Low-Intensity, High-Frequency Grazing Positively Affects Defoliating Behavior, Nutrient Intake and Blood Indicators of Nutrition and Stress in Sheep.

The intensity and frequency of grazing affect the defoliating strategy of ruminants, their daily nutrient intake, thus nutrition and physiological status. Italian ryegrass (Lolium multiflorum Lam.) pastures were grazed by sheep either under a low-intensity/high-frequency grazing strategy (Rotatinuous stocking; RN) with nominal pre- and post-grazing sward heights of 18 and 11 cm, respectively, or under a high-intensity/low-frequency strategy (traditional rotational stocking; RT) with nominal pre- and post-grazing sward heights of 25 and 5 cm, respectively. Treatments were arranged under a complete randomized design and evaluated over two periods, in different years. In 2017, the aim was to depict the type of bites that sheep perform during the grazing-down and associate them to the grazing management strategy according to their relative contribution to the diet ingested. In 2018 we estimated the total nutrient intake and evaluated blood indicators of the nutritional status and immune response to stress of sheep. The bite types accounting the most for the diet ingested by RN sheep were those performed on the "top stratum" of plants with around 20, 15, and 25 cm, whereas the type of bites accounting the most for the diet of RT sheep were those performed on "grazed plants" with around 10, 5, and ≤ 3 cm. In 2018, the RN sheep increased by 18% the total organic matter (OM) intake and by 20-25% the intake of soluble nutrients (i.e., crude protein, total soluble sugars, crude fat), digestible OM and of metabolizable energy, and had 17.5, 18, and 6.1% greater blood concentration of glucose, urea nitrogen (BUN) and albumin, respectively, but 17% lower blood neutrophil-to-lymphocyte (N:L) ratio. Sheep grazing vegetative Italian ryegrass pastures under the low-intensity/high-frequency grazing strategy (RN) ingested a diet of better quality from bites allocated on the top stratum of plants, had greater intake of soluble nutrients and blood parameters positively associated with nutritional status and immune response to stress.

What, how, and how much do herbivores eat? The Continuous Bite Monitoring method for assessing forage intake of grazing animals.

Determining herbage intake is pivotal for studies on grazing ecology. Direct observation of animals allows describing the interactions of animals with the pastoral environment along the complex grazing process. The objectives of the study were to evaluate the reliability of the continuous bite monitoring (CBM) method in determining herbage intake in grazing sheep compared to the standard double-weighing technique method during 45-min feeding bouts; evaluate the degree of agreement between the two techniques; and to test the effect of different potential sources of variation on the reliability of the CBM. The CBM method has been used to describe the intake behavior of grazing herbivores. In this study, we evaluated a new approach to this method, that is, whether it is a good proxy for determining the intake of grazing animals. Three experiments with grazing sheep were carried out in which we tested for different sources of variations, such as the number of observers, level of detail of bite coding grid, forage species, forage allowance, sward surface height heterogeneity, experiment site, and animal weight, to determine the short-term intake rate (45 min). Observer (Pexp1  = 0.018, Pexp2  = 0.078, and Pexp3  = 0.006), sward surface height (Pexp2  < 0.001), total number of bites observed per grazing session (Pexp2  < 0.001 and Pexp3  < 0.001), and sward depletion (Pexp3  < 0.001) were found to affect the absolute error of intake estimation. The results showed a high correlation and agreement between the two methods in the three experiments, although intake was overestimation by CBM on experiments 2 and 3 (181.38 and 214.24 units, respectively). This outcome indicates the potential of CBM to determining forage intake with the benefit of a greater level of detail on foraging patterns and components of the diet. Furthermore, direct observation is not invasive nor disrupts natural animal behavior.

Baseline Response, Monitoring, and Cross-Resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to Sodium Channel Blocker Insecticides in Brazil.

