Félix Humberto França

Potencial biótico da mosca-branca Bemisia argentifolii a diferentes plantas hospedeiras

The whitefly Bemisia argentifolii Bellows & Perring, 1994 has been causing damage in several economically important crops in Brazil. The purpose of this research was to determine the biotic potential of the insect in zucchini, dry bean, cassava, corn, poinsettia, cabbage and tomato. The experiments were carried out at the Experimental Station of Embrapa Hortalicas, located in Brasilia, in BOD chamber (28°C ± 2°C) and greenhouse (25°C ± 8°C), with a whitefly population continuously reared on poinsettia plants since 1995. Cabbage and dry bean were the host plants with shorter pre-imaginal periods, 20.5 and 21.9 days respectively. The highest mortality in this periods was observed in cassava (97.9%) and corn (94.2%). Sexual ratio (female:male) favored females. The insect presented a small range for the intrinsic rate of increase (rm), 0.18 for dry bean and 0.13 for cabbage, reflecting the similar adaptability to both hosts. Lower intrinsic rates of increase were observed in corn and cassava, with high female mortality (> 90%), suggesting that these two species were less suitable hosts for this whitefly population.

Forecasting insecticide susceptibility in Diamondback Moth populations from different areas of Brazil

The Diamondback Moth (DBM) is an important brassica pest and is controlled by several types of insecticides. On some occasions, the fields are sprayed two-four times per week without success. Sometimes this occurs because ineffective insecticides are used. Works showed that laboratory tests using the recommended field rate of insecticides can detect the ineffective ones. Here, we collected DBM larvae and pupae from the States of Ceara (Tiangua), Minas Gerais (Barroso), Bahia (Mucuge), Mato Grosso (Sinop) and the Federal District (Brazlândia and Embrapa Hortalicas). We reared the populations in the laboratory and larvae of the first laboratory generation were treated with the recommended field rate of abamectin, acephate, B. thuringiensis, cartap, chlorfluazuron, deltamethrin, and spinosad. We previously determined that an effective insecticide should cause more than 90% larval mortality. Insecticide effectiveness was different from field to field. Spinosad killed 100% of larvae; acephate, B. thuringiensis and cartap killed less than 90% of the larvae in Tiangua; abamectin and chlorfluazuron did not control the insect in Brazlândia and Mucuge respectively. Deltamethrin was inneffective in all areas tested. Diamondback Moth populations were resistant to one or more active ingredients and programmes to manage insecticide resistance must be implemented in Brazil.

Efficiency on cabbage production and impact of insecticide mixtures on parasitoids of diamondback moth

A producao comercial de repolho foi obtida de parcelas que re ceberam combinacoes de doses de deltametrina 25 CE e abamectin 18 CE as quais proporcionaram controle dos danos causados pela traca-das-cruciferas, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae). Os resultados foram comparaveis aqueles obtidos pela pulverizacao de formulacao concentrada emulsionada de Bacillus thuringiensis. A utilizacao isolada de deltametrina 25 CE e abamectin 18 CE (0,5 1/ha) resultou em baixos niveis de producao comercial, respectivamente 7 e 8%. As misturas deltametrina e abamectin produziram mais de 42%. A elevada densidade populacional da praga fez com que nao fosse obtida producao co mercial na area nao tratada. Os inseticidas ou suas combinacoes tes tadas nao provocaram qualquer impacto, estatisticamente mensuravel, sobre populacoes das especies dos parasitoides Diadegma spp. (Hymenoptera: Ichneumonidae) e Apanteles spp. (Hymenoptera: Braconidae).

