The antifeedant and insecticidal effects of two commercial neem ( Azadirachta indica ) oil formulations (Dalneem and Nim-I-Go) to Oebalus poecilus were evaluated on irrigated rice. To evaluate the ...antifeedant effect, both formulations were tested at 1% and 2% (v/v) concentration levels. The insecticidal effect was evaluated at 0.5%, 1%, 2%, and 4% (v/v) concentrations of Dalneem, by ingestion. Both experiments were conducted with four replications by treatment, containing one panicle and adult insects segregated by gender (two insects per plot for the antifeedant effect and five for the insecticidal effect). Both products were efficient, reducing the damage caused by insects. Insects fed less on the panicles treated with neem oil, causing lower number of feeding sheaths per panicle and lower percentage of damaged grains than the control. Spikelets weight was higher in panicles treated with neem oils. Females caused significantly higher damage than males in controls, for numbers of feeding sheaths and for the feeding deterrence index. Only at the 4% (v/v) concentration level, Dalneem caused adult mortality higher than in the control. Results showed that neem oil formulations, at >= 1% (v/v) concentration, can be used to reduce the quantitative and qualitative damages caused by O. poecilus in lowland rice.
KEY-WORDS: Small rice stink bug; Azadirachta indica ; qualitative damages; Oryza sativa ; botanical extract.
Avaliou-se o efeito das formulações comerciais de óleo de nim ( Azadirachta indica ) Dalneem e Nim-I-Go sobre a alimentação e sobrevivência de O. poecilus , em arroz irrigado. O efeito sobre a alimentação foi avaliado nas concentrações de 1% e 2% (v/v) das formulações. O efeito inseticida foi avaliado nas concentrações de 0,5%; 1%; 2%; e 4% (v/v) de Dalneem, por ingestão. Os experimentos foram realizados com quatro repetições por tratamento, contendo uma panícula e insetos adultos separados por sexo (dois insetos por parcela, para o efeito sobre a alimentação, e cinco, para o efeito inseticida). Os dois produtos foram igualmente eficientes na redução dos danos causados pelos insetos. Os insetos alimentaram-se menos das panículas tratadas, causando menor número de bainhas de estilete/grão e menos grãos danificados do que no controle. A massa das espiguetas foi maior nas panículas tratadas. Na testemunha, as fêmeas causaram danos significativamente maiores que os machos, para número de bainhas de estilete e Índice de Deterrência da Alimentação. Apenas na concentração de 4% (v/v), o Dalneem causou mortalidade de adultos significativamente superior à da testemunha. Conclui-se que os óleos de nim testados, em concentrações >= 1% (v/v), podem ser utilizados para reduzir os danos quantitativos e qualitativos causados por O. poecilus , em arroz.
PALAVRAS-CHAVE: Percevejo da panícula; Azadirachta indica ; danos qualitativos; Oryza sativa ; extrato botânico.
Several non-ionic surfactants can be used to enhance insecticidal performance of various bio-based products and agrochemicals. In this study, we describe the toxicity of four commercial non-ionic ...surfactants against immature Bemisia tabaci (Gennadius) biotype B whiteflies along with their spreading ability. Results revealed that trisiloxane-based surfactants (Break-thru® and Silwet® L-77) exhibited the highest toxicity to 1st–2nd (early) and 3rd–4th (late) instar nymphs as well as the greatest wetting performance. We also investigated whether sub-lethal concentrations of Break-thru® and Silwet® L-77 improved the insecticidal efficacy of the fungal entomopathogens Beauveria bassiana (Balsamo) Vuillemin (strain CG1229) and Isaria fumosorosea Wise (strain CG1228) conidial suspensions against whiteflies. Germination of hydrophobic conidia of both isolates were unaffected by these surfactants over the range 100–1000 ppm. The combinations of both fungi with trisiloxane carriers significantly increased nymphal mortality with mostly additive and synergistic effects on early and late nymphs, respectively. In screenhouse trials, both fungi (10⁷ conidia ml⁻¹) mixed with 200 ppm of Silwet® L-77 significantly improved effectiveness against early nymphs (72–74 % mortality) compared with controls treated with water and Silwet® L-77 alone. In addition, reduced volume rates of I. fumosorosea in Silwet® L-77 (equivalent to 100 l ha⁻¹) were at least as effective against late nymphs as higher volume rates (200 l ha⁻¹) at equivalent conidial doses. Our findings underline the compatibility and enhanced activity of silicon-based surfactants with B. bassiana and I. fumosorosea for use in integrated whitefly management programs.
