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GROWTH INHIBITING AND DETERRENT EFFECTS OF PLANT EXTRACTS ON MAJOR INSECT PESTS OF STORED GRAINS

Iqbal, Javed (2005) GROWTH INHIBITING AND DETERRENT EFFECTS OF PLANT EXTRACTS ON MAJOR INSECT PESTS OF STORED GRAINS. PhD thesis, University of Arid Agriculture, Rawalpindi.

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Abstract

Extracts of seeds of neem Azadirachta indica A. Juss, rhizomes of sweet flg Acorus calamus L. and turmeric Curcuma longa (L.) each in petroleum ether, acetone and ethanol at different application rates were evaluated for their repellent, growth inhibiting, feeding deterrent and synergistic effects against the red flour beetle Tribolium castaneum (Herbst), angumois grain moth Sitotroga cerealella (Olivier) and lesser grain borer Rhizoperha dominica (Fabricius). Petroleum ether extracts of neem and sweet flag applied to wheat grain, bag or both compared with Coopex dust (0.5%) and polythene enclosure (0.2 mm), provided efficient protection to wheat upto six months. Among the test plants, sweet flag was significantly better repellent upto two weeks but neem showing comparatively lower repellency upto two weeks persisted better upto eight weeks in Treated Paper Strip Repellency Method (contact) repellency). For olfactory repellency, evaluated in an Olfactometer for five minutes, sweet flag proved better repellent. In growth inhibition studies (T. castaneum fed for five days on wheat flour treated @ 1000, 500, 250, and 125 ug/gm of the plant extracts) significantly lower progeny (larvae, pupae and adults) was produced in sweet flag. Other plant extracts were also promising growth inhibitors. In feeding deterrent studies conducted by confining R. domninica adults on extracts treated filter paper discs treated at 1000, 500 or 100 ug/cm2 in a micro-cage paper treated with neem extracts had significantly lower number of feeding punctures as compared with those having turmeric and sweet flag extracts. Among solvents, extracts in petroleum ether were significantly better repellents and growth inhibitors but those in ethanol were significantly better feeding deterrents. Repellent, growth inhibition and feeding deterrent properties were dose-dependent. At higher application rates comparatively higher repellency, growth inhibition and feeding deterrence were achieved. Petroleum ether extracts of sweet flag being the most effective repellent and growth inhibitor was chemically fractionated by Thin Layer Chromatography (TLC), using petroleum ether: acetone (3:1) and five major fractions obtained from column chromatography using Silica get 60 G and elution with petroleum ether:acetone (3:1). Fractions 2 and 3 having Rf values of 0.75 and 0.63 respectively, were significantly better repellent and growth inhibitor. In synergistic studies or combined application of the petroleum ether extracts, sweet flag synergized with neem in different ratios but not with turmeric for inhibition of S. cerealella progeny. T.castaneum was less affected by combined applications. In warehouse trials, neem and sweet flag extracts applied to both bag @1000 ug/cm2 and wheat grain @ 1000 mg/kg provided efficient protection against major stored grain insects. It was concluded that better repellent and growth inhibiting effects of sweet flag were probably due to the presence of asarone (C12H16O3; MW 208) in its petroleum ether extract which has comparatively lower molecular weight and higher volatilization rate than azadirachtin (C35H44O16; MW 720) in ethanol extract of neem which showed better feeding deterrency due to its higher molecular weight. Petroleum ether extract of turmeric had turmerone (C15H22O; MW 218) and ar-turmerone (C15H2O; MW 216) which had medium level of behavioural and biological effects due to their molecular weight remained in between asarone and azadirachtin.

Item Type:Thesis (PhD)
Uncontrolled Keywords:plant extracts, insect, pests, grains, plant materials, neem, azadirachta indica a. juss, rhizomes of sweet flg acorus calamus l., turmeric curcuma longa (l.), deterrent,
Subjects:Agriculture & Veterinary Sciences(a) > Agriculture(a1)
ID Code:494
Deposited By:Mr. Muhammad Asif
Deposited On:05 Aug 2006
Last Modified:04 Oct 2007 21:01

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