Stingless bee Heterotrigona itama Cockerell (Apidae: Meliponini) as apotential pollinator in rock melon Cucumis melo L. cultivation

Rock melon (Cucumis melo L.) belongs to the family Cucurbitaceae and the genus Cucumis which comprises of 38 species worldwide. In Malaysia, the local demand for this fruit is increasing and there is also an enormous potential for international market. The normal pollination practice in rock melon is by hand pollination. However, hand pollination by human is currently not a preferred option since it is labor intensive and time consuming. Furthermore, rock melon produces lesser female flowers than male flowers, hence leading to poor fruit production. Application of insecticides is a major concern as it could harm insect pollinators, which result in colonies collapse. The first experiment was conducted using a sweep net that trapped insects, which were collected the insect and identified as pollinators in rock melon cultivation. Result showed H. itama population was the most abundant in rock melon cultivation and the peak hours of foraging activities was in the morning. The second experiment was determining the foraging activities, floral visitation frequency and activities rate of stingless bee in rock melon cultivation inside glasshouse. The foraging activities recorded were stingless bee flying into the hive, flying out from the hive and bring pollen into hive. The results showed, the flying out from hive activities was the highest number (1522 individuals) of stingless bees recorded. The peak hour for foraging activities by H. itama inside the greenhouse was in the morning, from 10 a.m. to 11 a.m. On floral visitation frequency, H. itama visited rock melon male flowers more frequently than female flowers. However, H. itama spent longer period foraging the female flowers (2.27 minutes) than the male flowers (1.49 minutes). The third experiment was conducted by using the ethylene to increase female flowers production. The source of the ethylene in this experiment were ethephon and epibrassinolide, with two concentrations of ethephon, at 250 ppm and 500 ppm. Concentrations for epibrassinolide were 10 μM and 1 μM, while distilled water was used as control. Result showed that the treatment with 250 ppm ethephon significantly increased (P<0.05) the production of female flowers. The application of ethylene with optimum concentration could increase the female flowers production without disturbing the natural growth of the rock melon crops such as the height of rock melon plant and the relative chlorophyll content. The final experiment was the bioassay on the H. itama to determine the toxicity level that cause mortality on stingless bee population. H. itama population was assessed with five common insecticides used in rock melon cultivation, namely Deltamethrin, Cypermethrin, Imidacloprid, Abamectin and Malathion. The insecticide with the highest toxicity was Imidacloprid, a low concentration at 57.53 ppm, after 24 hours significantly caused 50% mortality on the stingless bee population. The insecticide with the lowest toxicity on H. itama was Malathion, where a high concentration of 500.76 ppm resulted in 50% mortality after 24 hours. In conclusion, this study provides an overview for rock melon cultivation. H. itama was an effective and worthy pollinator candidate for rock melon cultivation. The application of optimal concentration of ethylene to boost female flowers production, and hence increase the yield of rock melon fruits. The use highly toxic insecticides are detrimental to populations of pollinators. Thus, the findings from the present study contribute to new and impactful knowledge gained by rock melon growers and is recommended as innovations on the cultural practice in modern rock melon industry in Malaysia.

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