BIOECOLOGY OF DIORYCTRIA ABIETELLA DENIS AND SCHIFF. A PEST OF CONIFERS IN THE NORTH-WESTERN HIMALAYA
AbstractCones and seeds of conifers, such as Pinus roxburghii, P. wallichiana, P. gerardiana, Cedrus deodara, Abies pindrow and Picea smithianaÂ 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 Â± 0.11 x 0.60 Â±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 Â± 1.9 days. The full-fed larva spun a cocoon around itself, sealed it with whiteÂ papery membraneÂ andÂ pupatedÂ insideÂ theÂ coneÂ orÂ anyÂ otherÂ outsideÂ protectedÂ place.Â The prepupal and pupal periods lasted for 7-8 and 10-14 days, respectively. The pupa was dark brown, 13.8 Â± 0.07 mm in length. Total period from egg to adult varied from 46 to 59 days (52.7 Â±4.8 days). Adults were dirty brown in appearance and were 13.59Â±0.115 mm long with an average wing expanse of 29.0 Â± 1.00 mm. They lived for 4 to 5 days. Under laboratory conditions, the pest completed two generations per year andÂ full-fedÂ larvaeÂ ofÂ 3rdÂ generationÂ overwinteredÂ duringÂ SeptemberÂ -Â October.Â TwoÂ larvalÂ parasites belongingÂ toÂ orderÂ HymenopteraÂ andÂ Diptera,Â andÂ aÂ fungalÂ pathogenÂ (FusariumÂ sp.)Â wereÂ 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.Â Â Â Â Â Â Â Â Â Â Â Â Â Key Words: Insect biology, Insect ecology, Dioryctria abietella, Coniferae, North-Western Himalaya, Forest pests
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