Conservation of biotic agents in apple orchards of Himachal Pradesh.
Field studies carried out in apple orchards in the Shimla district of Himachal Pradesh, India, during April-May, 1988-89, showed that a single spray of dormant miscible spray oil (2% HP Spray oil E or Akrur Spray oil) at the pink bud stage effectively controlled Pseudaulacaspis sp. and was safe for the predators Chilocorus bijugus and Pharoscymnus flexibilis on treated trees. The spray schedule adopted (spray oil + insecticide, followed by an insecticidal spray a week after the bloom) was, however, detrimental to predators. Monocrotophos 0.05% alone did not give an effective level of control and was detrimental to predator activity. In various orchards, populations of Thrips flavus remained below the economic injury level and at many places the high predator activity of the anthocorid Orius sp. kept the pest population low. In orchards sprayed at the pink bud or bloom stage, predator activity was 2.5-fold poorer on the ground flora around the tree basin compared to activity in sprayed locations. The coccinellids Coccinella septempunctata and Hippodamia variegata, appearing in large numbers during April-May, also prevented a population build-up of Eriosoma lanigerum.