Comparative assessment of the fumigant action of volatile oils from three garlic cultivars on faba bean beetle Bruchidius incarnatus ( Boh . )

The study aims to assess the insecticidal activity, oviposition inhibitory and ovicidal effects of volatile oils from different garlic cultivars on faba bean beetle, Bruchidius incarnatus (Boh.) (Chrysomelidae: Bruchinae). The oils were tested at various concentrations and time intervals. Results showed that all volatile oils caused significant mortality to the test insects. The effects were time and dose-related. The 72 h median lethal doses (LD50%) of male and female B. incarnatus were 0.03 and 0.006% (Chinese oil); 3.77 and 0.06% (Egyptian oil) and 0.03 and 3.77% (Sudanese). The respective median lethal times (LT50, at 0.01%) for male and female were 55.88 and 57.57 h (Chinese oil); 48.62 and 57.76 h (Egyptian oil) and 79.93 and 84.99 h (Sudanese oil). The results of egg hatchability of B. incarnatus exposed to the lowest concentration (0.01%) were: 31, 32 and 34% for Chinese, Egyptian and Sudanese oils, respectively. The respective median lethal doses (LD50 %) for Chinese, Egyptian and Sudanese oils were 0.025, 0.034 and 0.21%. The results indicated that there were significant differences among the three garlic oils; however, the efficacy of the three types of garlic oils against the test insects can be in this order: Chinese> Egyptian> Sudanese oil.


INTRODUCTION
In Sudan, faba bean constitutes an important component of human diet both in rural and urban areas.The crop is grown in 58,000 ha in Sudan, with an average yield of about 251 kg/ha (FAO, 2001).Sixty percent of the cultivated land is allotted to faba bean in Northern State, and 3.6% in the Nile State.Most of the production comes from the Northern and River Nile states, with a small amount from Khartoum, Gezira, Jebal Marra and Rahad Schemes (Abdul- Bari and Nygaard, 1982).The postharvest losses have been estimated at 5 to 10% with the majority attributed to insect infestation.The duration of storage affects the relative abundance and succession of insects.The major storage pests of faba bean in the Sudan are the faba bean beetle Bruchidius incarnatus *Corresponding author.E-mail: a.aziz30@gmail.com.Tel: +249915378530.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License (Boh.)(Chrysomelidae: Bruchinae).Infestations by these insects lead to serious losses in quantity, quality, and germination percentage of stored faba bean.Insect damage to stored grains and pulses may reach up to 40% in countries where modern storage technologies have not been introduced.Currently, the measures to control pest infestation in grain and dry food products rely heavily upon the use of gaseous and liquid insecticides, which may pose possible health hazards to warmblooded animals and an increased concern to the environment.Fumigation is still one of the most effective methods used for the protection of stored food, feeds stuff and other agricultural commodities from insect infestation.However, the number of chemicals for insect control decreased drastically as problems of insect resistance intensified and social pressures against the use of toxic chemicals in stored food started to gain increased concern for health environmental reasons (Varma and Dubey, 1999).Based on this the requirements for safer means of pest management became crucial.Therefore, the use of safe, low toxic botanical pesticides is now emerging as one of the prime means to protect crops and their products as well as the environment from pollution by pesticides (Prakash and Rao, 1997).
Botanical pesticides can cause less damage to human health and environment than conventional insecticides.Many of them degrade rapidly and do not accumulate in the body and environment while some are very pest specific and do little or no damage to other organisms.The body of scientific literature documenting bioactivity of plant derivatives to arthropod pests continues to expand, yet only a handful of botanicals are currently used in agriculture in the industrialized world, and there are few prospects for commercial development of new botanical products (Nabil, 2013).Garlic products are marketed in the European Union (EU) (Commission Directive, 2003) as foodstuffs as well as herbal medicinal products.Majority of these products are sold with health claims.In contrast, garlic medicinal products are available only in a limited number of EU member states.This difference is due to discrepancies among the national laws of EU member states.European legislation does not distinguish between medicinal products prepared from chemical substances and those produced from plants or other natural substances.However, garlic is regulated by the same rules as all other medicinal products.In general, manufacturers of herbal products have difficulty in satisfying all the requirements of European directives and guidelines for medicinal products (Commission Directive, 2003;Krose, 2006).
In Sudan, Ahmed (1998) reported the promising potential of the fumigant action of garlic oil in the control of stored products pests.Abdalla (2003) evaluated the fumigant action of garlic volatile oils against major storage pests and revealed the insecticidal properties of local garlic cultivar volatile oil with promising results.Khiralla (2007) evaluated the efficacy of oil extract from Chinese garlic cultivar against two major bruchids.Taha (2007) reported the efficacy of Egyptian garlic cultivar oil against two stored legumes pests.The efficacy of garlic oil and aqueous extract against the Cowpea beetle was reported (Ahmed and Abdelbagi, 2014;Abdalla et al., 2017).Based on the promising results obtained by previous authors this present study was conducted to investigate the use of volatile oils from three garlic cultivars (Chinese, Egyptian and Sudanese) as fumigants against the adult of broad bean beetle B. incarnatus (Boh.), and to study the insecticidal efficacy, antioviposition and ovicidal effects of these oils.

