L. G. Leite

Screening of entomopathogenic nematodes (Nemata: Rhabditida) and the efficiency of Heterorhabditis sp. against the sugarcane root spittlebug Mahanarva fimbriolata (Fabr.) (Hemiptera: Cercopidae)

Este estudo teve por objetivo avaliar a patogenicidade de seis nematoides contra ninfas da cigarrinha da raiz da cana-de-acucar Mahanarva fimbriolata (Fabr.), em condicoes de laboratorio, e a eficiencia do mais virulento no controle do inseto em condicoes de campo. No laboratorio, foram avaliados sete tratamentos representados por dois especimes do genero Heterorhabditis, tres de Steinernema, um especime de Steinernema glaseri (Steiner),e a testemunha. No campo foram realizados dois experimentos. No primeiro foram avaliados nove tratamentos: Heterorhabditis sp. (CB-n5) aplicado sobre a palhada nas doses de 3,3 x 109, 6,6 x 108, 3,3 x 108 e 6,6 x 107 juvenis infectivos (JI)/ha; os nematoides aplicados no solo (embaixo da palhada) nas mesmas quatro doses; e a testemunha. No segundo experimento foram testados quatro tratamentos: Heterorhabditis sp. (3,3 x 108 JI/ha); Metarhizium anisopliae (2,6 x 1012 conidios viaveis/ha); tiametoxam (Actara 200 WG) (1 kg/ha); e a testemunha. Em laboratorio, Heterorhabditis sp. (CB-n5), Steinernema sp. (CB-n6) e Heterorhabditis sp. (CCA) foram os mais patogenicos, causando mortalidades de 100%, 98% e 96%, respectivamente. No primeiro experimento de campo, o nematoide Heterorhabditis sp. proporcionou ate 70% de controle da cigarrinha, nao havendo diferenca significativa entre as doses e quanto a aplicacao sobre a palhada ou sobre o solo. No segundo experimento, o inseticida proporcionou 67% de controle, nao diferenciando significativamente do nematoide (56%) e do fungo (44%), em avaliacao realizada sete dias apos aplicacao.

Steinernema brazilense n. sp. (Rhabditida: Steinernematidae), a new entomopathogenic nematode from Mato Grosso, Brazil

A new entomopathogenic nematode, Steinernema brazilense n. sp., was isolated from a single soil sample collected from a natural forest in Mato Grosso do Sul state, Brazil. S. brazilense n. sp. is characterized morphologically by features of infective juveniles (IJ), males and females. For the IJ, body length averaging 1157 (1023-1284)microm, distance from anterior end to excretory pore 95 (87-102)microm, from anterior end to end of esophagus 148 (139-153)microm, tail length 85 (80-104)microm, D% and E% values 63 (58-70) and 106 (95-118.0), respectively. Lateral field pattern variable; the formula for the arrangement of ridges from head to tail is: 2, 4, 6, 8, 6, 2. For the male, the diagnostic characters include spicule averaging 83 (75-89)microm; D% about 65; the ratio SW% about 192. The length of spicule head is greater than width. Lateral field with one narrow ridge. First generation females are characterized by the presence of a ventral postanal swelling. S. brazilense n. sp. is morphologically close to Steinernema diaprepesi. It can be differentiated from S.diaprepesi by its longer IJ body length (1157 vs 1002microm), longer distance from anterior end to excretory pore (110 vs 75microm), a longer tail length (103 vs 83microm); males of the new species with longer spicule (83 vs 79microm). The new species can be distinguished further from other members of Steinernema glaseri group by characteristics of rDNA of ITS and D2D3 regions.

Application technology for the entomopathogenic nematodes Heterorhabditis indica and Steinernema sp. (Rhabditida: Heterorhabditidae and Steinernematidae) to control Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) in corn

The effects of different application technologies were evaluated on the concentration, viability, and efficiency of infective juveniles of the nematodes Heterorhabditis indica Poinar, Karunakar & David and Steinernema sp. (IBCB-n6) to control Spodoptera frugiperda Smith on corn plants. Two hundred and eighty infective juveniles of Steinernema sp. were required to kill 100% third-instar fall armyworms in petri dishes, as compared to 400 infective juveniles of the H. indica nematode to obtain 75% fall armyworm control. It is possible to spray entomopathogenic nematodes without significant loss in their concentration and viability, with equipment that produces electrical charges to the spraying mix, and with those using hydraulic and rotary nozzle tips. The concentrations of infective juveniles of H. indica and Steinernema sp. nematodes were reduced by 28% and 53%, respectively, when hydraulic spraying nozzles that require 100-mesh filtrating elements were used. Tensoactive agents of the organosilicone and ethoxylate groups did not affect the viability of infective juveniles of Steinernema sp. juveniles. Spraying corn plants (V6 growth stage) with up to 288 million infective juveniles of Steinernema sp. per hectare, diluted in the spraying mix up to 800 L ha-1, with 0.01% ethoxylate tensoactive agent, or at the same volume followed by artificial rain (6 mm water depth) was not sufficient to control S. frugiperda in a controlled environment.

