When locusts attack a country in great swarms and destroy crops and plants, they are to be combated even by killing them with insecticides or any other way, for man’s interest is given priority over animals’.
Sheikh `Atiyyah Saqr, former head of Al-Azhar Fatwa Committee, states: Locusts are a kind of flying insect that are lawful to eat according to Islam. The Prophet (peace and blessings be upon him) was reported to have said: “Two kinds of dead animals and two kinds of blood are lawful (for Muslims) to eat: fish and locusts, and liver and spleen” (Reported by Ash-Shafi`i, Imam Ahmad, Ad-Daraqutani and Al-Bayhaqi).

It was also reported on the authority of `Abdullah ibn Abi Awfa who said: “We participated with the Prophet (peace and blessings be upon him) in six or seven battles, and we used to eat locusts with him” (Reported by Al-Bukhari).
Hence, it is lawful to eat locusts after they have been killed, unless they are killed by harmful insecticides.
According to Hayat Al-Hayawan Al-Kubra, the Prophet (peace and blessings be upon him) was reported to have said: “Do not kill locusts, for they are the greatest kind of Almighty Allah’s hosts” (Reported by At-Tabarani and Al-Bayhaqi). If this hadith was proved to be authentic, the order of not killing locusts would be conditional on their having not destroyed crops and plants, but if they did, they are to be combated in any way.
Hence, killing locusts is lawful if they destroy crops and other plants, for preserving man’s interest is to be given priority over animals’. Animals are created to be subservient to man; he is to slaughter them for food and use them for other purposes in the framework of the proprieties of Shari`ah.
According to Tafsir Al-Qurtubi, jurists are unanimous that locusts are to be killed if they destroy crops and plants. Besides, the Prophet (peace and blessings be upon him) allowed that a Muslim may fight another Muslim in defense of his property; if this is the case with a human being, it should be so, with greater reason, in the case of locusts on threatening people’s properties. Furthermore, jurists agree that snakes and scorpions are to be killed, for they harm human beings; so is the case with locusts, and thus they are also to be killed.