Despite its bumper production, the mango growers in Thakurgaon are deeply worried as several hundred hectares of mango orchards got submerged due to heavy rains for the last several days.   According to farmers, some 500 hectare of mango orchards in the district went under rainwaters due to torrential rain, making it difficult for them to harvest mangoes.   Besides, the natural colour of mangoes have turned fade with black spots being visible on them, forcing the farmers to sell their produce at lower prices.