Insect culture
The source of faba bean infested with B. incarnatus (Boh.) was Dongola Research Station, Agricultural Research Corporation, Sudan.The obtained culture was brought to the Department of Crop Protection, Faculty of Agriculture Laboratory and sieved by mesh No. 10 to remove adult insects.Adults were reared in rearing glass jars of 3 kg, and half filled with sound grain of faba bean local variety; each jar was covered with a muslin cloth, fixed with rubber bands and kept in the laboratory at room temperature.Newly emerged (24 h) insects were used.Females were kept for 10-15 min with a surplus of newly emerged males, to allow mating (Ahmed, 1998).

Preparation of garlic (A. sativum L.) volatile oils
The volatile oils of the three cultivars of garlic (Chinese, Egyptian and Sudanese) were tested against adult and eggs of faba bean beetle B. incarnatus.Volatile oils of Chinese and Sudanese cultivars were obtained by the extraction procedure described below, while oil of Egyptian cultivar was obtained as ready-made oil from an Egyptian company (El-captain Company for Extraction of Natural oils, CAP PHARM, Cairo, Egypt).The mortality, fecundity, and ovicidal effects were assessed following exposure to the fumes emanating from garlic volatile oils (Abdalla, 2003;Khiralla, 2007;Taha, 2007).

Garlic preparation
The cloves of the garlic were cleaned, sliced and dried under shade in dark room for 19 days in winter and 11 days in summer.The dried garlic was ground using kitchen grinder "Moulinex".The powder was subjected to steam distillation and soxhlet extraction using ethanol (Guenther, 1961).

Steam distillation
Steam distillation was done according to the method of Abdalla (2003).300 g of Chinese garlic powder was placed in five liters round bottom flask and 1.5 L of distilled water was added.The mixture was thoroughly shaken for 20 min manually.The content was subjected to steam distillation at 65 to 70°C for 3 h.Anhydrous sodium sulfate (0.1 g/mL oil) was added to absorb the moisture.Oil was collected in glass containers and kept in a refrigerator at 4°C for bioassay (Abdalla and Abdelbagi, 2015).

Ethanol extract
Sudanese garlic powder (500 g) was placed in five liters round bottom flask and 2 L of ethanol (96%) was added.The mixture was subjected to Soxhlet extraction at 60 to 70°C for 6 h.The oil obtained was kept in a refrigerator at 4°C for bioassay.

Fumigation chamber
Airtight glass (5 mm thickness) fumigation chambers (16×16×16 cm) with sliding doors were prepared according to Abdallah (2003).Small pieces of glass (4×4 cm) were sealed together using Silicon adhesive.A stool of wire net was laid open inside the fumigation chamber to hold the jute sacs during the fumigation process.

Sexing of B. incarnatus
Sexing was done based on the morphology of antennae, pygidia and abdominal sternite as described by Shomar (1963).Sexing was also done based on Elkifl and Metwally (1971) who stated that the pygidia of the male and the female are characteristically different; those of the female have two large dark colored patches on the dorsal side separated by a line of white pubescence; in male such patches are lacking and the male last abdominal sternite is not emarginated.

Separation of eggs
The eggs of B. incarnatus were isolated according to Ahmed (1987) who stated that the eggs are small (less than 1 mm in length), smooth, oval in shape, flattened at the dorsal and ventral sides and rather transparent in color when newly laid.The eggs glued to the seed tests and were laid singly.

