Interaction effects of entomopathogenic nematodes and insecticides for the management of grubs of Holotrichia longipennis and Brahmina coriacea

Aim: Laboratory studies were conducted to study the potential of entomopathogenic nematodes and their interaction with the commonly used insecticides viz., clothianidin, imidacloprid and chlorpyriphos against first, second and third instar grubs of H. longipennis and B. coriacea.Methodology: Two entomopathogenic nematodes viz., Heterorhabditis indica Poinar and Steinernema caprocapsae Weiser were tested against I-III instar grubs of Brahmina coriacea (Hope) and Holotrichia longipennis (Blanchard) under laboratory conditions @1600IJs per cup by soil application. The mortality data was recorded after every 24 hrs up to 5 days. For evaluating the interaction effects among different tested biocontrol agents with insecticides, each entomopathogenic nematode species and insecticides was tested alone and in combination. H. indica and S. carpocapsae were applied @ 400IJs per cup. Insecticides were applied at a lower concentrations viz. 150, 100 and 75 ppm for chlorpyriphos, imidacloprid and clothianidin, respectively and were applied on the same day of nematode application with a gap of 2 hrs. Mortality data was taken after 24 hrs. Results: Individual application of H. indica and S. carpocapsae @1600 IJs per cup had clearly lethal effect and produced mortality to the tune of 55.5-90.7 % in both the species of white grubs. H. indica revealed higher virulence as compared to S. carpocapsae against both the species. Combination of both the species with all the tested insecticides yielded synergistic interactions and H. indica+ imidacloprid combination proved to be the most promising among all the tested combinations. Interpretation: Tested entomopathogens and insecticide combination produced synergistic interactions more effectively to first, second and early third instar grubs (H. longipennis and B. coriacea).

Preliminary screening of the larvicidal effect of Brevibacillus laterosporus strains against the blowfly Chrysomya megacephala(Fabricius, 1794) (Diptera: Calliphoridae)

: This study evaluated whether different strains of Brevibacillus laterosporus could be used to control larvae of the blowfly Chrysomya megacephala , a pest that affects both human and animal health.

Efficacy of Spodoptera litura multiple nucleopolyhedrovirus after serial passage through the homologous insect larval host.

An originally isolated baculovirus, Spodoptera litura multiple nucleopolyhedrovirus (SpltMNPV) was serially passed through the S. litura larvae for upto four generations to determine the mean number of occlusion bodies (OBs) harvested per larva and their efficacy in terms of infectivity, feeding cessation and speed of kill of host larvae. The results revealed that the mean number of OBs harvested per larva increased significantly with increase in the dose of SpltMNPV at each passage and the yield was significantly lower in original stock wild-type SpltMNPV (P0) as compared to serially passed SpltMNPV (P1, P2, P3 and P4). Laboratory bioassays indicate that median lethal doses (LD50), median times to feeding cessation (FT50) and median survival times (ST50) of P0, P1, P2, P3 and P4 were significantly different from each other. The OBs of each passage when tested for their cross-infectivity against Spodoptera exigua and Spilarctia obliqua revealed significant reduction in their mortality. These results indicate that serially passed SpltMNPV is more host specific and more effective biocontrol agent than the original stock wild-type virus and can be adopted for mass production as a viral pesticide for control of the S. litura.

Toxicity and residual control of Plutella xylostella L. (Lepidoptera: Plutellidae) with Bacillus thuringiensis Berliner and insecticides / Toxicidade e controle residual de Plutella xylostella L. (Lepidoptera: Plutellidae) com Bacillus thuringiensis Berliner e inseticidas

Plutella xylostella L. is the most important worldwide pest of cruciferous plants and indiscriminate use of insecticides has led to the resistance of the species to different groups. This research was conducted to compare the toxicity and persistence of two strains of Bacillus thuringiensis to P. xylostella larvae. Concentrations between 125 and 500g 100L-1 of water of the commercial products were evaluated and compared to the insect growth inhibitor diflubenzuron and to the neurotoxic pyrethroid deltamethrin. The efficacy of the insecticides was compared between treated plants kept indoor greenhouse and outdoor. Third instar larvae were more susceptible to B. thuringiensis than first instar ones. Agree and Dipel showed similar control rates of third instars until 10 days after treatment, but on the 15th day, Agree was significantly more efficient than Dipel. Both B. thuringiensis formulations showed a reduction in mortality after 10 days when the treated plants were exposed to natural weather conditions in comparison to the same treatments kept inside greenhouse. Dimilin (100g 100L-1 of water) and deltamethrin (30ml of commercial product 100L-1 of water) were not efficient to control third instar larvae of P. xylostella. This inefficiency cannot be attributed to a resistant population of P. xylostella since the larval population used in the experiments was not subjected to insecticide pressure, once the crop was organically cultivated all year round. The results showed that both formulations of B. thuringiensis are sound alternatives for the control of the diamondback moth in organically conducted cruciferous crops, considering the high residual control provided under subtropical weather conditions.

