The effect of some different watermelon varieties on Melon Weevil Acythopeus curvirostris persicus population in Sulaimani Governorate

This study was conducted during April–August 2020, in an open field at Qularasi Research Station, Sulaimani, Kurdistan Region-Iraq, to determine the effect of watermelon variety on population density of melon weevil Actopeus curvirostris persicus. Results showed that the melon weevil has distinct daily activities. Two activity peaks were observed in late-June and early-July. The general mean of population density on June 28 was (1.611) weevil /week, which was less than July 4 (2.583) weevils/week, the lowest number of weevils were observed at 7:00 am on the variety (Qamar F1) with (0.789) weevil/hour. Whereas, the highest number of weevil was observed at 7:00 am on Crimson Sweet variety with (1.525) weevil/hour. However, at 11:00 am, all varieties (Charleston Gray, Topgun F1, king Charles, Qamar F1, and Crimson Sweet) recorded the highest number of weevil (4.571, 4.238, 4.048, 4.048 and 1.524) weevil/hour, respectively. The population densities of melon weevil were high on all watermelon varieties in the last week of June and first week of July. Temperature, relative humidity, and wind speed correlations showed a great effect on melon weevil population density during the study period. The correlation was negative significant (-0.208) for temperature in the variety Crimson Sweet, while it was positive significant in the other varieties of Charleston Gray, Topgun F1, and King Charles with (0.165, 0.183 and 0.147), respectively. The correlation was positive significantly for relative humidity in the variety Crimson Sweet) with (0.165) however, it was negative significant for wind speed in the variety Topgun F1 with (0.137). on the adult melon weevil reaction to varieties Sweet, Charleston Top gun King


INTRODUCTION
Watermelon Citrullus lanatus Thumb belongs to the Cucurbitaceae family which includes about 118 genera and 825 species (Dane and Liu, 2007), other crops of importance in this family include cucumber Cucumis sativus L., melons (C. melo L.), and squash (Cucurbita moschata Duch). The crop is a warm, long-season, trailing, prostrate, annual which has monoecious and/or andromonoecious sexuality (Boualem et al., 2016). Now, it is found in Tropical and Subtropical climates worldwide Schippers, 2000, this crop has been reportedly cultivated for a long time in Africa, in the Middle East and Egypt Gichimu et al., 2009. The melon weevil Acytopeus curvirostris persicus Thompson (Coleoptera: Curculionidae) is one of the most important pests of watermelon fruits and flowers in Saudi Arabia (Al-Ahmed, 2010). According to Dane and Liu, 2007, the fruit reportedly contains 95% of water, carbohydrate 5 mg, calcium 8 mg, vitamins 64 mg, phosphorous 9 mg, and ascorbic acid 8 mg per 100g of edible portion. It has immense benefits to man due to its high nutritive (richness in vitamins A, C, potassium, magnesium and iron), therapeutic (possession of diverse antioxidants, diuretic, cancer and hypertension reducing properties) and economic (income generation and valuable contribution to national gross domestic product) values 5-7. Watermelon contain a citrulline gets converted to Larginine, an essential amino acid that helps treat muscle soreness (Abu-Nasser and Abu-Naser, 2018).watermelon crops production in Iraq reached 326,000 tones in 2009, while the production reached 31050 tones in sulaimani/Kurdistan region (FAO 2012). Several problems face watermelon production just from the seedling stage up to harvest such as environmental conditions, diseases, pests, mites, weeds…etc. From an insect point of view, several species of insects attack watermelon plants, for instance, the melon fly (Myiopardalis pardalina Big.) is a dangerous pest of melons, watermelon, pumpkin, and cucumber all over the world (Toreniyazov et al., 2010). Melon weevil, A. curvirostris persicus Thompson (Coleoptera: Curculionidae), is one of the most important pests of melons that is spread in the Middle East countries (Mohammad pour et al., 2013), the species was first described in 1874 and has been mentioned only twice as a crop pest, it was recorded in Egypt as emerging from watermelon fruits in large numbers (Adair, 1917). The larvae feed on the developing seeds inside the fruit and pupate there in cocoons constructed of small pellets consisting of dried fruit pulp mixed with a fluid, believed to be produced in the Malpighian tubules, that is squeezed from the anus. The preoviposition period lasts about four days, and the adults survive for several weeks. There are three generations per year, or four generations if weather conditions are favorable. (Rivnay, 1960).
This weevil selects cucumber (Cucumis sativus L.) fruit, 5-8 cm in diameter, which has a thin, succulent, skin for egg-laying, and after 1 to 2 days of tunneling in fruit and feeding, it begins to lay eggs, a curvirostris persicus subspecies usually lays a single egg in each cavity, the duration of egglaying is about 3-4 min. Oviposition location AA foam that is countable and a maximum of 38 eggs occurs in each oviposition holes used for feeding are not countable due to high numbers (Mohammadpour et al., 2015). We also studied the occurrence of melon weevil A.curvirostris persicus Thompson in different varieties of watermelon combined with climatic factors in Qularasi / Sulaimani Governorate.

MATERIALS AND METHODS
This study was conducted during April-August within the growing season 2020, in an open field at Qularasi Research Station, Sulaimani, Kurdistan Region-Iraq. Qularasi is located on the east of Sulaimani, 10 km from the city center, with 35°61'07.09"N, 45°36'63.92"E and 840 m above mean sea level. The climate of the study area is classified as a semi-arid region, hot and dry in summer and cold in winter (Najmaddin et al., 2017).

