Efficacy of Oleic Acid and Linoleic Acid Vapors on the Stable Phases of Trogoderma granarium (Coleoptera: Dermestidae)

The current study is conducted with the aim of evaluating two fatty acids effectiveness and efficiency of steaming, Oleic acid and Linoleic acid, as a natural and safe alternative to chemical pesticides in controlling the hairy grain beetle Trogoderma granarium Evert fixed phases (eggs, pupae). This laboratory study included the use of four concentrations (50, 100, 200, and 150) ppm, with exposure periods that varied according to the insect role. They were (24, 16, 8) hours in the first and (36, 24, 12) hours per/2nd. The results demonstrated the treatment of insect eggs with oleic and linoleic acid vapors presenting the hatching inhibition highest rates, reaching 72.22 and 76.66% at a concentration (200 ppm) and an exposure period (24 hours), with a superior effect of linoleic acid vapor in causing inhibition rates at all concentrations and exposure used periods. The reason for the inhibition in both may be attributed to the ability of the vapor of the two acids to penetrate the egg wall and affect its protoplasm, thus thwarting the growth and development of the embryo. Also, pupae treatment with the vapor of the two acids giving the killing highest rates, reaching75.55 and 71.10, respectively, at a concentration (200 ppm) and an exposure period of (36 hours), with superiority to the effect of oleic acid vapor in killing rates at all concentrations besides using exposure periods. The cause of killing in both vapors may be ascribed to their harmful effects on the respiratory and nervous systems of the pupae, causing them to suffocate and paralyze. As for the results of the statistical analysis, they indicate the significance of each of the effects of concentrations and periods of exposure and the overlap between them to the two acids at both phases.


Introduction
It is well known that grain crops, including wheat, contain high levels of carbohydrates, proteins, and fats.Therefore, the world population considers it one of its basic foods and calls for storing it in times of need or for exporting it [1].One of the most complex issues facing the storage of wheat is its infection with diseases [2], and store insect pests that are widely spread all over the world.In Iraq, 31 species of them were found, belonging to 16 genus, falling under eight families and two orders spread in most places where grain is stored.At the forefront of these insects is the granarium (Everts) Trogoderma.As it represents a major threat to it, and it is considered one of the worst species due to the difficulty of controlling it, because its larvae possess biological mechanisms that resist the harshest conditions [3].The chemical control of pests, such as fumigation with aluminum phosphide gas, greatly contributed to controlling the pest and reducing its numbers [4], but the insect larvae showed resistance to the action of chemical pesticides due to their entering into optional dormancy [5].Also, chemical control is not devoid of drawbacks represented by leaving its residues, as it is one of the important sources of pollution for the wild and aquatic environments and harms human and animal health and causes acute and chronic poisoning of fish.This is what prompted specialists in the field of pest control to search for alternative methods that contribute to protecting the environment and the safety of workers and consumers [6,7].One of the alternative methods for chemical pesticides in the field of pest control is the use of powders such as Silica powder [8], and Eucalyptus camaldulensis leaf powder in controlling them [9], and also plant extracts such as ethyl extract of leaves and seeds of Sesbania sesban in controlling population densities [10].Also, fatty acids have been used recently in the control of insect pests.They have been widely used, especially oleic and linoleic acids, as they have proven to have desirable insecticidal properties [11].Accordingly , the study aimed to know the contact effect of two fatty acids on the moving roles (eggs and pupae) of the hairy grain beetle with different concentrations and exposure times.

