127 research outputs found
Combinations of Metarhizium anisopliae with chemical insecticides and their effectiveness in Mahanarva fimbriolata (Hemiptera: Cercopidae) control on sugarcane
Some insecticides can be used jointly with entomopathogenic fungi, and therefore the combi-
nation of chemical and biological control measures can be a safe and effective method to con-
trol insect pests. The aim of this study was to evaluate the costs and efficacy of combinations of
Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae) with thiameth-
oxam and imidacloprid on spittlebug (Mahanarva fimbriolata (StÄl); Hemiptera: Cercopidae)
control on sugarcane. The experiment was conducted as a randomized block design (RBD)
with 10 treatments and 4 replications. The treatments included a control (untreated), thia-
â1
â1
12
â1
methoxam (250 g ha ), imidacloprid (700 g ha ), M. anisopliae (M. a.) (3 Ă 10 conidia ha ),
A1 (3 Ă 10 12 M. a. conidia ha â1 + 65 g ha â1 of thiamethoxam), A2 (3 Ă 10 12 M. a. conidia ha â1 + 125
g ha â1 of thiamethoxam), A3 (3 Ă 10 12 M. a. conidia ha â1 + 187.5 g ha â1 of thiamethoxam), A4 (3 Ă
10 12 M. a. conidia ha â1 + 175 g ha â1 of imidacloprid), A5 (3 Ă 10 12 M. a. conidia ha â1 + 350 g ha â1 of
imidacloprid), and A6 (3 Ă 10 12 M. a. conidia ha â1 + 525g ha â1 of imidacloprid). The reductions
in the numbers of M. fimbriolata nymphs per treatment compared to the control were similar
at 15 DAT (days after treatment) in all treatments except combination A5 (M. anisopliae
and thiamethoxam). At 30 DAT, the numbers of nymphs were significantly reduced in all
treatments except A3, and their effectiveness ranged from 14.28% to 92.85%. At 45 DAT the
numbers of M. fimbriolata nymphs per treatment were significantly reduced in the following
treatments: imidacloprid alone at 700g ha -1 , A1, A2, A3, A4 and A6; and the combinations A1
and A2 caused the lowest M. fimbriolata nymph infestations and effectiveness rates of 77.41
and 87.09 %, respectively. At 75 DAT the 2 best control efficacies occurred in treatments A1 (3
Ă 10 12 M. a. conidia ha -1 of + 65g ha -1 of thiamethoxam) (82.1%) and A5 (78.6%) (3 Ă 10 12 M. a.
conidia ha â1 + 350 g ha â1 of imidacloprid). At 90 DAT the number of nymphs in the control had
increased 2.8 fold over the number at 75 DAT. Very good control efficacies at 90 DAT occurred
in all treatments with the combination of the fungus with an insecticide. At 105 DAT the
numbers of nymphs had surged in all treatments, and no treatment provided effective control.
The treatments with the highest earnings per hectare were A1 (3 Ă 10 12 M. a. conidia ha -1 + 65
g thiamethoxam) and M. anisopliae alone at the recommended dose of 3 Ă 10 12 M. a. conidia
ha -1 . Our findings demonstrate the effectiveness of using either thiamethoxam or imidacloprid
in combination with M. anisopliae to control M. fimbriolata nymphs on sugarcane, but greater
net earnings per hectare occurred with the lowest rate of the thiamethoxam combination than
with any of the imidacloprid combinations.Algunos insecticidas se puede utilizar con hongos entomopatĂłgenos y por lo tanto, la aso-
ciaciĂłn de los controles quĂmico y biolĂłgico puede ser una estrategia segura y eficaz para
el control de insectos-plaga. El objetivo de este estudio fue evaluar los costos y eficacia de combinaciones de Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavi-
cipitaceae) con insecticidas thiamethoxam e imidacloprid para el control de la chicharrita
(Mahanarva fimbriolata (StĂ„l); Hemiptera: Cercopidae) en caña de azĂșcar . El experimento
fue conducido en un delineamiento en bloques casualizados (DBC), con 10 tratamientos y
4 repeticiones. Los tratamientos que incluidos el control (sin tratamiento), thiamethoxam
(250 g ha â1 ), imidacloprido (700 g ha â1 ), M. anisopliae (M.a.) (3Ă10 12 conidios ha â1 ), A1 (3Ă10 12
conidios ha â1 de M. a. + 65 g ha â1 de thiamethoxam), A2 (3Ă10 12 conidios ha â1 de M. a. + 125g
ha â1 de thiamethoxam), A3 (3Ă10 12 conidios ha â1 de M. a. + 187.5 g ha â1 de thiamethoxam), A4
(3Ă10 12 conidios ha â1 de M.a + 175 g ha â1 de imidacloprido), A5 (3Ă10 12 conidios ha â1 de M. a. +
350 g ha â1 de imidacloprido) y A6 (3Ă10 12 conidios ha â1 de M. a. + 525g ha â1 de imidacloprido).
