Ecofriendly Control for Stored-Product Pest, Oryzaephilus surinamensis (Order: Coleoptera, Family: Silvanidae)

It was reported that cereals were considered the major source of animal food. However, ≈25-50% of the total harvested cereals were lost during storage processes¹ - ³. Stored-product pests were considered the biggest challenge worldwide. The global economic losses resulting from non-standard storage conditions were estimated at thousands of millions of Euros a year 4 . An overview of the present and past pest-associated risks of stored products was published. The authors concluded that the stored product research did not attract merit funding support. This leads to the absence of both programmed systematic surveillance, and risk assessment studies of storage pests from the agendas of many countries worldwide 5 . Stored-product insects were regarded as the main cause of quantity and quality loss in stored grains 4-7, 8-11 . Especially coleopterans including the saw-toothed grain beetle, O. surinamensis , were regarded as the most serious primary pests of stored products worldwide 12-14 . Additionally , O. surinamensis was recorded as the most abundant and destructive species among stored-product coleopterans. O. surinamensis causes both direct injury by strong chewing mouth parts, and indirect Abstract Dates are considered one of the most important foods consumed in Arab countries. Dates are commonly infested with the sawtoothed grain beetle, Oryzaephilus surinamensis . Consequently, the date yield, quantity, and quality (economic value and seed viability) are negatively affected. This study was designed to investigate the effectiveness of air evacuation as eco-friendly and safe control method against adult O. surinamensis . Insects were obtained from the infested date purchased from a private store in sakaka city, Aljouf region, Saudi Arabia. Air evacuation (using a vacuum pump) and food deprivation were applied to O. surinamensis , and insect mortality was observed daily in comparison with the control group (administered both food and air). Application of both air evacuation, and food deprivation, significantly, increased the percentage of daily mortality when compared to control. Percentage accumulative mortality displayed very strong positive correlation with the time course in both cases of air-deprived and food-deprived groups. On the basis of lethal time values, the air evacuation method resulted in a comparable effect of food deprivation. Conclusively, the air-evacuation of the package is a very effective Eco-friendly and safe control method against O. surinamensis .

Therefore, the present study aims to investigate the effect of air evacuation on the mortality of adult O. surinamensis and use it as an eco-friendly control method in comparison to food deprivation.

Sample collection and insect identification
Adults of the saw-toothed grain beetle, O. surinamensis were collected from infested date fruits purchased from a private store in Sakaka, Aljouf, Saudi Arabia.Insects were maintained at temperatures 25± 2 °C and 70± 5% RH inside plastic jars (10 cm height x 5 cm diameter).Each jar was supplied with sterile wheat flour as food, and covered with gauze fixed with a rubber band.Insects were identified according to the available keys for the identification of stored products beetles 30 .

Effect of air deprivation and food deprivation on mortality of adult O. surinamensis
Five replicates of three groups of adult insects (10 newly emerged O. surinamensis adults per each replicate) were put in plastic sacks (19 cm height x 5 cm diameter).The first group (Control) was supplied with date fruits as food.Sacks of this group were sealed off, and punctured with a sterile needle for ventilation (air-supply).The second group (Air-dep) was supplied with date fruits as food, and deprived of air.Air was evacuated from the sacks using a vacuum pump.The third group (Food-dep) was supplied with air as previously described, and deprived of date fruits (food).
Mortality was observed daily for each replicate of the three groups, and average percentage mortality was calculated.The insect was considered dead if they don't move when shaking or stimulated with a brush.The experiment was repeated three times.

Determination of LT50 of air-deprived and fooddeprived adult O. surinamensis
As the control mortality was less than 5%, no corrections were done to the final mortality of the treated groups.Consequently, experimental data were subjected to probit analysis 31 .LT20, LT50 and LT95 were determined for both Air-dep and Fooddep groups.The significance level of mortality differences was determined by comparing the 95% confidence limits of both groups at LT20, LT50 and LT95.Interfering 95% limits were considered insignificant.

Statistical analyses and calculations
One-way analysis of variance (ANOVA) and posthoc tests for daily mortality data were performed.The significance level was calculated at P< 0.05.Additionally, Pearson's and Spearman's correlation coefficients (r) were calculated at a significance level of P < 0.01.All statistical analyses were done by using SPSS ver.27.0.1.0software.

