INCIDENCE OF INSECT PESTS IN RICE—RICE ECOSYSTEM IN RELATION TO WEATHER PARAMETERS
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Date
2000
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Professor Jayashankar Telangana State Agricultural University
Abstract
A field experiment was conducted at experimental fields ofrice section, Agricultural ResearchInstitute, Rajendranagarto studytheincidenceofinsectpests and their relation with weather in rice with two varieties (ie. Tellahamsa and SambaMahsuri inlr/rarif: TellahamsaandIR-64in Rabi)and threeplantings (15th July, 4th August and 22nd August in khm‘ifand 16th December, 4th January and 23rd January in rabi) during kharif98 and Rabi 1998-99 in a randomized block design (Factorial). The results of experiments revealed that thrips damage was higher upto 15 daysaftertransplantation and laterdecreased. Second fortnightofAugustduring kharifand second fortnight ofJanuary duringrabi arefavourable forthe incidence of thrips in.Rice. Late planting favoured the whorl maggot and its damage was higher when the crop is at 15—30 DAT during lr/mrifand 30-45 DAT during rabi season. Significant positive relationship was observed between whorl. maggot incidence and rainfall and number ofrainy days during rabi season. Gall midge was noticed only in k/mrr‘fbut not in rabi. Activity ofgall midge increased from August to October with its peak in second fortnight of
October. There was no significant relationship between gallmidge incidence and weather parameters. Leaf folder incidence was noticed only in khariffrom first fortnight ofAugust and increased significantly till firstfortnight ofOctober and there was no incidence in rabi. There was a significant negative relationship between morning relative humidity and leaffolder incidence. Incidence of stem borer was initiated in second fortnight of July and increased gradually with peak incidence in second fortnight of October during khan‘fseason. During rabi, its activity was peak in second fortnight of March. There exists a significant negative correlation with minimum temperature and afiemoon relative humidity during kharifwhile positive relationship with maximum and minimum temperatures and negative relationship with morning and afternoon relative humidity during rabi season. Insect pests cause. yield losses to an extent of 25.3 per cent in [than]1998 and 7.9 per cent in rabi 1998-99 in no protection compared to need based protection in rice. From the above results, itwas concluded thattheprevailing agroclimatic conditions are the most important factors contributing towards pest inc1dence, multiplication and population build up ofinsect pests in rice.
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D6063