STUDIES ON MANGO WEBBERS WITH SPECIAL REFERENCE TO LEAF WEBBER Orthaga exvinacea Hampson (Pyralidae Lepidoptera)
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Date
2000
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Professor Jayashankar Telangana State Agricultural University
Abstract
Studies on the seasonal incidence of different leaf and flower webbers including 0. exuinacea Hampson were carried out on mango (var. Bangalora) during August 1999 to July 2000 at Agricultural Research Station, Anantharajupeta. The leaf webber incidence first appeared during second fortnight of June. The peak activity of leaf webberwasobservedduringsecondfortnightofOctober. Theincidence ofleafwebberwascompletely absentduringFebruaryto Maymonths due to less congeniality of climatic factors (High temperature). The incidence of flower webbers was at low ebb and occurred only during January-Februarymonths. Observations on the biology, morphometrics and developmental durationsofmangoleafwebberO.exuinaceaunderlaboratoryconditions (27 i 2°C) indicated that incubation period lasted for 3.75 days. The mean duration oflarval, prepupal andpupal stages lasted for 34.09, 3.00and 14.22days, respectively. Thetotallifecyclewascompletedin 51.81 days.
Studies on intra—plant' distribution of mango leaf webber in relationtotreeheightanddirectionrevealedthatthewebberpopulation was more in the lower region (1.5 to 8.0 m height) and Southern direction ofthe tree and low webber population was recorded in the upperregionandnorthdirection. Thirteencultivarsofmangowerescreenedunder fieldconditions againstmangoleafwebberduringpeakinfestationperiod. Thecultivars Neelum,SwarnajahangheerandHimayuddinwerefoundhighlyresistant toleafwebber. Whereasthe cultivarsBangaloraandPanchadarakalasa XWillardwerefoundtobe highlysusceptible. Experimentsorientedtodocumentthebiochemicalconstituentsof mango leaves revealed that the total phenols, reducing sugars and chlorophyllcontentwerecomparativelyhighinlowMLWinfestedgroup Viz., Neelum(25.05, 91.00and0.54mg/g), Neeleshan(19.89, 85.00 and 0.44 mg/g) and Swarnajahangheer (13.69, 73.00 and 0.711 mg/g). Whereas in the highly susceptible cultivars Viz., Bangalora and PanchadarakalasaxWillard,thephenol,reducingsugarandchlorophyll contents were 8.44, 52.00and 0.230; and7.69, 43.40 and 0.321 mg/g, respectively. A field trial was conducted to understand the influence of insecticidesthatweresprayedagainstmangohoppersduringFebruary 2000onMLWO. exvinaceaincidence. Itrevealedthatthe incidence of MLWwasmoreininsecticidetreatedtreeswhencomparedtountreated plants. Highest number of leaf webs was observed in imidacloprid treatment,whilelowestnumberofleafwebswasobservedinuntreated check.
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D6238