Survey area: The survey was conducted in the fifteen major maize grown areas in Bangladesh viz. Rangpur, Dinajpur, Gaibandhah, Bogura, Joypurhat, Naogaon, Rajshahi, Kushtia, Jassore, Khulna, Kumilla, Chattagram, Sylhet, Mmensingh, Gazipur during July to December 2017. The study was conducted to assess the major pests associated with stored maize, the damage and losses they cause in Bangladesh. This research zone lies between latitudes 24°00'N and longitudes 90°00'E. It situated under sub-tropical climate, which is characterized by high temperature, high humidity and heavy precipitation with occasional gusty winds from April to September and scanty rainfall associated with moderately low temperature and humidity from October to March. Sampling: A survey was conducted to find out the status of insect pests, damage and losses in stored maize in major maize grown areas in Bangladesh. Generally, these areas were favorable for storage pest infestations owing to its environmental conditions. The study was also conducted when maize grain was in storage for three to six months and infestation and grain damage levels were most likely to be serious. Fifteen (15) survey sites were selected based on their maize production status (major maize producing areas) of Bangladesh. 60 farm stores from all selected survey were visited and 1 kg maize grain samples were collected from at least two sites of each selected area. Selection of sites, storage containers and samples were made in such a way that they are the representative of all major maize grown area of Bangladesh at random. The samples of grains were obtained from as many different parts of the various storage facilities as possible (top, sides, center and bottom). Each sample was put in a paper bag and labeled with the necessary information for further inspection in laboratory as per the methods used by Firidissa (1999). Inspection of the samples was made within two weeks of collection in the laboratory of Department of Entomology of Bangladesh Agricultural University (BAU), Mymensingh-2202, Bangladesh. Laboratory study: Laboratory study was done at the Department of Entomology of Bangladesh Agricultural University (BAU), Mymensingh-2202. After collection of samples, grains were sieved over a 2 mm mesh sieve (Abraham, 1995) according to each sample of survey areas. Insects were removed, counted and grouped to order & family, and were preserved dry as pinned collections or in 75% ethanol for identification. Identification was made using combination of insect identification keys, books, journals, handbook, pictures, booklet and comparisons with already identified specimens in laboratory. Again, it was identified and confirmed with the help of specialized persons of the Department of Entomology, BAU, Mymensingh. Then, rate of insect infestation were recorded from each sample of the selected areas. Data collection, Grain weight loss: After collection of samples, 100 grains were randomly taken from each sites of each collected sample and they were separated into damaged and undamaged categories. Then these grains were separately counted and weighted. Percentage weight loss was calculated using count and weight method for each sample of all sites of survey areas (Adams, 1976).
Weight loss (%) = {(Wu×Nd)−(Wd×Nu)}/{Wu×(Nu+Nd)} x 100
Where, Wu = Weight of undamaged seed, Nu = Number of undamaged seed, Wd= Weight of damaged seed, Nd = Number of damaged seed Percentage grain damage: Insect damage was assessed by the count method. 100 grains were randomly taken from each sites of each collected sample and they were separated into damaged and undamaged categories. Then, percentages of insect damaged grains were calculated as follows:
Insect damaged grain (%) = Number of insect damaged grain/Total number of grain×100