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•Adults of Tibraca limbativentris are more susceptible to thiamethoxam than to lambda-cyhalothrin.•T. Limbativentris exhibited a natural resistance to Metarhizium anisopliae.•Subdoses ...of chemical insecticides enhanced susceptibility of T. limbativentris to M. anisopliae.
This study investigated the interaction of the fungus Metarhizium anisopliae (Metsch.) Sorok. with sublethal doses of synthetic chemical insecticides thiamethoxam and lambda-cyhalothrin for the control of Tibraca limbativentris adults under laboratory and field conditions. Median lethal time (LT50) was reduced significantly when M. anisopliae (5×106–5×108 conidia/mL) was combined with a sublethal dose (0.77ppm AI) of thiamethoxam compared with fungus only. A similar response on host mortality was observed for M. anisopliae at 5×107 conidia/mL in combination with sublethal dose of lambda-cyhalothrin at 9.33ppm (AI). Additionally, the thiamethoxam-fungus combination increased overall mortality and percent mycosed insects in comparison to their counterparts alone. Increasing fungus concentration did not increase insect susceptibility when combined with thiamethoxam either at 0.77 or 0.38ppm (AI). In a field experiment, the combination of M. anisopliae at 1×1012 viable conidia/ha with thiamethoxam at 12.5g (AI)/ha (¼ full dose) synergistically increased mortality and mycosis of adults of T. limbativentris. Therefore, enhanced T. limbativentris control could potentially be achieved within label rates of fungus (5×106 conidia/mL) and sublethal thiamethoxam (0.77ppm). The strategy of using sublethal doses of chemical insecticides in combination with entomopathogenic fungi is a promising approach to battle the rice stalk stink bug in rice fields.
The objective of this work was to determine the most susceptible nymphal stage of Bemisia tabaci biotype B to neem (Azadirachta indica A. Juss.) oil applied to dry bean (Phaseolus vulgaris L.) in a ...screenhouse. A solution of commercial oil (Dalneem) extracted from neem seeds was sprayed directly on each nymphal instar at 0, 0.1, 0.25, 0.5, 1 and 2% concentrations for lethal concentration (LC) determination, and at 0, 0.5 and 1% concentrations for lethal time (LT) determination. The number of living and dead nymphs was recorded five days after spraying for LC determination, and daily during six days for LT determination. The LC50 estimated for fourth instar nymphs occurred at 0.56% concentration. For all instars, LC50 and LC95 were estimated at 0.32 and 2.78% concentrations, respectively. The estimated values of LT50 at 1% concentration were 2.46, 4.45, 3.02 and 6.98 days for the first to fourth instars, respectively. The LT50 occurred at five days for 0.5% and at four days for 1% concentration in all instars. A mortality rate of over 80% was observed on the 6th day for the first to third instars at 1% concentration. The first three nymphal stages were more susceptible to neem oil when compared to the fourth nymphal stage.O objetivo deste trabalho foi determinar o estágio ninfal de Bemisia tabaci biótipo B mais suscetível ao óleo de nim (Azadirachta indica A. Juss.) aplicado em feijoeiro (Phaseolus vulgaris L.), em casa telada. Foram avaliados o tempo letal (TL) e concentração letal (CL) do óleo comercial de sementes de nim Dalneem. Para CL, concentrações de 0, 0,1, 0,25, 0,5, 1 e 2% do produto foram pulverizadas diretamente sobre as ninfas em cada ínstar. Para TL, o produto foi avaliado a 0, 0,5 e 1% de óleo de nim em cada ínstar. Ninfas vivas e mortas foram contadas cinco dias após a pulverização para CL e diariamente para TL durante seis dias. Para o quarto ínstar, a CL50 foi de 0,56% de óleo de nim. Considerando todos os ínstares, CL50 e CL95 foram estimadas em 0,32 e 2,78% de óleo de nim, respectivamente. Os TL50 para 1% de nim foram estimados em 2,46, 4,45, 3,02 e 6,98 dias para o primeiro, segundo, terceiro e quarto ínstares, respectivamente. Os TL50 estimados para 0,5 e 1% de óleo de nim foram de cinco e quatro dias, respectivamente, considerando todos os ínstares. No sexto dia, foi observada mortalidade superior a 80% para o primeiro, segundo e terceiro ínstares a 1% de óleo de nim. Os três primeiros ínstares foram mais suscetíveis ao óleo de nim que o quarto ínstar.
