Repelência de extratos vegetais de plantas daninhas sobre adultos de Sitophilus spp. em sementes de arroz

Abstract

With an estimated production of 11 million tons, Brazil ranks ninth in the ranking of the largest producers of rice, especially the largest producer outside Asia. However, only the attack of pests during storage losses reach 20% of total production. The insect Sitophilus spp. Linnaeus (1763) (Coleptera, Curculionidae) is considered a major pest of grain and can be easily found attacking paddy in silos and warehouses. To control this insect, chemical insecticides are the most used, they can bring many problems to humans and the environment, thus it is necessary to search for alternative control methods to prevent such problems. Therefore, the objective of this study was to evaluate the repellent activity of plant extracts on weed adults of Sitophilus spp. in rice seeds under laboratory conditions. The experiment consisted of two tests in order to evaluate the effect of aqueous extracts 10% w/v of leaves and branches of Macae Wort (Leonurus sibiricus L.), Black cock (Bidens pilosa L.), Mary soft (Senecio brasiliensis Less.) and fruits of castor bean (Ricinus communis L.). In the first test, samples of rice of rice seeds were treated with the extracts and distilled water (control), and arranged in arenas along with insects, where after 24 hours were counted the number of insects per sample. In the second test, kraft paper tapes were treated with the extracts and distilled water (control), and were arranged in trays surrounding untreated samples of grain, so the insects were placed and evaluated after 24 hous the number of insects per treatment. In each tray there was a treatment with the extract and a control treatment.Both in the first and the second test extract showed better results black cock repellency. From the results presented in the two tests it was found that laboratory extract showed better activity Black Cock repellent to Sitophilus spp.