Biology, morphology, and varietal distribution of Saw-toothed grain beetle, Oryzaephilus surinamensis (L) on date palm dry and semi-dry dates at district: Khairpur, Sindh-Pakistan

The biology of saw-toothed grain beetle, O. surinamensis was assessed on two different dry and semi-dry dates (Aseel and Dadhi) varieties under laboratory conditions at Date Palm Research Institute, SALU-Khairpur during, 2019-20. The results showed that the overall mean of eggs was observed at (60.63±10.41) on both varieties and the eggs incubation period (4.09±0.50), hatching (82.08±4.42) % which was almost found higher on dry dates. The duration of various larval stages was also observed from 1 stage larvae to 4 stage (2.95 to 7.09) in days thus, the mortality and survival rate with % at (4.78 to 46.32) and (3.56 to 88.34) with the pupae period was (12.24). While as; an adult male (10.84) and female (15.91) days consumption and total life spawn (46.78) and (51.86) with a sex ratio (0.90) and (1.11) was remained fluctuated, thereof the maximum infestation on Dadhi dry fruit was observed (9.45±1.28), semi-dry (9.01±6.44) and Aseel dry fruit (5.65±0.73) and semi-dry dates (4.97±3.02), respectively. The result of the present work indicates that this insect pest frequently relay a negative effect on both types of fruits but the high peak of infestation observed during September and October. It was calculated that 3 and 4 larvae found a voracious feeder that gently hits dates fruit. The present investigation suggested that there is a vital need to introduce environment-friendly integrated pest management techniques and sufficient measures to secure this golden industry of this region.


Introduction
The sawtoothed grain beetle, Oryzaephilus surinamensis Linnaeus (Coleoptera: Silvanidae), is one of the keys stored grain pests that occur globally [1, 2]. Although the biology of O. surinamensis has been studied by many researchers [3] on various hosts, detailed studies on the biology of O. surinamensis on semi-dry and dry dates is not documented properly. This insect is highly sensitive to reach stored foods stuffs due to fruit fragrance and they make attempt to find their way to reach food availability [4], but in UAE, Tunisia, Saudi Arabia, Jordon, Egypt, Algeria, Sudan, and Pakistan saw-toothed grain beetle is a most important pest of stored dates [5], but dates are widely attacked by O. surinamensis both at field conditioning and stock places. The larvae of this pest insect create quality and quantity degradation; reduce the germination power of the seed, and lowering the date's nutritional value and dates fruit are attacked by O. surinamensis both at the field and stock stuff [6]. The larval infestation of O. surinamensis severely reduces the essential amino acids, lipids, polar, and no polar lipids, phospholipids, methionine, galactolipids, lysine, and isoleucine [7]. The beetle distribution is affected by many factors such as processing practices, availability of food, the interaction between species and temperature conditions but frequently found and serve best in pantry areas [8].
The O. surinamensis are small-sized insects and at storage places, they hide due to this nature it is difficult to control them through the application of insecticides [9]. There are three genera of Oryzaephilus and all these genera possess a series of teeth like appearance behind the eyes projection [10]. Female and male are nearly morphologically similar but the male has a posterior margin on hind trochanter and medially spine-like projection and margin at the upper hind femur [11]. The saw-toothed grain beetles are almost omnivorous in their feeding behavior. It is necessary to update all feeding habits in response to introducing sustainable and suitable control measures to reduce infestation attacks [12]. These pests also cause disease problems and retard the growth of date palm trees [13]. Many scholars used their stamina to perform the study on the profit of dates from its seeds or fruits, antifungal, hepato-protective activities, antiviral, and antioxidant [14]. The present research study shows the biological, morphological investigation of the saw-toothed grain beetle on Aseel and Dadhi varieties of stored dried and semi dries dates commodities. In District; Khairpur Mir's about 20% dates fruit is destroyed due to insufficient methods and poor management here only two research institutes are operational, date palm research institute at Kot Diji, and next is at Shah Abdul Latif University Khairpur. It is of paramount importance to know about the biology and life table parameters of this pest. Prevention of losses in stored products due to insect pests is of paramount importance. Hence; the present investigations on biology and morphology of this insect on two stored commodities are informative and crucial for developing management practices. By characterizing host-associated genetic variation in this cosmopolitan insect we attempted to obtain basic information with the potential to be used for future strategies.

Collection of O. surinamensis
For the proper biological study, two pestinfested dates varieties namely; T1= Dadhi, T2= Aseel (semi-dry dates), T3= Dadhi and T4= Aseel (dry dates) were collected from the stores, houses, shops, homes and mostly from Khajoor and Chuhara mandy of district: Khairpur for the purpose to conduct the biology and morphology parameters of this pest during the consequent years from May 2019 to April 2020. After collection infested dates were poured into plastic jars and brought under laboratory conditions for culture maintenance. The laboratory research work was carried out at Date Palm Research Institute (DPRI), Shah Abdul Latif University, Khairpur during, 2019-20.