Primeiro Registro de Zoophthora radicans (Entomophthorales: Entomophthoraceae) em Adultos da Ampola-da-Erva-Mate, Gyropsylla spegazziniana Lizer & Trelles (Hemiptera: Psyllidae), no Brasil

We report the first occurrence of Zoophthora radicans infecting adults of Gyropsylla spegazziniana Lizer & Trelles in a commercial Paraguay tea plantation (Ilex paraguariensis), in Cascavel, PR, Brazil. The fungus prevalence was high (90% of mortality), considered a natural epizooty.

Virulência de nematóides entomopatogênicos (Nematoda: Rhabditida) a Sphenophorus levis (Coleoptera: Curculionidae)

The sugarcane billbug, Sphenophorus levis (Coleoptera: Curculionidae) is an important underground pest of the sugarcane crop in Sao Paulo state, causing losses up to 30 tons of cane/ha/year. This study aimed to evaluate the virulence of 17 strains of entomopathogenic nematodes on the genus Steinernema and Heterorhabditis against adults of S. levis, and the effect of the four most virulent ones in three dosage each one. The research was done in laboratory conditions, performing four tests related to the virulence study and one related to the dosage study. S. brazilense IBCB n6, Heterorhabditis sp. IBCB n10, Heter- orhabditis sp. IBCB n24 and Heterorhabditis sp. IBCB n44 were the most virulent ones, differing significantly from the respec - tive control with 45%, 40%, 20% and 31% mortality of insects using the concentration of 240 infective juveniles (IJ)/insect. For the dosage test, the strains IBCB n10, IBCB n24 and IBCB n44 of Heterorhabditis noteworthy concerning the virulence for adults of the sugarcane billbug, differing significantly from the control at the higher dosage (1200 IJ/insect) with insect mortality levels of 60%, 65,7% e 74,3%, respectively.

Entomopathogenic nematodes in agricultural areas in Brazil

Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) can control pests due to the mutualistic association with bacteria that kill the host by septicemia and make the environment favorable for EPNs development and reproduction. The diversity of EPNs in Brazilian soils requires further study. The identification of EPNs, adapted to environmental and climatic conditions of cultivated areas is important for sustainable pest suppression in integrated management programs in agricultural areas of Brazil. The objective was to identify EPNs isolated from agricultural soils with annual, fruit and forest crops in Brazil. Soil samples were collected and stored in 250 ml glass vials. The nematodes were isolated from these samples with live bait traps ([Galleria mellonella L. (Lepidoptera: Pyralidae) larvae]. Infective juveniles were collected with White traps and identified by DNA barcoding procedures by sequencing the D2/D3 expansion of the 28S rDNA region by PCR. EPNs identified in agricultural areas in Brazil were Heterorhabditis amazonensis, Metarhabditis rainai, Oscheios tipulae and Steinernema rarum. These species should be considered pest biocontrol agents in Brazilian agricultural areas.

Trans-cinnamic acid and Xenorhabdus szentirmaii metabolites synergize the potency of some commercial fungicides

Development of novel approaches for the control of fungal phytopathogens is desirable. In this study we hypothesized that the combination of commercial fungicides with certain enhancing agents could result in synergistic levels of control. Prior research has indicated that trans-cinnamic-acid (TCA), a metabolite of the bacteria Photorhabdus luminescens and metabolites of Xenorhabdus szentirmaii are particularly toxic to various phytpathogenic fungi when compared to metabolites of other Xenorhabdus or Photorhabdus spp. In this study we explored the efficacy of commercial fungicide interactions when combined with either TCA or X. szentirmaii. Fungicides (active ingredient) included Abound® (Azoxystrobin), Serenade® (Bacillus subtilis), Elast® (dodine), Regalia® (extract of Reynoutria sachalinensis), Prophyt® (potassium phosphite) and PropiMax® (propiconazole). In laboratory experiments, singly-applied or combined agents were assessed for fungicidal activity against four plant-pathogenic fungi, Monilinia fructicola, Rhizoctonia solani, Colletotrichum gloeosporioides and Fusarium oxysporum. Fungicidal activity was measured by the phytopathogens growth on potato dextrose agar with and without fungicide. The interactions between fungicidal agents were determined as antagonistic, additive or synergistic. For suppression of M. fructicola, synergy was observed between TCA when combined with certain concentrations of Elast®, PropiMax®, Regalia®, Prophyte® or Serenade®, and for combinations of X. szentirmaii with Abound®. For suppression of R. solani, synergy was observed between TCA combined with Regalia® or Serenade®. Additionally, when TCA was combined with X. szentirmaii synergistic levels of suppression to M. fructicola were observed. Other combinations of TCA or X. szentirmaii with the fungicides or using alternate concentrations were either additive or occasionally antagonistic in nature. Our results indicate that TCA and X. szentirmaii can each act as strong synergists to enhance fungicidal efficacy. These results may be used to reduce negative environmental impacts of pesticide use while improving control of plant diseases. Additional research is needed to explore the diversity of the synergistic effects and confirm our observations under field conditions.

