Insecticide selectivity to two species of Trichogramma in three different hosts, as determined by IOBC/WPRS methodology.

BACKGROUND: The use of Trichogramma species is a potential key strategy in integrated pest management. However, its effectiveness depends on the use of chemicals that do not interfere with parasitism and parasite population growth. Here, a study was made of the effects of synthetic insecticides on Trichogramma pretiosum and Trichogramma exiguum in different hosts (Ephestia kuehniella, Plutella xylostella and Spodoptera frugiperda) and the influence of International Organisation for Biological Control (IOBC/WPRS) methodology in selectivity studies using different Trichogramma species. The insecticides used were commercial formulations (triflumuron at a concentration of 0.2 mL L(-1) water, etofenprox at a concentration of 0.47 mL L(-1) water and endosulfan at a concentration of 7.5 mL L(-1) water); the control treatment consisted of distilled water. Eggs attached to cardboard cards were offered to parasitoids inside glass cages. Parasitised eggs, parasitism and adult emergence rates and parasitism reduction were evaluated. RESULTS: Endosulfan and etofenprox, classified as class-4 toxic products, were extremely toxic to the parasitoids. Triflumuron, classified as a non-toxic product, was selective to the parasitoids in eggs of all hosts. CONCLUSIONS: The methodology recommended by IOBC/WPRS influenced results regarding the use of different species of parasitoids, and the use of a single parasitoid species in their experiment is questionable.

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 nematóides contra ninfas da cigarrinha da raiz da cana-de-açúcar Mahanarva fimbriolata (Fabr.), em condições de laboratório, e a eficiência do mais virulento no controle do inseto em condições de campo. No laboratório, foram avaliados sete tratamentos representados por dois espécimes do gênero Heterorhabditis, três de Steinernema, um espécime 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 nematóides 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 conídios viáveis/ha); tiametoxam (Actara 200 WG) (1 kg/ha); e a testemunha. Em laboratório, Heterorhabditis sp. (CB-n5), Steinernema sp. (CB-n6) e Heterorhabditis sp. (CCA) foram os mais patogênicos, causando mortalidades de 100%, 98% e 96%, respectivamente. No primeiro experimento de campo, o nematóide Heterorhabditis sp. proporcionou até 70% de controle da cigarrinha, não havendo diferença significativa entre as doses e quanto à aplicação sobre a palhada ou sobre o solo. No segundo experimento, o inseticida proporcionou 67% de controle, não diferenciando significativamente do nematóide (56%) e do fungo (44%), em avaliação realizada sete dias após aplicação.

The pathogenicity of six entomopathogenic nematodes was assessed against nymphs of the sugarcane root spittlebug Mahanarva fimbriolata (Fabr.), in the laboratory. The efficiency of the most virulent agent was tested in the field. Seven laboratory treatments were designed with two specimens of the genus Heterorhabditis, three of Steinernema, one specimen of Steinernema glaseri (Steiner), and acontrol group. In the field, two experiments were conducted. The first experiment involved nine treatments:the control, four treatments with Heterorhabditis sp. (CB-n5) applied to the straw mulch at doses 6.6 x 107, 3.3 x 108, 6.6 x 108 and 3.3 x 109 IJs/ha, and four treatments with the nematodes applied to the soil and beneath the straw mulch layer, at the same doses. The second experiment contained four treatments: the control and applications of Heterorhabditis sp. (3.3 x 108 IJs/ha), the fungus Metarhizium anisopliae (2.6 x 1012 viable conidia/ha), and the chemical insecticide thiamethoxan (Actara 200 WG) (1 kg/ha). Heterorhabditis sp. (CB-n5), Steinernema sp. (CB-n6), and Heterorhabditis sp. (CCA) were the threemost virulent nematodes (100%, 98%, and 96% mortality, respectively). In the first field experiment, Heterorhabditis sp. controlled 74% of the insects, with no significant difference among doses or between application to the soil or mulch. In the second experiment, the chemical insecticide provided 67% control, not differing statistically from nematode (56%) or fungus (44%) control, seven days post-treatment.