Eficiência técnica e econômica do controle biológico da traça-do-tomateiro em ambiente protegido

Technical and economic efficiency of biological control of the South American tomato pinworm in protected environment The economic and technical efficiency of controlling the South American tomato pinworm (Tuta absoluta) by the parasitoid Trichogramma pretiosum was evaluated in protected environment, in Luziania, Goias State, Brazil, during the summer of 1999-2000. The research was conducted in two greenhouses, each one submitted to the following pest control regimes: (1) habitual farmer practices: pesticides sprayed based on presence/absence of the pest and rotation of products (deltamethrin; abamectin; Bacillus thuringiensis (at the recommended dose); and soap at 0,5% concentration). (2) inundative release of T. pretiosum associated with weekly sprays of Bacillus thuringiensis as an emulsifiable concentrate formulation (at the recommended dose). Insecticide sprays and parasitoid mass release were initiated just after the first adults were observed. Mass release consisted of weekly display of two cards (20x30 cm) of parasitized eggs by T. pretiosum that were gradually increased until the reached six cards each week, by the time of tomato harvest. Once a week, 50 leaflets were collected in each greenhouse. The number of eggs was determined in the laboratory and kept inside chambers to determine the number of larvae or the percentage of parasitism. Tomato production and damage to the fruits were determined weekly from 50 tomato plants randomly chosen in each treatment. The productivity of the treatment using biological control was 6,160 polystyrene trays/600g and 6,833 trays/600g when chemical control was used. The variable costs of production were R

Efeito de Bacillus thuringiensis Berliner e inseticidas químicos sobre a traça-das-crucíferas, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) e seus parasitóides

3,9 thousands and R

Identification and rearing of four thrips species vectors of Tospovirus in the Federal District, Brazil

4,7 thousands for the biological control and chemical control, respectively. The loss limit in each cropping season for both production systems, estimated by the technical-economic efficiency, was higher for the biological control (61,7%). The coefficient of economic efficiency was significant (2.62) and the internal rate of return (24.9%) confirmed that the system of production that used the biological control by T. pretiosum was economically efficient.

Avaliação de acessos de batata-doce para resistência à broca-da-raiz, crisomelídeos e elaterídeos

Three biopesticides based on Bacillus thuringiensis (Dipel, Florbac and Biobit), and two chemical insecticides (deltamethrin and abamectin) were evaluated in field trials against Plutella xylostella (L.) and its parasitoids in Brazil. Plots treated with Florbac, Biobit and abamectin produced 100% marketable cabbages. Dipel and deltamethrin also resulted in acceptable control (85% yield). In the control plot, 97.2% of the yield was lost. The rate of parasitism on the plots treated with biopesticides was between 35.7 and 60.5%, in the control was 42.9% and in those treated with chemical insecticides was 9.0 and 25.8 %. These results indicate that the biopesticides had no adverse effect on the parasitoids, in contrast to the classic chemical products.

Manejo integrado da mosca-branca Bemisia argentifolii.

The disease caused by the viruses belonging to the genus Tospovirus is a serious problem in horticultural and ornamental crops in Brazil. In the field, this virus group is transmitted by the insect vector, thrips. Little is known about the thrips species occurring in Brazil, and which species are important for the dissemination of these diseases. For the study of epidemiology of this virus group, different thrips populations, which may have the capacity to be vectors of tospoviruses, were collected in the Federal District. Four species were identified: Frankliniella occidentalis Pergande, F. schultzei Trybom, Thrips palmi Karny and T. tabaci Lindeman. This is the first report of the occurrence of F. occidentalis and T. palmi in the Federal District. A methodology for the rearing of these four thrips is described in this report.

Uso de inseticidas para o controle da traça-do-tomateiro e traça-das-crucíferas: um estudo de caso

Three hundred sixty six sweet potato plant accessions of the Sweet potato Germplasm Bank of Embrapa Hortalicas (Brazil) were evaluated in the field for resistance to the Wireworm-Diabrotica-Systena (WDS) pest complex: Diabrotica spp., Conoderus sp., Epitrix sp., and West Indian sweet potato weevil, Euscepes postfaciatus. About 21% of all plant accessions showed high resistance to chrysomelids and elaterids. Seven clones, among them CNPH 005, CNPH 026 and CNPH 258 were more resistant than the standard resistant commercial cultivar Brazlândia Roxa. These sweet potato accessions and CNPH 088, CNPH 295, CNPH 314 and CNPH 318, were the most promising sources of resistance against the West Indian sweet potato weevil because they had 7% or less, of their roots damaged by Euscepes postfasciatus, compared to commercial cultivars Brazlândia Branca (23.3%) and Princesa (53.3%). The application of these results in an integrated control of sweet potato pests approach is discussed.