Results and Discussion
The effect of air deprivation and food deprivation on daily mortality of adult O. surinamensis were compared.One-way analysis of variance (ANOVA) revealed that the overall differences in daily mortalities of O. surinamensis were significant (Table 1).Post-hoc tests revealed that the difference in daily mortality between air-deprived and control groups was insignificant (P> 0.05) at the 1 st day from the start of application (Fig. 1).Meanwhile, the difference in daily mortality between food-deprived and control groups was insignificant (P> 0.05) at the 4 th and 5 th days from the start of application (Fig. 1).However, the differences with control group were significant (P< 0.05) at the 2 nd , 3 rd , 4 th , and 5 th days from the start of application for airdeprived group (Fig. 1).In parallel, the differences with control group were significant (P< 0.05) at the 1 st , 2 nd , and 3 rd days from the start of application for food-deprived group (Fig. 1).Additionally, the differences in daily mortality between air-deprived and food-deprived groups were insignificant (P> 0.05) at the 1 st , 3 rd , and 4 th days from the start of application (Fig. 1).However, the differences in daily mortality between air-deprived and fooddeprived groups were significant (P< 0.05) at the 2 nd and 5 th days from the start of application (Fig. 1).and 2B.Both Pearson's and Spearman's correlation analyses regarding mortality time, air deprivation, and food deprivation are summarized in Table 2. Generally, all pairs exhibited significant positive strong (r > 0.941-0.973for Pearson's and r > 0.985-1.000for Spearman's coefficients) correlations.Time-airdeprivation, Time-food-deprivation, and airdeprivation-food-deprivation pairs exhibited positive significant strong correlations for both correlation coefficients (Table 2).

Determination of LT50 of air-deprived and fooddeprived adult O. surinamensis
Using probit analysis, LT20, LT50 and LT95 were determined for both air-deprived and food-deprived adult O. surinamensis (Table 3).The estimated values of LT20, LT50 and LT95 were found different between air-deprived and food-deprived groups.Statistical analysis revealed that these differences in LT values were insignificant in all estimated LT O surinamensis is a well-known serious pest of stored products including cereals and related amylaceous products.Due to its higher mobility, O. surinamensis is also capable of infesting a wide variety of crops 21,[32][33][34] .The present work tested the efficacy of air deprivation as a safer control method for adult O. surinamensis in comparison to food deprivation effect.
Our results revealed significantly increased daily mortalities of air-deprived and food-deprived adult O. surinamensis when compared to the control group.Accumulative daily mortalities of both airdeprived and food-deprived adult O. surinamensis displayed a very strong positive correlation with the time.The differences in estimated LT20, LT50 and LT95 of air-deprived and food deprived groups were statistically insignificant.These results clarified that the air-deprivation method was as efficient as food deprivation in controlling adult O. surinamensis.It is concluded that as the majority of insects, the rate and efficiency of respiration of O. surinamensis are affected by changes in the concentrations of the O2: CO2 ratio 35 .These results could be interpreted by the CO2-avoidance behavior.It was previously suggested as an anti-stress mechanism in D. melanogaster adults subjected to elevated CO2 levels 36 .In consistence, egg laying, embryonic development, hatching and post-embryonic development of D. melanogaster, declined when CO2 concentration rises 36 .In addition, the chemosensation and response to cellular oxidation, nitrosation and acidosis caused by the hypercapnia lead to insect mortality 36 .

Conclusion
This study presented that air-deprivation significantly increased the 2 nd , 3 rd , 4 th , and 5 th daily mortality when compared with control.Meanwhile, food-deprivation significantly increased the 1 st , 2 nd , and 3 rd daily mortality when compared with control.Additionally, differences in daily mortality between air-deprived and food-deprived groups were significant at the 2 nd and 5 th days.However, differences were insignificant at the 1 st , 3 rd , and 4 th days.Time-air-deprivation, Time-food-deprivation, and air-deprivation-food-deprivation mortality pairs exhibited positive significant strong correlations for both Pearson's and Spearman's correlation coefficients.Furthermore, probit analysis revealed that the differences in LT20, LT50 and LT95 values between air-deprived and food-deprived groups were insignificant.Conclusively, air-evacuation of the package was as effective, safer and eco-friendly method as food-deprivation for protecting stored products against the saw-toothed grain beetle, O. surinamensis.

Figure 1 .
Figure 1.Daily mortality of control, air-deprived and food-deprived O. surinamensis adults.The lowercase letters on the columns refer to the significance level.Different letters refer to significant differences and the same letters refer to insignificant differences at P < 0.05 using LSD post hoc tests.Time-mortality correlation of air-deprived and food-deprived adult O. surinamensis The correlation of accumulative daily mortality and time course of air-deprived and food-deprived adult O. surinamensis were investigated (Figs.2A and 2B).Accumulative daily mortalities of both air-deprived and food-deprived adult O. surinamensis were increased by increasing the time course of the experiment.The percentage mortality displayed a very strong positive correlation with the time in both cases of air-deprived (R 2 = 0.952) and

Figure 2 .
Figure 2. Correlation between (A): time and % mortality due to food-deprived, (B): time and % mortality due to air-deprivation of O. surinamensis adults.