Survival Rates of Ephestia kuehniella and Plodia interpunctella (Lep.: Pyralidae) First Instar Larvae in Different Storage Temperatures and Periods

In biological control, mass production of host insects is essential for the production of beneficialinsects, as they are used as food and breeding grounds. To produce sufficient numbers ofbeneficial insects, it's crucial to have a high host insect population not only during productionbut also during application periods to boost beneficial insect populations. To achieve this, lowtemperature storage studies are of great importance for both backup and synchronization withthe beneficial insects during periods when the host population is high. This study aimed todetermine the survival rates of first-instar larvae of Ephestia kuehniella Zeller (Lepidoptera:Pyralidae) and Plodia interpunctella Voegele (Lepidoptera: Pyralidae), which are mass-rearinghosts for many beneficial insects, at two different temperatures and six different storagedurations. For this purpose, larvae were stored at 5°C and 8°C for 2, 4, 6, 8, 10, and 12 days inrefrigerators. The experiments were set up with 10 replicates for each storage duration. Eachreplicate consisted of 10 first-instar larvae, 0-6 hours old, in an Eppendorf tube. At the end ofthe storage periods, the Eppendorf tubes were removed from the refrigerators and placed in aclimate chamber (25 ± 1°C temperature, 60-65% relative humidity). After a 30-minuteacclimatization period, the number of live and dead larvae was determined under astereobinocular microscope. Survival rates were calculated from these data, and ANOVA wasused to compare the means to determine the effect of different storage temperatures anddurations. In cases where significant differences were found, Tukey's multiple comparison testwas used to identify which means were statistically different from each other. The study'sresults showed no significant difference in the survival rates of first-instar E. kuehniella and P.interpunctella larvae at 5°C across all storage durations. However, at 8°C, the survival rates ofE. kuehniella larvae were statistically higher than those of P. interpunctella larvae across allstorage durations. For Ephestia kuehniella stored at 5°C, no significant difference was observedbetween 2-day and 4-day storage, but the survival rate progressively decreased with longerstorage periods. For the same species at 8°C, the 2-day storage duration resulted in asignificantly higher survival rate compared to all other storage periods. When comparing thestorage temperatures for the same storage durations for E. kuehniella, the survival rate of larvaestored at 8°C was significantly higher than at 5°C for all storage durations. Regarding thesurvival rates of P. interpunctella larvae at 5°C, the 2-day and 4-day storage durations resultedin significantly higher survival rates compared to other durations. The 6-day storage durationalso showed a statistically significant higher survival rate compared to the 8, 10, and 12-daystorage periods. For the same species at 8°C, the 2-day storage duration had a significantlyhigher survival rate than other durations, and the 4-day storage duration also showed a highersurvival rate than the other days. When examining the differences between temperatures for P.interpunctella at different storage durations, no significant difference was found betweentemperatures for the 2, 6, 8, and 10-day storage periods. However, at 4 days of storage, thesurvival rate at 5°C was determined to be higher than at 8°C. A statistical comparison could notbe made for the 12-day storage duration as all larvae died at both temperatures. In conclusion,both storage temperature and duration have a significant impact on the survival rates of firstinstar E. kuehniella and P. interpunctella larvae. In both species, the survival rates of larvaesignificantly decreased as the storage duration increased, with nearly all larvae dying after 12days of storage. The only exception was E. kuehniella at 8°C, where some larvae remained alive50on the 12th day. This suggests that 8°C is a more suitable temperature for longer-term storageof E. kuehniella. The complete mortality of P. interpunctella larvae even at 8°C indicates thatthis species is more sensitive to the adverse effects of low temperatures than E. kuehniella. Thedata obtained from this study are considered preliminary and valuable for future research onthe storage of host insects in other life stages. <br> Keywords: Biological control, cold storage, host, mass production, synchronization.