O percevejo-do-colmo, Tibraca limbativentris Stal, 1860 (Heteroptera: Pentatomidae), é altamente prejudicial à cultura do arroz no Brasil, principalmente em sistemas de cultivo irrigados por ...inundação. O efeito de duas formas de aplicação, conídios em suspensão e veiculados em grãos de arroz autoclavado, da cepa (CP) 172 de Metarhizium anisopliae (Metsch.) Sorok., no controle do percevejo, foi avaliado em três experimentos conduzidos em 1991, 1993 e 1994, em lavoura comercial de arroz irrigado. Em 1991, tanto a pulverização de conídios como a distribuição manual grãos de arroz cobertos com material fúngico em dosagem equivalente a 7,2 x 10(13) conídios.ha-1, sobre o solo e entre os colmos de arroz, onde os percevejos estavam alojados, reduziram significativamente a população natural do inseto com eficiência de controle de 52,6% e 61,8%, respectivamente. Ainda em 1991, estudo sobre o estabelecimento e persistência da cepa no solo do arrozal, com base na contagem de unidades formadoras de colônias (UFC), indicou que o fungo manteve-se viável na entressafra, até 216 dias após a aplicação, época da implantação de novos arrozais. O número de UFC foi maior nas parcelas tratadas com os grãos de arroz cobertos com material fúngico. O crescimento linear do número de UFC, no solo nas parcelas testemunhas, evidenciou disseminação do fungo para partes anteriormente não tratadas do arrozal. Resultados significativos de controle com a aplicação da suspensão de conídios e dos grãos de arroz com o fungo, na dose de 5 x 10(13) conídios.ha-1, também foram obtidos em 1993, com 51,8% e 48,2% de eficiência, respectivamente. Em 1994, a aplicação da suspensão de 5 x 10(13) conídios.ha-1 resultou em 39,5% de controle do inseto. O índice de confirmação de infeção, contudo, foi baixo, nos dois anos, atingindo, no máximo, 20%, em 1993. O baixo número de insetos com micose, em comparação ao índice de mortalidade, pode provavelmente reduzir a taxa de disseminação do fungo nos arrozais e, por conseqüência, ser desfavorável à ocorrência de epizootias.