Spodoptera frugiperda (J.E. Smith) is one of the key cross-crop pests in Brazilian agroecosystems. Field-evolved resistance of S. frugiperda to some conventional insecticides and Bt proteins has already been reported. Thus, the use of insecticides with new mode of action such as sodium channel blockers (indoxacarb and metaflumizone) could be an important tool in insecticide resistance management (IRM) programs. To implement a proactive IRM, we conducted baseline response and monitoring to indoxacarb and metaflumizone in 87 field populations of S. frugiperda collected from major maize-growing regions of Brazil from 2017 to 2020, estimated the frequency of resistance alleles to indoxacarb, and evaluated cross-resistance of indoxacarb and metaflumizone to some selected insecticides and Bt proteins. Low variation in susceptibility to indoxacarb (4.6-fold) and metaflumizone (2.6-fold) was detected in populations of S. frugiperda in 2017. The frequency of the resistance allele to indoxacarb was 0.0452 (0.0382-0.0527 CI 95%), by using F2 screen method. The mean survival at diagnostic concentration, based on CL99, varied from 0.2 to 12.2% for indoxacarb and from 0.0 to 12.7% for metaflumizone, confirming high susceptibility of S. frugiperda to these insecticides in Brazil. No cross-resistance was detected between sodium channel blocker insecticides and other insecticides (organophosphate, pyrethroid, benzoylurea, spinosyn, and diamide) and Bt proteins. These findings showed that sodium channel blocker insecticides are important candidates to be exploited in IRM strategies of S. frugiperda in Brazil.

Resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to spinetoram: inheritance and cross-resistance to spinosad.

BACKGROUND: The use of spinosyn insecticides is one of the major control strategies of the fall armyworm, Spodoptera frugiperda (J. E. Smith) in Brazil. In this study, we selected a spinetoram-resistant strain from a field-population of S. frugiperda to characterize the inheritance of the resistance and cross-resistance relationship between spinosyn insecticides. RESULTS: The values of LC50 (95% CI) obtained from concentration-response bioassays were 0.63 (0.55-0.73) µg spinetoram mL-1 for the susceptible strain (SUS), and 1170.96 (1041.61-1323.89) µg spinetoram mL-1 for the strain resistant to spinetoram (SPT-R). These values resulted in a resistance ratio of 1844-fold. The SPT-R strain showed cross-resistance with spinosad (resistance ratio = 1196-fold). The reciprocal crosses showed LC50 values of 3.91 (2.97-5.84) and 5.37 (4.52-6.52) µg spinetoram mL-1 , suggesting that the resistance of S. frugiperda to spinetoram is autosomal and incompletely recessive. The backcrosses of the F1 progeny with the SPT-R strain suggest a resistance with polygenic effect. Estimates of the effective number of loci with equal contributions to the resistance effect were from 1.18 to 1.76, suggesting that resistance to spinetoram is associated with a few genes. CONCLUSION: The inheritance pattern of resistance of S. frugiperda to spinetoram was characterized as autosomal, incompletely recessive and polygenic. Cross-resistance between spinosyns was confirmed in S. frugiperda. The importance of this information for implementing insect resistance management strategies is discussed in this paper. © 2020 Society of Chemical Industry.

Detection of a ryanodine receptor target-site mutation in diamide insecticide resistant fall armyworm, Spodoptera frugiperda.

BACKGROUND: Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), a major lepidopteran pest in Latin and North America, has very recently invaded the continents of Africa and Asia. FAW has evolved resistance to different insecticides and transgenic corn expressing Bacillus thuringiensis (Bt) toxins. Here, we investigated the extent and mechanisms of resistance to diamide insecticides in a Brazilian field-collected FAW strain selected using chlorantraniliprole. RESULTS: Continuous laboratory selection of a field-collected FAW strain with chlorantraniliprole resulted in resistance ratios of 225-fold and > 5400-fold against chlorantraniliprole and flubendiamide, respectively, when compared with a susceptible strain. Pre-exposure to different synergists known to inhibit detoxification enzymes did not result in significantly increased larval toxicity, suggesting a minor role for metabolic resistance. Sequencing of the FAW ryanodine receptor (RyR) C-terminal domains II to VI revealed a single nucleotide polymorphism, resulting in a I4734M mutation recently said to confer target-site resistance to diamides in lepidopteran pests. Genotyping by pyrosequencing of field-collected FAW larvae sampled in the 2018 crop season suggests a low resistance allele frequency. Furthermore, we developed a fluorescent polymerase chain reaction (PCR)-based allelic discrimination assay for rapid genotyping of field-collected FAW samples, because diamides are increasingly used in Bt-/non-Bt corn. CONCLUSIONS: Recently, the identified RyR mutation has been shown to confer field resistance in other lepidopteran pests such as diamondback moth, tomato leafminer and striped rice stem borer. The developed PCR-based allelic discrimination assay will help to monitor the frequency and future spread of diamide resistance allele in FAW field populations and help to implement appropriate resistance management measures. © 2019 Society of Chemical Industry.

Molecular characterization of Cry1F resistance in fall armyworm, Spodoptera frugiperda from Brazil.

