Comparative study of Cucurbit fly : Dacus ciliatus Loew ( Diptera : Tephritidae ) infestation on Zucchini squash ( Cucurbita pepo L . ) at Huraimila and Diraab , Riyadh Region , Saudi Arabia

Dacus ciliatus Loew (Diptera: Tephritidae) infestation was studied on regular and hybrid varieties of Zucchini squash (Cucurbita pepo L.) in summer growing season at two locations, Huraimila and Diraab educational farm, Riyadh, Saudi Arabia. The experiments were laid down following randomized complete block design (RCBD). Results indicated no significant differences between the varieties for fruit fly (D. ciliatus) infestation within each location. Huraimila had significantly greater fruit fly infestation as compared to Diraab. In Huraimila, infestation peak was observed in the last week of May whereas, in Diraab no significant change was observed during the month of May but a significant reduction in infestation was recorded in the mid of June. Results indicated a correlation (r = 0.66 at <0.0001) between average number of zucchini squashes harvested and number of infested squashes per line.


INTRODUCTION
Zucchini squash (Cucurbita pepo L.) is an economically important vegetable crop grown in Saudi Arabia.The crop is heavily infested by fruit fly: Dacus ciliatus Loew (Diptera: Tephritidae).Family Tephritidae comprises over 4000 species, around 700 species belonging to Dacine fruit flies (Fletcher, 1987).About 250 species are economically important and widely distributed in temperate, sub-tropical, and tropical regions of the world (Christenson and Foote, 1960).D. ciliatus is a serious pest of cucurbits in Saudi Arabia (Fischer and Petersen, 1989).
D. ciliatus was reported in India in 1914 for the first time and was collected first from Ombo, Upper-Egypt, in February 1953 (Weems, 2008).D. ciliatus is distributed throughout most of eastern, southern, and central Africa, Malagasy Republic (Madagascar), Mauritius and Reunion Islands, the Arabian Peninsula, Pakistan, India, Bangladesh and Sri Lanka (White and Elson-Harris, 1994).
D. ciliatus generally deposit 4-8 eggs in a single puncture made in the fruit by the ovipositor of the female typically near the stalk and complete life cycle within 19-22 days in which egg stage lasts two to four days, the larval stage four to six days, the pupal stage eight to 10 days, the pre oviposition period takes at least four days (Weems, 2008).
The genus Dacus causes heavy damage to fruits and vegetables in Asia (Nagappan et al., 1971).D. ciliate is a serious agricultural pest (White and Elson-Harris, 1992) and considered as an important quarantine pest in different countries (European and Mediterranean Plant Protection Organization, 2008).D. ciliates seriously damage cucurbits in many countries, Egypt (Azab et al. 1970), South Africa (Hancock, 1989), the Island of Reunion, and other islands in the Indian Ocean (Dehecq, 1995).The female deposit her eggs into the cucurbit fruit where larvae developed inside the fruit leading to the fruit deformation and rottening (El-Nahal et al., 1970;Fletcher, 1987).
The pupation usually takes place on ground inside the upper layer of soil (Malihi, 1998).Greater larval exit from the fruit before pupation and adult emergence occur around morning and are controlled by light and temperature (Malan and Giliomee, 1968;Arai, 1976).Moreover, Dacus ciliatus oviposit on shady rather than fruit area exposed to the sun (Syed, 1969).Availability of abundant hosts restrict the movement of mature flies to foraging flights to explore food, water and oviposition sites (Bateman, 1972).Dacine flies exhibit a daily pattern of movement between hosts and surrounding vegetation which is more evident in cucurbit infesting species including D. ciliatus (Matanmi, 1975).
The objective of the present study was to determine fruit fly (Dacus ciliatus) population density and degree of infestation on Zucchini squash (Cucurbita pepo L.) in Huraimila and Diraab areas, Riyadh Region, Saudi Arabia.

MATERIALS AND METHODS
Experiments were carried out during summer growing season of Zucchini squash (Cucurbita pepo L.) at Huraimila and Diraab educational farm, Riyadh region, Saudi Arabia.
The experiments were laid down following complete randomized block design (CRBD) with 2-blocks and 2-Zucchini squash (Cucurbita pepo L.) varieties as treatments where each treatment had 3-replication lines.Zucchini squash regular and hybrid varieties were grown in each block having three replication lines to study and compare level of fruit fly (D. ciliatus) infestation in Huraimila and Diraab.
When the Zucchini plants reached to fruiting stage, all fruits were harvested with one week interval from each replication line, separately.Within each replication large and small size Zucchini fruit were separated to compare the level of infestation between younger and older Zucchini.All samples were collected in marked plastic containers covered with muslin cloth for adequate ventilation and transferred to entomological research laboratory in the department of plant protection at the college of food and agriculture sciences, King Saud University, for processing.In the laboratory, the Zucchini fruit was carefully observed for fruit fly infestation.Infested Zucchini fruits were easily recognized by the presence of puncture hole made by the female fly during oviposition.
Data was analyzed using the analysis of variance (ANOVA) PROC GLM procedure of SAS (SAS 2002) and means were separated using the Duncan's Multiple Range Test (P = 0.05).
Comparative study of Cucurbit fly: Dacus ciliatus Loew 95 Fruit fly infestation was also correlated with abiotic factors.Results indicated a significant negative correlation with average temperature while positive correlation with average relative humidity in Diraab.Whereas, in Huraimila a significant negative correlation was observed with average relative humidity and wind speed (Table 5).
Results indicated a significant correlation (0.66 at <0.0001) between average number of zucchini squashes harvested and number of infested squashes per line.

CONCLUSIONS
There were no significant differences between Zucchini squash (Cucurbita pepo L.) regular and hybrid varieties for fruit fly (D. ciliatus) infestation.Huraimila had significantly greater fruit fly infestation as compared to Diraab.In Huraimila, infestation peak was observed in the last week of May whereas, in Diraab no significant change was observed during the month of May but a significant reduction in infestation was recorded in the mid of June.Results indicated a correlation (r = 0.66 at <0.0001) between average number of zucchini squashes harvested and number of infested squashes per line.

Table 2 :
Size wise comparison of average Dacus ciliatus infested Zucchini squash (Cucurbita pepo L.) per line within each variety in Huraimila and Diraab.

Table 3 :
Block wise comparison of average Dacus ciliatus infested Zucchini squash (Cucurbita pepo L.) per line within each variety in Huraimila and Diraab.

Table 4 :
Comparison of average Dacus ciliatus infested Zucchini squash (Cucurbita pepo L.) per line in Huraimila and Diraab.column followed by the same letter are not significantly different α = 0.05