Toxicity assay
The mortal effect of garlic volatile oils on the adults of B. incarnatus was assessed.Twenty adults (10 males and 10 females) of 24 h old and of the same size were chosen from the main culture.To obtain the adults, the culture medium was sieved to remove the adult beetles therein and the adults emerging in the following day were collected for the experiment.The test insects were introduced into small jute sacs containing 50 g of sound grains of local faba bean and/or cowpea varieties purchased from the local market; they were recently harvested, free from any infestation and never received fumigation treatments.Sacs were then laid over the wire net stools and placed into a different fumigation chamber.Series of dilutions (10, 5, 1, 0.1, and 0.01%) of each type of garlic oils were prepared using ethanol 96% as a solvent, and diluted to 10% with distilled water.Petri dishes (covered with muslin cloth fixed with a rubber band to avoid insects from falling in the fumigant) containing 2.5 mL of each concentration were placed beneath the jute sack.The amount of each oil ranged from 0.5 to 5 ml/kg.The mortality of the test insects was calculated every 24 h for a week.The test insects without legs, antennal movement and not reacting to probing were considered dead.Recoveries of test insects were observed for a week.The experiment was kept in an incubator (Gallenkamp) at 28 to 35°C and 60 to 70% relative humidity (Khiralla 2007).
The experimental units were arranged in a completely randomized design with four replicates.Two controls treated with only the solvent or distilled water were included.

Oviposition inhibitory test
The oviposition inhibitory property of garlic volatile oils was determined by fumigating newly emerged adults.Different concentrations of garlic volatile oils were used.Ten pairs of B. incarnatus (10 males and 10 females) of 24 h old and of the same size were chosen from the main culture.To obtain the 24 h old adults, the culture medium was sieved to remove the adult beetles therein and the adults emerging in the following day were collected for the experiment.The test insects were introduced into small jute sacs containing 50 g of sound grains of faba bean and/or cowpea local varieties purchased from the local market.Sacs were placed over wire net stools and the fumigation chamber.Series of dilutions (10, 5, 1, 0.1, and 0.01%) of each type of garlic volatile oils were prepared using ethanol (96%) as a solvent, diluted to 10% with distilled water.Petri dishes (covered with muslin cloth fixed with a rubber band to avoid insects from falling in the fumigant) containing 2.5 ml of each concentration were placed beneath the jute sacs.Mating took place soon after emergence of the adults indicating that both sexes have fully developed sex organs.The number of eggs laid was counted every 24 h for a week (Abd El-Aziz, 2001).The temperature and RH were 28 to 35°C and 60 to 70%, respectively.
The experimental units were arranged in a completely randomized design with four replicates.Two controls treated with only the solvent or distilled water were included.

Ovicidal assay
An assay was carried out to study the ovicidal property of Chinese, Egyptian and Sudanese garlic volatile oils.Ovicidal test of the volatile oils was done by fumigating eggs with different concentrations.Adults of tested insects of 24 h old were allowed to lay their eggs on sound grains of local faba bean and/or cowpea varieties for 24 to 72 h.Seeds bearing 1 to 5 eggs were selected from the culture using a hand lens.A total of fifty eggs were tested per replicate, and selected seeds with their eggs were introduced into opened plastic cups (Ibrahim, 2000).
Series of dilutions (20, 10, 1, 2, 0.1, 0.05 and 0.01%) (V/V) of each cultivar of garlic oils were prepared using ethanol (96%) diluted to 10% using distilled water.5 ml of each concentration was placed in a glass Petri-dish and in the fumigation chambers.The exposure period was a week.The fumigated eggs were transferred to glass jars of 250 g; they were covered with muslin cloth, fixed with rubber bands and kept in an incubator (Gallenkamp) at 32°C and 60 to 70% RH.The emerged insects from the test eggs were counted every 24 h for 17 days.The eggs were considered dead if not hatched after 5 days before the end of the experiment (that is after 22 days).The experiment was kept at 28 to 35°C and 60 to 70% RH (Sabbour and Abd-El-Aziz, 2010).
The experimental units were arranged in a completely randomized design with four replicates.Two controls with only the solvent or distilled water were included.