Fall armyworm, Spodoptera frugiperda (J.E. Smith) is a major lepidopteran pest of maize in Brazil and its control particularly relies on the use of genetically engineered crops expressing Bacillus thuringiensis (Bt) toxins such as Cry1F. However, control failures compromising the efficacy of this technology have been reported in many regions in Brazil, but the mechanism of Cry1F resistance in Brazilian fall armyworm populations remained elusive. Here we investigated the molecular mechanism of Cry1F resistance in two field-collected strains of S. frugiperda from Brazil exhibiting high levels of Cry1F resistance. We first rigorously evaluated several candidate reference genes for normalization of gene expression data across strains, larval instars and gut tissues, and identified ribosomal proteins L10, L17 and RPS3A to be most suitable. We then investigated the expression pattern of ten potential Bt toxin receptors/enzymes in both neonates and 2nd instar gut tissue of Cry1F resistant fall armyworm strains compared to a susceptible strain. Next we sequenced the ATP-dependent Binding Cassette subfamily C2 gene (ABCC2) and identified three mutated sites present in ABCC2 of both Cry1F resistant strains: two of them, a GY deletion (positions 788-789) and a P799 K/R amino acid substitution, located in a conserved region of ABCC2 extracellular loop 4 (EC4) and another amino acid substitution, G1088D, but in a less conserved region. We further characterized the role of the novel mutations present in EC4 by functionally expressing both wild type and mutated ABCC2 transporters in insect cell lines, and confirmed a critical role of both sites for Cry1F binding by cell viability assays. Finally, we assessed the frequency of the mutant alleles by pooled population sequencing and pyrosequencing in 40 fall armyworm populations collected from maize fields in different regions in Brazil. We found that the GY deletion being present at high frequency. However we also observed many rare alleles which disrupt residues between sites 783-799, and their diversity and abundance in field collected populations lends further support to the importance of the EC4 domain for Cry1F toxicity.

Selection and characterization of the inheritance of resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to chlorantraniliprole and cross-resistance to other diamide insecticides.

BACKGROUND: Understanding the genetic basis of insect resistance to insecticides can help to implement insecticide resistance management (IRM) strategies. In this study, we selected a strain of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) resistant to chlorantraniliprole using the F2 screen method, characterized the inheritance of resistance and evaluated patterns of cross-resistance to other diamide insecticides. RESULTS: The chlorantraniliprole-resistant strain (Chlorant-R) was selected from a field-collected population with an estimated allele frequency of 0.1316. The estimated median lethal concentration (LC50 ) values were 0.011 and 2.610 µg a.i. cm-2 for the susceptible (Sus) and Chlorant-R strains, respectively, resulting in a resistance ratio (RR) of 237-fold. The LC50 values of the reciprocal crosses were 0.155 and 0.164 µg a.i. cm-2 , indicating that resistance is autosomally inherited. Resistance was characterized as incompletely recessive and monogenic at concentrations close to the recommended field rates of chlorantraniliprole. Survival of the resistant strain and heterozygous larvae in maize plants treated at the field rate was ∼ 60 (similar to the susceptible strain on untreated maize) and 15%, respectively. The Chlorant-R strain showed low cross-resistance to cyantraniliprole (RR ∼ 27-fold) and very high cross-resistance to flubendiamide (RR > 42 000-fold). CONCLUSIONS: The frequency of chlorantraniliprole resistance allele was moderately high in a field-collected population of S. frugiperda. The inheritance of chlorantraniliprole resistance was characterized as autosomal, incompletely recessive and monogenic. S. frugiperda showed cross-resistance to other diamide insecticides. These results provide essential information for the implementation of IRM programs to preserve the useful life of diamide insecticides for controlling S. frugiperda in Brazil. © 2019 Society of Chemical Industry.

Biology of Anastrepha grandis (Diptera: Tephritidae) in Different Cucurbits.

Anastrepha grandis (Macquart) (Diptera: Tephritidae) is one of the main pests of cucurbits in Brazil. Losses occur due to the damage caused to the fruits and the embargo on exports, as A. grandis is considered a quarantine pest in countries that import Brazilian cucurbits. This study aimed to evaluate the development of A. grandis in hosts of the Cucurbitaceae family. The hosts used were stem squash (Cucurbita pepo L.), squash (Cucurbita moschata Duchesne), chayote [Sechium edule (Jacq.) Swartz], mini watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai], Spanish melon (Cucumis melo L.), hybrid squash "Tetsukabuto" (C. moschata×Cucurbita maxima Duchesne), and salad cucumber (Cucumis sativus L.). We evaluated the viability and duration of egg-to-pupa period, pupal weight, sex ratio, and average number of pupae per fruit under controlled conditions of temperature, relative humidity, and photophase. The preoviposition and oviposition periods, fecundity, fertility, and longevity of females were determined for adults. Hosts of the genus Cucurbita provided a better development of A. grandis in comparison with other hosts, and presented a greater number of insects on fruit as well as higher infestation rate. Fecundity and longevity were also higher for females that developed in hosts of the genus Cucurbita, although values of these biological parameters varied between stem squash, squash, hybrid squash "Tetsukabuto."