Eficiência de nematoides entomopatogênicos e inseticidas químicos contra Sphenophorus levis e Leucothyreus sp. em cana-de-açúcar

The sugarcane billbug, Sphenophorus levis (Coleoptera: Dryophthoridae), is an important pest of sugarcane crops in the Sao Paulo State, Brazil. Their larvae damage plants rhizome, causing losses of up to 30 t ha -1 year -1 of sugarcane. In order to evaluate the effectiveness of entomopathogenic nematodes and chemical insecticides against the sugarcane billbug and the scarab beetle Leucothyreus sp., three field trials were carried out in Brazil. For the first one, 10 treatments were considered: 1) thiametoxan (Actara 250WG) 500 g ha -1 of commercial product (c.p.); 2) thiametoxan 1.0 kg ha -1 c.p.; 3) thiametoxan 1.5 kg ha -1 c.p.; 4) Steinernema brazilense 10 8 infective juveniles (IJ) ha -1 + thiametoxan 250 g ha -1 c.p.; 5) S. brazilense (10 8 IJ ha -1 ) + thiametoxan 500 g ha -1 c.p.; 6) Heterorhabditis indica (10 8 IJ ha -1 ) + thiametoxan 250 g ha -1 c.p; 7) H. indica (10 8 IJ ha -1 ) + thiametoxan 500 g ha -1 c.p.; 8) S. brazilense (10 8 IJ ha -1 ); 9) H. indica (10 8 IJ ha -1 ); and 10) Control. The second one consisted of five treatments: 1) thiametoxan (Actara 250WG) 800 g ha -1 c.p.; 2) fipronil (Regente 800WG) 250 g ha -1 c.p.; 3) S. brazilense (10 8 IJ ha -1 ); 4) S. brazilense (10 8 IJ ha -1 ) + thiametoxan 200 g ha -1 c.p.; and 5) Control. In the third one, all treatments already mentioned for the second trial plus the mixture S. brazilense (10 8 IJ ha -1 ) + fipronil (Regente 800WG) 62.5 g ha -1 c.p. were considered. All treatments with the insecticides and nematodes provided higher sugarcane yield, when compared to their respective controls, which were most damaged by S. levis , but without statistical significance. S. brazilense was more efficient on controlling this pest, if compared to H. indica , but without statistical significance. S. brazilense provided a 50% control of Leucothyreus sp. larvae, meanwhile the best treatments against this scarab were the mixtures of this nematode with fipronil (78%) and thiametoxan (83%).

Mortality of Conotrachelus humeropictus in response to combined application of the nematode Steinernema brazilense and the fungus Beauveria bassiana

Arq. Inst. Biol., v.85, 1-9, e0092016, 2018 RESUMO: A broca-do-cupuaçu, Conotrachelus humeropictus, é uma das principais pragas da cultura, podendo ocasionar perdas de 50% na produção. O presente trabalho envolveu uma seleção prévia de isolados de Beauveria bassiana em larvas de Conotrachelus psidii, utilizado como inseto teste por ser próximo taxonomicamente à C. humeropictus. Com o objetivo de avaliar causa-efeitos da interação na aplicação combinada, foi estudada a capacidade do nematoide carrear conídios de B. bassiana e Metarhizium anisopliae pelas camadas de solo. O trabalho também objetivou avaliar o controle biológico da broca-do-cupuaçu, através do uso do fungo B. bassiana 10 kg/ha, e do nematoide entomopatogênico Steinernema brazilense 1, 3, 9 e 27 JI/cm2, aplicados em tratamentos isolados e em combinação. Na seleção de isolados de B. bassiana para C. psidii, os isolados IBCB 276 e IBCB 165 foram os mais promissores, causando, respectivamente, 86 e 84% de mortalidade confirmada. O isolado IBCB 276 foi aplicado em campo para controlar C. humeropictus. No estudo de carreamento de conídios, o nematoide S. brazilense foi capaz de carrear conídios de B. bassiana para a camada de 7 a 10 cm de profundidade no solo. A mesma ação não foi observada com M. anisopliae, encontrado somente na camada superficial do solo. Nos ensaios de campo contra C. humeropictus, B. bassiana promoveu 15,6% de mortalidade. O nematoide promoveu 60,0% de mortalidade na maior concentração utilizada e, na combinação dessa concentração do NEP com B. bassiana (10 kg/ha), a mortalidade atingiu 65,6%, observando-se interação aditiva entre os dois entomopatógenos.