INVESTIGATIONS have shown that selenium salts, among other substances applied to the soil, are taken up by plants and will make the plants so treated poisonous to certain pests that attack them. Selenium compounds, such as sodium selenate, have lately been tried by a few growers for the control of chrysanthemum eel worm and some other pests of flower crops. This is dangerous because selenium compounds are poisons to man ; moreover, they may persist for long periods in the soil, and if food crops are grown later in treated soil the plants may take up the poison in sufficient amount to make them injurious to health if eaten. For the present, neither sodium selenate nor any selenium compound should in any circumstances be used for pest control purposes. The Ministry of Agriculture and Fisheries understands that no proprietary insecticide containing selenium is manufactured in Great Britain.