ASPECTS OF THE BIOLOGY AND CONTROL OF 3 SPECIES OF ACORN WEEVILS INFESTING OAK ACORNS IN KUMAUN HIMALAYA

Biology and ecology of three acorn weevils: Dicranognathus nebulosus R edt. (Col., Attelabidae), Sitophilus glandium (Mshl.) (Col., Curculion idae) and Curculio sikkimensis (Hell.) (Col., Curculionidae), which in fest acorns of Quercus leucotrochophora A. Camus and Q. floribunda Lin dle was studied in the laboratory and in the field. Adults of D. nebul osus and C sikkimensis laid one egg per infested acorn, and S. glandiu m laid 0 to 8 (means 5.2 +/- 0.47) eggs in an infested acorn of Q. leu cotrichophora. Only a single larva of D. nebulosus and C. sikkimensis developed per acorn, and 1 to 5 (mean 3.8 +/- 0.3) larvae of S. glandi um developed per acorn through the last instar. Larvae of D. nebulosus and S. glandium completed their development in the infested acorn, an d C. sikkimensis emerged from the acorn through the last instar and co mpleted its development in the soil. Good synchronization was observed in the life cycle of acorn weevils and phenology of Q. leucotrichopho ra. An average of 88.7 % of acorns were infested by the acorn weevils. Injury to live acorns by weevil larvae reduced germination and seedli ng growth. Weevil larvae could be controlled by hydrothermal treatment (20 min at 45-degrees-C) of infested acorns in the germination experi ments.