Statistical analysis
The data collected were expressed as percentage and subjected to the analysis of variance based on the procedure described by Gomez and Gomez (1984), using SAS software for Windows version (2004).The median lethal doses (LD50) and median lethal times (LT50) were calculated following the probit analysis method of Finney (1971) using Minitab software version 13.3 (Minitab, 2000).

Insecticidal effect of garlic volatile oils on B. incarnatus (adults)
The analysis of the data showed that all three cultivars of garlic volatile oils induced greater mortality of test insects (male and female) compared to the control.

Toxicity assay
The results in Figures 1 to 6 indicated that all exposure periods (24 to 168 h) to garlic volatile oils caused significant mortality to the test insect (B.incarnatus) compared to the control.The Chinese garlic volatile oil was the most effective with initial rapid action causing 100% mortality against both sexes at the concentration of 5% or greater within 24 h; its two lowest concentrations (0.1 and 0.01%) reached at least over 80% in both sexes within 96 h (Figures 1 and 4).On the other hand, the Egyptian garlic volatile oil ranked second with initial rapid action that causes complete mortality of both sexes at the highest and medium concentrations (1, 5, and 10%) within 72 h; however, its two lower concentrations perform slightly better than the Chinese oil causing over 75% mortality in both sexes within 72 h (Figure 3).However, the Sudanese garlic volatile oil appears to have the slowest and least effective action; its two highest concentration caused over 80% mortality after 96 h, while its two lower concentrations (0.1 and 01%) caused over 75% mortality in both sexes after 144 h (Figures 4 to 5).Results showed that 24 h exposure had the highest mortality.However, the highest mortality with Egyptian cultivar was 50% against both sexes at 10%.While Sudanese cultivar induced 52.5% mean mortality against male and 47.5% against the female at 10% (Figure 1).Responses of both sexes were dose-related.In the male, the top four concentrations of the three oil types are significantly different from the control and the female response followed similar trend except in case of Chinese cultivar oil where all concentrations are significantly different from the control set.
However, the result of 48 h shows that the highest mortality was recorded with Chinese garlic volatile oil which caused 100% mortality in both sexes at 5 and 10%.The highest mortality with Egyptian cultivar was 77.5% in male at 10%.While Sudanese cultivar induced 60% mortality in male and 55% in female at 10% (Figure 2).On the other hand, the results of 72 h showed that the highest mortality was recorded with Chinese garlic volatile oil which caused 100% mortality in male at 1, 5 and 10% concentrations and in female at concentrations of 5 and 10%.The highest mortality caused by the Egyptian cultivar was 100% in male at concentrations of 5 and 10%.While Sudanese cultivar induced 82.5% mortality in both sex at a concentration of 10% (Figure 3).
The results of 96 h showed that the highest mortality was recorded with Chinese garlic volatile oil which caused 100% mortality in male at the concentration of 1, 5, and 10% and in female at concentrations of 5 and 10%.The Egyptian cultivar caused 100% mortality at all concentrations in both male and female.While Sudanese cultivar recorded 87.5% mortality in both sexes at concentration of 10% (Figure 4).Both Chinese and Egyptian garlic volatile oils caused 100% mortality in both male and female of the test insect at all concentrations after 144 h.While the Sudanese cultivar induced 100% mortality in both male and female at concentrations of 5 and10% (Figure 5).After 168 h of exposure, the statistical analysis of the data showed that the highest mortality was recorded with Chinese and Egyptian oils which caused 100% mortality in male and female at all concentrations.While Sudanese type induced 100% mortality in male at a concentrations of 0.01 and 100% female mortality at concentrations of 5 and 10% (Figure 6).
All treatments were significantly different from the control sets (Figures 1 to 6) and responses of both sexes      were dose-related.Based on the mortality percentage the efficacy of the three oils can be ordered as follows: Chinese garlic volatile oil > Egyptian garlic volatile oil > Sudanese garlic volatile oil.These results are in accordance with Abdalla (2003) who studied the insecticidal effects of Chinese garlic essential oil on some major storage pests and reported that the garlic oil vapor can penetrate the jute sacs to exert its action.However, Taha (2007) reported that Egyptian garlic oil induced 100% mortality in B. incarnatus and Callosobruchus maculatus after 24 h exposure.However, Taha (2007) and Ahmed and Abdelbagi (2014) reported that Egyptian garlic oil induced 100% mortality in faba bean beetle, B. incarnatus and cowpea beetle, C. maculatus after 24 h exposure.Abdel-Tawab (2016) studied the insecticidal activity of some terpenes extracts from essential oils of garlic and mint against eggs, larva, and pupae of Agrotis ipsilon.He found that they caused high reduction in egg deposition (67.4%) and egg hatchability (69.4%) at sublethal concentration.Further, garlic essential oil reduced egg laying capacity in Callosobruchus chinensis adults either by fumigation or contact method as they reduced hatching rate in fumigated eggs (Mukesh, 2014).Garlic volatile oil was reported to have insecticidal effect on test insect due to the inhibition of acetyl cholinesterase as reported by Bhatnagar and Pal (1974) and Singh and Singh (1996) or disruption of the cytochrome oxidase system of the mitochondria as reported by Dugravot et al. (2004).