Euplectrus furnius parasitizing Spodoptera frugiperda in maize in Brazil / Euplectrus furnius parasitando Spodoptera frugiperda em milho no Brasil

Brazil is among the world's biggest maize producers and fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), is the main insect pest on this crop in the country. Despite the importance of its natural enemies, there still is a lack of information about parasitoids species that attack this insect-pest, such as larval parasitoids. This research reports Euplectrus furnius Walker (Hymenoptera: Eulophidae) parasitizing S. fugiperda larvae on maize crop in Brazil.

O Brasil está entre os maiores produtores de milho do mundo e a lagarta-do-cartucho, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) é o principal inseto-praga nessa cultura no país. Apesar da importância de seus inimigos naturais, ainda existe uma falta de informação sobre as espécies de parasitoides que atacam esse inseto-praga, tais como os parasitoides larvais. Este trabalho relata Euplectrus furnius Walker (Hymenoptera: Eulophidae) parasitando larvas de S. frugiperda em milho no Brasil.

Tamanho de amostra para a estimação da média de duração dos períodos larval, pupal e larval mais pupal de Microtheca spp. por bootstrap / Sample size for estimating the average duration of larval, pupal and larval stage plus pupal periods in Microtheca spp. by bootstrap

O objetivo deste trabalho foi determinar o tamanho de amostra (número de insetos) para a estimação da média de duração dos períodos larval, pupal e larval + pupal de Microtheca ochroloma e de Microtheca semilaevis (Coleoptera: Chrysomelidae). Foram coletados adultos dessas espécies em uma área experimental de 0,25ha de nabo forrageiro (Raphanus sativus L.) e foi estabelecida uma criação em laboratório (temperatura de 25±2°C, umidade relativa de 60±10 por cento e fotoperíodo de 12 horas). Após, foram mensurados os períodos larval, pupal e larval + pupal, em dias, de 119 e 81 insetos, respectivamente, de M. ochroloma e de M. semilaevis. Foram calculadas medidas de tendência central e de variabilidade. Foi determinado o tamanho de amostra por meio de bootstrap, com reposição de 10.000 amostras. Para a estimação da média dos períodos larval, pupal e larval + pupal, com intervalo de confiança de bootstrap de 95 por cento de um dia, 42 e 35 insetos são suficientes, respectivamente, para M. ochroloma e M. semilaevis.

The objective of this research was to determine the sample size (number of insects) to estimate the average duration for larval, pupal and larval + pupal periods for M. ochroloma and M. semilaevis. Adults of both species were collected at a 0.25ha experimental area of forage turnip (Raphanus sativus L.) and for laboratory rearing (temperature 25±2°C, relative humidity 60±10 percent and photoperíod 12 hours). Afterwards larval, pupal and larval + pupal periods were measured, in days, of 119 and 81 insects, respectively, M. ochroloma and M. semilaevis. It was calculated measures of central tendency and variability and determined the sample size using bootstrap with replacement of 10000 samples. For estimating the average larval, pupal and larval + pupal periods, with amplitude of bootstrap confidence interval of 95 percent, equal a day, 42 and 35 insects are sufficient, respectively for both M. ochroloma and M. semilaevis.

Primeiro registro de Aphis craccivora Koch 1854 (Hemiptera: Aphididae) sobre plantas daninhas em Santa Maria, RS / First record of Aphis craccivora Koch 1854 (Hemiptera: Aphididae) on weed in Santa Maria, RS State

Aphis craccivora Koch (Hemiptera: Aphididae) é um afídeo-praga que ocorre em diferentes cultivos e causa danos relacionados ao hábito da sucção de seiva. No Brasil, são raros os registros de plantas daninhas hospedeiras dessa espécie, particularmente no Estado do Rio Grande do Sul (RS). Plantas daninhas infestadas com afídeos foram encontradas em área experimental localizada no campus da Universidade Federal de Santa Maria (UFSM), RS, em duas datas, 22/02/2010 e 25/03/2010. No segundo registro (25/03/2010), cada planta daninha foi medida e avaliada quanto ao número de afídeos. A espécie foi identificada como Aphis craccivora e as plantas daninhas hospedeiras, como Amaranthus hybridus Linnaeus, 1753 (Amaranthaceae), caruru-roxo, e Solanum americanum Mill, 1768 (Solanaceae), maria-pretinha. Este trabalho faz o primeiro registro de A. hybridus e S. americanum hospedando A. craccivora em Santa Maria, no Rio Grande do Sul.

