Rafael Egewarth

Ação de extratos de plantas na oviposição e na mortalidade da traça-das-crucíferas

The diamondback moth, Plutella xylostella (L.) (Lepidoptera, Yponomeutidae), is one of the most important insect pest species of the Brassicaceae family plants in Brazil and in the world. The use of insecticidal plants extracts in the control of this insect is a promising alternative. Therefore, this research goal is to evaluate, in laboratory, the plants extracts effect on the oviposition and mortality of P. xylostella. In order to analyze the effect on the oviposition, kale leaf pieces were treated, in cage, as following: aqueous extracts (10% p/v) of leaf of chinaberry (Melia azedarach), of branch of chinaberry, of tobacco powder (Nicotiana tabacum), besides DalNeem (commercial product, based on Azadirachta indica), at 10% v/v. Inside the cage, 50 adults of P. xylostella were put and, 48h later, the egg number per leaf was counted, in seven repetitions. A second assay was consisted of the exposition of three larvae to the same cited extracts, in glass tube with a kale leaf piece previously treated. Three glass tubes were used per treatment, with four repetitions. The number of death larvae was evaluated daily. The aqueous extracts of chinaberry leaf, chinaberry branch and tobacco powder, besides DalNeem, reduce the oviposition of P. xylostella and the use of tobacco powder extract, DalNeem and chinaberry branch extract result in efficient control of P. xylostella larvae after the second, fifth and sixth days after application, respectively.

Ocorrência de parasitóides e patógenos em adultos de Chrysomelidae (Coleoptera) em estufa plástica, em Santa Maria, RS

Greenhouses represent an alternative for horticultural crops when the climatic conditions are unfavorable. Cucumber (Cucumis sativus L.) is one of the most cultivated horticultural crops in these protected environments. Among its main insect pests are the chrysomelid beetles. The objective of the present research was to determine the natural enemies of chrysomelids in cucumber grown in protected environment. The cucumber was seeded on the first week of March, 2003, in plastic greenhouse located in the experimental area of the Federal University of Santa Maria, in Santa Maria, Rio Grande do Sul, Brazil. Chrysomelids were collected every two or three days/week during the whole cultivation period, totalizing 28 collection dates. In the first 22 samplings, 50 chrysomelids/date were collected and, in the others, 30/date. The species of chrysomelids identified were: Diabrotica speciosa (Germar), Cerotoma arcuata Olivier and Acalymma bivittula (Kirsch). Celatoria bosqi Blanchard (Diptera: Tachinidae) was the only parasitoid specie identified parasitizing most frequently D. speciosa. Beauveria bassiana (Bals.) Vuill. infected adults of D. speciosa and A. bivittula, and the first specie was more susceptible. This is the first record of the occurrence of C. bosqi and B. bassiana on chrysomelids in crops cultivated in protected environment.