Probit analysis
Data of various exposure periods showing uniform responses were subjected to probit analysis.From on the probit analysis, the 144 and 168 h exposure data for Egyptian oil and 168 h for Chinese oil at concentrations of 5 and 10% did not show a uniform response covering the entire dose range.The results are summarized subsequently.

Responses as related to dose
Dose-response data of male and female of B. incarnatus fumigated with oils from the three garlic cultivars are shown in Tables 1 and 2. The result of probit analysis indicated that both sexes of the test insects were sensitive to the vapor action of garlic oils as indicated by their low LD 50 values.The LD 50 values for 48 h exposure period to Chinese, Egyptian and Sudanese garlic oils were 0.05, 0.144 and 2.43% for males and 0.08, 0.56 and 6.1% for females following the same order.However, raising the exposure period to 96 h led to a significant reduction in the LD 50 values to 0.03, 0.006 and 3.77% for males and 0.06, 0.03, and 3.77% for females, correspondingly.The male and female LD 50 values of the Chinese oil reached a further much lower value after 144 h (0.007%).The slopes of the three oils ranged from 0.75 to 3.4 for the male and from 0.85 to 2.85 for female (Tables 1 and 2).Based on this, Chinese oil was more effective against the test insects as further indicated by its low LD 50 value with narrow fudicial limits, narrow LD 90 /LD 50 ratio and low relative potency value followed by Egyptian and Sudanese oils (Tables 1 and 2).
The population of the male and female of the test insects has relatively same homogeneity when tested against Chinese oil as indicated by their relatively similar slopes; but the population of the female was more homogenous compared to the male population tested against Egyptian oil as indicated by its high slope.However, the male population was relatively more homogenous compared to the female exposed to Sudanese oil as indicated by its high slope.The overall efficacy for both sexes followed the order: Chinese garlic volatile oil > Egyptian garlic volatile oil > Sudanese garlic volatile oil.The result showed that the female insects were more sensitive than males to Chinese oil; however, males are relatively more sensitive to Egyptian and Sudanese oils compared to females as indicated in their line slopes (Tables 1 and 2).This result agreed with that of Taha (2007) who stated that the population of B. incarnatus was more homogenous compared to C. maculatus with Egyptian garlic oil.