Aphis craccivora Koch (Hemiptera: Aphididae) is an aphid pest which occurs in different crops and causes damages related to habit of sucking sap. In Brazil information about host weed species are rare, particulary in Rio Grande do Sul (RS) State. Weeds infested by aphids were found at an experimental area located at the Universidade Federal de Santa Maria, Santa Maria, RS, in two different dates, February 22nd and March 25th 2010. In the second record (March 25th), each weed plant was measured and evaluated on the number of aphids. The aphid species was identified as Aphis craccivora and the host weed as Amaranthus hybridus Linnaeus, 1753 (Amaranthaceae), and Solanum americanum Mill, 1768 (Solanaceae). This is the first report of both A. hybridus and S. americanum hosting A. craccivora in Santa Maria, Rio Grande do Sul State.

First record of larvae of Allograpta exotica Wiedemann (Diptera, Syrphidae) preying on Aphis gossypii Glover (Hemiptera, Aphididae) in watermelon in Brazil

First record of larvae of Allograpta exotica Wiedemann (Diptera, Syrphidae) preying on Aphis gossypii Glover (Hemiptera, Aphididae) in watermelon in Brazil. Brazil is one of the largest world producers of watermelon (Citrullus lanatus Thumb. Mansf.) and Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) is among the most important pest on this crop. Larvae of Allograpta exotica Wiedemann, 1830 (Diptera, Syrphidae) were found preying on A. gossypii in watermelon crop, in Santa Maria, Rio Grande do Sul State, what represents the first report of this tritrophic association in Brazil.

Primeiro relato de larvas de Allograpta exotica Wiedemann (Diptera, Syrphidae) predando Aphis gossypii glover (Hemiptera, Aphididae) em melancia no Brasil. O Brasil é um dos maiores países produtores de melancia e Aphis gossypii Glover, 1877 (Hemiptera, Aphididae) está entre as pragas mais importantes da cultura. Larvas de Allograpta exotica Wiedemann, 1830 (Diptera, Syrphidae) foram registradas predando A. gossypii em cultivo de melancia em Santa Maria, Rio Grande do Sul, o que representa o primeiro relato desta associação tritrófica no Brasil.

Carcass traits of feedlot crossbred lambs slaughtered at different live weights / Características da carcaça de cordeiros cruzados, confinados e abatidos em diferentes pesos

Carcass traits of twenty Texel x Ile de France crossbred lambs slaughtered after weaning (52 days of age), or at 25, 30 and 35kg live weight were evaluated. Lambs were placed in individual stalls (1.5m²) and fed ad libitum with a diet composed of sorghum silage (Sorghum bicolor (L.) Moench) and a concentrate mix (ground corn, soybean meal, calcium carbonate and salt). Commercial dressing percentage was related quadratically with slaughter weight, being highest in lambs slaughtered after weaning. Real dressing percentage increased linearly. Shoulder proportion decreased with slaughter weight, whereas leg, rib and neck proportions remained constant. Carcass fat was positively correlated to the slaughter weight. Slaughter of feedlot Texel x Ile de France crossbred lambs can be recommended at 28kg live weight.

Foram avaliadas as características da carcaça de cordeiros Texel x Ile de France abatidos após o desmame (52 dias de idade) ou aos 25, 30 e 35kg de peso vivo. Utilizaram-se 20 cordeiros, confinados em baias individuais (1,5m²) e alimentados ad libitum com dieta composta por silagem de sorgo (Sorghum bicolor (L.) Moench) e mistura concentrada (grão de milho triturado, farelo de soja, calcário calcítico e sal comum). O rendimento de carcaça comercial relacionou-se quadraticamente ao peso de abate, sendo máximo para os animais abatidos após o desmame. O rendimento de carcaça real elevou-se linearmente. Foi observado decréscimo linear da proporção de paleta à medida que se elevou o peso de abate, ao passo que as proporções de perna, costela e pescoço permaneceram constantes. A proporção total de gordura da carcaça foi positivamente correlacionada ao peso de abate. Recomenda-se que o abate de cordeiros Texel x Ile de France confinados seja realizado aos 28kg de peso vivo.