of each Spodoptera species, with approximately 100 eggs offered to the parasitoids. The treatments were: 1) 10 females of T. pretiosum; 2) nine females of T. pretiosum and one female of T. remus; 3) eight females of T. pretiosum and two females of T. remus; 4) seven females of T. pretiosum and three females of T. remus; 5) six females of T. pretiosum and four females of T. remus; 6) five females of T. pretiosum and five females of T. remus, and 7) 10 females of T. remus. The parameter evaluated was the percentage of parasitized eggs. Results showed that treatments combining both parasitoid species with only 1 T. remus for each 9 T. pretiosum (10%) and only 2 T. remus for each 8 T. pretiosum (20%) were enough to significantly increase the parasitism observed on eggs of S. cosmioides and S. frugiperda, respectively. This association of T. pretiosum and T. remus in different proportions is very promising for biological control in IPM programs because it provides wide spectrum of control.

Host preference of the egg parasitoids Telenomus remus and Trichogramma pretiosum in laboratory

Host preference of the egg parasitoids Telenomus remus and Trichogramma pretiosum in laboratory. This research aimed to evaluate the host preference of the egg parasitoids Telenomus remus and Trichogramma pretiosum. Trials were carried out in laboratory, under controlled environmental conditions (25 ± 2ºC temperature; 70 ± 10% RH; and 14 h photophase). The parasitoid searching behavior was evaluated based on the distribution (%) of eggs parasitized by each parasitoid, on egg masses of each host species. Results showed the host preference of T. remus by Spodoptera cosmioides eggs. T. pretiosum, reared in A. gemmatalis eggs, choose to parasitize always eggs of the host where the parasitoid had been reared. The egg preference was not observed when T. pretiosum was reared in S. frugiperda eggs. These results show that, in general, host preference of T. remus is less influenced by the host where it is developed than T. pretiosum. Host preference is an important parameter for biological control programs because more than one pest species may occur in the field, different from those where they were reared in the laboratory.

Caracterização dos danos de Spodoptera eridania (Cramer) e Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) a estruturas de algodoeiro

The cotton plant, Gossypium hirsutum, hosts various pests that damage different structures. Among these pests, Spodoptera cosmioides (Walker) and Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae) are considered important. The objectives of this study were to characterize and to quantify the potential damage of S. eridania and S. cosmioides feeding on different structures of cotton plants. For this purpose, newly-hatched larvae were reared on the following plant parts: leaf and flower bud; leaf and boll; flower bud or boll; and leaf, flower bud and boll. The survival of S. cosmioides and S. eridania was greater than 80% and 70% for larvae fed on cotton plant parts offered separately or together, respectively. One larva of S. eridania damaged 1.7 flower buds, but did not damage bolls, while one larva of S. cosmioides damaged 5.2 flower buds and 3.0 cotton bolls. Spodoptera eridania and S. cosmioides can be considered species with potential to cause economic damage to cotton plants because they can occur throughout cotton developmental stages causing defoliation and losses of reproductive structures. Therefore, the results validate field observations that these two species of Spodoptera are potential pests for cotton.

Selection and characterization of the Bacillus thuringiensis strains toxic to Spodoptera eridania (Cramer), Spodoptera cosmioides (Walker) and Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae)

Among the pests of cultivated plants, the Spodoptera species complex is one of the most important. This genus is composed of polyphagous insects that attack, among other crops, cotton, corn, soy and castor bean. In Brazil Spodoptera frugiperda has been recognized as a primary pest in cotton, and Spodoptera eridania (Cramer) and Spodoptera cosmioides (Walker) species are important pests in cotton and soy. This study was performed in 2008 and was focused on selecting and characterizing Bacillus thuringiensis strains highly pathogenic to S. cosmioides, S. eridania and S. frugiperda and identifying Cry proteins toxic to these species. One hundred strains that exhibited toxicity to Lepidoptera were evaluated through bioassay and the most toxic ones were characterized through morphologic, biochemical and molecular analyses and LC 50 values were determined. Since the cry1Aa, cry1Ab, cry1Ac and cry2Aa genes were present in most of the toxic strains, recombinant Bt producing toxins encoded by representative genes from these families, were individually tested. The Cry proteins showed different levels of toxicity to the three Spodoptera species, with Cry1Aa and Cry1Ab the most toxic to S. cosmioides, Cry2Aa the most toxic to S. eridania and Cry1Aa, Cry1Ab and Cry2Aa most toxic to S. frugiperda. Cry1Ac, a component of some transgenic cotton varieties such as Bollgard I, extensively used in Brazil, presented low toxicity to the three species studied.

Estágios imaturos de Spodoptera cosmioides (Walker) (Lepidoptera, Noctuidae)

There are 30 species in the genus Spodoptera Guenee, 1852 worldwide distributed, occurring mainly in the warm regions. Fifteen species are considered plagues feeding on several important agricultural crops as soybean, corn, rice and potato. The immature stages morphology of this genus is not well known. In about one third of the most economically relevant species, the caterpillar is not described and, also, few information related to the chrysalis and the eggs are available. Spodoptera cosmioides (Walker, 1858) is one of the most important pest among the noctuids occurring in Brazil with no information about its immature stages. Detailed morphological descriptions and illustrations of the immature stages of S. cosmioides , as micropilar area of the egg, chaetotaxy, spinneret, caterpillar ground color, arrangement of the appendages and natural openings of the pupa, are presented for the first time. Taxonomic remarks are also provided.