Field experiment
Qulqrasi open field, with 19.25 m length, 17.5 m width, with a total area of 336.87M 2 was used in the research, it was divided into three lines, then applied with 3 replications; each replicate was divided into 5 treatments (plots), a total number of 15 plots, each with 3.75 ×1.5 m were used with 2.5 m distance between the plots, 4 m between the replicates, the distance between the seedlings within a plot was 0.75 m and the total number of plants in each plot was 10 watermelon plants, the watermelon varieties (Crimson Sweet, Charleston Gray , Topgun F1, King Charles, Qamar F1) seeds were obtained from the local market, sowing of the seedlings was carried out in the plastic house on April 3, 2020, after then , the emerged seedlings were planted in Qularasi open field, the soil was already prepared .

The Experimental design
A randomized complete block design (RCBD) was applied with 3 blocks; each block was divided into five varieties with a total number of 15 plots.

Statistical analyses
The results were analyzed using a randomized complete block design (RCBD) and means were compared by Duncan's multiple range test (P≤0.05), using statistical software ready XL-STAT.7. S.2 with a simple correlation analysis (Addinsoft, 2005).

Study of the collected adults
After flowering, all watermelon varieties (Crimson Sweet, Charleston Gray, Topgun F1, King Charles, Qamar F1) grown in the Qularaisi location were studied for one week (June 28-July 4, 2020) every day (from 7:00 AM to 6:00 PM), in which the adults of melon weevil were collected by hand, put in plastic bags and labeled on weekly basis during the research period. The population density of the adult insects was studied on the different plant parts of the watermelon crop (leaves and stems), to record the number of adults on watermelon plants of the five varieties. The records (number of adult/plant) were repeated on 10 plants for each replicate and each variety separately.
The population density of the watermelon weevil was studied on the five varieties during the insect activity season of 2021, by recording the numbers of adults for the period from April to August and by recording the number of adults on one plant to find out the average number of adults/plant by recording the number of adults on 10 plants in the field for each variety, each replication, and each reading date separately.
Population density of adults was also recorded at the different hours of the day, starting from 7:00 AM until 6:00 PM. The readings included 12 consecutive hours from morning until evening, during seven days. The population densities were also studied on the different parts of the plants of the cultivars, which were the leaves and stems. The adults who existed on each variety were collected separately. The date of collecting the insect specimens was manually caught and placed inside vials, all the necessary and important information and data related to this experiment were recorded to be used in conducting the statistical analyses.

RESULTS AND DISCUSSION
The results shown in Table 1 indicate that the highest population density of the adults of melon weevil 2.194 was recorded on June 28 on the watermelon variety King Charles. While the highest population density of the adults 2.583 was recorded on the variety Topgun F1 on July 4. On the other hand, the results in the same table show that the lowest population density of adults 1.861 was recorded on June 28 on the variety Charleston Gray, meanwhile, and the lowest population density 0.833 of the adults was recorded on July 4 on the variety Crimson Sweet. There were significant differences among sampling data in the number of adults. The general means of population density for June 28 was 1.611 weevil/week, this was less than that of July 4 which was 2.583 weevil/week. These results agree with (Azzam Al-Ahmed. 2000) that was worked on population density of melon weevil (Acytopeus curvirostris persicus.) on the plant parts (leaves, stems and flowers). The data presented in Table 2 illustrate that the adults population density of melon weevil varied over the five cultivars of the studied crop. It was found that the highest average density of weevil adults which is 1.619 was recorded at 9.00 am on the first variety Crimson Sweet, while the lowest average density of the watermelon weevil adult was 0.667 recorded at 3:00 and 4:00 pm.

Table (1): The appearance of the adult melon weevil (Acytopeus curvirostris persicus.) on the plant parts (leaves, stems and flowers) for a week (June 28-July 4, 2020) in the Qularasi/Sulaymaniyah
It was also found that the highest population density of weevil adult was 4.571, which was recorded at 11.00 am on the variety Charleston Gray, while the lowest average density of the adult of melon weevil was 0.579 recorded at 6.00 pm .
Thus, it became clear that the highest population density of weevil adults was 4.571, which was recorded at 2.00 pm on the variety Topgun F1, while the lowest average density of the adult was 0.619, recorded at 4.00 pm. These results agree with (Mohammadpour et al., 2013)) who declared that the adult of melon weevil has distinct daily activity. Two activity peaks were observed at 7:00-9:00 am and 5:00-7:00 pm. Maximum flight activity was observed in the afternoon (14:00 hour) in field condition. Table (3) shows the effect of a variety of watermelon on the total weekly adult melon weevil (A. curvirostris persicus) at Qularasi location during 2020 with the simple correlation between adult/variety and climatic factors .
It was revealed that the population density of adults of melon weevil on the five watermelon varieties in the Qularaisi location was correlated with temperatures, relative humidity, and wind.
The results showed that the infestation started in the last week of June and gradually increased slightly during the next month, as was noted in the data of the previous two tables No. (1) and (2). In general, the highest number of adults was at the end of June and reached a mean value of 2.194 adults on the variety King Charles at average temperature (36.709 oC), relative humidity (11.443), and wind speed 10.209. The last data collection of the first week of July and the highest number of adults was occurred on July 4 and reached a mean value 2.583 adults in the variety Top gun F1 at average temperature (38.669), relative humidity (6.337), and wind speed (0.654).  The present study provides scientific information on the adult melon weevil reaction to different varieties (Crimson Sweet, Charleston Gray, Top gun F1, King Charles, Qamar F1) of watermelon C. lanatus Thumb plants under the specific environmental condition of temperature, humidity, and wind speed. These results agree with (Faraj, 2013) who worked on the correlation between the climatic factors and population density of pomegranate fruit worm adults . CONCLUSION According to the results obtained from present study, the following points could be concluded: