MONITORING AND VARIETAL SCREENING CUCURBIT OF FRUIT FLY, BACTROCERA CUCURBITAE COQUILLETT (DIPTERA: TEPHRITIDAE) ON CUCUMBER IN BHAKTAPUR AND KATHMANDU, NEPAL

Monitoring of cucurbit fruit fly by using four different types of traps was conducted in Sipadole VDC of Bhaktapur district during 2012 to observe the population dynamics. Three different types of fruit flies were recorded, in which the number of B. cucurbitae dominated to other species. Only B. cucurbitae damaged the cucumber, which was trapped 92.68%, 87.05%, 90.61%, and 69.38% in cue-lure, banana pulp bait, sticky traps and fly catcher, respectively. The highest number of fruit flies (167.5 male fruit flies/3traps) was recorded in cue-lure trap during the first week of September, which coincided with 85.45% RH and 21.67°C and 25.04°C minimum and maximum temperature, respectively. Positive relation of temperature, relative humidity and fruit fly catches was observed. Thus, cue-lure was the most effective traps for monitoring of fruit fly population. In varietal screening, among the six different varieties of cucumber, i.e. Kathmandu local, Kusle, Kamini, Malini, Kasinda and Mahyco Green Long, they were highly significant difference in yield. Kamini gave the highest marketable fruit 26.66 mt/ha yield and the lowest by Kusle (5.05 mt/ha). All the varieties were affected by cucurbit fruit fly. The highest number of unmarketable fruit set was observed in Kamini (22.29 fruits/plant).


Introduction
Cucurbits are tropical in origin and grown mostly in Africa, tropical America, and Asia, mainly Southeast Asia. Cucumber (Cucumis sativus L.) occupies fourth importance in the world (Tatlioglu, 1993) compared to other vegetable. Cucumber and other cucurbit fruits are generally fat-free and low in sodium. It is basically a summer season crop grown both in the hills and Terai region of Nepal. In fiscal year 2011/12 about 1, 24,262 mt cucumber is produced from 8,500 ha land with productivity of 14.6mt/ha in Nepal (VDD, 2012).
Cucurbit fruit fly (Bactrocera cucurbitae Coquillett) is one of the serious problems that limits the production and productivity of cucumber. It is also known as melon fly and melon fruit fly. The extents of damage due to cucurbit fruit fly vary between 30 to 100% depending upon the season and susceptibility of the crops species and varieties (Dhillion et al., 2005). Pradhan (1976) reported that the degree of infestation varied from 19.4-22.1% in cucumber. It prefers to infest young, soft skinned ovaries even before anthesis. When the humidity is high, intensity of cucurbit fruit fly damage becomes severe. Its abundance increases with increase in daily temperatures, however higher than 31°C is not ideal for its growth and reproduction (Dhillion et al., 2005).
Several management techniques are being applied to overcome this pest because three of its life stages are hidden and the only adult stage is the usual target of the pest control activities. Some of the management strategies such as hydrolyzed protein spray, para-pheromone trap, spraying of ailanthus and cashew leaf extract, neem products, bagging of fruits, field sanitation, food baits, and spray of chemical insecticides are being adopted. But these methods are not able to control the pest population completely. Farmers of Nepal are also using different chemical insecticides in routine basis to combat this pest which is very hazardous to growers, consumers and also results environmental pollution (NARC, 1998). Now-a-days, due to the ever increasing global awareness about the undesirable side effects of deadly chemicals on human health, the plant protection strategies have been shifting from the use of chemicals to integrated pest management (IPM) because of increasing failure of chemical pesticides in controlling major pests and diseases. Field sanitation, diversion from the main crops, use of cue-lure traps, food baits and Research Article R. Maharjan et al. (2015) Int J Appl Sci Biotechnol, Vol 3(4): 714-720 This paper can be downloaded online at http://ijasbt.org & http://nepjol.info/index.php/IJASBT hydrolyzed protein bait are some of the appropriate IPM tools (Satpathy and Rai, 2002).
Numerous varieties of cucumber have been developed with their specific characteristics in terms of yield, stress tolerance, diseases resistance. Unfortunately success in developing fruit fly-resistant varieties has been limited. There is a distinct possibility of transferring resistance genes in the cultivated genotypes from the wild relatives of cucurbits for developing varieties resistant to melon fruit fly through wide hybridization. Most of the research works related to varieties conducted in different government and NARC farms have shown that commercial varieties, such as Green Long and Poinsett for Terai, and Kusle and Bhaktapur Local for the hills are suitable for fresh fruit production during March-April (Pandey and Adhikari, 1996).This study is carried out to study the pest abundance in relation to climatic parameter and also find out level of resistance in different varieties commonly grown in Nepal against cucurbit fruit fly. So this study help to develop pest management strategies against cucurbit fruit fly.

