STUDY ON THE DYNAMICS OF INSECT PESTS OF SUGARCANE IN THE TARAI REGION OF UTTARAKHAND AND EVALUATION OF VARIOUS SUGARCANE GERMPLASM AGAINST MAJOR INSECT PESTS”
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Date
2023-07
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G. B. Pant University of Agriculture & Technology, Pantnagar-263145
Abstract
Study on the population dynamics of insect pests and varietal screening of sugarcane was carried out at N.E.B. Crop Research Centre, G. B. Pant University of Agriculture and Technology, Pantnagar during 2022-23. During study, a total of eight insects viz. early shoot borer, top shoot borer, internode borer, pyrilla, mealybugs, whitefly, ash weevil and grasshopper were found infesting sugarcane. The maximum percent infestation by early shoot borer (26.67 percent) was observed in the second fortnight of June, top borer (36.67 percent) activity was reported maximum in first fortnight of September. The internode borer (26.67 percent) and pyrilla (3.03 eggs, 5.50 nymphs 6.23 adults/leaf) maximum activity was recorded in the month of November and December, respectively. Peak activity of whitefly (2.03/3 leaves) and mealybug (49 percent) was observed in the month of October and November, respectively. Correlation studies revealed that minimum temperature positively correlated with early shoot borer infestation (r = 0.696*) while negatively correlated with infestation of internode borer (r = - 0.709*) and pyrilla egg population (r = - 0.614**); maximum temperature had inverse effect on internode (r = - 0.677*) and pyrilla egg population (r = -0.474*). The morning humidity and afternoon humidity had significant positive correlation with internode borer (r = 0.763), mealybug (r = 0.492*), top borer (r = 0.632*) and ash weevil infestation (r = 0.708*). Rainfall had a positive impact on early shoot borer infestation (0.749*). The activity of natural enemies namely, coccinellids (0.27 adults/plant) and spider (1.20/plant) were found to be maximum in second fortnight of December and August, respectively. Cheiloneurus sp., an egg parasitoid was reported and found parasitizing the eggs of pyrilla from second fortnight of August, 2022 till first fortnight of January and maximum parasitisation was observed in the first fortnight of November (73 percent). An ectoparasitoid F. melanoleuca marked its appearance in field in first fortnight of July and reached maximum in the second fortnight of October (2.30 cocoons/leaf) and highest parasitization of nymph (58.33 percent) and adults (51 percent) of pyrilla was observed in second fortnight of October, respectively whereas, no record of natural enemies of borers associated with sugarcane was found.
Evaluation of sugarcane germplasm for their reaction against borer complex and sucking pests was conducted with ten germplasm and five checks. The results of the screening revealed that germplasm CoPant 12221 was found least susceptible against all borers, pyrilla and mealybug infestation followed by CoPant 13224 and CoPant 12226. Other germplasm viz. CoPant 17223 and CoPant 19221 were found moderately susceptible against borers and sucking insect pests whereas, CoPant 17224 and CoPant 18222 were found to be least susceptible only against sucking pests. All the germplasms were found to be least susceptible against internode borer and mealybug infestation. Biophysical and biochemical studies were also performed for determining resistance traits in germplasm against borers and sucking pests. The results revealed that at 90 DAP, leaf number showed significant positive correlation with early shoot borer infestation (r = 0.609*) and with pyrilla (r = 0.644**), at 180 DAP leaf width was significantly correlated with top borer infestation (r = 0.767**) and leaf number showed positive correlation with pyrilla (r = 0.614*) and mealybug (r = 0.519*). At 270 DAP, leaf number was found to be positively correlated with pyrilla infestation (r = 0.610*). The percent infestation of early shoot borer was significant positively correlated with total soluble carbohydrates (r = 0.609*). Those germplasm that incurred resistance showed these traits such as narrower leaf width, low number of leaves, wider leaf angle, higher levels pf antioxidant and phenol and decreased total carbohydrate content. These characteristics effectively led to reduced insect pests attack.
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Theses of M.Sc.