Susceptibility of some dry date cultivars to infestation by Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae).

Susceptibility of eight date cultivars (namely Barhi, Barni Al Madina, Deglet Noor, Rushodia, Sukari, Ajwa, Mabroom and Nabtat Ali) to an attack by saw-toothed grain beetle Oryzaephilus surinamensis (L.), was estimated under laboratory conditions. Physical characteristics (texture, shapes and colour) and chemical constituents (total amount soluble solid, sugar, moisture, nitrogen, lipids, and fatty acid and percentage of ash) of the tested date cultivars were recorded. The laboratory evaluation indicated that the most preferable cultivar to eggs deposition and attack adults of the saw- toothed grain beetle was Sukari while the most resistance cultivars were Deglet Noor and Ajwa. The growth index of immature stages increased in the most susceptible cultivars (Sukari) but decreased in the resistance one (Deglet Noor and Ajwa). On the other hand the susceptible index indicated that three cultivars as Sukari, Barhi, and Rushodia were the most susceptible cultivars compared to others. There was a positive and significant correlation between moisture contents and the susceptible index while ash content elicited negative and highly significant correlation with susceptible index. During six months of storage, the highest rate of weight loss of tested date cultivars, that caused by infestation of saw-toothed grain beetle, was for Barhi followed by Barni Al Madina, Rushodia, and Sukari.


INTRODUCTION
Few plant species have developed into an agricultural crop so closely connected with human life as has the date palm. The date palm (Phoenix dactylifera L.) yields a variety of products for use in agricultural production and for domestic utensils of human. The world date palm cultivation is concentrated mostly in the Near East and Africa, favored by the most suitable dry sub-tropical and high temperature climate prevailing in these regions.
The dates are the important product of palm which used directly as fresh or dry in different countries, especially in the Arab region. During storage, the dry dates are attacked by numerous pests which caused to loss its' quality and quantity, as Oryzaephilus surinamensis, Tribolium castaneum (Herbest), Ephestia (Cadra) cautella (Walker), Tribolium confusum (Jacquelin du val), Plodia interpunctella (Hubner), Carpophilus hemipterus (L.) and Lasioderma serricorne (F.) [1]. Recently, many researches were carried out to improve some of physical and chemical properties of palm tree, by trying to overcome infestation of different pests that might caused to decrease its quality and quantity. The presence or absence of various external or internal factors in different date cultivars makes them to be more resistance or sensitive to insect infestation. The fact that insects may be prevented from feeding by certain chemicals is the potential value in crop protection [2].
The aim of the present study was to measure the susceptibility of date cultivars to O. surinamensis infestation, and determination of the rate of loss during storage.

Rearing O. surinamensis
Infested dates were collected from storehouse at plastic containers and carefully investigated to isolate adult stage (female and male) of saw-toothed grain beetle by using stereomicroscope according to description of Al-Bidawy, A.E and El-Derham, Y.N. [1]. After that five pairs of males and females beetles were put on plastic container (8x12 cm 2 ) which contains 150g of disinfested dates and then tight close it. The rearing containers were placed in incubators at 27±1ºC and 65 ±5% rh for three weeks. The infested dates were isolated in another plastic container and repeated that till obtain the pure 3 th generation of saw-toothed grain beetle to start laboratory experiment.

Determination of the Infestation by O. surinamensis
The experiments were carried out to determine the susceptibility of different date cultivars according to epiphylaxis and endophylaxis factors as follows:

Epiphylaxis factors
It was evaluated through oviposition preference (non choice test) and t to adult stage (choice test) of saw conducted:

Non-choice test (oviposition preference)
Five pairs of males and virgin females were released in Petri one type of tested dates cultivars. It was investigated in daily basis to determine the number of deposited eggs for up to fifteen days. Each experiment was replicated five times.