Responses as related to time
The mortality response which was uniformly distributed over the entire time range against the test insects was subjected to probit analysis.Based on this, the probit analysis was carried out at the concentrations of 0.01, 0.1, 1, 5 and 10% except for the data of 5 and 10% Chinese oil as it did not show a uniform response covering the entire dose range.Time-response of male and female of B. incarnatus fumigated with garlic volatile oils up to 168 h is shown in Tables 3 and 4. Results indicated that both sexes of the test insects were sensitive to the vapor action of the three garlic cultivars and their responses are time dependent as indicated by the LT 50 values ranging between 79.73 and 17.47 h for males and 64.03 and 18.95 h for females.The result generally indicated that the male of the test insects was more sensitive to the three garlic cultivars oils vapor compared to the female as indicated by its low LT 50 values, narrow fudicial limits and narrow LT 90 /LT 50 ratio (1.64-3.64 for male and 1.80-3.37 for female).The slopes of probit lines ranged from 0.17 to 0.44 for males and from 0.99 to 0.38 for females.The result indicated that the response of the female population was more homogenous to Chinese oil compared to the male population as indicated by the high slope of its probit line.However, both sexes have similar slopes when tested against Egyptian oil.The response of the males was more homogenous than that of the females to Sudanese  2 : Chi-square; DF: degrees of freedom; LD10: lethal dose that induces 10% mortality of a certain population; LD50: lethal dose that induces 50% mortality of a certain population; LD90: lethal dose that induces 90% mortality of a certain population; (-) the data are not homogeneous therefore not subjected to probit analysis.--  2 : Chi-square; DF: degrees of freedom; LD10: lethal dose that induces 10% mortality of a certain population; LD50: lethal dose that induces 50% mortality of a certain population; LD90: lethal dose that induces 90% mortality of a certain population; (-) the data are not homogeneous therefore not subjected to probit analysis. 2 : Chi-square; DF: degrees of freedom; LT10 ≡ Lethal time that induce 10% mortality of a certain population; LT50≡ Lethal time that induce 50% mortality of a certain population; LT90 ≡Lethal time that induce 90% mortality of a certain population; (-) the data are not homogeneous therefore not subjected to probit analysis.oil as indicated by the high slope of their probit line.Chisquare values were small indicating good execution of the experiments.Generally, the result showed that the male insects were more sensitive to the three oils compared to the female insects as indicated by their low line slopes (Tables 3 and 4).
The knockdown and recoveries among the insects fumigated with garlic essential oil were reported by Ahmed (1998), Abdalla (2003), Khiralla (2007) and Taha (2007).The significance of watching recoveries of treated insects is essential for better reading of the end-point mortality as evaluated by Beard (1949) and Winks (1982).The end-point mortality was defined by Beard (1949) as an observation period in which treated individuals either die or recover (that is, the poison has exerted its full toxic effect).The results of the current study indicated that no significant recoveries were observed in the different fumigation trails within the various exposure periods (7 days).These findings are in accordance with Abdalla (2003) who reported that the adult of C. maculatus did not recover after four days and Khiralla (2007) who stated that the adult of B. incarnatus did not recover after five days following the end of the exposure period.This may indicate that the Bruchid beetles were very sensitive to garlic oil vapor and the effects were long-lasting.

Oviposition inhibitory assay
A number of eggs laid per female are as shown in Figure 7. Results showed that fewer eggs were laid after a week of exposure to Chinese garlic volatile oil which recorded lowest number of eggs with a mean of 3.25 at the highest concentration 10%; while the highest numbers of eggs, with mean of 22.75 were observed at the lowest concentration of 0.01.The result was significantly different compared to the control set which recorded average number of eggs of 51.75 and 50.25, respectively.Also, there are significant differences among the different treatments.While in Egyptian oil the lowest number of eggs (4.5) was recorded at the highest concentration (10%) and the highest number of eggs (22.75) was observed at the lowest concentration (0.01%).Results showed that all the three oils induced a significant reduction in the number of eggs laid by exposed females compared to the controls and effects were dose-dependent (Figure 7).Generally, Chinese oil was the most effective followed by Egyptian and Sudanese oil.
Table 5 shows the log-dose of oviposition responses of B. incarnatus exposed to garlic oils.The result indicated that the test insect is more sensitive to Egyptian garlic oils compared to the Sudanese oil with LD 50s of 36.39% for the Sudanese garlic oil and 1.88×10This result agrees with Singh and Singh (1996) who reported that allyl disulfide, a component from garlic oil, decreased the fecundity and adult emergence of Rizopertha dominica.The results are also in accordance with Ho et al. (1996), who demonstrated that garlic oil is effective in reducing F1 progeny production in both Tribolium castaneum and Sitophilus zeamais, and is toxic to the eggs, adults, and larvae of T. castaneum.
The suppression in egg lying induced by garlic volatile oils may be due to their actions on some hormones or due to harmful effects on the reproductive system of the test insects or behavioral effects by obscuring the recognition of host.It was also observed that there was a decrease in egg laying with the increase in concentrations used.These findings agreed with Fagger (1999) who found that Usher Calotropis procera, Neem kernel Azadirachta indica and garlic A. sativum (oil and powder) have negative effects on the fecundity, hatchability and adult emergence of B. incarnatus (Boh.).