The antifeedant and insecticidal effects of two commercial neem (Azadirachta indica) oil formulations (Dalneem and Nim-I-Go) to Oebalus poecilus were evaluated on irrigated rice. To evaluate the ...antifeedant effect, both formulations were tested at 1% and 2% (v/v) concentration levels. The insecticidal effect was evaluated at 0.5%, 1%, 2%, and 4% (v/v) concentrations of Dalneem, by ingestion. Both experiments were conducted with four replications by treatment, containing one panicle and adult insects segregated by gender (two insects per plot for the antifeedant effect and five for the insecticidal effect). Both products were efficient, reducing the damage caused by insects. Insects fed less on the panicles treated with neem oil, causing lower number of feeding sheaths per panicle and lower percentage of damaged grains than the control. Spikelets weight was higher in panicles treated with neem oils. Females caused significantly higher damage than males in controls, for numbers of feeding sheaths and for the feeding deterrence index. Only at the 4% (v/v) concentration level, Dalneem caused adult mortality higher than in the control. Results showed that neem oil formulations, at > 1% (v/v) concentration, can be used to reduce the quantitative and qualitative damages caused by O. poecilus in lowland rice.
Avaliou-se o efeito das formulações comerciais de óleo de nim (Azadirachta indica) Dalneem e Nim-I-Go sobre a alimentação e sobrevivência de O. poecilus, em arroz irrigado. O efeito sobre a alimentação foi avaliado nas concentrações de 1% e 2% (v/v) das formulações. O efeito inseticida foi avaliado nas concentrações de 0,5%; 1%; 2%; e 4% (v/v) de Dalneem, por ingestão. Os experimentos foram realizados com quatro repetições por tratamento, contendo uma panícula e insetos adultos separados por sexo (dois insetos por parcela, para o efeito sobre a alimentação, e cinco, para o efeito inseticida). Os dois produtos foram igualmente eficientes na redução dos danos causados pelos insetos. Os insetos alimentaram-se menos das panículas tratadas, causando menor número de bainhas de estilete/grão e menos grãos danificados do que no controle. A massa das espiguetas foi maior nas panículas tratadas. Na testemunha, as fêmeas causaram danos significativamente maiores que os machos, para número de bainhas de estilete e Índice de Deterrência da Alimentação. Apenas na concentração de 4% (v/v), o Dalneem causou mortalidade de adultos significativamente superior à da testemunha. Conclui-se que os óleos de nim testados, em concentrações > 1% (v/v), podem ser utilizados para reduzir os danos quantitativos e qualitativos causados por O. poecilus, em arroz.
The antifeedant and insecticidal effects of two commercial neem (Azadirachta indica) oil formulations (Dalneem and Nim-I-Go) to Oebalus poecilus were evaluated on irrigated rice. To evaluate the ...antifeedant effect, both formulations were tested at 1% and 2% (v/v) concentration levels. The insecticidal effect was evaluated at 0.5%, 1%, 2%, and 4% (v/v) concentrations of Dalneem, by ingestion. Both experiments were conducted with four replications by treatment, containing one panicle and adult insects segregated by gender (two insects per plot for the antifeedant effect and five for the insecticidal effect). Both products were efficient, reducing the damage caused by insects. Insects fed less on the panicles treated with neem oil, causing lower number of feeding sheaths per panicle and lower percentage of damaged grains than the control. Spikelets weight was higher in panicles treated with neem oils. Females caused significantly higher damage than males in controls, for numbers of feeding sheaths and for the feeding deterrence index. Only at the 4% (v/v) concentration level, Dalneem caused adult mortality higher than in the control. Results showed that neem oil formulations, at >= 1% (v/v) concentration, can be used to reduce the quantitative and qualitative damages caused by O. poecilus in lowland rice. KEY-WORDS: Small rice stink bug; Azadirachta indica; qualitative damages; Oryza sativa; botanical extract.
Observations on the bioecology and damage of
Teratopactus nodicollis
Boheman on
Phaseolus vulgaris
were carried out on field samples by assessing the number of larvae and root damage in 40 ha of a ...dry bean field from the Federal District, Brazil (16°4′28.41″ W; 47°30′21.13″ S). Larvae caused the greatest damage at the stage of germination, emergence, and primary leaves, producing 50 % stand reduction. Most larvae pupated in August and September, and adult emergence occurred in middle October. Some larvae were infected with the fungus
Metarhizium
spp., a biological agent that would be naturally controlling this insect.
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