Choice test
The experiment was carried out at ar diameter), divided to eight parts by plastic partitions and left its center open to facilitate locomotion of released beetle between tested cultivars (Fig cultivars data were introduced in each partition of arena, released 10 pairs of adult stages of saw-toothed grain beetles and tight closed it. After seven days, each one was investigated to count number of beetle attacked to calculate preferable date's cultivars to adult stage tested beetle.  Five pairs of males and virgin females were released in Petri-dish (9 cm.) which contained one type of tested dates cultivars. It was investigated in daily basis to determine the number of deposited eggs for up to fifteen days. Each experiment was replicated five times.
The experiment was carried out at arena apparatus which made of plastic plate (20 diameter), divided to eight parts by plastic partitions and left its center open to facilitate locomotion of released beetle between tested cultivars (Fig. 1). Equal weight of tested ntroduced in each partition of arena, released 10 pairs of adult stages of toothed grain beetles and tight closed it. After seven days, each one was investigated to count number of beetle attacked to calculate preferable date's cultivars to adult stage

Susceptibility of Different Date's Cultivars to
The experiments were carried out to determine the susceptibility of different date cultivars he attractive cultivars toothed grain beetle, the following experiments were which contained one type of tested dates cultivars. It was investigated in daily basis to determine the number of deposited eggs for up to fifteen days. Each experiment was replicated five times.
ena apparatus which made of plastic plate (20 cm in diameter), divided to eight parts by plastic partitions and left its center open to facilitate 1). Equal weight of tested ntroduced in each partition of arena, released 10 pairs of adult stages of toothed grain beetles and tight closed it. After seven days, each one was investigated to count number of beetle attacked to calculate preferable date's cultivars to adult stage of

Endophylaxis factors
In order to evaluate endophylaxis factors the following experiments were carried out:

Susceptibility index
Fifty grams of each tested dry date varieties was taken separately in a plastic container (500 ml) and 5 pairs of males and virgin females of saw-toothed beetles were released inside the container for ten days. After that the beetle were removed and the test was follow up till new generation is obtained [5]. Calculate the susceptible index according to Dobie [6] and Sarin et al. [7] as follows: = total number of released weevil. D = duration needed to release 50% of new generation.
Experiment was carried out at incubator (27±1ºC and 65±5%) and each one replicated five times.

Growth index of immature stages (larvae and pupae)
Ten pairs of virgin males and females were released in Petri dish (9 cm.) which contained 2g flour and acted as eggs deposition substrate. Daily, the flour was investigated to obtained 1 st instars larvae. The obtained larvae were released on 10g of the tested date cultivar which put at plastic container (500ml). The tested container were tight closed and kept at incubator. Growth index of immature stages was calculated according to equation of Al-Dosari et al. [8] as follows: Where, D = the total development time. N = Larvae that become adult (%).

Effect of Saw-Toothed Grain Beetle Infestation on the Weight Loss of Stored Date Cultivar
The test was carried out by using separately 100 g of tested date cultivars at sack clothes , placed inside plastic container (500 ml.) and then released 10 pairs of virgin saw-toothed beetles. After six month, the dates were weighted to calculate the weight loss according to Metwaly, et al. [9] equations as follows: Where; ܹ = real weight loss due to infestation. ܹ݁ = weight of date lost after six month of infestation. ܹܿ = weight loss at the control (without infestation ‫ܫܹ‬ = weight of dater before infestation.).

Estimation of the Physical and Chemical Properties of Tested Date Cultivars
The results indicated to the variation in physical and chemical properties of tested date cultivar which might lead to variation in its susceptibility. It was recorded as following:

The physical characters
The Fig. 2 described that there were variations between tested dates in texture, co shape. The texture of Barhi, Barni Al Madina but Ajwa, Mabroom and Deglet Noor were curly, little and much wrinkle.

American Journal of Experimental Agriculture, 3(3):
= real weight loss due to infestation. = weight of date lost after six month of infestation. = weight loss at the control (without infestation = weight of dater before infestation.).