Mass-rearing
The infested dates placed in plastic jars containing 1.5 kg capacities were used and jars kept incubated at room temperature 25±2°C and 60-70%. During the eggs hatching process, the focus was taken from egg to adult stages such as; incubation period, female fecundity, egg fertility, larval survival rate, larval developmental stages, adult longevity, the sex ratio of males and females were observed. The couples were identified and separated by using of stereomicroscope under laboratory conditions and placed in 18cm x 12 plastic cylindrical dimension containing Aseel and Dadhi dry and semi-dry verities of dates as a source of food and for female oviposition media covered with the muslin cloth with rubber band secured it to provide restriction for external insects and avoid the escape of trapped insects. For the proper observations, the jars were arranged in row manner. Again for authentic conformation observation was replicated five times. When female laid eggs inside the plastic jars which were taken by the source of camel hairbrush and placed into separate jars for hatching and observation of different life stages. Mortality and survival of different stages of the pest formulated by using the following formula: The rate of mortality= No. of dead insects/Total no. of insects x 100 Survival percentage= No. of survival insects/Total no. of insects x 100 Again for the population fluctuation on dry and semi-dry date fruits were collected from godowns at Khairpur Khajoor mandi and brought under laboratory conditions at a fortnightly interval basis and the sawtoothed population was counted by the help of magnifying glasses. The purpose was to find out which variety is severely affected than others and to determine the choice and no-choice of varieties. For this purpose, the most resistant and susceptible variety was highlighted in this research work besides, the most divesting stage was kept under observation.

Morphological attributions
During laboratory conditions, the attention was taken on all morphological attributions of the saw-toothed grain beetle, O. surinamensis such as; size and shape of eggs, the morphology of larvae with changing coloration, an adults morphological variation weight, and size, etc.

Statistical analysis
The analysis of variance was made through the randomized complete block design of all biological parameters and means were separated through (LSD) test at 5% probability to measure up the different treatments through the help of student package statistics software 8.1 versions, USA.  (Table 3). The overall mean of population fluctuation on both varieties was also observed (9.01 to 9.45) and (4.97 to 5.65), respectively. When statistical data were analyzed that shows the significant difference among all stages of pest and least significant differences were found varied from each other.

Population fluctuation of Saw-toothed grain beetle on (dry and semi-dry dates fruits on Dadhi and Aseel varieties
When the semi-dry dates were reached at the Khajoor and Chuhara mandi, district: Khairpur during the season, 2019-20. In the month of first May, samples of about 100 semi-dry and dry dates of two different varieties were purchased from the stored godowns of dates for checking the population variation on a fortnightly interval basis throughout the year. Thus, the peak population was observed from September to October and the least population was observed from January to February. Among both varieties, the Dadhi variety found most vulnerable with the saw-toothed grain beetle on semi-dry dates whereas, the Aseel variety was found less affected with pest, O. surinamensis on semi-dry and dry dates of the market. The analysis of variance shows the nonsignificant difference every month started from May 2019 to April 2020 on semi-dry dates at (DF=1, 23; F=1. 154; P=0.2270), respectively (Fig. 1). Whereas; the analysis of variance shows the significant difference among these months fortnightly interval basis data (DF= 23, 1; F= 4.97; P=0.0001) as described in under given (Fig. 2), respectively.

Morphological description of sawtoothed grain beetle
Female of the O. surinamensis, laid fresh eggs in a single manner which found whitish in color and oval in shape, as time passed those smoothly became dark brownish as found near to hatching stage into larval stages (Fig. 3). The first stage larvae were observed whitish and somewhat moved very slowly around the food masses thus, the second stage of larvae was observed whitish but anteriorly contained brownish pigmentation and posteriorly pointed body. At this stage, the larvae gradually moved for food purposes likewise, the third stage of larvae contained the elongated body, yellowish to whitish. In this stage, the jointed appendages found visible in the thoracic region. At this stage, the larvae found posterior blunt and anteriorly head with antennae and have more need of food for their survival. The fourth stage larvae observed more active as compared to other stages and severely infested the date fruits. This stage of larva found brownish and anteriorly much darker brown and at head region contained paired antennae and eyespots at the head region. Pupae color is found much darker and brown with a constricted body. Pupae are also found with protected cocoon layers. Like the passing of a few days, the anterior silt-like appearance occurred and the new adult emerged. Adults were dark brown an active insect, slender shaped, having 2 to 3 mm in size, with characteristic teeth like running down the side of the prothorax with smaller eyes with broader and triangular-shaped head. A tooth on the femur of the hind legs makes differentiation in males from the female. A paired beadle shaped antennae used for certain behavioral activities, further as described as in hand made diagrams as given as under.  who documented biology, morphology, and taxonomy of lesser date moth on dates at the same district on two different temperatures under laboratory conditions. Keeping in view, it is firmly needed to know about the rate of losses during the developmental stages of the pest insect and introduce the crucial and informative management strategies to minimize the losses from the vigorous pest insects during storage periods. In present findings, it was positively found the infestation attacks on both varieties throughout the year but significant development prolongation and shortening duration found with low and high fluctuations. In present scientific-based researches investigating the biology of insects on the fruit of two different varieties were observed and attention was given their severe losses. In this context, basic knowledge and sustainable management practices are needed to minimize the storage product losses.

Conclusion and recommendations
The biological study of O. surinamensis on dates was performed the first time in this area and focus was taken on Dadhi and Aseel varieties during present work. Phoenix dactylifera locally called Khajoor and dates trees are the main source of the live hood of the district: Khairpur, it was frequently concluded that this insect pest is widely harming dry and semi-dry dates fruit of Aseel and Dadhi verities throughout the year but mostly at stock places. Aseel dates are the most economical and valuable known as queen variety of this area. In present research findings, the fruit of Dadhi and Aseel variety (dry and semi-dry) were observed with less infestation in the May month and with high infestation during October. Similarly, the minimum pest population was observed on dry dates during May and maximum in September. The present work is recommended that will be supportive and informative to know about this pest insect and its O. surinamensis harmful hazards.