Materials and Methods
The monitoring was done to study the occurrence of fruit fly in Sipadol VDC of Bhaktapur district during July-September, 2012. A varietal screening experiment was carried out during March-July, 2012 in Manamaiju VDC of Kathmandu district. The cucurbit fruit fly was monitored with the help of three types of traps and one bait, i.e. cue lure traps (5 drops of cue-lure and 10 drops of malathion), banana pulp bait (500 g banana pulp, 10 ml molasses 2.5 ml Malathion, 10g borax and water), sticky traps and fly catchers. Traps were installed on 9 th July, 2012 in cucumber field of farmer at Sipadol, Bhaktapur at 1m height from ground. Three traps of each type were set in four ropani land of farmers. Regular monitoring was carried out from the date of flowering to harvesting. The pheromone was replaced in each trap at 15 days interval and banana pulp bait at four days interval. The trapped insects were counted at 3 days interval in each trap. Male, female and other species of fruit fly were counted separately in each trap. The weather data were collected from Tribhuvan International Airport (TIA), Kathmandu. Varietal screening was conducted during spring-summers of 2012 at Manamaiju-5, Kathmandu. There were three plots and area of each plot was 12 m 2 . Each plot consists of 6 different varieties containing of total 12 plants two plants of each variety that were replicated thrice. The varieties were Kathmandu local, Kamini, Malini, Kusle, Kasinda and Mahyco Green Long. The cultural practice like weeding, staking, irrigation etc were carried out as per necessities. The observation was made 24 hours before spray at 57 DAT, 3 days after spray, 7 days after spray and 10 days after spray. Related to cucumber yield and yield attributes, plant height, no. of leaves, primary branches, secondary branches, male flower, female flower, no. of fruits (marketable and unmarketable) and weight of fruits (marketable and unmarketable) were taken into consideration. The raw data obtained from field experiment were tabulated by using EXCEL and analyzed by using MSTATC software package. Duncan's multiple range test (DMRT) was used to compare the mean at 5% level of significance.

Results and Discussion
The total numbers of B. cucurbitae trapped in eighteen counting were 1628, 72, 275 and 14 in cue-lure, banana pulp bait, sticky traps and fly catcher, respectively (Table 1). Similarly, the percentage of B. cucurbitae was found 92.68%, 87.05%, 90.61%, and 69.38% in cue-lure, banana pulp bait, sticky traps and fly catcher, respectively. Out of total fruit flies captured in cue-lure traps, the abundantly captured species was B. cucurbitae (92.68%). Other two species B. scutellaris and B. caudata were also noted during monitoring period. B. scutellaris infested the young flowers of cucurbits, such as pumpkin and gourds and the males were attracted to cue-lure. It is generally not regarded as a pest as it infests the flowers only and not the fruits. Out of three recognized species of Bactrocera, only one B. cucurbitae was found damaging to cucurbits crops. Anonymous (2007) categorized two groups of parapheromone traps for Bactrocera spp. and cue-lure (BioCue) is recommended for B. cucurbitae, B. frauenfeldi, B. neohumeralis, B. newmanii and B. tryoni. Messing (1999) mentioned that five types of fruit fly para-pheromone traps and concluded that cue-lure was mainly for B. cucurbitae, however it may attract other species too.
The highest number of fruit fly catch was in cue-lure traps, i.e. 167.5 adults (80.55%) followed by sticky traps (14.21%), banana pulp bait (3.96%) and fly catcher, i.e. 2 adults (1.28%). The sex attractant cue-lure traps are more effective than the food attractant tephritlure traps for monitoring the B. cucurbitae in bitter gourd (Pawar). Methyl eugenol and cue-lure traps have been reported to attract B. cucurbitae males from mid-July to mid-November (Ramsamy et al., 1987;Zaman, 1995;Liu and Lin, 1993) (Fig. 1). Thus, cue-lure was one of the most effective tools for monitoring the population of fruit fly.  The number of fruit flies captured was strongly related with the climatic factors, such as temperature, rainfall and relative humidity. Daily maximum and minimum temperature had positive correlation while there was negative relation with rainfall. Also relative humidity had strong relation with cucurbit fruit fly population over the crop growing period. The lowest number of fruit flies (38 flies/3 traps) was trapped at high rainfall of 18 mm and high temperature 30° C on 29 th July, 2012 in cue-lure traps. In cue-lure traps, the highest number of fruit fly population was recorded on 1 st September with the peak population of 167.5 male fruit flies/3 traps where the temperature ranging from 22-25°C and relative humidity of 85%. Population of fruit fly drastically increased after the rainfall reaching the population of 135.5 male fruit flies/3 traps during 19 th August. Looking at the weekly counts of flies, the highest number of flies were recorded in the week of September (167.5 male fruit flies/3traps) followed by August third and fourth week with 139 and 135.5 flies per 3 traps, respectively. The weekly mean catches of males in cue-lure showed that populations declined in June-July but increased again in August, reaching another peak in September in Pakistan (Abdullah, 2008). He further reported that fruit fly population gained two major peaks, one in spring (March) or late spring while (April) other in early fall (September) or late summer (August). Whereas the fruit fly population dropped either in summer (June) or in fall (December and January). Khan et al. (2003) reported a peak of fruit flies catches was observed from last fortnight of August to first fortnight of September in Shekhupura, Pakistan. Similar trend was observed in present studies. The positive relation of temperature and fruit fly catches observed in the present studies was supported by Mehmood and Mishkatullah (2007) who observed positive relation between temperature (maximum and minimum) and population dynamics of fruit fly. Bhatia and Mahato (1969) found that the shortest life cycle was at 27.5°C while Hollingsworth et al. (1997) recorded that development of cucurbit fruit fly from egg to adult was optimum at 29°C. Similarly, Dhillon et al. (2005) reported that fruit fly actively bred when temperature was below 32°C and relative humidity around 70%. He further reported that fruit flies hide under dried leaves that ultimately reduced the insect activity during winter season.
In sticky traps, the highest number of fruit fly population was recorded in 29 th July with the peak population of 28.5 male fruit flies/3traps. Sticky trap was the second effective trap after cue-lure trap as it also contains very few amount of cue-lure. But it catches both harmful as well as beneficial insect.   * indicates significant, ** indicates highly significant, NS indicates non-significant at 0.05 level of significance, means followed by the same letter are not significant by DMRT at 5% level, values after ± indicate standard error