Ovicidal assay
The ovicidal effects of the three oils were measured by the hatchability of the fumigated eggs as displayed in Figure 8. Volatile oils of the three garlic cultivars had different effects on the eggs of B. incarnatus.The concentrations used were 0.01, 0.05, 0.1, 1, 2, 10 and 20%.The upper dose (20%) in all the three oils recorded 0 hatchability and caused significant ovicidal effect compared to the rest of the concentrations.The average hatchability of eggs recorded at the lowest concentration of 0.01% was 31, 32 and 34% for Chinese, Egyptian and Sudanese oils, respectively.Results showed that all the three oils induced a significant reduction in the hatchability of fumigated eggs compared to the controls (49.75%) and effects were dose-dependent (Figure 8).Generally, Chinese oil was the most effective followed by Egyptian and Sudanese oil.
Dose-response data of the fumigated eggs are shown in Table 6.The result of probit analysis confirms the sensitivity of fumigated eggs to the vapor action of the three garlic cultivars as indicated by their LD 50s values of 0.025, 0.034 and 0.21% for Chinese, Egyptian and Sudanese oil, respectively.Slopes of their probit lines are 0.46, 0.58 and 0.93 following the same order.The test eggs were more sensitive to Chinese oil as indicated by their low LD 50 value with narrow fudicial limits and narrow   2 : Chi-square; DF: degrees of freedom; LD10 ≡ Lethal dose that induce 10% mortality of a certain population; LD50≡ Lethal dose that induce 50% mortality of a certain population; LD90 ≡ Lethal dose that induce 90% mortality of a certain population.
LD 90 /LD 50 ratio followed by Egyptian oil and lastly Sudanese oil.The population of the test eggs was more homogenous in response to Sudanese oil as indicated by its high slope followed by Egyptian and Chinese oils.Chisquare values were small indicating good execution of the experiments.
Similar results were obtained by Neveu et al. (1997) who reported that garlic compounds may toughen the structure of the egg, preventing hatching in a way similar to that of dehydration.Mukesh (2014) claimed that the garlic essential oil significantly reduced the hatching rate in C. chinensis eggs when fumigated.He also indicated that the mean number of eggs hatched per 25 eggs was reduced to 20.33 (81.32%) and 5.16 (20.64%) when fumigated with lowest and highest concentration, respectively as compared to 22.33 (89.32) eggs hatched

Figure 1 .
Figure 1.The 24 h mortality of male and female of faba bean beetle Bruchidius incarnatus exposed to garlic volatile oils.

Figure 2 .
Figure 2. The 48 h mortality of male and female Bruchidius incarnatus exposed to garlic volatile oils.

Figure 3 .
Figure 3.The 72 h mortality of male and female Bruchidius incarnatus exposed to garlic volatile oils.

Figure 4 .
Figure 4.The 96 h mortality of male and female Bruchidius incarnatus exposed to garlic volatile oils.

Figure 5 .
Figure 5.The 144 h mortality of male and female Bruchidius incarnatus exposed to garlic volatile oils.

Figure 6 .
Figure 6.The 168 h mortality of male and female Bruchidius incarnatus exposed to garlic volatile oils.

Figure 7 .
Figure 7. Average number of eggs laid per female Bruchidius incarnatus exposed to garlic volatile oils for a week.
slopes of the inhibition regression line were steep and positive, indicating the homogeneity of the population or fast action of garlic oils.Chi-square values ranged from 0.44 to 12.45.

Figure 8 .
Figure 8. Hatchability of eggs of Bruchidius incarnatus exposed to garlic volatile oils.

Table 1 .
Dose responses of the male Bruchidius incarnatus exposed to garlic volatile oils at different exposure periods (h).

Table 2 .
Dose responses of the female Bruchidius incarnatus exposed to garlic volatile oils at different exposure periods (h).

Table 3 .
Time responses of the male Bruchidius incarnatus exposed to garlic volatile oils at different concentrations (%).

Table 3 .
Contd. 2 : Chi-square; DF: degrees of freedom; LT10 ≡ Lethal time that induce 10% mortality of a certain population; LT50≡ Lethal time that induce 50% mortality of a certain population; LT90 ≡Lethal time that induce 90% mortality of a certain population; (-) the data are not homogeneous therefore not subjected to probit analysis. 

Table 4 .
Time responses of the female Bruchidius incarnatus exposed to garlic volatile oils at different concentrations (%).

Table 5 .
Dose response of eggs of faba bean beetle Bruchidius incarnatus exposed to garlic volatile oils.