ABSTRACT
ABSTRACT In two independent bioassays, size and flight ability of parasitoids reared on eggs of Corcyra cephalonica for 19 generations and parasitoids reared on a natural host (Spodoptera frugiperda eggs) for 250 generations were compared as fast quality control procedures for insect rearing. The size of parasitoids was examined by morphometric analysis using a stereoscope. Length and width of the wings, right hind tibia, and the body of 20 individuals (males and females) were measured. In the analysis of flight ability, parasitoids were divided into three groups: individuals able to fly ("flyers"), individuals that did not fly but had no visible deformation ("walkers"), and individuals with visible deformation ("deformed"). We observed that parasitoids were larger when reared on the natural host than on the factitious host for all evaluated morphological characters. However, there was no significant difference between the treatments regarding the number of "flyers", "walkers" or "deformed" parasitoids. This indicates that even though the rearing of T. remus on a factitious host affects parasitoid size, it does not necessarily affect its flight ability and therefore suggests that C. cephalonica is suitable as a factitious host for mass rearing of T. remus. Other biological parameters still need to be evaluated, such as host finding ability, parasitism capacity, and parasitoid field efficacy in order to provide a more complete picture of the effects caused by a host change. However, because fast laboratory tests are needed in rearing facilities, the one used in this study might be useful to rapidly assess parasitoid quality.
ABSTRACT
Objetivou-se avaliar a interação tritrófica no complexo hospedeiro-vegetal (brássicas) x praga/hospedeiro-natural Plutella xylostella Linnaeus x inseto-entomófago (parasitóides - Trichogrmma pretiosum Riley e T. exiguum Pinto & Platner), associada a alguns produtos químicos e vegetais com efeito inseticida, utilizando-se os cultivares de repolho verde - Chato de quintal e híbrido Midori; roxo - Roxo precoce e Híbrido roxo - TPC00682; e couve manteiga - Geórgia e hibrido Geórgia HS20, pulverizadas com os inseticidas: lufenuron (2,52 ml/100L) e deltametrina (32 ml/100L), os produtos vegetais óleo de nim a 0,16 por cento e extrato pirolenhoso a 3,0 por cento, controle (água). Foi avaliada a interação das cultivares com os compostos por meio da exposição de lagartas recém-eclodidas aos produtos, avaliando-se os insetos nas fases de desenvolvimento até a emergência dos adultos. Para avaliar o efeito desses compostos sobre os parasitóides, foram empregados ovos de uma geração F2 de P. xylostella oriunda de lagartas alimentadas com folhas de brássicas, pulverizadas com esses produtos. A associação de produtos químicos ou vegetais, com efeito inseticida, com as cultivares de brássicas permitiu o manejo mais eficaz, especialmente na interação extrato pirolenhoso x a cultivar de repolho Chato de quintal. Observa-se que a interação entre as cultivares e os produtos pode ser prejudicial à atuação do parasitóide Trichogramma, sendo necessária uma avaliação criteriosa para minimizar o efeito sobre inimigos naturais.
The aim of this work was to evaluate the tritrofic interaction in brassica complex: host-vegetable (brassica) vs. pest/natural-host (Plutella xylostella) vs. entomophagous-insect (parasitoid - Trichogramma pretiosum and Trichogramma exiguum), combined with chemical and vegetable products with insecticide action. The cultivar used were: green cabbage - Chato de quintal and Midori hybrid; purple cabbage - Roxo Precoce and purple hybrid - TPC00682; kale - Georgia and Georgia hybrid HS20. They were sprayed using the insecticides - lufenuron (2,52 ml/100L) and deltamethrin (32 ml/100L); the vegetal products - neen oil (0,16 percent) and pyroligneous extract (3,0 percent); and water (check). The cultivars interaction was evaluated with the products, by larvae exposition to the treatments, being analyzed the different phases of development through adults emergence. To evaluate the effect of these products on the parasitoids, P. xylostella, eggs from F2 generation were used. Eggs of this pest were collected from adults fed with brassica leaves that were sprayed with the mentioned products. The insecticides association and vegetable products combined with brassica cultivars became more effective to manage the pest control, especially in the pyroligneous extract x Chato de Quintal interaction. The interaction between the cultivars and products may be harmful to Trichogramma performance being necessary a discerning evaluation to minimize the effect on natural enemies.