Insect Tested Culture
Some different phases of Trogoderma granarium of the hairy grain beetle were obtained from infected grains from the insect laboratories of the Plant Protection Department / College of Agricultural Engineering Sciences / University of Baghdad in July 2022, and Ethical standards were considered in all steps of performing procedures and animal handling and the study was approved by the Ethical Committee [Approval letter No. UoM.Dent/A.L.66/21].No. Um.VET.2021. 5.In order breed it, the insect was placed in its various roles in clean, heat-sterilized plastic containers with a capacity of 700 ml containing wheat grains of Ibaa class 99, the most sensitive to insect infestation.To ensure the speed of their reproduction after making sure that they are free of other insect pests by subjecting them to freezing at a temperature of (-20) degrees Celsius for a period of (20) days [12].The pots were covered from above with burlap cloth, tied with a rubber band, and placed in a Jard incubator equipped with a hygrometer.The incubator was fixed at a temperature of 35 ± 1 ° C, a lighting period (hour) of 1 light: 23 dark, and a humidity of 65 ± 5. To stabilize the humidity, an amount of 3 g of KoH was placed in 100 ml of water in a tightly closed glass container [13].The farm has also been maintained by adding wheat grains to it continuously to ensure obtaining an abundance of numbers that provides the experiment with different phases.Flour and molting skins resulting from insect activity are also disposed of by sifting food from time to time [14].Insect eggs were obtained after isolating 10 pairs of newly hatched adults (males and females) in sterile plastic Petri dishes with a diameter of 9 cm and a depth of 1.5 cm, containing black blotting paper to facilitate the viewing of eggs laid by females, as The eggs are transferred to the treatment pots with a soft brush moistened with water using a magnification lens of 20 [15].while the pupae were obtained after observing the larvae in their last stage.Preparation of concentrations of each of oleic and linoleic acid The oleic acid concentrate prepared for control was prepared by placing 500 ml of concentrated ethanol 99% in a container of 1000 ml capacity, and 50 microliters of oleic acid with a concentration of 95% were dissolved in it, which was withdrawn by the microliter apparatus.Then the remainder was supplemented with distilled water, to finally reach a volume of 1000 ml, so that the ratio of the fatty acid to the solvent solution was (50) ppm.Thus, the rest of the concentrations were prepared as 100, 150, 200 ppm.In addition to the comparison treatment, which was only 50% ethanol, while the concentrations of linoleic acid were prepared in the same way, and the concentration of linoleic acid was 98% [16].

The Method of Fumigation with Fatty Acids
The fumigation control process included placing 10 individuals from each role (eggs, virgins) in a repeated cylindrical container with 3 repetitions for each treatment, the capacity of the container was 90 cm, and a smaller cylindrical container with a capacity of 9 cm was placed inside it, containing the pesticide at previously determined concentrations and With a quantity of 3 ml, the amount of evaporated pesticide was estimated at (1) ml, and it was closed from the top with silicone material, and entered into the incubator according to the previously mentioned conditions, with exposure periods of (8, 16, and 24) hours for eggs and (12, 24, and 36) hours for sperm.For virgins, as well as the control treatment (50% ethanol) (22), hatching inhibition rates for eggs and killing rates for virgins were calculated [17].

Statistical Analysis
The Statistical Analysis System -SAS [18], was used to analyze the data to study the effect of different coefficients on the studied traits according to a complete random design (CRD), and the significant differences between the means were compared with the Least Significant Difference-LSD test.

Effect of Oleic Acid Vapor on the Eggs of the Hairy Grain Beetle Trogoderma granarium
The results of Table (1) of the study of the effect of oleic acid vapor on the eggs of the hairy grain beetle Trogoderma granarium show the effect of oleic acid vapor on the rates of inhibition of their hatching at concentrations 50, 100, 150, 200 ppm and exposure times 8, 16,24 hour .The effect of concentrations on the rates of killing rates reached 15.55, 33.33, 56.66, and 72.22%, respectively, while the effect of exposure periods on the rates of killing rates reached 34.16, 42.49, and 56.66%, respectively.As for the best results of the interaction between the two factors, it was 86.66% at a concentration of 200 ppm and an exposure time of 9 hours, while the lowest was 10% at a concentration of 50 ppm and an exposure time of 8 hours.The results of the statistical analysis showed, in general, that the effects of concentrations and exposure times and the interaction between them were significant in the rates of inhibition of hatching of insect eggs.