Stage of fruit damage by cucurbit fruit fly
The fruit damage of less than 100g size is called post set damage. In varietal screening, out of total set fruits, nearly half (47.87%) (Table 3) of the fruits were damaged or dropped just after set (<100 g). Among the different varieties, the highest percent of unmarketable fruit set was observed in Kasinda (51.95%) followed by Kamini (51.21%) and the lowest in Mahyco Green Long (41.04%). But, there was comparatively less fruit damage (33.39%) during harvesting due to cucurbit fruit fly (Table 4). From above data it is clear that young and immature fruits are highly prone to fruit fly damage than mature fruits. Among the different varieties, Mahyco Green Long was found little damaged due to fruit fly as there was high marketable yield as compared to other varieties.

Marketable and damage yield of cucumber
There was a significant difference between the varieties on the total number of harvested fruits per plant. The total number of marketable fruit per plant was higher in Kamini (13.10 fruits/plant), whereas it was the lowest in Kusle (2.30 fruits/plant). The result indicated that 79.75% fruits were marketable out of total harvested fruit in Mahyco Green Long (Table 4).
The marketable fruit yield, damaged fruit yield and total fruit yield of cucumber differed significantly among the varieties. The marketable fruit yield of Kamini was more than double (26.66 mt/ha) as compared to the other varieties. On the other hand, the lowest marketable fruit yield was recorded in Kusle (5.05 mt/ha) that was five times lower than Kamini. Kamini variety was found superior as compared to the other varieties in terms of yield. Damaged fruit yield was also high (11.04 mt/ha) in Kamini as compared to other varieties (Table 5). Although the yield of Kamini varieties was found higher, however it was not preferred by the consumer due to its taste as well as low keeping quality.
A plant produced 2-13 marketable fruits with an overall average of 7 (6.75 fruits/plant). Kamini gave the highest marketable fruit yield 26.66 mt/ha followed by Malini (12.19 mt/ha), Mahyco Green Long (10.91 mt/ha), Kasinda (9.40 mt/ha), Kathmandu Local (9.22 mt/ha) and Kusle (5.05 mt/ha). All the varieties were affected by cucurbit fruit fly. There was no resistance found in any varieties. The experiment was conducted in the farmers' field conditions at Yampaphant, Tanahun, Nepal during April -July 2000 included one commercial cultivar namely Bhaktapur Local and the four exotic cultivars and hybrids namely Malini, Korean White, Japanese Green and Green Long. The hybrid Malini was found significantly more vigor and earlier (first picking at 42 days) and produced significantly higher number of fruits (252 thousands/ha) and significantly higher yield (69.6 t/ha) (Sharma and Bhattarai, 2006).

Natural Enemies
The populations of different natural enemies counted in the varietal screening plots at every 10 days interval were mostly predators and some unidentified parasitic wasps. The major predators recorded were different kinds of ladybird beetles, spiders, hover fly, paper wasp bees and staphylinids. The highest numbers of natural enemies were recorded in Malini after 30, 40 and 60 DAT. Kamini recorded the highest number of natural enemies at 50 DAT. The least number of natural enemies were recorded in Kusle and Kasinda throughout the study period. (Table  6).

Conclusions
A cue-lure trap was found to be the most effective for monitoring the population of fruit fly and could be one of the best tools for taking decision for its management. Among the different varieties tested for the resistance to cucurbit fruit fly, there was no resistance found in any varieties. All the varieties were damaged by cucurbit fruit fly. However, Kamini gave the highest yield.