There is disclosed a composition for preventing wilting of pines which comprises as an active ingredient a compound of the formula (I): whereinR.sub.1 is alkyl, cycloalkyl or alkenyl;R.sub.2 is hydrogen, alkyl, alkanoyl or alkylsilyl;R.sub.3 is hydrogen or optionally substituted hydroxyl;R.sub.4 is hydrogen, hydroxyl or alkoxyimino;the carbon-carbon bond X represents a single bond or double bond, provided that, when R.sub.4 is alkoxyimino, X represents a single bond, and when R.sub.1 is methyl or ethyl and R.sub.2, R.sub.3 and R.sub.4 are hydrogen, X represents a double bond; or a salt thereof, as well as a method of preventing the pine wilt using the same.Even if pine trees are infected with pine wilt nematodes, the pine wilt nematodes can be killed before the pine wilt nematodes start action in the trunks of the pine trees.