Danos em trigo, causados por Sitophilus oryzae e Rhyzopertha dominica, quando armazenado em diferentes temperaturas e exposto a níveis de infestação

Abstract

Wheat is one of the most cultivated cereals in the world, and of fundamental economic importance. Storage is a key step in maintaining the quality of the products until their final distribution. Insect pests are the main storage loss agents in grain storage environments. In storage of wheat grains the main insects that infest the grains are the species Sitophilus oryzae and Rhyzopertha dominica. The objective of this study was to evaluate the damage caused by infestation levels of Sitophilus oryzae and Rhyzopertha dominica in wheat grains stored for 360 days at different temperatures. The experiment was conducted at Embrapa Trigo- Laboratório de Entomologia, with R. dominica and S. oryzae being used for infestations. These insects were obtained by laboratory creation and conducted without age standardization. Initial infestation levels were; zero, two, four, six and eight non-sexed insects for each 0.3 kg of wheat grains, with four replicates each. The samples were divided into four separate "BOD" type chambers, each being set to maintain different temperatures during the storage period. The temperatures evaluated were 10, 15, 20 and 25 ° C (± 2 ° C). The evaluations were carried out monthly in a one-year period, and the variables dry matter (DM), hectoliter (PH) and population growth. After 12 months of evaluations, for the two species studied, at temperatures of 10 and 15ºC and for all levels of infestation, the insect population did not develop and grain damage in DM varied from 0 to 0.1%. For R. dominica, at 20ºC, there was an increase ranging from 1.8 and 3.0 times in the insect population and 0.81% of average damage to the grains. For this species, the temperature of 25ºC presented increment of the population, varying from 695 to 2,330 times and the damages in DM were between 59 and 75%. On the other hand, for S. oryzae the temperature of 20ºC was the one that provided the greatest population growth, with increase ranging from 689 to 1632 times, and damages in MS from 48 to 81%. The temperature of 25 ° C increased the population between 28 and 373 times and the damage in MS ranged from 1 to 13% for S. oryzae. It is hoped, with this work, to provide subsidies to optimize the management of pests in stored grain grains in relation to the effects of temperature and storage period.