BIOECOLOGY OF DIORYCTRIA ABIETELLA DENIS AND SCHIFF. A PEST OF CONIFERS IN THE NORTH-WESTERN HIMALAYA

T.D VERMA

Abstract


Cones and seeds of conifers, such as Pinus roxburghii, P. wallichiana, P. gerardiana, Cedrus deodara,
Abies pindrow and Picea smithiana  are seriously damaged by Dioryctria abietella Denis and Schiff.
(Lepidoptera : Pyralidae) in the North-Western Himalayan region of India. Bioecological studies carried out
during 1991 - '92 revealed that the females laid whitish, elliptical eggs singly on the depressed surface of the
young cones. The average egg size was 1.00 ± 0.11 x 0.60 ±0.08 mm and this stage lasted for 3 - 5 days. The
larval stage passed through five instars. All the instars differed in appearance, size and duration and larvae
became full-fed in an average of 24.8 ± 1.9 days. The full-fed larva spun a cocoon around itself, sealed it
with white  papery membrane  and  pupated  inside  the  cone  or  any  other  outside  protected  place.  The
prepupal and pupal periods lasted for 7-8 and 10-14 days, respectively. The pupa was dark brown, 13.8
± 0.07 mm in length. Total period from egg to adult varied from 46 to 59 days (52.7 ±4.8 days). Adults were
dirty brown in appearance and were 13.59±0.115 mm long with an average wing expanse of 29.0 ± 1.00
mm. They lived for 4 to 5 days. Under laboratory conditions, the pest completed two generations per year
and  full-fed  larvae  of  3rd  generation  overwintered  during  September  -  October.  Two  larval  parasites
belonging  to  order  Hymenoptera  and  Diptera,  and  a  fungal  pathogen  (Fusarium  sp.)  were  found
associated with this pest. The detailed biology, nature and extent of damage, along with its distribution have
been discussed and methods of control suggested.              Key Words: Insect biology, Insect ecology, Dioryctria abietella, Coniferae, North-Western Himalaya,
Forest pests

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DOI: http://dx.doi.org/10.11598/btb.1994.0.7.115

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