Las reducciones en el nĂșmero de ninfas M. fimbriolata por tratamiento en comparaciĂłn con
el control fueron similares a los 15 DAT (dĂas pos tratamiento) en todos los tratamientos
excepto A5 combinaciĂłn (M. anisopliae y thiamethoxam). A los 30 DAT, el nĂșmero de ninfas
se redujeron significativamente en todos los tratamientos, excepto A3, y su eficacia variĂł de
14,28% para 92,85%. A los 45 DAT, los nĂșmeros de ninfas M. fimbriolata por tratamiento se
redujeron significativamente en los siguientes tratamientos: imidacloprido solo en 700 g ha -1 ,
A1, A2, A3, A4 y A6; y las combinaciones de A1 y A2 causaron la mĂĄs bajo infestaciones de
ninfas M. fimbriolata y sus tasas de eficacia fueron de 77,41 y 87,09%, respectivamente. A los
75 DAT, los 2 mejores eficacias de control se produjeron en tratamientos A1 (3Ă10 12 conidios
ha â1 de M. a. + 65 g ha â1 de thiamethoxam) y A5 (78.6%) (3Ă10 12 conidios ha â1 de M. a.+ 350
g ha â1 de imidacloprido). A los 90 DAT, el nĂșmero de ninfas en el control habĂa aumentado
2,8 veces mĂĄs el nĂșmero a 75 DAT. Muy buenas eficacias de control en 90 DAT, se produjo
en todos los tratamientos con la combinaciĂłn del hongo con un insecticida. A los 105 DAT, el
nĂșmero de ninfas habĂan aumentado en todos los tratamientos, y ningĂșn tratamiento habĂa
proporcionado un control efectivo. Los tratamientos con los mayores rendimientos hectĂĄrea
fueron A1 (3Ă10 12 conidios ha â1 de M. a.+ 65 g de thiamethoxam) y M. anisopliae solo a la dosis
recomendada de 3Ă10 12 conidios ha â1 de M. a. Nuestros resultados demuestran la eficacia de
thiamethoxam y imidacloprido en combinaciĂłn con M. anisopliae para el control de ninfas M.
fimbriolata en caña de azĂșcar, pero mayores beneficio neto por hectĂĄrea se produjeron con la
tasa mĂĄs baja de la combinaciĂłn de thiamethoxam que con cualquiera de las combinaciones
de imidacloprid
Skp is a multivalent chaperone of outer membrane proteins
The trimeric chaperone Skp sequesters outer-membrane proteins (OMPs) within a hydrophobic cage, thereby preventing their aggregation during transport across the periplasm in Gram-negative bacteria. Here, we studied the interaction between Escherichia coli Skp and five OMPs of varying size. Investigations of the kinetics of OMP folding revealed that higher Skp/OMP ratios are required to prevent the folding of 16-stranded OMPs compared with their 8-stranded counterparts. Ion mobility spectrometryâmass spectrometry (IMSâMS) data, computer modeling and molecular dynamics simulations provided evidence that 10- to 16-stranded OMPs are encapsulated within an expanded Skp substrate cage. For OMPs that cannot be fully accommodated in the expanded cavity, sequestration is achieved by binding of an additional Skp trimer. The results suggest a new mechanism for Skp chaperone activity involving the coordination of multiple copies of Skp in protecting a single substrate from aggregation
Advances in estimation by the item sum technique using auxiliary information in complex surveys
To collect sensitive data, survey statisticians have designed many strategies to reduce
nonresponse rates and social desirability response bias. In recent years, the item count
technique (ICT) has gained considerable popularity and credibility as an alternative mode
of indirect questioning survey, and several variants of this technique have been proposed as
new needs and challenges arise. The item sum technique (IST), which was introduced by
Chaudhuri and Christofides (2013) and Trappmann et al. (2014), is one such variant, used
to estimate the mean of a sensitive quantitative variable. In this approach, sampled units are
asked to respond to a two-list of items containing a sensitive question related to the study
variable and various innocuous, nonsensitive, questions. To the best of our knowledge,
very few theoretical and applied papers have addressed the IST. In this article, therefore,
we present certain methodological advances as a contribution to appraising the use of the
IST in real-world surveys. In particular, we employ a generic sampling design to examine
the problem of how to improve the estimates of the sensitive mean when auxiliary information on the population under study is available and is used at the design and estimation
stages. A Horvitz-Thompson type estimator and a calibration type estimator are proposed
and their efficiency is evaluated by means of an extensive simulation study. Using simulation experiments, we show that estimates obtained by the IST are nearly equivalent to those
obtained using âtrue dataâ and that in general they outperform the estimates provided by a
competitive randomized response method. Moreover, the variance estimation may be considered satisfactory. These results open up new perspectives for academics, researchers and
survey practitioners, and could justify the use of the IST as a valid alternative to traditional
direct questioning survey modes.Ministerio de EconomĂa y Competitividad of SpainMinisterio de Educacion, Cultura y Deporteproject PRIN-SURWE
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