RESULTS AND DISCUSSIONS the Physical and Chemical Properties of Tested Date
The results indicated to the variation in physical and chemical properties of tested date which might lead to variation in its susceptibility. It was recorded as following: The physical characters 2 described that there were variations between tested dates in texture, co Barhi, Barni Al Madina, Rushodia, Sukari, and Nabtat Ali were smooth, but Ajwa, Mabroom and Deglet Noor were curly, little and much wrinkle. The results indicated to the variation in physical and chemical properties of tested date which might lead to variation in its susceptibility. It was recorded as following:-

Fig. 2. Photo shows the physical properties (texture, colour, shape and size) of
On the other hand, the colours were ranged between light brown to dark brown for Barhi, Deglet Noor, Rushodia, Barni Al Madina, Sukari and Mabroom, but Ajwa and Nabtat Ali were Maroon and dark colour, respectively. Generally, the shapes were ranged betwee oval to elongate.
These observations agree with Hussein et al. date cultivars and recorded the variat

The chemical composition
The results indicated that there was significant (p of different date cultivars as recorded in

Photo shows the physical properties (texture, colour, shape and size) of different varieties of date
On the other hand, the colours were ranged between light brown to dark brown for Barhi, Deglet Noor, Rushodia, Barni Al Madina, Sukari and Mabroom, but Ajwa and Nabtat Ali were Maroon and dark colour, respectively. Generally, the shapes were ranged betwee ions agree with Hussein et al. [10] who studied physical characters of six date cultivars and recorded the variations in size, colour, shape and weight among its.

The chemical composition
The results indicated that there was significant (p ≤ 0.05) variation in chemicals constituents of different date cultivars as recorded in Table (1). Barhi cultivar was recorded the highest ≤ 0.05 or 0.01) in total soluble solids (76.8%), and sugar content (68.98%) compare to Mabroom, Rushodia, Nabtat Ali and Sukari which were recorded the lowest one, ranged between 70 to 50 % respectively. While the acidity percentage of the most tested date cultivars were closely nearly to each other, except that Deglet Noor and Sukari were recorded significant (p ≥ 0.05) low percentage (0.156%). In addition to the highest percentage of moisture content in date cultivar was recorded to Rushodia (15.67%) while the lowest one was Barni Al Madina (11.38%).

651-663, 2013
656 Photo shows the physical properties (texture, colour, shape and size) of the On the other hand, the colours were ranged between light brown to dark brown for Barhi, Deglet Noor, Rushodia, Barni Al Madina, Sukari and Mabroom, but Ajwa and Nabtat Ali were Maroon and dark colour, respectively. Generally, the shapes were ranged between who studied physical characters of six weight among its. Table (1). Barhi cultivar was recorded the highest ds (76.8%), and sugar content (68.98%) compare to Mabroom, Rushodia, Nabtat Ali and Sukari which were recorded the lowest one, ranged between 70 to 50 % respectively. While the acidity percentage of the ch other, except that Deglet Noor and 0.05) low percentage (0.156%). In addition to the highest percentage of moisture content in date cultivar was recorded to Rushodia (15.67%)

Means with the same letters have no significant difference
Nitrogen, Lipids, Fiber and ash percentages in tested date cultivars were recorded the high significantly variation (p ≤ 0.01or 0.05) in Ajwa, being 5.45, 0.38, 11.25 and 3.3% while Barhi was recorded the lowest percentage of nitrogen, lipids and fibers, being 1.42, 0.13 and 4.23% and Mabroom was recorded the lowest percentages of ash content, reaching to 2.06%.
The obtained results agree with [11] who mentioned that there are significant variations in chemical composition of eight date cultivars. Also, many researches confirmed that there are variations in physical characters and chemical constituents among various date cultivars. [11,12,13]

Laboratory Evaluation the Susceptibility of Different Dates Cultivars to Infestation by O. surinamensis
From previous results, it is clear that each date cultivar has physical and chemical characters which might effect on its' susceptibility toward the saw-toothed grain beetles. The present work was carried out in order to evaluate such characters under laboratory conditions.
Epiphylaxis factors (external protection agencies) were determined through ovipositional preferences and attractive of adult stages (choice test); while endophylaxis factors (internal protection agencies) were determined through measurement the susceptible index and growth index. The effect of these factors was determined as follows:

Ovipositional preferences
Results presented in Table (2) show that the role of physical characters (external protection agencies) of different date cultivars in selection of the saw-toothed grain beetles to the site oviposition. The data indicated that there was highly significant difference (P ≤ 0.01) among the tested date cultivar. Sukari recorded the highest numbers of deposited eggs, being 61.67±1.7 eggs/five females/two weeks compared to Ajwa that recorded the lowest numbers of deposited eggs, reaching 2.67±0.9 eggs/five females/two weeks. The moderate susceptible one was Barhi, being 49.3 ± 3.2 eggs/five females/ two weeks while moderate resistance one was Mabroom cultivar, being 14±0.01 eggs/five females/two weeks.

