The VFR rated pilot continued flight in poor weather. Airframe icing caused the left wing to fail in flight. The aircraft lost control and crashed. The Lodestar was not equipped with de-icing boots. PROBABLE CAUSE(S): pilot in command – attempted operation with known deficiencies in equipment pilot in command – continued VFR flight into adverse weather conditions pilot in command – exceeded designed stress limits of aircraft airframe – wings: spars miscellaneous acts, conditions – overload failure FACTOR(S): miscellaneous acts, conditions – separation in flight weather – icing conditions-includes sleet, freezing rain,etc. miscellaneous acts, conditions – airframe ice weather briefing – briefed by flight service personnel, by phone weather forecast – forecast substantially correct