Predatory capacity and intraguild interaction between aphidophagous predators in the control of rose bush aphids

ABSTRACT Chrysoperla externa (Hagen) and Hippodamia convergens (Guérin-Meneville) are voracious generalist predators, and important aphid control agents. In an environment containing a complex of species, the occurrence of intraguild interactions can interfere in the predator behavior and consumption. The aim of this work was to know the number of nymphs of Rhodobium porosum (Sanderson) and Macrosiphum rosae (Linnaeus) consumed by larvae of C. externa and H. convergens, and the interaction between these predators when confined together. First, second and third instar nymphs of R. porosum and M. rosae were provided in Petri dishes containing rose leaflets and second instar larvae of the predators. Intraguild interaction was studied in Petri dishes containing first instar nymphs of both aphid species and a second instar larva of C. externa plus one of H. convergens. A third treatment consisted of dishes containing a second instar larva of both predators maintained in the absence of prey. The evaluations took place throughout the entire instar of the predators. C. externa consumed a greater number of R. porosum nymphs and H. convergens a greater number of M. rosae nymphs. For both species of prey, the highest consumption was verified on the last day of evaluation. There was a positive interaction when the predator's larvae were confined in the presence of aphid nymphs, with no mortality observed for any of them. In the absence of prey, there was 70% mortality of H. convergens larvae due to intraguild predation.

Compatibility between the predators Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) and Chrysoperla externa (Neuroptera: Chrysopidae) in the control of Planococcus citri (Hemiptera: Pseudococcidae) associated with rose crop

ABSTRACT Rose crops are attacked by many pests, including mealybugs. Although Planoccocus citri is not registered as a main pest of roses in Brazil, it is an increasing problem on roses inside greenhouses. Chrysoperla externa and Cryptolaemus montrouzieri are options against P. citri and other pests on roses, however using two predators in biological control programs may face problems like intraguild predation. This work aimed to assess the consumption of 1st instar nymphs and adult females of P. citri by adults of C. montrouzieri and 3rd instar larvae of C. externa, as well as the interaction between these predators when confined together. The following treatments were performed with ten replications in a completely randomized design: 1 - C. externa + 200 nymphs of P. citri; 2 - C. externa + 10 adults of P. citri; 3 - C. montrouzieri + 500 nymphs of P. citri; 4 - C. montrouzieri + 15 adults of P. citri. Each replication was set on rose leaflets inside a Petri dish (9cm Ø). Intraguild interaction was assessed by releasing both predators inside dishes containing 700 nymphs of P. citri. Before the releases, predators stayed 24 hours without food. We evaluated the prey consumption and intraguild predation for three hours. C. externa consumed significantly less (85,4±2,99) nymphs than did C. montrouzieri (387,0±3,02). There was no difference in adult mealybugs consumed, with an average of 1,85±0,19. No intraguild predation was observed, and an increase of 11,8% in consumption was observed when predators were released together compared to the scenario of no competition.

Toxicity of insecticides used in melon crops to Opius scabriventris (Hymenoptera: braconidae) / Toxicidade de inseticidas utilizados na cultura do meloeiro para Opius scabriventris (Hymenoptera: braconidae)

Melon cultivation is an important agricultural activity in the Northeastern Region of Brazil. During its commercial cultivation, the melon crop is attacked by pests, mainly leafminers Liriomyza sativae Blanchard and Liriomyza trifolii (Burgess) (Diptera: Agromyzidae). To keep leafminer populations below an economic issue level, it is essential to adopt control measures such as spraying insecticides and biological control. However, there is little information on the toxicity of insecticides used in the melon crop against leafminers' natural enemies. Therefore, the aim of this study was to evaluate the toxicity of insecticides used in melon crops against the parasitoid Opius scabriventris, a natural enemy of leafminers from the genus Liriomyza (Diptera: Agromyzidae). The experiment was conducted under controlled laboratory conditions, in a completely randomized design, using two bioassays: I - Contact of parasitoids with a recently sprayed surface; and II - Contact of parasitoids with a surface containing dried residues of the insecticides that were significantly toxic in the bioassay I. In both bioassays, the toxicity of the insecticides was evaluated by observing parasitoid mortality. In bioassay I, from eight insecticides tested, only Cartap hydrochloride and Abamectin + mineral oil were considered harmful (Class 4) and Deltamethrin showed to be slightly harmful (class 2). Only Abamectin + mineral oil was harmful (Class 4) to the parasitoid O. scabriventris in the bioassay II. These are the first results regarding the effect of insecticides used in the management of melon pests on the parasitoid of the leafminer fly O. scabriventris.

O cultivo do meloeiro é uma importante atividade agrícola na região Nordeste do Brasil. Durante seu cultivo comercial, o meloeiro é acometido por pragas, destacando-se as moscas minadoras Liriomyza sativae Blanchard e Liriomyza trifolii (Burgess) (Diptera: Agromyzidae). Para manter a população da mosca minadora abaixo do nível de dano econômico, é essencial a adoção de medidas de controle, como a aplicação de inseticidas e o controle biológico. No entanto, são escassas informações sobre a toxicidade dos inseticidas utilizados na cultura do meloeiro sobre os inimigos naturais da mosca minadora. Portanto, o objetivo deste trabalho foi avaliar a toxicidade de inseticidas utilizados na cultura do meloeiro sobre o parasitoide Opius scabriventris, inimigo natural de moscas minadoras do gênero Liriomyza (Diptera: Agromyzidae). O experimento foi conduzido em condições de laboratório, em delineamento inteiramente casualizado, utilizando dois bioensaios: I ­ Contato dos parasitoides com superfície recém pulverizada e II ­ Contato dos parasitoides com superfície contendo resíduos secos dos inseticidas que foram tóxicos no bioensaio I. Nos dois bioensaios, a toxicidade dos inseticidas foi avaliada por meio da observação da mortalidade dos parasitoides. No bioensaio I, dentre os oito inseticidas avaliados, somente Cloridrato de Cartap e Abamectina + óleo mineral foram considerados nocivos (classe 4), e Deltametrina mostrou-se levemente nocivo (classe 2). No bioensaio II, apenas Abamectina + óleo mineral foi prejudicial (classe 4) ao parasitoide O. scabriventris. Estes são os primeiros resultados relacionados ao efeito de inseticidas utilizados no manejo de pragas do meloeiro sobre o parasitoide da mosca minadora O. scabriventris.

Occurrence of Lysiphlebus testaceipes parasitizing Aphis gossypii in watermelon in the State of Rio Grande do Norte, Brazil / Ocorrência de Lysiphlebus testaceipes parasitando Aphis gossypii em melancia, no Estado do Rio Grande do Norte, Brasil

This is the first report of the parasitoid Lysiphlebus testaceipes (Cresson) as a biological control agent of the aphid Aphis gossypii Glover in watermelon crop in Vale do Açu, RN. It was observed that near the harvest, almost all collected aphids were mummified, and after analyzing the emerged parasitoids, the parasitoid L. testaceipes was identified. Therefore, in the future, this species may be included in A. gossypii integrated management programs.

Este é o primeiro relato do parasitoide Lysiphlebus testaceipes (Cresson) como agente de controle biológico do pulgão Aphis gossypii Glover na cultura da melancia, na região do Vale do Açu, Rio Grande do Norte (RN). Observou-se que próximo da colheita quase todos os pulgões coletados encontravam-se mumificados e, na análise dos parasitoides emergidos, constatou-se o parasitismo por L. testaceipes. Essa espécie, portanto, poderá ser incluída em um programa de manejo integrado de A. gossypii futuramente.