Srivastava, PoonamMehra, Vidhi2019-08-162019-08-162019-07http://krishikosh.egranth.ac.in/handle/1/5810122067Mango, Mangifera indica Linnaeus has a complex defense system against diverse insect pest due to the presence of natural enemies which confer extrinsic resistance. A total of 34 insect species were recorded in mango orchard during 2018-19. Out of which, 23 species of insect pests and 11 species of natural enemies were found. Among all the insect pest species, the abundance of mango hopper and mealybug was recorded throughout the year. The peak abundance of mango hopper was observed at the flowering stage i.e., on 16th SMW (14.52 hoppers/ panicle/ twig/ week). The population of mealybug was prevalent from the month of January to May, and it achieved the maximum population on 16th SMW (18.67 mealybugs/ panicle/ twig/ week). Studies on impact of insecticides on extrinsic resistance in mango revealed that insecticides killed both insect pests and natural enemies instantly, but after spray the insect pests multiplied rapidly. The abundance of natural enemies was higher in untreated mango trees than treated trees. Impact of insecticides on relationship between insect pests and natural enemies revealed that the correlation between mango hoppers and natural enemies (spiders r=0.840, R2=0.705, ladybird beetle r=0.928, R2=0.862) was higher in untreated plots than treated mango trees, where the correlation and regression between mango hoppers and natural enemies was lesser (spiders r=0.769, R2 =0.591, ladybird beetle r=0.856, R2 =0.732). Similarly, correlation of mealybug with its natural enemies (spiders r=0.713 and R2=0.508, ladybird beetle r=0.856, R2 =0.732) was higher in untreated mango trees, as compared to treated mango trees, where the correlation and regression between mealybug and natural enemies was lesser (spiders r=0.709 R2 = 0.502, ladybird beetle r=0.581 with R2 = 0.338). Thus, insecticides affected the extrinsic resistance adversely, by disturbing the abundance of natural enemies. Impact of abiotic factors revealed that maximum temperature and sunshine hours showed positive and significant correlation, while, morning relative humidity, evening relative humidity and rainfall had a negative and significant correlation on the population of mango hoppers, mealybug, and ladybird beetle, respectively. But, the population of spiders was correlated positively and significantly with maximum temperature, sunshine hours and morning relative humidity while it was negatively correlated with evening relative humidity and rainfall. Minimum temperature had no significant relationship with any of the insect pests and natural enemies. The yield as well as B:C Ratio was observed higher in the case of untreated mango trees (63.12q/ha, 5.05:1, respectively), as compared to treated mango trees (51.85q/ha, 3.81:1 respectively). This gave evidence that good yield can be attained by extrinsic resistance and the insect pest population can be managed naturally without use of insecticides. Furthermore, in a complex and diverse ecosystem of mango, insect pest management through extrinsic resistance once established, is sustainable in long run.ennullThesis