Attractive of adult stage (choice test)
Results shown in Table (3) indicated that there was an odd among tested date cultivars in the percentage of adult attack. The most preferable date cultivars were Rushodia and Sukari, reaching the attraction percentage to 28.75 and 22.5% while Al Ajwa and Deglet Noor were the least desirable cultivars, reaching to 3.1%. From the obtained results it is clear that the physical characters like as colour, texture, size, etc. may play a role in orientation of adult stage to attack certain cultivars more than others as mentioned by Sihacek and Murphy [14].

Measurement of growth index of immature stages
Results in Table (4) indicated that there was highly significant (P ≤ 0.01) variation in growth index of immature stages of Saw-toothed grain beetle among the most of tested date cultivars. The growth index of immature stage was increase with increase the percentage of larval development within short time, vise verse. The most preferable date cultivar was recorded to Sukari followed by Barhi and Rushodia, reaching 4.16±0.03, 3.22±3.7 and 3.22±0.08 larva to adult /day respectively. While Deglet Noor and Ajwa obstructed the growth of larvae, so it was recorded the lowest growth index, being 0.48±0.02 and 0.94±0.01 larvae to adult/day, respectively.

Relation between susceptibility index and chemical constituent of date cultivars
The susceptibility of tested cultivars toward Saw-toothed beetle affected by chemical constituents, as depicted in Table (6). The susceptible index of tested cultivar was insignificantly (P>0.05) increased with decreased total sugar, acidity, lipids, fibers and nitrogen content (correlation value ranged between -0.25 and -0.62) while ash content was highly significantly affected on SI (r= -0.833). On the other side, there was a positive correlation between SI and water content of tested cultivars (r= +0.71), which indicate that the susceptibility of date cultivars is increased with increasing water content. From the obtained results could be concluded that chemical composition of tested cultivars affected on its susceptibility toward Saw-toothed beetle. These observations agree with [8] who recorded that the rate of eggs deposition, longevity of larvae and pupae of O. surinamensis affected by date cultivars. [14] recorded the variations in growth rate of P.
interpunctella at different cereal cultivars and related that to the variation in the value of nutrition contents.
On the other hand there are many authors studied effects of others plant cultivars on growth index of larvae and deposited eggs of O. surinamensis as [15] on five wheat cultivars and [16] on corn cultivars.

Study the Weight Loss of Stored Date Cultivar Due to O. surinamensis Infestation
The dates in Table (7) cleared that there were gradual loss of date weight due to attack the saw-toothed beetles. The highest percentages of weight loss were recorded to Barhi follow by Barni Al Madina, Rushodia and Sukari, ranged between 62.7 to 43.7% after six months. While the least weight loss was recorded to Deglet Noor and Ajwa, reaching to 11.6 and 21.5% after six months.  Wheatley [5] while working with other date cultivars who found that the Al Mahlawi cultivar had lost weight when exposed to O. surinamensis after 90 days of storage. Generally, the heavy infestation by insects in storage leads to increase the temperature degree which leads to increase loss of water content of stored materials and that lead to increase moisture and agglomeration of stored materials [17].

CONCLUSION
Aims of the present study measure the susceptibility of different date cultivars to infestation by O. surinamensis. The obtained results can be summarized as following: 1-The most susceptible cultivars were Sukari, Rushodia and Barhi. 2-There were positive correlation between the susceptibility index of tested cultivars and water content.
3-There were negative correlation between the susceptibility index of tested cultivars and Ash.

4-Infestation by O. surinamensis caused loss in quality and quantity of Barhi, Barni Al
Madina, Rushodia and Sukari during storage.