Thermal requirements and estimation of number of generations of Grapholita molesta (Busck,1916) (lep: olethreutidae) in Pelotas, RS, Brazil

Abstract

The evolutive cycle of Grapholita molesta (Busck, 1916) was studied on an artificial diet, at constant temperature (20, 23, 26 and 30°C), relative humidity of 75⁺10% and photofase of 14 hours, with the objective to determine thermal requirements to different phases of development and to predict number of generations per and on peach trees in Pelotas, RS, Brazil. Low threshold temperature and the value of thermal constant in degree-days (DD) were done by using the hyperbole method. Lowest threshold temperatures were 6,47°C (egg), 9,04°C (larva), 12,78° (pre-pupa), 6,61°C (pupa) and 8,99°C (evolutive cycle). Thermal constants were 64,79 DD (egg), 223,63 DD (larva), 50,16 DD (pre-pupa), 155,46 DD (pupa) and 482,00 DD (evolutive cycle). Based on threshold temperature for the evolutive cycle it was estimated in the above locality that oriental fruit moth should have six to seven generations per year and four to five on peach trees.