Larvas de Plutella xylostella L. são as principais pragas de crucíferas cultivadas e o uso excessivo e indiscriminado de inseticidas tem levado a resistência da espécie para diferentes grupos de inseticidas. Este trabalho foi conduzido para comparar a toxicidade de duas formulações de Bacillus thuringiensis para larvas de primeiro e terceiro ínstar de P. xylostella. Concentrações entre 125 e 500g 100L-1 de água do produto comercial foram avaliadas e comparadas com o inibidor do crescimento diflubenzuron e com o piretroide deltametrina. A eficiência dos inseticidas foi comparada em plantas tratadas e mantidas dentro e fora da casa de vegetação. Larvas de terceiro ínstar foram mais suscetíveis a B. thuringiensis do que larvas de primeiro ínstar. Agree e Dipel apresentaram taxas de controle semelhantes até 10 dias após a aplicação, porém após 15 dias, Agree foi significativamente mais eficiente do que Dipel. Ambas as formulações apresentaram uma redução na mortalidade larval quando as plantas foram expostas às condições climáticas em comparação aos mesmos tratamentos mantidos em casa de vegetação. Dimilin (100g 100L-1 de água) e deltametrina (30ml de produto comercial 100L-1 de água) não foram eficientes para o controle de lagartas de terceiro ínstar de P. xylostella. Tal ineficiência não pode ser atribuída a um possível efeito de resistência da população de P. xylostella a esses produtos, uma vez que a colônia da espécie utilizada nos experimentos não estava sujeita à pressão de seleção, por se tratar de uma população coletada em área conduzida organicamente durante todo o transcorrer do ano. Os resultados mostram que as duas formulações de B. thuringiensis são alternativas viáveis para o controle de P. xylostella em cultivo orgânico de crucíferas, tendo em vista o expressivo controle residual observado para as condições climáticas dos subtrópicos.

Seletividade de agrotóxicos utilizados na cultura do arroz irrigado ao fungo Metarhizium anisopliae, agente de controle microbiano de Tibraca limbativentris / Selectivity of chemical pesticides used in rice irrigated crop at fungus Metarhizium anisopliae, microbial control agent of Tibraca limbativentris

Para subsidiar a utilização de táticas de manejo integrado para o inseto-praga Tibraca limbativentris, avaliou-se a compatibilidade in vitro entre o isolado CG 891 de Metarhizium anisopliae e os agrotóxicos utilizados na cultura do arroz irrigado. Os parâmetros avaliados foram crescimento vegetativo, esporulação e germinação em pré e pós-contato do fungo, com duas doses de fipronil, tiametoxam, fenitrotiona, carbofurano, pirazossulfurom-etílico, bentazona, clomazona, glifosato e quincloraque; e uma dose de triciclazol e azoxistrobina. Reduções significativas no crescimento vegetativo e esporulação de M. anisopliae foram observadas para fenitrotiona, carbofurano e azoxistrobina. Observou-se redução na germinação em pré-contato para o agrotóxico azoxistrobina. O valor percentual da germinação alterou a classificação dos agrotóxicos com relação a sua seletividade sobre o entomopatógeno. No entanto, os resultados mostram que in vitro os agrotóxicos fenitrotiona, carbofurano, glifosato e azoxistrobina são prejudiciais ao isolado CG 891 de M. anisopliae.

Searching for integrated control strategies for the insect-pest Tibraca limbativentris, the in vitro compatibility between isolated CG 891 of Metarhizium anisopliae and several pesticides used in the culture of irrigated rice was evaluated. The followings parameters were studied: vegetative growth, sporulation and the germination viability in pre- and post-contact of the fungus for two concentrations of fipronil, thiametoxan, fenitrothion, carbofuran, pyrazosulfuron-ethyl, bentazon, clomazone, glyfosate and quinclorac and one concentration of tricyclazole and azoxystrobin. Significant reductions in the vegetative growth and sporulation of M. anisopliae were observed for fenitrothion, carbofuran and azoxystrobin. The germination in pre-contact was affected by azoxystrobin. The percentage of germination changed the classification of pesticides in relation to its selectivity on the fungus. However, the results show that in vitro, the pesticides fenitrothion, carbofuran, glyfosate and azoxystrobin are harmful to isolated CG 891 of M. anisopliae.

Analysis of toxicity on Bacillus sphaericus from amazonian soils to Anopheles darlingi and Culex quinquefasciatus larvae / Análise da toxicidade em Bacillus sphaericus de solos da Amazônia em larvas de Anopheles darlingi e Culex quinquefasciatus

Bioassays under laboratory conditions aiming to determine the larvicidal activity of Bacillus sphaericus were carried out on Anopheles darlingi and Culex quinquefasciatus. In order to estimate the toxicity through median lethal concentration (LC50) and the relative potency of the strains to B. sphaericus standard strain 2362, probit analysis was performed utilizing the POLO-PC program. The findings of LC50 pointed out high effectiveness on strains IB15 (0.040 ppm), IB19 and S1116 (0.048 ppm), IB16 (0.052 ppm) and S265 (0.057 ppm). Strain IB15 presented nearly 50 percent more potency than strain 2362 in bioassays conducted on A. darlingi. It was observed that IB16 and S1116 strains were the most powerful against C. quinquefasciatus, showing to be about 300-400 percent stronger than 2362 strain. The results show that laboratory conditioned evaluation can be an important way to select promising bacteria with entomopathogenic action on biolarvicides production for use on mosquitoes breeding sites.

Bioensaios sob condições de laboratório foram realizados em larvas de Anopheles darlingi e Culex quinquefasciatus, visando determinar a atividade larvicida de Bacillus sphaericus. Para estimar a toxicidade através da concentração letal mediana (CL50) e a potência das estirpes em relação à estirpe padrão 2362, foi realizada a análise de probit utilizando o programa POLO-PC. Os resultados da CL50 apontaram alta efetividade para as estirpes IB15 (0,040 ppm), IB19 e S1116 (0,048 ppm), IB16 (0,052 ppm) e S265 (0,057 ppm). A estirpe IB15 apresentou potência cerca de 50 por cento maior que a estirpe 2362 nos bioensaios realizados com A. darlingi. Foi observado que as estirpes IB16 e S1116 foram as mais tóxicas para controle de C. quinquefasciatus, mostrando-se cerca de 300-400 por cento mais potente. Os resultados mostram que a avaliação em laboratório é uma importante etapa para selecionar bactérias com ação entomopatogênica a serem usadas na para a produção de biolarvicidas para uso nos criadouros das larvas de mosquitos.