Full mortality time prediction on eggs of S- and R-strains of Cryptolestes turcicus Grouville based on adult immobilization observed by video camera imaging in phosphine fumigation

Abstract

Several stored product insect pests have developed resistance to phosphine globally, which is related to the effective pest management and the use of phosphine is not easily to be alternated in the future. The flour mill grain beetle, Cryptolestes turcicus (Grouville), is a cosmopolitan pest existed in broken and milled grain. To date, There is little information about the response and resistance of this insect to phosphine in both adult and immature life stages. In this article, we identified a highly resistant strain (Rf = 92) and a susceptible one(Rf = 4). We compared the full mortality time of two strains after fumigation with phosphine at a concentration of 400 mL/m³ phosphine at 18, 23, and 28 °C. In addition, we observed the adult immobilization by remote-controlled camera monitoring, and then analyzed the relationship between adult immobilization and full mortality time of egg at the most resistant stage among all developmental stages. The results showed that the full mortality time of stages in highly resistant strain are obviously delayed, as well as at lower temperatures. The regression equations of adult immobilization ratio (x) and predicted time (y) of population extinction were established for the two strains, Based on this, we can calculate the completely death time of eggs and predict population extinction. This method and results can help predict the time of completely death by remote monitoring, preventing the development of resistance.