Effect of Linoleic Acid Vapor on the Eggs of the Hairy Grain Beetle Trogoderma granarium
The results of Table (2) of a study of the effect of linoleic acid vapor on the eggs of the hairy grain beetle Trogoderma granarium show the effect of linoleic acid on the rates of inhibition of hatching of its eggs at concentrations of 50, 100, 150, 200 ppm and exposure periods of 8, 16 and 24 hours.The effect of concentrations on the rates of killing rates reached 17.77, 39.99, 61.10, and 76.66%, respectively, while the effect of exposure periods on the rates of killing rates reached 37.49, 49.99, and 59.16%, respectively.As for the best results of the interaction between the two factors, it was 90% at a concentration of 200 ppm and an exposure time of 24 hours, while the lowest was 13.33% at a concentration of 50 ppm and an exposure time of 8 hours.The results of the statistical analysis showed, in general, that the effects of concentrations and durations of exposure and the interaction between them were significant in the rates of inhibition of hatching of insect eggs.(1,2) that the effect of linoleic acid vapor was superior to that of oleic acid vapor in inhibiting the hatching of eggs of the hairy grain beetle Trogoderma granarium at all concentrations and exposure times used, thus reducing the number of larvae emerging from them.The reason for this may be attributed to the fact that linoleic acid vapor works to penetrate the egg wall and affect its protoplasm, thus thwarting the growth and development of the fetus.It also has the ability to affect the muscle tissue of the fetus, causing it to lose the ability to breathe and thus the death of the fetus.Or it works as a growth regulator that interferes with the progression of biological processes for the growth and development of the fetus, such as affecting the metabolism of eggs, which prevents the partial or total formation of the fetus [19].The results showed that the vapor method has a good effect in inhibiting the same insect eggs, and this is consistent with what was stated by [20], when treating cowpea seeds with linoleic acid before laying eggs on them by the insect Callosobruchus maculatus (F.), as it was found to be effective in discouraging its hatching.As the results showed that the rates of inhibition of hatching of insect eggs increased with increasing concentration and duration of exposure.This is consistent with what was stated by [20],when using ozone gas in controlling some of the roles of the red flour beetle.

Effect of Oleic Acid on the Pupae of the Hairy Grain Beetle Trogoderma granarium
Table (3) results demonstrated the study of oleic acid vapor effect on hairy grain beetle Trogoderma granarium pupaedemonstrating oleic acid vapor e effect on insect pupae killing percentage at concentrations 50, 100, 150, 200 ppm and exposure times 12, 24, 36 per hour, Concentrations effect on killing rates reaching 18.88, 38.88, 66.66, and 75.55%, respectively, whereas the effect of exposure periods on killing rates reaching 31.66,51.66, and 66.66%, respectively.The best results of the interaction between the two factors are 90% at The concentration is (200 ppm) and the exposure time is (36 hours), whereas the minimum is 10% when the concentration is (50 ppm) and the exposure time is ( 12 hours).The statistical analysis results demonstrated, in general, significant effects of concentrations and durations of exposure besides the interaction between them in insect pupae killing rates, indicating an increase in killing rates with increasing concentrations and exposure periods.(3,4)the results of oleic acid vapor effect is greater to linoleic acid vapor effect on hairy grain beetle Trogoderma granarium pupae at all concentrations and exposure times used killing rates.The cause for this could be ascribed to its toxic effects on body tissues and cellular work sites following permeating them through the respiratory openings besides to its damage to the respiratory system itself, causing pupal suffocation, or that oleic acid vapor affecting the insect nervous system resulted in sending nerve impulses affecting the course of different biological processes contributed in gametes formation [21].The results demonstrated that the more killing rates with the more concentrations and exposure times, and this is consistent with what was mentioned [22], when using ozone gas in controlling some of the roles of the red flour beetle Tribolium castaneum(Herbst) .

Conclusion
Oleic acid and Linoleic acid vapors usage in controlling the Dermestidae grain beetle fixed roles: Trogoderma granarium Everts (Coleoptera) is very effective in eliminating large proportions of them, as this process can be adopted in integrated pest management.

Table 1 .
Effect of Oleic acid vapor on Trogoderma granarium eggs.

Table 2 .
Effect of linoleic acid vapor on Trogoderma granarium eggs.

Table 3 .
(4)ect of Oleic acid vapor on Trogoderma granarium papae.Table(4)results demonstrated the effect linoleic acid vapor on Hairy grain beetle Trogoderma granarium pupae , the effect of Linoleic acid on killing insect pupae percentage at concentrations of 50, 100, 150, 200 ppm and exposure times ( 12, 24 and 36 hours).Concentrations effect on the killing rates reaching 17.77, 32.22, 52.22, and 71.10%, respectively, whereas exposure durations effect on the killing rates reaching 29.16, 44.16, and 56.66%, respectively.The interaction best results between the two factors are 93.33% at a concentration ( 200 ppm).The exposure time is 36 hours, while the least is 10% at a concentration (50 ppm), and the exposure time is 12 hours.Statistical analysis results demonstrated, in general, concentrations and durations of exposure effects and the interaction between them are significant on killing insect pupae percentage.

Table 4 .
Effect of linoleic acid vapor on pupae.