The Effect of Solar Heating on Lesser Grain Borer, Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae)

Abstract

Abstract The experiments of this study were conducted in the Plant protection Department laboratories - College of Agriculture - Tikrit University in 2023 for the purpose of identifying the effect of solar heating on both larvae and pupae of lesser grain borer during four weeks of both July and Augast, 2023 at 10.00 a.m, 12.00 noon and 2.00 p.m. by using three exposure times. 15, 30, and 45 minutes It has been indicated from the results that the weeks of July and August have a distinct and significant impact on the larval stage mortality and the development of the visible adult insect, as the highest larvae killing 55.19% was recorded in the 4th week of August, while the lowest larvae killing 32.95% was recorded in the 1st week of August inside uncovered petri dishes. The July weeks, as you can see from these results, also has an effective effect on the mortalty larvae, by solar heating, as the highest larval mortalty was recorded at 63.33% for the 45-minute period at 12.00 noon inside uncovered petri dishes also., while the lowest percentage of killing larvae, 19.16%, was recorded for the exposure period of 15 minutes at 10.00 a.m.. It is worth noting here that the interaction between weeks and the exposure time also has an important and significant impact on the percentage of larvae killing, recording its highest percentage of 93.33% for the interaction between 4th Augast week and The exposure time 45 minutes at 2.00 p.m. in uncovered petri dishes, while the lowest larval stage percentage killing 10.00% was recorded for the interaction treatment between the 1st July week and the exposure time, 15 minutes for the treatment at 10.00 a.m. inside uncovered petri dishes. The results also showed that the effect of sunlight on the larval stage inside covered Petri dishes varied according to the three different exposure time included in this study. The highest rate of killing larvae was recorded, 100%, 100% larvae, all of which were observed for 15, 30, and 45 minutes for the two hour periods of larvae. 12.00 noon and 2.00 p.m. The results also showed that the four weeks observed in this study had a significant and clear effect on the rate of larval stimulation, recording its highest rate of 84.44% larvae in the 2nd Augast week inside covered petri dishes, while the lowest larval stage mortality 77.31% larvae was recorded in the 1st Augast week inside covered petri dishes also.