An out-break of pine defoliator (Dasychira sp.) occurred in 1977 in about 900 hectares of Chir pine forest in Swat. About 190 hectares of the forest was defoliated very heavily. The pest preferred southern, eastern and western aspects as an average population per tree on these aspects, respectively, was 1484, 1168 and 1031 with corresponding defoliations. Population per tree on northern aspects was 506 with medium defoliation while in most shady places and deep nullahs defoliation was either light or negligible with lowest population (208 per tree). An average population of 1788,794, 571and 208 larvae per tree, respectively caused complete, heavy, medium and light defoliations.