Loss assessment and management of major stored grain insect pests of wheat (Triticum aestivum Linn.) in Punjab

Despite improved grain yield of wheat (Triticum aestivum Linn.) under field conditions, it is heavily attacked by number of insect-pests during storage. An attempt was made to assess such losses caused by major stored grain pests. Initially the untreated control wheat samples were collected from Food Corporation of India (FCI), PAU and household storages. A subsequent sampling was performed at fortnightly intervals in the treated and untreated control. Mean grain damage ranged from 0.00-0.07 per cent (1000 grain count basis) and 40.93-48.17 per cent with subsequent weight loss of 0.00-0.04 and 15.71-23.28 per cent, respectively, in treated and untreated samples at various locations. Mean healthy and broken grains ranged from 99.93-100.00 and 4.27-5.60 per cent as against 54.07-58.64 and 2.743. 49 per cent, respectively, in treated and untreated control samples collected from various locations. The mean total of treated samples revealed maximum insect pest incidence (adults/100g grain sample) in household (3.96 adults) followed by PAU (0.28 adults) and FCI Moga outdoor (0.12 adults) storages. No incidence was recorded in FCI Moga indoor and Rampuraphool indoor storages. However, the mean total of untreated samples indicated maximum insect pest incidence in PAU samples (247.95 adults) followed by household (224.82 adults), FCI Moga outdoor (184.12 adults), FCI Rampuraphool indoor (181.26 adults) and FCI Moga indoor (175.71 adults) storages. The untreated control samples collected from various locations registered highest incidence of lesser grain borer (Rhyzopertha dominica) followed by red rust flour beetle (Tribolium castaneum), rice weevil (Sitophilus oryzae) and rice moth (Corcyra cephalonica). The fumigation with aluminium phosphide (tablets/10quintal grains) for control of various storage pests was found to be maximum in FCI Moga outdoor (30) followed by FCI Rampuraphool indoor (24), household (23.71), FCI Moga indoor (21) and PAU (5) storages. The studies on efficacy of plant powders and oils, and population buildup of R. dominica and S. oryzae were carried out in BOD incubator at 27±1oC temperature and 70±5 per cent R.H. On overall basis, neem kernel powder at 2.0 per cent (w/w) was found as the most effective against R. dominica and S. oryzae, respectively, which registered minimum adult emergence (14.75 and 16.08 adults/100g grains), grain damage (2.14 and 2.59%), weight loss (1.03 and 1.14%) and maximum inhibition rate (93.58 and 93.69%) followed by dharek kernel, neem leaf, dharek leaf, castor kernel and castor leaf powders where as untreated control registered maximum adult emergence (167.67 and 157.58 adults), grain damage (42.30 and 21.16%) and weight loss (32.15 and 13.82%). Similarly, neem oil at 0.20 per cent (v/w) was highly effective against R. dominica and S. oryzae , respectively, due to lowest adult emergence (22.58 and 22.83), grain damage (4.79 and 2.86%), weight loss (2.60 and 1.39%) and highest inhibition rate (88.92 and 91.06%) followed by eucalyptus and castor oils where as untreated control samples registered highest adult emergence (142.67 and 189.50 adults), grain damage (28.58 and 21.88%) and weight loss (18.39 and 10.50%). All plant powders and oils did not show any adverse effect on seed germination for up to 120 days after treatment. In population buildup experiments, the wheat variety HD2967 had highest susceptibility to R. dominica and S. oryzae due to maximum adult emergence, grain damage and weight loss followed by PBW621, PBW658, WHD943, PDW314 and PDW291. Ash content and crude fibre had a positive where as crude fat and protein negative correlation with grain infestation in all the six wheat varieties.